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Stephen Boniface - Stephen Boniface specialises in building conservation providing multi-disciplinary consulting services. He is Chairman of the Building Surveying Faculty and member of the Residential faculty. He serves on the RICS Building Conservation Forum Board and is the 'Agony Uncle' on the Period Property UK website (

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Our experts are all specialists in matters directly involved with older properties. So, if you have a problem with an older building - or if you think you might have a problem - ask an Agony Uncle...


SUBJECT: Basement conversions rarely eradicate damp completely over time
FROM: Dr Damian McHugh (Leeds, Yorkshire)
I own a large 1910 Millston Grit stonefaced terrace in Leeds. I have begun the job of converting the basement into habitable space for a growing family! In one of 3 rooms which require action downstairs, a raised wooden floor had been installed with access to only one sub-floor ventilation port. An injected DPC had been inserted 6" above the wooden skirtings and floor! The skirtings were unsurprisingly rotten and the floor joists I have looked at around the room periphery are also rotten (only 2-5 mm from wet bricks). The joists were resting on a 1 brick wall which had been laid on earth. My question is this. Is it imperative to install a solid floor with a damp proof membrane above which I would install well ventilated floor joists or is it worth considering joist replacement and a much-improved sub- floor ventilation system. I am leaning towards the latter option for 2 reasons (1) it should work (providing I insulate the room from the sub-floor) and (2) cost of building a new concrete floor.

Damian McHugh

Traditionally basements were always slightly damp but due to good ventilation etc. the dampness rarely caused any major problems. In my experience it is rare for a conversion of a basement to be entirely satisfactory and at some point problems begin to arise. How long before the problems become manifest will depend upon many different factors. Nevertheless, the view I take generally is a system that allows the passage of moisture and continues with a form of ventilation to hidden voids etc. is far more likely to be more successful than one that tries to prevent moisture movement (and therefore usually leads to moisture becoming trapped). In your particular instance I therefore believe that a suspended floor with a ventilated void beneath would be more likely to succeed, but you should be guided by someone who can look at the specific situation and advise precisely. There are a number of methods trying to ventilate the void. Without specific details and the precise design of the basement etc. I cannot offer more positive advice at present. I would merely confirm that in my view a suspended floor over a ventilated void is more likely to succeed. Wherever timbers are likely to be in contact or close to damp surfaces there should be some form of isolating membrane to reduce the risk of the wood rotting through direct contact.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500


SUBJECT: Will the use of a de-humidifier help stop damp in my basement?
FROM: Chris Jeffs (Preston, Lancashire)
Having just purchased an 1802 weavers cottage, a great environment in the cellar for spinning cotton due to the slight dampness. I would like to convert this area for living. Having spoken to a few EXPERTS all with different ideas?? I am considering a cavity wall with a viscous sheet and insulation behind plaster board to provide a warmer wall to stop any condensation. Also running a de-humidifier?? What would be your opinion?

Chris Jeffs

As mentioned to the question above, basement or cellar conversions are rarely 100% successful. However, it seems to be the general consensus that a ventilated/drained cavity system is more likely to succeed and be less problematic than the use of damp proofing renders, tanking, etc. Your idea to provide an insulated surface should limit the risk of a serious condensation problem, but is unlikely to stop condensation as such. The use of a dehumidifier is questionable particularly if it simply re-circulates the air back into the same room. If it is a permanent dehumidifier with an outlet to the outside air this might prove more successful. I would suggest that in the first place a simple ventilation system by way of a positive extractor (an extractor fan) might prove more successful. Some extractor fans can be connected to a humidity-controlled switch. Whilst I doubt if the problem of dampness and condensation will be totally eradicated the measures taken should limit the risk of a serious problem.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500


SUBJECT: Experiment with brick cleaning methods before ploughing ahead!
FROM: Steve Shadbolt (Hampshire)
The brickwork on the front of my late Georgian town house has been subjected to water from a leaking rainwater downpipe. There are now chalky white deposits on the old bricks. I have tried to remove them with standard bathroom de-scaling products, but these do not touch it. I am wary of using the brick cleaning products from the builders merchants as I feel they may be too caustic. Is this caution justified ? Is there anything else I can try ?

