Listed Buildings
A Practical guide for Builders and Householders
Andrew Cook
A Practical guide to working on Listed Buildings for Builders, Householders and Developers
Introduction
As a builder working in Bristol, I have been employed on many occasions to work on older buildings, many of which were listed. I enrolled on the Bristol University Diploma Course in Architectural Conservation to clarify some of the mysteries and practises of working with old buildings.
This text is an attempt to devise a simple guide to assist people working on listed buildings and to share some of the invaluable education that I have received on the Diploma course. It is intended for both builders and listed building owners in Bristol. I have not included information on Thatched roofs nor on Cob and Timber framed buildings as they do not often feature in our local townscape.
I hope that I can portray some of the enthusiasm that I have developed since I started to learn more about the techniques used in the construction and repair of older buildings. So often we carry out our work in the way that we have been used to without thinking: why ? To understand the reasons for using a particular technique forms part of the personally rewarding jig-saw puzzle of comprehension that we all need to conserve or preserve a building.
My initial interest in older buildings was kindled when my company was awarded the contract to restore and refurbish Hill House, Folleigh Lane, Long Ashton. (Grade II*). The house is in a beautiful setting and prominent position above Long Ashton village in clear view of Ashton Court. It had formerly been a medieval farmhouse and was upgraded in 1839 as a dower house for the Smythe family. Although upgraded in the early Victorian period many of the features were based upon Regency design, including classic Paladian style gables above two storey bow windows facing onto the South and West elevations. Early Georgian buildings would more commonly face the ‘polite’ areas (as opposed to service areas) on the shadier elevations as sunlight was discouraged.
View of front elevation of Hill House
The substantial house had been latterly used as an infirmary and finally as a commune before my clients bought it to restore as a family domain. The building had been considerably neglected over the years. The roof was in a poor condition, the metal gutters leaking at the joints. The heating of the property had been local to the family groups within the commune, probably intense in certain areas at irregular times and the draughts had been eradicated thus preventing any potential for evaporation. As a consequence the walls had become saturated and the evaporating qualities of the lime mortar had gone into reverse.
Our specified works included: re-roofing using reclaimed Welsh slate; repair of gutters by sealing and re-painting; new leadwork; one new window frame to match the original bow window; heating, plumbing, lime render repairs and the complete lime washing of external walls; re-painting woodwork and complete internal decoration using only “breathing” emulsion paints.
Regrettably there were two outbreaks of dry rot which occurred one year after the correction of the gutters, as the wall was drying out, but these were relatively minor in the overall scheme and were easily eradicated by exposing the wet areas, chemically treating and encouraging evaporation.
Another notable problem occurred externally at the eaves level on the larger than average horizontal over-sailing soffit. The original constructional material was lath and plaster which had been limewashed. The plaster had lost its key on the laths and was loose. We removed all of the material, treated the timbers and fitted waterproof ply sheeting which we then painted with oil based paint. The ply soffit soon developed a mouldy appearance. We consulted with a technical representative from the paint supplier who pointed out that limewash working correctly, unlike plastic paint, exudes moisture which was condensing under the soffit. In hind sight, a lath and plaster breathing surface, would have been more appropriate.
Six years on, Hill House has re-established its natural balance and looks wonderful with the one notable exception but this has been overcome by the use of fungicidal paint.
The Conservation Dilemma
Advice about working on older buildings tends to polarise into two camps:
1. The conservation camp who are quite purist about using traditional methods and materials. These can sometimes be difficult to use and can have time constraints.
2. The current building practices camp, whose methods can be more reliable in terms of application failure rates, and do not have the same time constraints, but sometimes can be wholly inappropriate for older buildings.
No hard and fast rules can be applied for each repair or application but it is important to understand that practitioners in building and planning will be more or less in sympathy with one or other camp. Equally it is important to realise that each camp has limitations. It is necessary to apply value judgements to each procedure therefore in any works.
Chapter 1
What is a Listed Building ?
The Chambers Dictionary Definition is; “One officially listed as being of special architectural or historic interest, which cannot be demolished or altered without (local) government consent.”
For much of the following chapter I have relied upon Suddards and Hargreaves, Listed Buildings, Third Edition, 1996.
In England, the protection of ancient buildings and buildings of special interest is relatively recent. William Morris founded the Society for the Protection of Ancient Buildings (SPAB) in 1877 to promote interest in preserving old buildings. SPAB remains an important organisation promoting conservation to this day. It was not until 1882 that legislation was first introduced to protect Ancient Monuments deemed worthy of preservation.
The listing process was formalised in 1913 with the Ancient Monument Board whose inspectors and commissioners of works were required to prepare lists of monuments. The 1944 Town and Country Planning Act (TCPA) encompassed the listing of general buildings of special architectural or historic interest for guidance of local authority. The current statute is provided by The Planning(Listed Buildings and Conservation Areas) Act 1990. This is a rigorous and well enforced law: failure to comply can result in heavy fines (up to £ 20,000) and/or terms of imprisonment (up to 12 months) as Mrs Teresa Gorman M.P. discovered recently when she faced 66 alleged offences in a Magistrates Court for “modernising” a 300 year old Grade II listed building.
The listing process is the statutory basis to protect our “built heritage”. English Heritage superseded the Historic Buildings Council for England and the Ancient Monuments Board for England in 1984 and was formed to provide the expertise to the Secretary of State for the Environment who has overall financial control and responsibility for broad policy matters.
Since July 1992 the control of listed buildings has been the responsibility of the Department of National Heritage. Formerly this was the responsibility of the Department of the Environment although they still retain responsibility for control over the demolition of unlisted buildings in conservation areas. There is close co-operation between the two departments and English Heritage acts as advisors to both departments.
Buildings appear on the list by one of three methods:
(1) By procedures following the methodical re-surveying of the country by English Heritage investigators, a procedure which has encompassed the whole country over the last 15 years.
(2) By Spot Listing which is used in particular to protect buildings which appear to be in immediate danger of being demolished. Spot listing can be applied in 24 hours.
(3) As a result of the service provided by a local planning authority of a building preservation notice.
