Listed Buildings and Other Period Properties

(A Brief Guide) - by Robert Bowdler C.S.R.T. M Inst SSE

When considering recommended remedial treatment to listed buildings, special consideration should be given to the proposed works as there are limitations and legal restrictions on what work may or may not be carried out and what materials may or may not be used. English Heritage (www.english-heritage.org.uk) has strict guidelines regarding the remedial treatment of listed buildings and this is usually enforced by the local Listed Building Inspector or Conservation Officer. It can be a criminal offence to carry out unauthorised works to a listed building without attending to the correct consultation procedures.

"The primary aim should be to retain as much as possible of the historic fabric and to halt further decay. Ensure intervention is kept to the minimum necessary to contain the problem in a manner which preserves the essential authenticity and historic value of the structure. In essence this means that the standard remedial methods in general use today are more likely to be inappropriate and unsuitable in the conservation context".

(Extract from 'Works to Historic Buildings - Contractors Manual).

Living in a listed building can have its advantages. Inevitably it will be a unique and interesting building, possibly with some history (Tracing the history of your house by Nick Barratt). It is possible, when carrying out alterations (not improvements or maintenance), to reclaim the VAT incurred on such work. It is also possible to obtain grants for some work where the property is of particular interest, although this is unlikely in a Grade II listed building.

(Go to www.buildingconservation.com/articles/legislation/legislation.htm for helpful information on listed properties, or ask pertinent questions at www.periodproperty.co.uk)

There are currently in the region of 500,000 listed buildings in England with over 90% being of Grade II status. A valuable source of information for the owner of a listed building is the Listed Property Owners Club and their excellent periodic publication 'Heritage' (www.lpoc.co.uk Tel: 01795 844939). Your property may also be present on the 'Images of England' web site (www.imagesofengland.org.uk), where a brief description and photograph would normally be found. Each property will have its own individual UID number. You may also obtain a copy of the 'listing' of your property by writing to the National Monuments Record Office (NMRO) (www.english-heritage.org.uk/knowledge/nmr). Unfortunately the list is not present on their web site. The local area list should be available for viewing at your local council offices.

DWC and all appropriately qualified damp and timber contractors working in this specialised field should be able to offer a GPT independent underwritten guarantee to cover their work (please visit www.gptprotection.co.uk). Needless to say DWC are full members of the PCA and offer underwritten guarantees.

 

 

 

DAMPNESS:

When inspecting a listed building for valuation or a full structural survey it is not uncommon for professionals to locate damp readings somewhere in the property. As soon as even moderate readings are found it has become common practice to recommend the installation of a remedial chemical damp-proof course to what may be completely inappropriate masonry, or where the insertion of a chemical damp-proof course may have no effect..

With any damp treatment it is important that any render applied to the wall is to a waterproof specification. The quality of the render has as much bearing on the relief of dampness as the presence and effectiveness of a damp proof course (DPC). However, in listed buildings this is not normally permitted and the use of cementitious based products is usually prohibited. English Heritage recommends the use of a range of lime based renders (heritage renders), which allow the wall to breathe and dry naturally as it was originally intended. The presence of lime within a render mix will inevitably reduce the waterproof properties of the mixture and will not form a waterproof or vapour barrier, nor prevent the migration of hygroscopic salts from the masonry to the internal wall surface.

Should there be particular problem areas of dampness in a listed building there are acceptable modern alternatives which do not involve the use of cementitious based products. The preservation industry in particular considers the use of breathable 'air gap' membranes (cavity drain membranes) to be a particular asset in the armoury to guard against dampness in buildings.

Of course this will not suit all eventualities and it may well be that the use of lime based renders need to be considered. However it should be borne in mind that as this is not a vapour barrier, on the completion of work, it would not be unusual to find the likes of hygroscopic salt deposits forming where the masonry is drying. Should it be felt that the use of modern cementitious waterproof render is the only sensible alternative, then listed building consent can be sought and if approval is given the product may be used. Alternatively you may simply approach your local conservation officer for his personal approval.