Steve Shadbolt

The choice is between mechanical or chemical removal. Mechanical would involve the use of some form of sanding machine (perhaps a disk on a drill) and chemical would involve the brick cleaning products you mentioned. Providing the brick cleaning products are used in accordance with instructions and the surfaces are properly cleaned and washed clear afterwards I do not believe that they would be "too caustic". However, if they are not sufficiently cleaned from surfaces they can lead to longer-term problems. My understanding from those that have used such products is that the cleaning of surfaces after the use of the product is as important as the use of the product itself. The use of mechanical means could cause damage to surrounding brickwork particularly if care is not exercised. My suggestion when trying to clean such surfaces would be to find a small relatively hidden area and experiment with various means to see which of the methods is most successful and least damaging before embarking on the whole project.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500


SUBJECT: Sacrificial limewash coat to protect bricks
FROM: Dr Matt Fletcher (Somerset)
We are in the process of purchasing a converted 19th Century Glove Factory in Somerset. The main part of the building is stone, but there is a two storey brick extension at the rear. The brickwork is English bond, and on the gable wall, there is considerable spalling and weathering which is causing lateral dampness within. I am aware that either cement rendering or waterproofing this wall would cause more of a problem than a solution. We are not keen on cladding as this would be out of keeping with the rest of the property. What are our options to reduce the penetrating damp, but not seal it in.

Matt Fletcher

In your question you do not state whether the brickwork is aesthetically important, whether this is an area of the building that is highly visible, etc. Further, you do not state what type of brickwork you are dealing with. Nevertheless, my initial suggestion would be to use a lime wash as a shelter coat. The application of a lime wash will create a white finish (unless coloured with suitable pigments). It will provide a finish that can be readily re-applied in years to come and is almost a sacrificial surface that will protect the bricks beneath. An alternative to a simple lime wash would of course be to apply a lime render. If this is an exposed area of the property it would be sensible to use a naturally semi-hydraulic lime (although guidance from a lime specialist is advisable to take account of your specific situation). These are the solutions I would favour if you do no wish to go down the route of cladding.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500


SUBJECT: Timber fillets to rid sky views from inside of house
FROM: Leigh Wimpory (Kent)
Our 500 year old Grade II listed barn conversion in the Kent Weald is full of holes at the eaves level, and in my opinion poorly sealed off from the outside world. What would you advise to be the best method of filling the gaps and stopping us seeing through to the sky at the join of the roof to the walls? The gaps are about 2-4cm square. There are also many gaps where the beams interlock and there is quite a draft through these holes, what can we do to alleviate this problem?

Leigh Wimpory

My preferred solution would be to stop up the gaps etc. using timber. In this instance I assume that the timber frame structure is of oak and I would therefore use oak to fill the gaps, oak slips to fill thin gaps, etc. This would also avoid an unsightly appearance by the use of a different inappropriate material. However, if the elevations of your building are finished with a lime wash, you could consider the use of a lime mortar as a filler. When the frame and the rendered surfaces are lime washed it could be continued over the timbers as well and the filler would not be so highly visible. To ensure that the lime stays in place you will have to include hair in the mix for the backing coats and finish with a lime wash application. My only slight concern is that the use of any mortar is introducing moisture into the pockets and voids where there could already be problems of rot etc. that are not yet manifest to the surfaces. I am therefore reluctant to suggest this as 'the' solution. My advice would be to follow the route of using timber to fill these gaps etc. in the first instance but perhaps use lime mortar, etc. for some of them. This does of course depend upon the rest of the finishes to the elevations and the overall appearance of the building.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500


SUBJECT: How do I remove paint from my Bath stone property?
FROM: Paul Mellor (Trowbridge)
I live in a mid-Victorian property constructed of Bath stone. Unfortunately, at some stage the exterior walls were painted over. I was wondering if there is a way to remove the paint and restore the stone to its former glory?

Paul Mellor

There are a couple of possible methods to remove the paint. Chemical removal is of course one option, provided the stone is then carefully washed and cleaned down after the use of chemicals. Another might be to use a steam system. Yet another would be mechanical (scraping, disc, etc.). Whenever removing a paint from stone or any other substrate it is best to undertake a small trial area in a relatively hidden area to establish the success or otherwise the system before using it over the whole elevation. Your local conservation officer or the regional officer of English Heritage should be able to provide names and addresses of specialist contractors experienced in dealing with removal of paint, etc. from stone surfaces.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500