The most prolific lister was Sir Nikolaus Bernhard Leon Pevsner, (1902-1983), an eminent German-born historian of art and architecture. Pevsner is best known for the Buildings of England, an indispensable series of county guides to architecture which he began to research in the late 1940s. The first volume of the Buildings of England appeared in 1951. By 1974, 46 volumes had been published, mostly written by Pevsner, covering the whole of England; separate series for Wales, Scotland, and Ireland followed. Pevsner was a major historian of 19th-century architecture and a founder of the Victorian Society. He held a number of academic positions, including chairs at the universities of Oxford, Cambridge, and London, and was awarded the Royal Gold Medal for Architecture in 1967. He died on August 18, 1983. (information provided by Kenneth Powell MA)
In 1995 in England there were a total of 447,043 listed buildings (of which 11,600 were Grade I) 4,600 listed buildings in Bristol alone, 15,437 scheduled ancient monuments and 8,315 designated conservation areas. The current re-survey is nearing completion and there are reported to be 500,000 listed buildings.
Secular Listed buildings fall into three categories (this also applies to redundant Anglican churches, college chapels and churches of other denominations)
1. Grade 1: These are buildings of exceptional interest (about 1.4% of the total)
2. Grade II*: Particularly important building of more than special interest (4.1% of the total)
3. Grade II: Buildings of special interest which warrant every effort to preserve them. (95% of the total).
There was formerly a Grade III category which has now in certain areas become a local planning authority list of locally important buildings for which Listed Building Consent (LBC) for demolition will not be granted.
What does listing mean ?
Listing is sometimes misconstrued as the permanent “freezing” of a building’s condition or style. Sir Hugh Casson while giving evidence for Barclays Bank in the connection with a building at 39/40 Lombard Street, London, in April 1976 summarised the relationship between listing and the granting of Listed Building Consent (LBC) as follows: “ While the facade is not distinguished, in my view the Inspectorate was correct in listing the building as Grade II. Listing, however, means no more than it says. It permits time for study and second thoughts. Such study should properly balance the practicalities of preservation with the visual loss to the street of demolition.” The last line refers to demolition verses preservation but same would apply to alteration and/or extension.
It is important to remember that listing includes the interior as well as the exterior of the building, and it also usually applies to the grounds and any walls or fences surrounding the building (the curtilage).
Some Grant Aid is usually available for repair work to Grade I and II* buildings. It is not usually available for Grade II buildings.
Chapter 2
To prepare listed building alteration or demolition consent
· Contact the local planning authority.(LPA) The point of contact may be the authorities Conservation Officer, or, if you are unsure of the existence of a Conservation Officer, contact the Chief Planning Officer. Tell them what you want to do and ask for their advice.
· If they think that Listed Building Consent (LBC) is required, ask them for an application pack which contains four application forms and notes for completion. Ask if they foresee any difficulties which could be overcome by amending your proposal. It can save time and trouble later on if the proposals you want to carry out also reflect what the council would like to see. There are special concessions should you need to demolish a listed building deemed to be dangerous.
· Prepare your application by first obtaining “the listing”, available at your Local Authority Offices in a series of files called “Green Backs” listed in areas, street names and numbers. You may also feel inclined to further research the history of your house or its former occupants at the local reference library. In Bristol this is on the third floor of the Central Library or visit the Bristol Records Office, ‘B’ Bond Warehouse, Smeaton Road, BS1 6XN Tel 0117-9225692. This can be quite an arduous task but if successful is extremely fascinating and rewarding.
With your listing information and historic (relating directly to the building) or historical (famous people or events that have been associated with your building) documentation to hand you will be more aware why your building has been listed. Although the listing does not mention all aspects of the building, the listing applies to the entire building. The TCPA 1990 Act section 336 states “any structure or erection as so defined but does not include any plant or machinery comprised in a building”. The Act also includes a) Any object or structure fixed to the building. b)Any object or structure within the curtilage of the building which although not fixed to the building, forms part of the land and has done so since before 1st July 1948. Please note that any, post 1948, structures attached to the building are considered part of the listed building. Sometimes curtilage buildings or objects (e.g. stables and garden features) are listed in their own right.
· Send the completed application forms to the local planning authority (LPA) with a comprehensive schedule of the proposed work, photographs of the existing situation and drawings if applicable as well as documentation to prove that the building is owned by you.
· Any alterations that you propose, both internal and external, must not affect the character of the building’s special architectural or historic interest. You may prefer to employ an agent who should be an Architect or Surveyor, familiar with listed building consent (the LPA will happily advise). However if you choose to apply yourself , there are many publications to assist your submission, the most important being the PPG 15. PPG stands for Planning Policy Guidance Note, a series of government publications on planning procedure. Building Conservation is covered in number 15 of that series. A further selection of appropriate literature on features such as windows, doors, methods and materials used at the time of construction are available from various sources (see Bibliography) but more complicated applications are better addressed by an experienced professional.
The council should acknowledge your application within 28 days. Review by the listed building consent panel and, if successful, full consent will take about 8 weeks.
If your listed building consent is refused, the council must report the panel’s reasons.
· If you are unhappy or unclear about the reasons for refusal, talk to the planning department.
· Ask them if changes to your proposals might make a difference.
· If you think that the panel’s decision is unreasonable you can appeal to the Secretary of State. Appeals must be made within 6 months of the date of the council’s notice of decision. You can also appeal if the council do not issue a decision. A booklet “Planning Appeals- A Guide” is available from the Department of the Environment, Planning Inspectorate, Tollgate House, Houlton Street, Bristol BS2 9DJ
Note:
1. Appeals are intended as a last resort. They take several months to decide. It is often quicker to discuss with the council whether changes to your proposal would make it more acceptable.
2. There is no formal appeal against listing. There is, however, power to amend the list and the PPG15 states that the Department will consider requests to remove the buildings from the statutory lists where new evidence can be produced to show that they do not possess the special architectural or historical interest ascribed to them.
There are however several redeeming aspects with ownership of Listed Buildings:
· There is no charge for Listed Building Consent Application.
· If your property is Grade I or Grade II* certain grants for repair work are available directly from English Heritage. For Grade II or buildings in a conservation area there may be a grant available for 25% of the cost of the work if your property is in one of the designated conservation areas. In Bristol these are particular areas in Bedminster, Stokes Croft, Old Market and Portland Square. Should you be successful in obtaining a grant under the Conservation Area Partnership Scheme (CAP) you will have to adhere to a specification requirement (appendix ix). This is a very well specified document and could be adopted as a general specification for working on listed building.