In some instances it may also be possible to reclaim VAT charged for work retrospectively from HM Inland Revenue & Customs but only when official listed building consent has been granted. More information on this can be obtained from The Listed Property Owners Club, and H.M. Inland Revenue & Customs.

In summary, the presence of high damp readings in a listed building should not be viewed as unusual and using modern waterproof products should not be considered as a matter of course. The property will usually require sympathetic treatment, or even no treatment whatsoever combined with adequate ventilation and heating. Long term management of any moisture ingress based on sound advice is essential

It is worth mentioning that chimney breasts and in particular inglenook fireplaces and/or sandstone surrounds will virtually always give high readings to modern sensitive moisture meters. This is usually due to the presence of hygroscopic salts which have been deposited within the masonry from the burning of fossil fuels over a long period. Again the installation of a chemical DPC will have little or no effect. Should effervescence salting persist and become unsightly salt neutralising solutions are available and are easily applied.

All cases of lateral penetrating dampness MUST be addressed and the source of the moisture identified in the first instance. Where possible allow the internal wall surfaces the opportunity to dry naturally.

It is worth noting that on the Wealden District Council web site (www.wealden.gov.uk/planning), "damp proofing" is amongst the list of items which require 'listed building planning consent'.

 

 

 

TIMBER:

Invariably surveys on timbers of listed buildings will result in the requirement for an inspection by a qualified CSRT surveyor with full membership of the PCA (Property care Association previously the BWPDA). The structure of listed buildings will likely be a combination of both hard and soft woods or in some instances completely of hardwoods. The timbers used in period properties were often reclaimed timber, which had been used in previous constructions such as timber taken from redundant horse drawn vehicles, or commonly, timbers reclaimed from ship building particularly near coastal areas.

Inevitably these timbers would be of unusual shapes and may have had completely unrelated joints, shakes and crevices. It is also inevitable that these timbers will have been infected by some form of wood borer insect during its lifetime. In particular Wharf borer and Marine borer beetle are often found in decayed timbers or extremely damp hardwood and softwood timber. The insect flight holes present in the timbers are commonly mistaken for active infestation by Death Watch Beetle (Xestobium rufovillosum) or Common furniture beetle (Anobium punctatum), when in fact the timber can be solid and the infestation long standing and inactive. When dry, these hardwood timbers become extremely dense and it can be difficult to insert fixings such as screws or nails. Insect bore dust from legitimate previous infestation can remain in the timber for many years after introduction into the property and may be dislodged when the interior of the property is re-designed resulting in falling bore dust which is mistaken for new active infestation.

Again the infestation of these old timbers should, as a rule, be viewed as normal. It would be our opinion that blanket treatment of hardwood timbers within any building should not be carried out as a matter of course. Apart from softwoods found in roof spaces, which are readily accessible, the use of modern timber treatment products should be limited to actual areas of proven active infestation. This can usually be limited to softwoods, or hardwoods where they abut softwoods, or where the hardwood contains an amount of moisture and in particular where timber is embedded within masonry without the provision of a damp proof membrane or DPC.

Some species of wood borers insects do not actually require any treatment. The Wood-boring weevil, Euophryum confine, is one such case. The simple removal of the moisture source will result in removal of the infestation without the need to resort to chemical treatment. Bark borer beetle, Ernobius mollis, is also regularly mistaken for an active infestation requiring chemical treatment when in fact it will usually be longstanding and inactive. If an active infestation is found removal of the bark (its food source) is the only remedial treatment required.

Active infestation by wood boring beetle can and is found in older properties. When this is the case it is prudent to isolate the area of the outbreak and treat accordingly with regular monitoring, possibly on an annual basis, during the active season (currently March to early August). Thatched roofs may be treated but whenever possible non flammable materials should be used.

