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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: Should I seal my repaired brick worth with Thompson Water Seal?
FROM: Stephen Ledger (Sheffield)
I have an Edwardian property that is in need of re-pointing in many areas. Some of the bricks show frost damage. As well as re-pointing and replacing frost damaged bricks, the builder has recommended applying Thompson Water Seal. There is no internal damp penetration.

Stephen Ledger

The pointing should be the sacrificial element of the elevation rather than the brickwork. The mix used for re-pointing should therefore be relatively soft. It should not be a hard dense cement mortar but rather a softer lime gauged mortar. This will help relieve some of the damage to the brickwork.

Regarding your second point about the application of a sealant, I do not recommend this. This building has survived probably 90 years or so with only some (not all) brickwork beginning to show frost damage etc. By applying a sealer you could increase the rate of deterioration. Whilst the sealant will help prevent some water penetration it also prevents moisture within the brickwork (or from within the building) from escaping. Further, I have often found that these sealants are impossible to apply uniformly and there will inevitably be areas where water will be able to get through due to poorly applied sealant or a gap in the sealant that is invisible to the naked eye. Once the water is behind the sealant it will cause damage and because it is trapped within the brickwork it will cause more rapid and more extensive deterioration. I therefore suggest that you ensure that careful re-pointing and repair is undertaken but no more than this.

Period Property UK would like to thank Stephen Boniface, Tony Redman and other partners at the The Whitworth Co-Partnership with Boniface Associates for responding to this question.



SUBJECT: Surveyors provide conflicting advice concerning damp
FROM: Karen Rhodes (Edinburgh)
I live in a Georgian tenement building. Part of our bedroom (about 1/2 is below street level. Over the last four years I can see deterioration of decor below street level, wrinkling of wallpaper and mould growth. This wall is also very cold and a gable end. The first expert came and said it was a problem of condensation and that we should install a device which would take moist stale air out of the room and replace it with heated warm air from outside. Today I had a surveyor from a very reputable company round. He suggested that the wall should be tanked to prevent moisture from penetrating from outside and then an insulating plasterboard applied on top. This involves moving cornicing and skirtings and redoing decor. We bought the house seven years ago and the sellers insisted the wall had a course of damp proofing and there was a guarantee in place. I know now that this is not true. There was a chimney breast in the middle of the room on the damp wall which has a vent over it. However it is still blocked and the developers have just placed ordinary plasterboard on top. The second surveyor said that even if we could unblock the chimney a bit more the wall should still be tanked. Can you give me advice on which person to believe.

Karen Rhodes

From your description neither of the individuals you have brought in so far appears to have got to the bottom of the problem. It would seem that neither have undertaken a full and properly detailed assessment. With a wall that is partly below street level (ground level) there are several possible causes of dampness. One is of course rising damp, another is penetrating damp (laterally through the wall from the ground beside the wall itself) and the other is condensation damp. I suspect that you may be suffering a combination of all three. You must first assess the primary cause of dampness, which would require further investigation.

The damp proofing that the vendor suggested they might have undertaken would only prevent rising damp but not laterally penetrating damp. The fact that you seem to believe that this was not undertaken suggests that there could be an on-going problem of both rising and penetrating damp to the wall below ground level. As the base of the wall is below ground and there is automatically going to be a problem of lateral penetration of water I see little point in injecting the wall for rising damp itself.

If rising and/or penetrating damp are identified I would suggest a form of internal damp treatment to the surfaces of the walls rather than horizontal chemical injection. My preferred course of action would be a ventilated or drained cavity system rather than a waterproof render. The only way to establish whether you have got a problem of rising and/or penetrating damp is to have the walls properly tested by a company that is prepared to undertake sampling from the wall brickwork and test this for its moisture content and the presence of salts etc.