· VAT is zero rated when a domestic or residential listed building with granted LBC is altered but N.B. this does not apply to repairs. There are several exclusions e.g. kitchen furniture but not kitchen appliances can be zero rated however bedroom furniture should be charged at 17.5%. Carpets do not qualify for zero rating. Materials are charged at 17.5% unless supplied and used in the alteration of a listed building. Professional fees (e.g. Architect’s and Structural Engineer’s fees) are subject to VAT at 17.5% unless the builder works on a design and build basis whereupon fees which encompass alterations are zero rated. Your builder will be liable for any VAT which has been incorrectly apportioned and may be reluctant to offer any concession. It is, therefore, in your interest to obtain a copy of VAT Act, 1994 Sched.8 and/or read the section in Suddards and Hargreaves, Listed Buildings Third Edition.
· If you alter/restore your listed building using the advised procedures you will achieve an indefinable homogenous balance that arrives with an old building that is “breathing” in the correct way. Aesthetically you will enhance your building and thus improve the saleable value as well as have a beautiful and comfortable living environment.
Chapter 3
History and The Listed Building in Bristol
Shipping had been the mainstay of wealth in Bristol since the 15th century. Since then, local merchants have been circumnavigating the globe and have had access to a vast selection of resources.
The development of commerce with America and the West Indies made Bristol the third richest city in England by about 1700 and the second largest seaport with 165 ships of an average of 105 tons. At the height of Bristol’s prosperity in the middle of the 18th century Bristol merchants were among the richest in the world and their wealth helped to fuel the substantial building boom which has shaped our current townscape. In a local school history exercise it was established that the round trip, (which took 6-12 months, and consisted of cloth and munitions to Africa, slaves to the West Indies and American rum, sugar and tobacco back to Bristol) could benefit the sponsor of the ship, including slave losses, by a sum to the approximate current value of £ 1 Million. A risky business but ‘When your boat comes in’ an extremely profitable one !
This reproduction of a contemporary engraving shows how slaves were packed in the boats from Africa to the West Indies. It is not surprising that many died on the voyage.
The wealthy merchant could display his wealth and his knowledge of the classics by breaking from the vernacular style and adopting the favoured neo-classical designs, displayed in the numerous publications, many of which had been adopted from the Four books of Architecture, a scientific treatise written by Andrea Palladio (1508-1580).
The trading of cloth, munitions, slaves, ivory, sugar, rum and tobacco compounded the wealth of the merchants who later financed the developing industrial revolution and the ever improving transportation systems fed the growing demands. This self perpetuation of wealth and industrially produced goods continued for over a century. In 1850 Britain produced more iron than the rest of the world, 2/3 of the coal and more than half of the cotton cloth.
At the 1851 Great Exhibition more than half of the 14,000 exhibitors represented Great Britain and her colonies. Albert, Victoria’s Prince Consort was reported to have written about the Great Exhibition ‘The products of all quarters of the globe are placed at our disposal and we only have to choose that which is best and cheapest for our purposes, and the powers of production are entrusted to the stimulus of competition and capital’.
It is this heritage of wealth and enterprise which listed buildings represent today and hold in trust for future generations. That heritage is important throughout the country but it is especially important in the historic city of Bristol.
Chapter 4
Stonework: Repair, Pointing and Cleaning
In this and the next six chapters I will describe the practical considerations of working with listed buildings - the nuts and bolts of building. Please note all quoted prices are approximations and do not include v.a.t.
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Most of the listed buildings in the Bristol area are of stone construction rather than of brick. The stone used for building in Bristol is mainly Pennant Sandstone and Bath limestone, although there are many local variations as you would expect in a hilly area with a complex geological past. I have listed some of the typical stones found in the area below but some stone has been quarried very locally at the time of construction and are only used for a few houses.
A good example of this is in Napier Road in Redland. The stone found there is a soft brown colour similar to Somerset Ham stone and has been used on just 15 houses in Napier Road and the corner of Clyde Road.
Picture of a panel of coursed sandstone walling at 4 Napier Road, Redland.
Pennant stone is a sandstone which varies in colour from grey to green to red and is fairly impervious to water. Sandstone seams are often situated close to coal seams and as Bristol and its surrounding areas are rich in coal, the sandstone, as a by-product of the coal industry, became a easy source of a very good building material.
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Sandstone when mined from the ground is quite easy to cut and shape but as it oxidises it become extremely hard and durable.
Sometimes it is in slate form (i.e. can be divided along its seams or slaked) but more often it is in block form and is dressed on one surface only. Pennant stone is still available. It is used for paving (£25 per metre reclaimed, £ 80 for new) , kerb stones, sets, copings, coursed stone walling (regular shapes, costs approx. £ 25 per metre) or random rubble walling (£65 per tonne, £18 per metre).
Coursed pennant stone walling
Limestone is a soft workable yellow porous stone. The most commonly used limestone comes from the Bath area (the great oolite of the Jurassic period). Although limestone has been substantially extracted in Bath for building uses only one seventh of the available stone has been mined. Other sources include Dundry and Doulting (inferior oolite) both used on Bristol Cathedral. Cut or dressed limestone is described as
“ashlar”. However the stone quarries further define this as Ashlar, being vertical stone work with the grain running horizontally and Coping being horizontal stonework with the grain running in the same plane. When purchasing limestone it is important to specify the correct terminology as the position of the seam or the grain will affect its weathering capability. Limestone is easy to carve, cut and shape hence its widespread use in building. Areas of unsound stone in a building should be carefully cut out and replaced. The CAP specification states that face patches should never be less than 100 mm deep but most of the Victorian ashlar stonework is 50 mm thick and has stood the test of time (£ 70 per metre for 50 mm Bath limestone and £ 100 for placing, jointing and dressing). Plastic in situ repairs using premix are approximately half the cost but should only be used in very small areas and will only last from 5 - 10 years.
An example of Bath limestone plinths, quoins, door surround, keystone, cornice , parapet walling with decorative fretwork panel and coping also at 4 Napier Road in Redland (stonework carried out by Steve Parsons). The coursed rubble walling is reclaimed Cotswold stone which was the closest available match to the original locally mined sandstone. The steps are Yorkstone, risers slate and the paving is reclaimed pennant stone.
Brandon stone, a deep red, millstone grit (carboniferous) sandstone mined from Brandon Hill and used prolifically in Clifton and Clifton Wood. It is invariably used for rubble walling but it not as durable as pennant stone (reclaimed stone is usually £ 65 per tonne, 3m per tonne).
Ham Hill Lias, a Jurassic limestone with a light brown soft appearance mined at Ham Hill in Somerset. An important example is the Colston Hall.
Picture of base of column at Colston Hall.
Keynsham Lias, a yellow or grey Jurassic limestone used for walling, either coursed or randon (see below). Porous but durable.