SUBJECT: Do I need a specialist surveyor?
FROM: Derek Harrrison
I have moved into a mid 19th century farm over 4 years ago after full chemical injection to solid brick walls and the render replaced in all ground floor rooms up to four feet high from the ground (solid bitumen covered stone on concrete). Damp remained, serious in parts. All sources were checked for plumbing, roof and rain with remedial work where necessary including external painting with 2 coats of Liquid Plastics' monolastic smooth. I recently removed the render in several areas for inspection and found salts emerging in a white deposit in some parts up to 7 or 8 feet from ground level. I presume the salts got there from a mixture of rising damp and some previous use of the farm kitchen perhaps storing fertiliser and a running leak from an overflow (possible nitrate in the tap water)when I first moved in. The question is, is my only solution to remove all the render and have the walls 'tanked' using a cement mix render containing an additive to combat an agroscopic sucking in of condensation due to the salt in the bricks?

Derek Harrrison

Your problem is slightly complicated by the fact that you have brick walls that seem to have become wet in the past and may still contain moisture combined with the presence of a high proportion of salt due to the past use of the premises. From what you describe, it seems that moisture and salts are trapped within the wall. My preference is for a solution that would release these and allow moisture to evaporate away and for salts to come to the surface and be cleaned off. My advice is therefore to expose the brick surfaces by removing the render, paint finishes, etc. both internally and outside. You do not mention whether the ground level is high and if necessary ground levels might have to be lowered. I assume that all other sources of dampness have been dealt with. You might find it necessary to encourage salts to the surfaces by the use of poultices. There are specialist companies that undertake this work (see the Building Conservation Directory). Once the majority of salts have been removed it should be possible to replaster with traditional plasters, etc. Although a modern render with a salt inhibiting additive could be used my experience is that these have a limited effective life and eventually fail. The amount of salt in the wall will be finite and at some point the salts will cease to come through to the surface. Another possibility is to use a ventilated/drained cavity system internally that would effectively create a false inner wall (dry lining) behind which any moisture and slats would exist without causing damage to the surface. The only drawback with this is that if there are many salts it could block the cavity itself and prevent the system functioning properly. It is important externally to allow the wall to breath. However, if you want a finish other than the brickwork to the elevations I suggest the use of lime washes or lime renders rather than modern paints, which tend to be impermeable. In answer to your basic question of whether you need a specialist surveyor I would answer yes. Whether in fact the specialist is a surveyor or another professional is perhaps not as important as insuring that the individual properly understands and has experience in dealing with this type of problem in historic buildings. The RICS does have a list of specialist surveyors and information on surveyors for your area can be obtained from the administrator of the RICS Building Conservation Forum, Mr Kieron Higgs on 020 7222 7000.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500


SUBJECT: Advice required concerning insulating loft space
FROM: Ken Brown (Devizes)
We have just moved to our Georgian property, and have had 50mm loft insulation removed to properly treat the roof timbers. Replacing the insulation material is the challenge as the beams are irregular in height and space between them. The current recommended 200mm depth of insulation would be way above the height of the beams. Assuming adequate ventilation is maintained, is this a suitable option, or would the beams both "sweat" and suffer from cold bridging? Is there an alternative material that could be used?

Ken Brown

Occasionally I come across properties where insulation laid between the ceiling joists has lead to the joists themselves becoming a cold bridge and for stains to occur on the ceilings below. However, in my experience this is relatively rare. It is conventional to lay insulation between the ceiling joists and it is unlikely to pose a serious problem, although I fully accept that it is far better to lay insulation over the joists. The drawback is if the roof space is to be used for storage (lightweight!) or if you gain access to it regularly, you will need to create specific walkways with boards laid onto the joists. The insulation can then be sandwiched between the joists and boards. As an alternative to conventional modern insulation quilt, you could use recycled paper but this could increase the fire risk within the roof space. Another alternative would be lambs wool insulation, which is becoming increasingly popular. Whenever insulating a roof space you should ensure that electric cables are above the insulation (to reduce the possibility of over-heating) and any pipes or tanks above the insulation should be lagged. As a side issue, if the roof space is to be used for storage or if walkways are to be installed I recommend carefully screwing down boards as this helps reduce the amount of cracking to the ceilings below and reduces the flexing of the surface generally.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500


SUBJECT: Breathing floor solution to damp
FROM: Nick Townley (Cheshire)
I reside in a semi-detached cottage which is approximately 180 to 200 years old. It has recently come to my attention that damp was coming up through the ground floor in the dining room. On investigation, I found the floor construction to be a screed type material (layed in two layers) on top of quarry tiles which have been in turn laid directly on to brick/earth. The ingress of damp is not uniform but merely in several patches varying in size. The remainder of the ground floor has quarry tiles as the finish surface (these were under carpets when we purchased the property) My question is twofold, is the type of floor construction in my dining room 'normal' for this type of property and what can be done to eliminate the ingress of damp? Will this necessitate the complete removal of the original floor down to the earth and a 'new' floor being put down?