The other problem is that a basement in a Georgian building was never intended to be perfectly dry and when converted to form a flat etc there would normally need to be some form of work to reduce the risk of moisture causing problems. My view is that retrospective damp proofing of any form is never 100% successful in the long term but some systems tend to stand a better chance of a longer life and in my opinion the drain/ventilated cavity systems provides a better form of longer lasting treatment. This view is not necessarily shared by all surveyors and if you decide for economic or other reasons to opt for a system that involved a waterproof render (tanking etc.) this should provide satisfactory service for a number of years (10 - 15) before requiring further attention.

Whether there is lateral or rising damp to the wall below ground level there could still be a problem of condensation. You should ensure that the room is well heated and if there is a system of radiators it would be sensible to have one of the radiators against the external wall/s in question as this will help increase their temperature generally. You could incorporate insulation behind any re-plastering that is undertaken to the walls.

With regard to condensation the insulating of walls and the improvement of heating will help relieve the problem, but you will also need to ensure good ventilation. In my view it would be sensible to open up the chimney breast and use this as a natural ventilator for the room by installing an appropriate air brick straight into the flue void (having of course ensured that the flue void is swept clean and clear). You might find that you will also have to install some form of positive extraction system (an extractor fan) to force the air changes and reduce the risk of stale moist air staying in the room.

In the answer above I hope I have covered all possibilities. Before you undertake any actual work I suggest that the true cause of the dampness be established. One simple method that is sometimes used is to place a glass against the wall with the mouth of the glass closed up on to the wall face. You will need to secure this perhaps with a clear mastic sealant (such as is used for glazing etc.). If, over time, the moisture forms on the outside of the glass it would indicate that you have a condensation problem. If the moisture forms on the inside of the glass it indicates a penetrating or rising damp problem. If you get both then it indicates a combination of all problems. This is a rather crude but reasonably effective method of establishing what sort of dampness you might have. Beyond this, as mentioned above, you ought to have proper testing undertaken. An adequate solution to your problem can only be established once the true cause of the problem has been discovered.

Period Property UK would like to thank Stephen Boniface, Tony Redman and other partners at the The Whitworth Co-Partnership with Boniface Associates for responding to this question.



SUBJECT: Advice required for chimney stripping
FROM: Steve Collins (Essex)
I would like to strip an internal Chimney Breast back to the brick and was wondering what to use. There are many layers of paint ranging from modern gloss through to distemper and whitewash. I saw a poultice being used very effectively on Grand Design recently, is this the way to go and where can I obtain some?

Steve Collins

Some form of chemical removal or poultice is perhaps the most appropriate. With regard to the modern paints a modern paint stripper might do the job but rather than take a risk in this matter I suggest that you contact Strippers (their details can be found on this site or through the Building Conservation Directory site) and ask for them to send a representative round to advise fully. As they are based in Suffolk they are not too far distant from you. It would be sensible to try the suggested method on a localised area that is not too visible before progressing to do the rest of the work.

Period Property UK would like to thank Stephen Boniface, Tony Redman and other partners at the The Whitworth Co-Partnership with Boniface Associates for responding to this question.


SUBJECT: Increased ventilation & limewash finish for police station bathroom
FROM: Rev Andrew Warburton (Borders of Scotland)
We live in an old Police Station in the wilds of the Scottish Borders. The original cell is still in place along with a door made on site in the 1860's

The cell was turned into a bathroom in the late 1960s, and in the 70s the surface (plaster and distemper) was painted with an oil based paint. This oil based surface is now causing real problems and there is constant pealing.

We want to take this surface off, and return the surface to its original state. Our questions:

(1) How do we strip away the paint?

(2) Given its use as a bathroom, what kind of whitewash should we go for in the redecoration?

I should add that the cell has an arched ceiling 1 metre thick and metre thick walls. Both ceiling and wall were built of whinstone gathered from around the site. The floor is limestone, the flags being at least 5 inches thick.

Andrew Warburton

I would refer you to my answer above with regard to the stripping of the surface. There are a number of chemical removals systems that should be appropriate for this type of work to remove the oil based surface in particular. Strippers operate an approved contractor system throughout the country.