Blue Lias, a dark coloured limestone, used for example at the old GWR Station. (see right). New dressed lias is available from Clutton at £ 80 per tonne, approximately 3 metres per tonne. Reclaimed stone is available from J.A.Tyler, Environmental Reclamation, Winford - Tel. 01275-333589 also at £80 per tonne.
Re-pointing (between stone or brickwork)
Stone is held together, and the joints sealed by mortar, typically referred to as pointing. Over time the mortars weather and re-pointing may be necessary to weather proof and maintain the integrity of the building.
Firstly consider whether re-pointing is necessary. The CAP grant schedule states; “Re-pointing of external brickwork should be kept to the absolute minimum structurally necessary and a comprehensive re-pointing for cosmetic reasons is not acceptable”. I have been asked several times to re-point brick chimney stacks because damp is showing on the bedroom chimney breast. More often than not the pointing is intact and working well but there are two or three open chimney pots letting in substantial amounts of water, the chimneys are no longer in use and hence there is little evaporation and the damp is apparent by the joints of the corbelling where the chimneys have been turned. Sand and cement pointing in this instance and most others is a complete waste of time and money and will compound the problem.
The golden rule in pointing is that the mortar mix should be weaker than the adjacent masonry.
Notice in this photograph how the stone has decayed leaving the mortar in tact. This hard sand and cement mortar is probably about 15 years old and is either 1:2 or 1:3 cement to holm sand.
The most important function of pointing is to materially support the stonework.
The second most important function is to extract the moisture from the surrounding stone or brick and act as a sacrificial element. It should be placed to encourage evaporation through the mortar mix.
For the latter reason it must be very porous and should have the maximum potential surface area for evaporation. A rough brushed lime pointing mix using irregularly sized sand/aggregate particles pushed well back into the joint has the optimum potential for setting and evaporation and conversely a hard smooth sand and cement mortar can be only detrimental to the surrounding material.
Notes:
· Lime in the above text should be well matured lime putty usually costing £10.50 for 40 kg. In Bristol we are very fortunate to have a good local supplier (H.J.Chard & Sons Tel 0117-9777681)
· Hydrated lime should not be used for producing a set as it will have often carbonated in the bag.
· Cement mortars are too strong to use on old stonework. A mix of one part Portland Cement (the colour of Portland Stone) and three parts of sand should show a tensile strength of 19.4 kg per sq. cm (275 lb. per sq. in) after being immersed in water for one week. Cement is also environmentally expensive to produce. It takes 1 kg of coal powder burnt at temperatures between 1540° and 1600° C to produce 2 kg of cement.
Soft, lime mortar mixes are critically important with soft brick and limestone but are equally important for long term protection of the harder sandstone.
Types of Pointing;
Unfortunately in the Bristol area strap pointing (raised pointing) has become a fashion. Usually this consists of hard impervious sand and cement mortar pointing that not only prevents evaporation but actually contains the moisture in ledges against the stone and accelerates the decay of the surrounding stone. Fortunately frost and time usually exfoliate the pointing before too much damage occurs but the practice should be avoided at all costs. Strap pointing probably originated as a way of increasing the surface area of the pointing and hence improving the evaporating potential of the mortar but something has been lost in the passage of time and with the advent of non-evaporating cement rich mortars.
Other types of pointing include;
· Tuck pointing, a method of pointing in a dark colour, cutting out the centre and over pointing with a light colour. Only for the extremely skilled mason with a lot of time on his or her hands.
· Lined out pointing, where the pointing mix was placed and tooled to a shape before setting. Also a skilled method but slightly detrimental to the evaporating qualities of the mortar.
We have recently pointed a random rubble building in Clifton Wood. The mortar pointing mix was specified by Frank Webber, an experienced local surveyor on the Diploma course, as 1 part lime putty, 4 parts coarse sand including black ground up clinker block and ½ pozzolanic brick (obtainable from W.Bedford in Whitehouse Street, Bedminster). Both the clinker block and the brick act as pozzolanic agents (the name derives form the volcanic ash in Pozzuli in Italy and was used by the Romans to encourage better setting of lime mortars). The pozzolans absorb the moisture from the mortar mix and accelerate the set. The mortar was mixed in a bucket with a whisk on a drill. The stones were wetted before placing the mortar, and the resultant mix was easier to apply than a sand and cement mortar and required no extra attention, it brushed up roughly, had an authentic dark grey appearance and looks excellent. The mix was applied on a mild dry day and the building was not in direct sunlight. Caution must be exercised when frost, rain or extreme heat is likely to occur and the building must be adequately protected until the mortar has set - a process which takes about three days.
I feel that the above is a breakthrough because lime mortar pointing is normally three times the cost of sand and cement( £36 for lime pointing and £12 for sand and cement). This mix, however, costs no more than the cement mix and has all of the inherent benefits of lime mortar. ,We have in the past used coal dust instead of the clinker block. This keeps the mortar a light colour and brushes up well, showing the aggregate and the coal but because the coal is not absorbent, the set takes longer. There are numerous books and publications about lime mortar: several are listed in the bibliography.
Jane Schofield’s list of mixes taken from Lime in Building. A practical guide.
The Cleaning of stonework.
Annex C of PPG 15 (paragraph C18) states that:
“Cleaning a building usually requires listed building consent. This is not only because cleaning can have a marked effect on the character of the buildings, but also because cleaning processes can affect the historic fabric.” Many owners wish to clean their buildings, either for the aesthetic effect or because they believe it will assist the conservation of the building. A cautious approach must however be adopted. Aesthetically, the cleaning of a single property within a homogenous terrace would obviously affect the appearance of the terrace as a whole. And all cleaning methods can cause damage if carelessly handled. Cleaning with water and bristle brush is the simplest method, although water cleaning can lead to saturation of the walls and outbreaks of rot in the timbers. Other methods, including abrasive and chemical cleaning, can damage wall surface and destroy detail. Local planning authorities should satisfy themselves that such cleaning is both necessary and worthwhile to remove corrosive dirt or to bring a major improvement in appearance, and should ensure that cleaning is carried out by specialist firms and under close supervision. Areas not being cleaned should be protected
In summary, discuss with your local planning authority before cleaning and take advise before you appoint a cleaning contractor. Mistakes can be extremely costly.
Chapter 5
Re-rendering and plastering
The fundamental difference between old and modern building techniques is in the wall construction. Walls of modern buildings generally consist of two layers of impervious blocks or bricks with a cavity between to further eradicate the potential of water ingress to the inner layer. The exterior is often covered with a waterproof render and an impervious plastic paint.