In England the Death watch beetle is one of the major enemies of historic buildings and its favourite food is oak. It is extremely difficult to eradicate. Generally the infestation will be in timber with some decay or moisture content. As an infestation can only be detected by the presence of insect 'flight' holes, the beetle will usually be well established before being detected. The cycle from lava to adult insect can be as little as 5 years but 10 years is considered normal. However a 20 year cycle has been known but much depends on the type of timber and its moisture content. Emergence of adult insects after treatment should be anticipated for several years prior to complete eradication. . "Death Watch beetle is extremely rare in Scotland and has only been recorded twice in Ireland. There is no recorded infestation within a property constructed entirely of coniferous timber, which seems to confirm the opinion that attacks originate only in hardwood."

Outbreaks of wet rot may only require the removal of the moisture source. Dry rot (Serpula lacrymans) however, should be treated with extreme caution and specialists will be required to eradicate the outbreak thoroughly for which you should always obtain a long term and underwritten guarantee from a PCA registered company. This particular fungus is a 'cancer' to buildings and can spread rapidly causing major structural defects. Evidence of such rot should be treated urgently. The presence of Wet rot fungus is again commonly mistaken for Dry rot. DWC's surveyors will diagnose the type of rot at the time of their inspection. Please refer to the identifying characteristics of dry rot elsewhere on this web site.

 

 

 

 

 

 

STRUCTURAL INTEGRITY (MASONRY & TIMBER):

Masonry:Where the property is constructed of masonry there may be signs of structural cracking, instability, failed lintels, ground movement etc. This need not necessarily be a major concern as there are several methods of remedial action which may be undertaken to relieve these problems. In particular such procedures as installing 'Lateral Restraints' or 'Anchor Systems' which tie the masonry to timber frames or floors or other stable structures may be used together with crack stitching and/or mortar bed reinforcement procedures which involve inserting narrow flexible helix profile steel bars in to the mortar beds.

"Rebuilding may not be the only answer, it is just the last resort".

In addition, we must not forget that listed buildings may not only be of solid construction but may be built using a cavity wall system. Many Roman properties are known to have cavity wall construction as are properties of a more contemporary design and interest. Whatever the case, some form of fixing will have been used between the inner and outer leaves of masonry. These fixings may consist of metal fixings, brick or slate. Whatever the problem, a remedial measure is usually available, just ask DWC Regent Homeguard Contractors & Surveyors!

Timber: Where a structural defect is evident within a major structural timber beam, again 'major surgery' may not be the only answer. There are approved systems which involve replacing sectional timbers which use embedded steel 'Re-bar' within a pre-cut hardwood timber section. This remedial procedure would replace the rotted section of timber (end or middle) without resorting to replacing a complete beam. Again, just be aware of remedial alternatives. Call DWC Regent Homeguard on 0845 130 4566 if you require any further information.

We trust the above guide may be of some assistance to those involved with or purchasing a listed property. The foregoing is certainly not exhaustive; however the list of useful web site addresses should answer any further queries on this subject. For first hand advice on listed buildings see also English Heritage web page: www.english-heritage.org.uk/heritageprotection

As they say on the BBC's 'Crimewatch' programme, "Don't have nightmares" You can bet your Grade II Listed Property will outlast many of the modern 'New Builds' and it will certainly be far more rewarding and fun!

 

References & further reading:

The following publications are readily available and contain much more useful information:

The Repair of Historic Buildings (English Heritage)

Works to Historic Buildings - Contractors Manual (Chartered Institute of Building)

Lime and Lime Mortars (Donhead Publishing Ltd)

Listed Buildings, Conservation Areas & Monuments (HMSO)

Conserving Buildings - A Manual of Techniques & Materials (Preservation Press)

Conservation of Timber Buildings (Donhead Publishing Ltd)

Conservation of Historic Buildings (Architectural Press)

Recognising Wood Rot & Insect Damage in Buildings (Building Research Establishment)

Historic Churches - The Conservation & Repair of Ecclesiastical Buildings (A BCD Report)