With regard to what sort of finish you should use bearing in mind the use as a bathroom, I would suggest that a traditional lime wash (using pigments to colour it if necessary) should be acceptable. As it is a breathable paint the moisture generated in a bathroom should simply be absorbed and dry out naturally. Of course, it would be sensible to ensure that with a bathroom in this particular situation there is good extraction facility to rapidly remove moist air and that you use the extractor fan for this very specific purpose of taking away moist air after the bathroom has been used. This should help reduce the amount of moisture that the walls and floors have to deal with otherwise.

Period Property UK would like to thank Stephen Boniface, Tony Redman and other partners at the The Whitworth Co-Partnership with Boniface Associates for responding to this question.



SUBJECT: Water seeps through our 3ft thick walls.
FROM: Sian Thomas (Highlands and Islands)
We have an old stone house which we have been told has some porous stone. Water is seeping through the 3ft thick walls and running down to the concrete floors and being absorbed by the plasterboard. What would be the best solution to remedy this? It has been suggested we spray the walls with a silocone water repellent, or that we render all the walls - as it's a listed building this is really not an option.

Sian Thomas

Most stone is porous to some extent. Some stone is far more porous than others. You do not state precisely what type of stone the house is built from. Neither do you suggest where the water is seeping from. If this is simply a matter of the walls having absorbed a lot of moisture over time I do not believe that any form of sealing the wall would result in a satisfactory solution. Rather, I would suggest that the use of water repellent or any form of tanking or modern rendering etc would simply exacerbate the problem and cause more damage in the longer term. Sealing the walls will simply result in the wall structure becoming a reservoir of moisture. I would prefer to go down the route of using traditional lime renders and plasters on surfaces to provide some protection. You do not say if the exterior is rendered or covered in any way. With a stone house in an exposed location it is sometimes appropriate to apply a lime based render as a protective coat or even lime wash on its own.

Of course, if you find that gutters have been leaking or there are other obvious sources of water ingress this should be dealt with first. In any event, I believe that part of the problem you face is the fact that plasterboard has been used in the past to provide an internal finish. This will naturally absorb moisture and deteriorate. A traditional lime plaster direct on to the stone or even on to a form of traditional dry lining (pre-treated timber battens and laths) would be far more appropriate and would cope better with moisture in that it forms a breathable surface.

Period Property UK would like to thank Stephen Boniface, Tony Redman and other partners at the The Whitworth Co-Partnership with Boniface Associates for responding to this question.


SUBJECT: Advice required for work on non-listed property e.g building regulations.
FROM: David Penrose (Suffolk)
I have so far lived in and restored three listed buildings, and am in the process of buying my fourth home that needs a fair bit of restoration. However, this one - although it's an 18th century cottage - is not listed. I am not familiar with the rules about what type of work does or does not require planning/building regs consents in a non-listed building. Can you please give me some guidelines?

David Penrose

With a non listed building and assuming that the building is not in a conservation area, area of outstanding natural beauty, national park, etc, etc, then the same rules apply to your property as any modern building. The way I often describe the difference between planning and building control is that planning deals with the aesthetics of a building whereas building regulations deal with the technical aspects. This is a rather broad definition but is often a helpful way of viewing the two different 'consent' regimes.

Planning permission will be required for any extension of the building that involves increasing the volume of the property. Depending on the specific nature of the property a certain volume of extension post 1947 is permitted and is classed 'permitted development'. However, if the property has already been extended at any point since 1947 the volume of that extension would be part of the permitted development and as soon as the total extension volume (past and present) step over the threshold beyond what is permitted you will need to get consent. Most local Authorities have free booklets that provide more detailed guidance on planning permission under normal circumstances. You should also bear in mind that some local policies might have to be considered whenever a building in a given area is extended. These could govern certain aesthetic and even size considerations.

Turning to builder regulation approval, these regulations apply to structural works to a building. This can mean extension or alteration, but in more recent times has come to include such things as replacement of windows. For example, changing a roof covering from a traditional slate to a heavier concrete tile would normally require building regulation approval because of the change of structural loading. The removing of chimneybreasts, the creation of through rooms by removing internal walls, all require building regulation approval. The connection of a new WC into the drainage (if it is a new drainage connection) will require approval. From this you will see that structural and technical alterations will often require building regulation approval.