Prior to cavity wall construction, however, buildings were made of a single wall which varied in thickness according to the material used. The walls would often have been rendered externally in a lime render and internally with lime plaster. Lime mortars are very porous and act as a wick to extract moisture from the adjacent wall, the moisture freely evaporates with the effects of sunlight and wind. Rain will obviously be absorbed by the render but only to a shallow depth unless there is an unusually great intensity of water e.g. a defective gutter.
Lime renders, however, can only be applied successfully during the dry and frost free months of the year and depend upon the craft of the plasterers to know how and when to apply the renders. When cement became freely available at the beginning of the 19th century it added a new dimension to the application of mortars. Rendering could be carried out virtually throughout the year without failure because of the fast setting times and the craft of the plasterer was not so important. Regrettably we now know that cement rich mortars are impervious and do not allow the free passage of water, and they also develop cracks which suck in moisture through capillary attraction and evaporation only occurs through the cracks. Often an osmotic effect occurs where the dry wall sucks in moisture, the joists between the stone or brick become wet and begin to move causing further cracking on the exterior hard render and the problem accelerates.
The dilemma is thus:-
· Lime renders are ideal for single wall construction but are unreliable, expensive to apply and require some expertise (£ 60 per metre).
· Cement rich waterproofed mixes are easy and cheap to apply but crack and are detrimental to the building (£ 20 per metre).
· Weak mix cement mixes crack less but are more difficult to apply than waterproofed mixes as the second and subsequent coats dry back rapidly into the first coat. This can be overcome by wetting. (£ 25 per metre)
In conclusion the preference for single wall construction must be the lime mortar mix (1:3 lime putty:sand: plus 1/2 pozzolanic brick dust if preferred) but if adverse weather condition prevail i.e. there is a likelihood of a severe frost within one week then a 1:1:6 (cement: lime: sand) maximum strength mix should be adopted with a preference for white cement which is chalk based and purer than lime based cements and the lime should be matured putty lime and not hydrated lime.
An alternative mix could be 1:2:9 which is effectively a lime mortar mix using the cement as the pozzolanic agent. Protection would still be required in frosty conditions but this is a successful mix and still promotes evaporation.
According to Jane Schofield, the Devon based conservation consultant English Heritage tested a 1:3:9 cement: lime: sand mix (The Smeaton Project) and found the resultant mix to be weaker and less durable than a lime mortar mix. She suggests that pozzolanic additives in exposed conditions would be a better alternative. John and Nicola Ashurst, in Practical Conservation do not share this view.
Warning !
In April 1990 an Injunction of £ 25,000 for contempt plus costs was placed upon the owner of Grade II Palace House Mansion, Newmarket, Suffolk for unauthorised application of cement rendering.
Internal Plasters
In general, the same rules apply to the plaster internally as to rendering externally. Evaporation should be encouraged but for comfort it is preferable to ensure that the main effect of evaporation occurs externally. The issues of heating and ventilation should be considered.
Areas of buildings that were not designed to be entirely damp proof e.g. basements and utility areas require special consideration. An option is to form a waterproof box with the installation of a damp proof membrane, concrete waterproofed floor, tanked sand and cement walls and an injection course to contain the moisture. I feel that in most instances this is an expensive and very fallible approach. Water contained is a very formidable adversary and if it wins, as often it does, it creates a host of problems elsewhere in the building e.g. dry rot. Another option is to retain the room in marginally damp condition for the purpose it was built or to consider an option that allows for evaporating mortars without causing inconvenience.
Damp proof courses (DPC) are often a prerequisite of the mortgage lender. In single wall construction, post construction DPC treatment cannot hope to prevent the passage of water rising through rubble fill walls nor dense brick and stonework. The sole barrier becomes the 1.2 metre high water-proofed render. English Heritage in their advice leaflet for grant aided works state that: The provision of a damp-proof course simply because of the existing structure was built without one is ineligible for grant-aid. Experience has shown that the provision of damp-proof courses and membranes in historic structures has often diverted damp problems to other areas. It is cheaper to change the mortgage lender than the plaster.
The first consideration in areas of damp or damaged plaster is to eradicate the source of the damp and to dry the wall out. Small repairs can be effected on lime mortars by using Chardstock premixed lime mortar at £ 4.80 per 50 kg bag or, for thicker repairs, £5.00 for haired mortar. Neat lime putty can be applied as a finish coat once the base coat has dried: however we have found from experience that the putty sets too slowly, and that the addition of 10% casting plaster (available from Hayles and Howe, Picton Street, Montpellier) accelerates the set without affecting the evaporating qualities of the mortar.
Jane Schofield suggests 1 part lime putty to 2 parts sand with ¼ white hair but we have found that the sand drags and the hair is very difficult to mix.
Larger areas can be plastered as follows;
· With site mixed lime mortars to reduce the cost.
· Limelite or renovating plaster but these would be skimmed with gypsum which does not look correct against the sandier appearance of lime mortar.
· Sand and cement mortar but this affects the breathing capability of the plaster and often compounds the problem at the intersection of old and the new and leaves a damp appearance on the gypsum plaster.
· The current trend is to use an insulated plasterboard stuck onto the hacked off wall. This is a slightly more expensive but good option as it allows for evaporation, internally it is a dry surface and has the inherent advantage of extra thermal insulation. This is a particularly good option for single brick walls but the appearance of the gypsum plaster still applies.
Chapter 6
Roofing
In the UK climate the requirement for an efficient rain shedding roofing material is an important one. Equally, the townscape impact of inappropriate roofing materials can be considerable, especially in a hilly town like Bristol where roofs form part of many cross town views. Roof work is expensive, usually requiring scaffolding. For all these reasons it is essential to get an effective and appropriate answer to the roofing requirements of a listed building.
The choice of material, if selected correctly will not often affect the longevity of the roof. In old slate and tiled roofs it is usually the fixings and the battens which fail before the slates or tiles decay. Slate roofs cause slightly more of a problem due to the method of fixing (i.e. each slate is nailed) however clay double roman tiles have a lug which hooks over the batten hence replacement is usually easier.
When chosing a material it is very important to consider the structural impliction on the roof timbers and the supporting walls. Contrary to popular belief new clay tiles are often heavier than concrete. I weighed a new concrete double roman tile, an old clay double roman tile, and two old Welsh slates with an equivalent covering dimension to the tiles. The clay double roman tile was 200 grams lighter than the concrete but the two slate together were 1 kg lighter than the clay tile.
