for People with a Passion for Period Property
Ask an Agony Uncle!
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 (

Ask our Agony Uncles ...

You can write to our panel of experts free of charge on any subject, providing it's got something to do with Period Properties.

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...

o How to spot woodworm. Nadine Cordell (Hertfordshire)
o Pebble-dash victim strikes back. Paul Robinson (Greater London)
o How do I protect my flagstone floors from damp. Geoffrey Watson (Durham)
o Conflicting advice from plasterers concerning lime. Donald Black (Colchester)
o Surveyor urges caution over purchase of sandstone house. Sue Lenton (Cheshire)
o Ghostly damp patches re-appear. Carolyn Moore (Horsham)
o Concrete sills & PVCu windows .can you be serious? Steve Dixon (Exeter)

SUBJECT: How to spot woodworm.
FROM: Nadine Cordell (Hertfordshire)
We have recently exposed the floorboards in our Victorian house. There is evidence that woodworm have been in some of the floorboards, although I am unsure whether it is still active. Our house is centrally heated in all rooms.

I wondered whether it would be possible for me to tell whether the woodworm is active or not?

Nadine Cordell

If the sub-floor void seems generally dry and has good air flow through it the chances are that the woodworm is old and inactive. The presence of central heating reduces the risks further, as it dries the timbers and creates an environment that would not normally sustain active woodworm.

However, Springtime is the time of year that the woodworm start breeding and are at their most active and now is a good time to discover if the woodworm is active. Find an easily accessible area where woodworm holes exist, but where boards can be lifted without too much disturbance. Clean away dust, frass etc from the areas and then wait. In May/June expose the area and see if there is any fresh frass. Frass is the deposit of the woodworm and looks like very fine sawdust. See if there are any obviously new holes. You could try applying paint to a hidden surface or even sticking some paper over an area (they will normally chew through the outer surface of the wood and the paper thus causing a hole to appear) - anything that will help to distinguish new holes from old. If there is activity and it is causing weakening of the timbers it would be sensible to have some localised treatment undertaken, together with appropriate repairs to timbers.

As woodworm holes are created by being chewed from the inside out (the opposite direction to a nail hole) the edges of the hole are very crisp (unlike a nail hole) and inside the hole the wood will be clean. However, as the holes are small you need to look closely. If it is fresh there may still be frass in the hole..

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


SUBJECT: Pebble-dash victim strikes back.
FROM: Paul Robinson (Greater London)
A year ago we bought a late Victorian end-of-terrace house with damaged pebble-dashed render (the render was a later addition; it's probably 20-50 years old). On the premise that damaged render is the worst of all worlds (letting moisture in but not out - not to mention looking ugly) I decided to see how easily it could be removed, what it's made of and what is underneath. I've exposed enough (through careful mallet /chisel work and some wire brushing) to see the face is yellow brick (appearing to be in good condition) with some decorative red brick (esp. around the portico and bay - this red brick is crumbling to nothing).

I now want to call in the professionals. My assumptions are: best case scenario: the rest of the render can be removed, brickwork can be replaced, repaired, re-pointed and cleaned; worst case scenario: remaining render can be roughly removed, brickwork can be roughly repaired, and the whole thing can be re-rendered in something breathable and more eye-pleasing than damaged pebble-dash. Can you tell me if I'm completely na´ve, and can you recommend any "professionals" who can take over the job?

Paul Robinson

Gentle tapping of the surfaces (preferably with a timber mallet) will reveal hollow areas, therefore areas where the render has lost its key. The greater the area that is hollow the more likely it will be to remove it without too much damage. Nonetheless, there will inevitably be areas where it will not come away easily. You are quite right in suggesting that you cannot really leave it as it is, but whatever you do is now fraught with potential problems. Some would argue to take off loose and hollow render, but leave the sound areas and simply go over the whole building again with new render. I am not in favour of this, but it is probably the cheapest and quickest option.

I think your summary of possibilities is fair and reasonable. Provided you have the money to undertake the work whichever scenario occurs, I see no problem with what you propose. Of course, the contractor must take care not to cause unnecessary damage.

The removal of the render is not highly skilled, but care must be taken - particularly where there are soft red bricks. It is the repair and future finishing that will need high quality skills. Until the render is removed you will not know whether you will need a good bricklayer/pointer or simply someone who can apply a new appropriate render.