There can be situations where you will not require planning permission but will require building regulation approval. For example, a small extension that is within permitted development might not require planning permission but will nevertheless require building regulation approval. On the other hand there can be some small forms of extension such as porches and conservatories that would not necessarily require building regulation approval but might nevertheless require planning permission. A lot will depend upon the history of the building and what has already been done in the past. I hope this provides you with more of a guide.

Period Property UK would like to thank Stephen Boniface, Tony Redman and other partners at the The Whitworth Co-Partnership with Boniface Associates for responding to this question.



SUBJECT: 1 part cement to 4 sand - is this right?
FROM: Ian Perry (Taunton, Somerset)
I have to make a quick decision. We are having 2 walls completely replastered in our stone farmhouse (1863). The builder wants to use a cement render and skim with paster. He says the traditional mix is 1 part cement to 4 sand. I'm concerned this will not allow the walls to breath and as the walls have some movement will crack badly. We do not have much time as we have to move into the house in 4 weeks. If we have to use a cement render as a base for the plaster should it not be of a weak mix and possibly with lime. Can anybody suggest a suitable or improved mix and finish.

Ian Perry

Although various forms of mortar that we now call cement mortar have been known for the past 2000 years, modern cement was not commonly used in the 1860s. I therefore doubt if the traditional mix is actually cement and sand. However, it might be a form of lime mortar that is hydraulic and therefore has similar characteristics to cement . Hydraulic lime can naturally occur through clay or other impurities within lime.

If there are cracks and signs of movement I would agree with you that there should be a relatively weak mix. If you are to use a cement-based mortar I would nevertheless suggest that you have a mix of, say, 1 cement : 1 lime : 6 sand. Such a mix can still be finished with a lime plaster.

Period Property UK would like to thank Stephen Boniface, Tony Redman and other partners at the The Whitworth Co-Partnership with Boniface Associates for responding to this question.



SUBJECT: Does my roof really need underfelt?
FROM: Beverley Dodd (Cambridgeshire)
I have a flint cottage built c 1790 with a clay pantiled roof that is unlined (the roof was replaced in 1930s). When I purchased the cottage 8 years ago my survey reported that the roof should be lined. I asked a roofer friend to give me an unbiased opinion/estimate and was told to leave the roof alone and the reason the roof was in such good shape for its age was due to the amount of ventilation. Gaps can be seen between the tiles. The roof is always dry and even in the worst storm always survives intact and dry. I'm now selling my house and the buyers surveyor has once again pointed out the need to get the roof lined - what should I do????

Beverley Dodd

Ask them to get a different surveyor to give a proper professional opinion!

The advice you were given by your roof friend was quite correct. There is of course a risk that water will penetrate a Pantile covered roof that has no lining. However, with the amount of ventilation that is in the roof space this will probably evaporate or dry out very quickly. Similar comment applies to snow. Of course, the roof space would not be useable for storage etc unless the stored material was carefully wrapped in plastic bags; but as the roof space is not intended to be used for such this should not pose any problem.

The view I often take when looking at this type of roof is that if there is no evidence of a problem and the roof covering is still basically sound I would advise my client that if and when it eventually deteriorates to the point of requiring re-covering then a breathable modern lining could be used under the re-covered roof. It is never advisable to install a lining under the rafters, as any water penetrating through will then simply run down the lining into the eaves (a lining properly applied when re-covering takes place will lap over the eaves and into the gutter). I believe it to be a total waste of time, effort and money to strip a perfectly sound roof simply to put a lining in place when there is no evidence of any particular problem.

I suggest you get your purchaser to log on to this site and read the various postings in the discussion forum - or even this reply.

Period Property UK would like to thank Stephen Boniface, Tony Redman and other partners at the The Whitworth Co-Partnership with Boniface Associates for responding to this question.