The CAP grant specification states; “ Generally, roof works should be of a comprehensive nature and any necessary associated repairs (to the roof structure, chimneys, leadwork or rainwater goods for example) should be undertaken at the same time”. There is a comprehensive list of specifications for the range of methods and materials required. For the sake of this text I have provided a table of estimated costs for stripping, felting, battens and relaying or providing new material. The ultimate decision will be arrived after consulting with the local planning office.
Material |
Material /metre |
Labour/Metre |
Total |
Welsh Slate |
£ 48.91 |
£ 20.00 |
£ 68.91 |
Reclaimed or new Spanish |
£ 21.00 |
£ 20.00 |
£ 41.00 |
Clay plain tiles |
£ 18.00 |
£ 20.00 |
£ 38.00 |
Concrete plain tiles |
£ 13.00 |
£ 20.00 |
£ 33.00 |
New clay tiles D.Romans |
£ 10.00 |
£ 12.00 |
£ 22.00 |
Reclaimed clay tiles |
£ 6.00 |
£ 12.00 |
£ 18.00 |
Concrete tiles |
£ 6.00 |
£ 10.00 |
£ 16.00 |
|
|
|
|
Lead step flashings |
|
per linear m. |
£ 20.00 |
Lead valleys 300 mm |
|
per linear m. |
£ 10.00 |
Lead soakers |
|
per linear m. |
£ 10.00 |
I have provided costs exclusively for lead without listing any other material.
Copper is an extremely durable but very costly and slightly unsightly material (e.g. the green roofs of the flats in Clifton Vale).
Zinc gained popularity in the post war period. It can be laid successfully in one continuous 9 metre length which overcomes the need to form steps in valleys. Zinc however is purchased in six or eight foot sheets which need to be soldered at the joints using a soldering iron, silver solder and a very mildly acidic flux called Bakers fluid. Good soldering techniques are very difficult to perfect and there are very few plumbers in this country capable of carrying out the work. This is not the case in France where its use is very comprehensive and widespread. Zinc is relatively cheap to purchase but decays quickly when exposed to sulphurous or acidic climatic conditions.
Mineral felt, nuralite, torch on felt etc. are not adequately durable and their appearance is not usually acceptable for the older buiding.
Leadwork however is readily available, malleable, attractive and durable. Good leadwork should last for 80 years if carried out in accordance with the recommendations set out by the Lead Sheet Association, Hawkwell Business Centre, Maidstone Road, Pembury, Tunbridge Wells, Kent. TN2 4AH Tel. 01892-822773.
The photograph below shows various roofing materials; from left to right these are Welsh slate, Spanish slate, concrete plain tile, new clay plain tile, reclaimed clay tile, new clay double Roman tile, reclaimed double Roman tile, smooth concrete double Roman tile and granular finish concrete double Roman tile.
Chapter 7
Timber Repairs
Probably the most common timber repair in a listed building will be the replacement of timbers which have decayed as a result of an ensuing water problem. This is usually due to a leaking roof, a defective gutter, inadequate paintwork , excessive moisture in adjacent plaster or masonry coupled with inadequate ventilation. Typical problems include:
True dry rot Serpula Lacrymans, (the weeping fungus) arrived in this country circa 1750 in infected timber from the Himalayas. It will not propagate in materials with a moisture content less than 20% (preferred 26%) but it can transport its own moisture through a root system and feed itself, hence its name. Its spread is fortified by calcium. It is prevalent in conditions where external ground levels are higher than those inside. It is a problem for softwood, particularly fast grown timbers which have a greater sapwood content, imported since the 1900’s when the main stock of wild grown indigenous softwood expired. It is a brown rot which destroys the timber from the centre outwards by removing the sap, hence the name Dry Rot. Remedies include exposing and torching the fungus and it root system, taking out affected timber sections, reducing moisture contents in walls and chemically treating the infestation. Avoid chemical wall irrigation: this has been proved worthless by the Timber Research Establishment (TRE) as quoted by Brian Ridout, the EH advisor on timber decay. There are currently developments in progress to create a natural remedy: The research is being carried out by Dr Jaquit Singh on behalf of the St Albans Consulting Engineers, Oscar Faber. It involves one natural predator of the Himalayan wild species of the dry rot fungus called Trichoderma Harzianum. Test, which are believed to be nearing conclusion, have been carried out under control conditions at Taymoth Castle, Dundee.
Wet rot: Is the generic name to describe any fungal attack of timber. Water does not decay timber unless a fungus is present. Most fungi require moisture contents in excess of 20% to survive.
White rot; is the main attacker of hardwood. The rot destroys the lignin.
Death Watch beetle; pest of hardwood, predominantly oak with a moisture content greater than 10-15%. It starts life as an egg laid on timber, takes 21-22 days to hatch and burrows into the centre of the timber where it remains for about 6 years searching for nitrates. It pupates in autumn and emerges in spring (April -June). There is no effective chemical treatment, it does have natural predators, spiders, lacewings and bats but these are effected by chemical treatment.
Woodworm; (Common furniture beetle). Infestations generally quite localised usually in softwood. Should be chemically treated as soon as beetle damage is evident. Can be avoided by using denser or treated timbers.
In general terms Structural timber repairs should generally be carried out using a similar sizes and species to the original timber.
English Oak can be purchased locally from Oscar Windebank & Sons
Corsham, Wilts SN13 8ER Tel. 01225 742929
Oak, Ash and Elm (if available) from Bendrey Bros. Warmley Tel 9674382.
Columbian Yellow pine (similar to Pitch pine except in colour) from Robbins Timber, Bedminster, Tel 963-3136 who have extensive stocks of many other hard and softwoods.
Most timbers and good advise is available from Nicks Timber in Gloucester Tel 01452-525531 who have been importing for over a century.
Chapter 8
Windows and Doors.
Windows and doors together provide the detail to the building’s facade which gives it character. Windows and doors are somewhat like the eyes on the human face - small in area, but critical to recognition. Being made of thin section timber and exposed to the elements, they are likely to need some repair or perhaps replacement after a century or more of installation.
CAP Grant specification states:
“Existing window and/or external doors should be carefully repaired wherever possible. If replacement is unavoidable, the new windows should be accurate replicas of the original design in both pattern and detail. Timber sections, especially mouldings, should be the original profile; this is of particular importance for glazing bars and meeting rails to horizontal sashes. Double hung sliding sashes without horns (unless the original sashes were to this pattern) and should be hung on cords with weights. Spring balances for sashes are not acceptable.”