As for 'professionals' you do not say where in London you live and it is difficult to give names because some professionals or contractors will not travel across London. You could tackle this work by employing a good contractor without the need for a surveyor or architect. However, a professional consultant could give independent advice and administer the contract, deal with problems that arise, etc and generally act as the go-between (buffer) between you and the contractor.

The work will require scaffolding and you should therefore use the opportunity to get other high-level work undertaken and the joinery will require redecoration after the work is complete.

If any of the walls in question are party walls you may find the Party Wall Act applies.

Initially, I suggest you get an architect or surveyor to give you further on-site advice on all the relevant issues and other works that may need to be considered, even if only ancillary to the main work. The local Conservation Officer may be able to guide you to a suitable person.

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 protect my flagstone floors from damp.
FROM: Geoffrey Watson (Durham)
We have purchased an early Victorian terraced house. It is a beautifully proportioned artisan house. It is damp and hasn't been occupied for over 1 year. The flagstone floors in the hall and kitchen are laid on small stones and earth. The walls are being injected to control dampness. Shall I attempt to clean the flagstones and leave them open to the newly heated, lived-in environment? In the kitchen, I hope to use units that are on legs rather than kicker boards to the ground. Some have a thin layer of black gloss and those in the kitchen have some latex adhesive that retained some vinyl tiles! I am worried that, if I attempt to lift the flag's, they will split and - in any case - what would I relay them upon?

Geoffrey Watson

If it is not too late I suggest you hold off the injection of the walls.

Whilst I am not totally anti-treatment I strongly believe that such treatment should be the LAST RESORT. Once injected it cannot be extracted!

Tackle other problems first that might be causing damp, get some heating into the property and get air circulating. If the walls are injected you could find that dampness to the floor becomes worse - especially at perimeters. I strongly urge you to get further independent advice from an architect or surveyor who properly understands older structures and how they work.

Turning to the flagstones, I would prefer to leave them as originally laid. However, it sounds as if some careful cleaning, or at least removal of old material from surfaces, will be needed. This is probably best done in-situ rather than lifting them. I am not sure why you are so certain they will split if lifted? Provided care is taken I see no reason why too many would be damaged. That said, I do not know if lifting will be necessary.

In any event, I would prefer to see the flagstones laid back onto a hardcore and sand blinding surface on a bed of lime mortar without a damp-proof membrane. However, precisely how you tackle the problem will depend upon a number of other factors. Are ground levels high around the building, is it liable to flooding, what other works have been undertaken, what floor coverings (if any) do you intend to lay???

I suggest you seek advice from a suitably experienced architect or surveyor that understand these old buildings and knows the area. The local Conservation Officer may be able to guide you to a suitable person.

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


SUBJECT: Conflicting advice from plasterers concerning lime.
FROM: Donald Black (Colchester)
We have a recently purchased a 300+ yr. old cottage and are currently setting about redecorating. There are areas of the internal lime plaster work that need repair, however we have received conflicting advise from plasterers regarding materials for the repair, with one saying that it was not possible to use lime and the other saying that it was fine. Obviously we are now confused as to who is correct. The areas concerned are general no more than 1ft sq., and we are keen to use traditional materials.

Donald Black

If there is lime plaster existing and you properly prepare the area in question there is no reason why a lime plaster cannot be used for the repair.

Essex County Council Historic Buildings Department run courses at Cressing Temple, including lime plaster repairs. They can also advise you on suitable contractors and suppliers of materials. In the first instance ask to speak with Pauline Hudspith.

I suggest you ignore the plasterer that says it can't be done and follow the lead of the plasterer who seems to know what he is talking about. However, be warned that the extent of work required is rarely as little as at first seems to be the case.

For lime plaster you would normally use lime putty supplied in a tub. This is simply mixed with sand to produce the plaster. The lime putty can be stored in the tub (provided the lime has a layer of water on the top surface) in your garage and brought out whenever it is needed for repairs. Depending on what it is mixed with it can form a mortar, render, pointing mix, plaster, limewash, etc. It would therefore be a sensible investment to get some lime putty.

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


SUBJECT: Surveyor urges caution over purchase of sandstone house.
FROM: Sue Lenton (Cheshire)
I'm purchasing a listed property partly constructed of Sandstone and the surveyor is very concerned about the penetrating damp. He doesn't feel there's an easy way to resolve the issue and is urging us to be cautious. Is this a common problem with Sandstone and are there any particular things I need to know before calling the damp companies in?