Nick Townley

The answer to your question of whether the construction is "normal" is' No', in that it is not original. It sounds as if the floor has built up over time with the brick floor being the earliest followed by the quarry tiles and then the screed material being the most recent surface. It sounds as if there is no damp proof membrane and dampness has probably become trapped under the floor and is appearing in areas where the screed may have failed or cracked in some way. Where there are merely quarry tiles these could be laid on earth or onto brick on earth. Quarry tiles are breathable in that they allow moisture to permeate through and evaporate from the surface. I suspect that these floors are functioning quite adequately. This therefore points to a solution for the dining room floor. I suggest that your carefully take up the screed material, which might have damaged the quarry tiles, etc. below. The floor should then be re-formed with bricks and/or quarry tiles as necessary. In re-forming the floor I would suggest omitting the use of a damp proof membrane. Although ground moisture will then be able to pass through the floor it would normally evaporate without causing any major problem. If a membrane is inserted it would usually trap moisture under the building and the moisture will then find another route out, usually through perimeter walls, the chimney, etc. In these areas a damp problem may appear where none exists at present. With historic buildings I would prefer to work with a method that has been tried and tested over the years, which is to allow the floor to breath. That said, it is important that the solution is specifically devised for your property and advice from someone local, who properly understands how old buildings function, should be sought. In dealing with this work I recommend that whatever method you select in re-forming the floors, you ensure that the external ground level is at least 150mm below the internal floor level.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500


SUBJECT: Synthetic coating requires mechanical method to remove
FROM: Alex Jeffs
Trying to remove wall coating (applied by company I believe were called London Coatings) - have reached the stage of having removed the small chippings, now having difficulties in removing the adhesive used - substrate Victorian red & white brickwork - any ideas!

Alex Jeffs

I know of the system you refer to, which is a cementitious mix including resins, etc. It is as you say an adhesive and as such would not readily come away. There may be small localised areas where it has failed and would chip off but the majority will be well adhered. As far as I am aware the only satisfactory method of removing this material is by mechanical means. Unfortunately it is unlikely that the brickwork below will be salvageable in terms of the surface finishes. As advised elsewhere for any removal of surfaces from elevations, it is sensible to try various methods in isolated areas. You might find that the Building Research Establishment has more information on this particular product and may have suggestions as to how it could be removed. Unfortunately, I am not aware of any chemical removal methods and unless you are advised otherwise I believe the only way of taking off this material is some form of mechanical means.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500


SUBJECT: Should seal my York stone floor?
FROM: Julie Friday (Stockport)
I own a beautiful cottage that may date back to 16th century. The floors down stairs were carpeted when I bought it or had rugs laid over what appeared to be a concrete floor. The floors were very bumpy and lumpy and when replacing some of the carpets I decided to investigate what was causing it. It turned out that in two rooms a screed had been put over York stone flooring and it was the York stone underneath that was uneven. I replaced broken flags and had the floor restored. I have two questions. Firstly what should I use to seal the York flagging and will it cause and condensation problem? Also I note suspect the other rooms downstairs (kitchen, snug, back hall and bathroom) Have York stone flooring under this horrible screed. While I like the stone floors I don't wish to have them throughout the downstairs of my house but I am wondering if having them covered in this compound may cause damp problems and whether I would be better exposing them.

Julie Friday

The answers in short are quite simple. I do not recommend sealing the York flag stones as I believe it could cause problems in the longer term. I do not recommend covering the York stone with any compound that would prevent the breathability of the surface. If you do not wish to have York stone flooring throughout the building you should consider a covering that will hide the stone flags but allow the floor surface to breath. Modern carpets are not appropriate but the increasingly popular use of natural materials such as sisal carpets etc. could work well in this instance.

Period Property UK would like to thank Stephen Boniface Associates for answering this question. Stephen Boniface can be contacted on 01279 421 500