It is often quite difficult to establish whether the current window is original. On a vertical sliding sash window (introduced circa 1715) the easiest method of “snap dating” is by the evidence of horns. These are the 50-75 mm moulded sections at the end of the side rails beneath the bottom horizontal rail of the top sash and above the top rail of the bottom sash. The purpose of the horn was to increase the durability and the strength of the sashes. As a general rule horns were not fitted prior to 1860. Usually a visual inspection of the adjacent houses gives an indication of the authenticity of the window style but beware, do not underestimate the prowess of the Victorian sash window salesmen. For example John Wood’s Circus in Bath, dated 1754 and consisting of 30 buildings has only 3 with the original timber windows without horns.
The advent of the horn also coincided with the mass production of sheet glass which consisted of molten plate glass mass fed into rollers and formed into sheets which were ground and polished. The glass was more consistent and generally cheaper, thicker and thus heavier than the former Crown glass, i.e. blown glass which was heated and spun in a “punty” until it finally opened out to a flat disc which was cut to the required size. In the PPG15 the retention of the Crown glass is preferred. This must not be confused with the 2 mm thick post war glass which is prevalent in Bristol due to wartime bombing and does not comply with the current Building Regulation requirement of 4 mm thick glass in sash windows above 800 mm. (safety glass below 800 mm).
Another indication of the date of the window or door is the style of the moulding, e.g. Georgian sections usually consisted of a lambs tongue moulding which has a longer centre section and generally is slimmer than the subsequently preferred Victorian moulding which was ovolo, a rounded centre moulding which suited the thicker timber section. A closer scrutiny of the sections used at the time of construction will further assist the authentic replacement of windows and doors.
Picture of Regency styled window showing thin glazing bars with lambs tongue moulding, no horns and thin meeting rails.
|
Picture of late Victorian style sash window, thicker sections, ovolo mouldings and horns evident. |
Modern UPVC and aluminium windows and doors would appear to have many advantages:
· They are cheap to manufacture and easy to install
· They are immune to the problem of decay that affect timber windows therefore they can be installed in areas where moisture contents are high. This might be a consideration where an outbreak of dry rot has occurred.
· They do not require painting (in the short term)
· They are draught proof and thermally efficient.
They have, however, several disadvantages in respect to listed buildings:
· Their sections cannot be made to match the size nor the style of traditional windows therefore they affect the character and appearance of the building.
· In the short term the UPVC would appear to be maintenance free but, as with plastic guttering, it can degrade quickly in sunlight. I would be very surprised to see the average plastic window or door surviving longer than 20 years. We are still painting and maintaining wooden windows which are over 200 years old - and consider the age and condition of the average church door.
· Windows and doors should not be entirely draught free. The current building regulations insist upon a permanent free air space which in a sealed window has to be achieved by the application of a trickle vent. Vertical sliding sash windows do not need trickle vents unless draught seals are fitted.
· UPVC windows and doors present a high security risk. Although they are generally fitted with 3 point locking systems these are easily and quietly removed with a heat gun or blow torch.
· They are generally inappropriate on the older building and will decrease the value and saleability of your property.
·
Inappropriate window fitting without LBC can result in prosecution. In October 1986, Hove Borough Council prosecuted the owner of a listed building for removal of windows by a replacement window company. The owner had to pay a fine of £ 500 and was ordered to pay costs.
Roof lights: Velux(or similar) Roof windows:
Velux is the brand name of a roof window so popular that it has almost become the generic name for the roof-light. The windows are extremely good value (starting at £150) and easy to install. In conservation areas, Velux windows fitted within the roof line can be fitted without planning consent however this is not the case with listed buildings. Velux make a conservation roof-light which is smaller than the average Velux and has an authentic external appearance but a rather disappointing plastic interior. You will still have to obtain listed building consent before placing even a conservation roof-light.
Chapter 9
Guttering and Pipework
As a general rule, if your building has iron pipework in a reasonable condition, it is better to repair the joints and paint rather than replace. For the sake of the following I am assuming a comparison of gutters and down-pipes on the prominent elevation of an old building. One would hope that the soil and waste pipes are on the rear or a less conspicuous part of the building.
Cast iron pipework is immensely durable, it is costly to fit and requires regular painting. Paint on iron pipe-work retains its gloss appearance for longer than paint on other materials e.g. plastic. It is easy to repair at the joints and is not as prone to suffer from the expansion / contraction problems that occur with plastic. It is more attractive in appearance and in certain instances complements the appearance of an old building.
Aluminium pipework is very costly, and its durability over cast iron is negligible as both require regular painting. Aesthetically it is not as attractive as the sections are generally extruded and not cast and, as with many issues related to listed building, I do not see the advantage of using a close imitation when the correct product is easily available and cheaper.
Plastic pipework is cheap, easy to use and readily available. Its durability is considerably less than cast iron, it becomes brittle, the colour fades and the joints fail quickly when exposed to sunlight. It will accept paint, particularly when it has faded, and by using an etching primer when new. It does not particularly fit in with the overall appearance of the listed building but hopefully it should be relatively inconspicuous and should not be an issue. 112m gutter, 2m long, costs £3.87; 68 mm rainwater pipe, 2.5m long, costs £4.97
In a test case in Allerdale, Cumbria (APP/R0905/E/84/800327) in a restaurant conversion the council was concerned about the unsympathetic qualities of plastic goods, but the appellant had used them because the requirements of the condition were onerous and costly. The Secretary of State noted that the plastic gutters and downpipes which had already been placed on the building were not prominent and toned in well with the building’s surrounding stonework. He allowed the appeal and discharged the condition.
Chapter 10
Painting
Annex C of PPG15 (paragraph C17) states that:
“ Painting-or repainting such as a change of colour-requires listed building consent when it could affect the character of a listed building. Previously unpainted surface should not normally be painted over. (An exception to this rule can be made for sheltercoating with a lime-based mixture). In many cases the colour of the paint may be less important than the first application of an unsuitable covering which could be damaging to remove. Cement based or other waterproof and hard gloss paints should not be used on surfaces covered with traditional render. The correct finish for traditional renders and plasters is limewash (although much 19th century stucco has been traditionally coated in oil paint). When inappropriate paint has been applied, expert advice should be obtained on suitable methods of removal”
Wall painting;
Limewash is cheap to buy and easy to apply. A tub of mature lime putty, from Chards in Bristol, costs £ 10.50 for 40 kg. This, when diluted 1:2 Putty to water, makes the basic lime wash which can be applied to wetted lime render or onto wetted stone. It is preferable to apply several thin coats rather than few thick coats which will crack and brush off when dry. It is an effective covering to tired lime renders as it fills in the cracks and prevents consolidated water ingress to the inner parts of the wall. Limewash is totally water permeable and hence allows water ingress during rainfall and evaporation afterwards. Colouring can be achieved by the addition of powder dyes. The intensity of the colour varies with the amount of dye used and the number of applications. Prices vary for the different colours starting at £ 1.50 per kilo for yellow, £2.50 for red from Chards and going up to £8.78 per kg for brown and other colours from J.W.Bollom. Consistency of colour usually takes about 3 or 4 coats of wash but it is important to record the proportion of the mix and to keep frequently mixing the wash in the container during application to keep the colour consistent. Linseed oil or tallow is sometimes used to stabilise the finish but this is a preference of the painter and quite frankly is not necessary. Limewash can be applied to cement renders but does not last because the impervious substrate causes runoff of the permeable, water soluble material.