Sue Lenton

Is there an actual problem or is it something he has said could happen?

If the former, it may not be easy to resolve, but calling in those who merely wish to chemically treat everything is not the best way forward. In any event, I doubt if chemical treatment would work well in a sandstone wall.

Sandstone can be problematic, but the same principal applies in that the building should remain breathable. Look at the possible causes of damp and deal with these first (look at previous answers and the discussion forum to give ideas of what to look for).

Sometimes it is necessary to provide some protection to a wall without affecting its breathability. In such instances a limewash or render might be appropriate; sometimes a cladding such as weatherboard or tile hanging would provide protection.

In some instances it is not possible to do anything to the exterior and one has to accept a degree of water penetration. In such circumstances it would be sensible to consider a form of dry-lining. This then allows the wall to breathe but between its inner surface and the finished dry surface is a gap through which moisture can permeate and drain/evaporate away. Traditionally this was achieved by battens with lath and plaster, but now there are the modern membranes that create a 'drained cavity'. A reason many older buildings have panelling, etc is to create a form of dry-lining.

If the building is listed any alteration to the elevations etc would require consent. You should speak to the Conservation Officer. However, it sounds as if you should find an architect or surveyor who properly understands this type of building in your area. The Conservation Officer may be able to give guidance to a suitable professional consultant.

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


SUBJECT: Ghostly damp patches re-appear.
FROM: Carolyn Moore (Horsham)
I have a 100 year old house (standard 2 up, 2 down design). About 2 years ago I discovered damp patches on the walls of 3 rooms (all rooms share the same outside wall). I had it checked and was told it was penetrating damp (a dpc has been installed). The brickwork had previously been painted and the cavity walls filled. I called out the cavity wall insulation company, who found items in the cavity which were bridging the gap - they removed these and refilled the gaps. I also had some areas repointed, and then the outside painted with an oil-based paint (Dulux Weathershield I think). However - the problem has come back! I have had several damp "specialists" round but they can't say where the water is coming from - it seems unlikely that it is still penetrating through the walls. Any ideas - or do you know who I could get round who can find the cause once and for all?

Carolyn Moore

My immediate thought is that it could be condensation. However, make doubly sure that there are no areas where water could be penetrating (redundant flues, down through the head of the wall, etc.). I am not sure that the various finishes that have been applied are the best thing for the building, as I prefer to leave a building to breathe, but at this stage I would suggest leaving those finishes alone. You should seek independent advice from someone who understands old buildings.


Those reading these answers may think I am anti- the treatment industry. This is not the case, as there are situations where treatment is needed. However, I believe treatment to be a last resort, partly because it is something that once done cannot be undone if it is proven incorrect. Further, whilst many operatives are trained, one does have to question whether they are really surveyors or salesmen? Another problem is that they have a rather blinkered approach to buildings. An experienced surveyor or architect will take a more holistic view.

In your instance it seems that those advising have taken the blinkered view approach. You now need someone who can examine the whole building, find and advise on any defects that could be a source of the problem, as well as advising generally on why you still experience damp patches to this wall.

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


SUBJECT: Concrete sills & PVCu windows .can you be serious?
FROM: Steve Dixon (Exeter)
We are replacing the windows and sills in our 150-yr. old farmhouse. The frames are currently brown painted rotten softwood and the sills are mainly rotten wood but some are concrete (in a poor state of repair). we want to put in PVCu wood effect windows (not listed or in conservation area) and new concrete sills. We have been told get the sills done first by a builder then a window company can do the windows. What is the best way to make the cills cast in situ or have them made to measure else where and then fitted? Some of the sills are quite large (under 2 sash windows).

Steve Dixon

I think anyone reading this site will know my feelings about plastic windows and you should look at the comments in the discussion forum before making your final decision on the window replacement.

However, your main point is regarding the sills. A sill cast in-situ should fit without a problem, but quite often the finish is not as good - it really depends upon how good the shuttering is. I think a better appearance can be obtained with a sill cast separately. However, the company undertaking the work must ensure that they take accurate measurements. Of course, the sill could be cast on site, but not in-situ. The larger sills may have to be cast in separate sections whether in-situ or not.

The sills themselves should not be bearing any loads, apart from the window frames. If they do, one has to questions other matters regarding the window openings. Ensure that the depth and profile of the sills are correct - adequate overhang, drip groove, etc. Also check that the depth does not have a significant affect on the window frame - get the window installers to liaise with those making the sills.

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