Keim is a proprietary calcium-silicate German developed paint available through distributors in England (tel. 01746-714543 ) It is reported to be 80% permeable (group 3 of the ISO permeability class rating) and can be painted internally and externally directly onto previously lime-washed surfaces, lime-mortars, stone or cement rendered surfaces without a stabilising solution which is an important aspect, because stabilisers reduce porosity. Surfaces should be prepared by brushing with a stiff brush and in areas where algae growth is apparent apply a fungicide. It will cover in two coats and is easy to apply. It is available in a large range of colours but is very expensive at £3.00 per metre for the material alone.
Two pictures of Keim paint at Wellinton House, 21Canynge Road, Clifton. Right hand picture is an enlarged view at the corner of the step. Notice matt effect of paint.
Water based plastic paints for external uses e.g. Sandtex, Dulux Weathershield and Crown Stronghold. These are only about 25-30% permeable (group 2 of the ISO permeability class rating). The manufacturers state that plastic paint should only be used on rendered walls that have a damp proof course. This virtually excludes 80% of single wall construction buildings. The permeability of the paint is further affected by application of stabilising solutions, the thickness of application and the number of coats. The paint is easy to apply, cheap to buy (£ 12-18 per gallon) and usually covers in two coats. It is a very good and effective product for covering cement rendered cavity walls with a DPC and carries a 15 year guarantee. Regrettably, it is not appropriate for the older building.
Solution polymer paints: e.g. Sandtex 365, London coatings etc. These are about 5% permeable (group 3, ISO rating). They are effectively vapour barriers which are entirely inappropriate for single wall construction.
Contract matt emulsion: This is an interior paint sometimes called high opacity paint. It is the cheapest, thinnest emulsion paint (£ 8-12 per gallon). It is designed to be used after plastering because it is very permeable (ISO 3 rating). The standard colours are white and magnolia but with the advent of the colour toning machines it can be purchased in a variety of 3,000 colour shades. However the merchant may be reluctant to use the colour machine.
Vinyl Matt Emulsion: Very similar to the contract paint but slightly thicker and hence slightly less permeable still ISO 3 but going towards 2. Once again, permeability is affected by the number of coats and the thickness of application. A vast selection of colours are available from numerous suppliers. (£10- 16 per gallon)
Vinyl Silk Emulsion: A shiny version of the above. Easy to clean. Not very permeable (ISO 2).
Others materials; Distempers, oil based paints, cement based paints (e.g. Snowcem) etc. are not readily available but can be purchased if required or specified for particular purposes as needs permit.
Wall papers on interior walls should be discouraged if any excessive damp is present. Evaporation is affected by the thickness of the wall covering and the paste will act as a nutrient for fungal growth. Paper is useful however to apply on to Gypsum finished walls. Paper has an appearance similar to a lime plaster and will overcome the polished, non-authentic appearance of gypsum.
Timber Painting:
I will not dwell upon this subject as the current oil based gloss system on a dry substrate is the most successful material and lasts from 3-5 years. Dark colours should be avoided on sunny elevations. We have recently tried the Cuprinol ultra flexible opaque wood finish which is reported to last 6-8 years. The opaque finish is probably more traditional than a modern high gloss. There are currently 50 colours available and a selection of stains and varnishes. It appears to be a very good product but only time will tell. The use of stained timber is discouraged when applying for an English Heritage CAP scheme grant.
Chapter 11
Conclusion
In a brief guide one cannot hope to cover all aspects and methods used when working with older buildings. I have not intended to provide a text book rather a distillation of experience which I feel is relevant. Working with older buildings is a privilege and tremendously rewarding when you see and feel marked improvements that you have helped to achieve. I have listed some books / contacts that I have used when writing this text and some that will assist your value judgements that you will need to apply when you work with “Our Built Heritage”.
Bibliography and further contacts:
Chapter 1
Suddards, R.W., Hargreaves, J.M.. Listed Buildings 1996. Sweet and Maxwell L
Planning Policy Guidance Note 15, (PPG 15),DOE and DONH, HMSO.
Chapter 2
Georgian Group, 37 Spital Square, London, E1 6DY Tel. 0171-3771722
J & M Miller. Period Details, A Source Book for House Restoration 1994. Mitchell Beazley
The Victorian Society, 1 Priory Gardens, London W4 Tel. 0181-9941019
SPAB, 37 Spital Square, London, E1 6DY Tel. 0171-3771644
English Heritage, 23 Savile Row, London W1X 1AB Tel. 0171-9733000
Chapter 3
Asa Briggs, A Social History of England 1983. Book Club Associates.
J S Fry and Sons Ltd, English City The Story of Bristol 1945 University of London Press.
Chapters 4-10
Jane Schofield, Lime in building. A practical guide, 1995 Black Dog Press
Christopher Brereton, The repair of historic buildings: advice on principles and methods. Available from English Heritage Publications.
John and Nicola Ashurst, Practical Conservation: Volumes 1-5” EH Publication
Guidance notes by the Society of Protection of Ancient Buildings (SPAB)
SPAB Information sheet No 4, The need for Old Buildings to Breathe, P.Hughes
Bruce and Liz Induni, Using Lime, Lydeard St.Lawrence, Tel. 01984-667253
The Smeaton Project, Factors Affecting the Properties of Lime based Mortars EH Publications.
Lead sheet Manuals 1-3, Lead sheet Association. Tel 01892-822773
I.C.Bristow, Interior house-painting Colours and Technology 1615-1840, Yale University Press Tel 0171-4314422
Microsoft Encata, 97 Encylopedia World English Edition,Microsoft.