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 Sandblasting Chris Woollett (Sheerness, Kent) & Suzanne Evans (Worcestershire)
o Roof Repairs Chris Wilber (Derby, Derbyshire)
o Future Problems Mr Smith (Truro, Cornwall)
o Paint Stripping plaster coving Jackie Needham (Somerset) & Vince Vitulli (Essex)
o Sealing an unglazed tiled floor Eileen Chandler (Malpas, Cheshire)
o Underpinning Ritu Kapoor (Kingston Upon Thames, Surrey)
o Replacing high windows Paul Marsh (Bury, Lancs)
o Vandalous pebbledash Maureen Wilkinson (Norfolk)
o Improving a loose flagstone surface Chris Wallis (Beaminster, Dorset)
o Glue removal David Flockhart (Kent)
o Removing Pebbledash Rendering David Weisfeld (Hertfordshire)

SUBJECT: Sandblasting
FROM: Chris Woollett (Sheerness, Kent) & similar question from Suzanne Evans (Worcestershire)
We are about to purchase a period property with many exposed oak beams dating back nearly 600 years. Unfortunately many of them have been treated with a modern varnish/paint which I wish to remove. The question is how? Shotblasting has been advised by friends however this sounds very severe. Should I take this route would we be advised to bring in professionals and if so could you perhaps recommend someone in the vacinity!

Chris Woollett

Chris and Suzanne because one of the fundamental aims of is to promote the use of traditional materials and techniques for the repair, maintenance and renovation of period properties we shy away from advocating sand blasting. Yet, we can understand why people sometimes see this as a preferable course of action. In one clean sweep, normally lasting a day most small cottages can have both paint and varnish removed from their exposed timbers leaving an almost 'new wood' look. But there are problems. Firstly, sand blasting can lead to timbers which have suffered a heavy infestation of wood boring insects in the past being decimated. Secondly, the natural patina of the timbers will be lost and thirdly, particularly on bressumer beams, ancient scribings such as witch marks can be removed with out trace.

To remove the varnish/paint your first port of call should be Strippers of Sudbury on 01787 371 524. They will be able to recommend which poultice to use and supply a trial pack to help you get a feel for the time involved and the final effect if you use this method to strip the beams or decorative plasterwork. It's a time consuming process, but the use of a poultice will remove varnish or paint without damaging the wood or plaster. Finally, The Society for the Protection of Ancient Buildings (SPAB) have published a useful factsheet on the subject. You can obtain it by ringing 020 7 377 1644 and asking for publications. Note, a small fee is payable to SPAB.


SUBJECT: Roof Repairs
FROM: Chris Wilber (Derby, Derbyshire)
We have recently moved in to the old village school, which was built 1830 and converted to residential use in 1976. We have had mainly cosmetic work done but we have one potentially large job. The roof is back pointed and while it is predominantly in good condition, there are some quite large sections where the pointing is missing or damaged. Also, the ridge tiles show rather more sky through them than I would like! What is your opinion on the under tile sealants/insulators that are available as an alternative to a re-roofing - the existing Staffordshire blue tiles seem to be in good condition.

Chris Wilber

Chris, from your description its sounds as if your Staffordshire tile roof is in fairly good order and a quality roofer should will be able to undertake the various repairs you have listed. You also mention the use of back pointing to fill in gaps between the tiles. Assuming the mortar used is a lime and horsehair mix why don't you simply re-point the damaged areas using traditional materials which allow the roof to breath and will prevent any water or snow being blown into the roof void.

On the subject of spraying the underside of your tiled roof with a foam material a word of caution. Firstly the foam makes it difficult to remove or re-use tiles. Secondly, the use of foam increases the likelihood of condensation in the rafters and battens which in turn could lead to wood rot. For a more detailed explanation of the problems associated with the underspraying of roof tiles with foam take at look at the article on Jeff Howell's website



SUBJECT: Future Problems
FROM: Mr Smith (Truro, Cornwall)
We are considering whether to buy a cottage in North Devon constructed of cob under an asbestos slate roof. The house was renovated in 1988 which included application of a 5:1:1 sand cement lime render and emulsion paint external finish. Internal walls were finished with a similar cement render topped with gypsum plaster. An injection damp proof course was added to the stone underpin layer. Is such treatment likely to cause problems in the future (no cracking is evident at present) and if so would remedial treatment be costly?

Mr Smith

Mr Smith , over time temperature and moisture cycles tend to result in micro cracking of all renders. Water is not easily absorbed into cement-based renders, therefore rain will run down the render and collect or seep into cracks. Once moisture enters cracks in a cement render it is unable to escape easily resulting over time in damp conditions in sections of the wall. If the cob is allowed to become very wet it will most likely suffer progressive deformation and in some rare cases total collapse. If the walls were rendered in lime moisture would be absorbed into the render and then released back into the atmosphere relatively freely.

Short-term you should seek the advice from an experienced surveyor who has extensive experience in cob buildings to get an insight to any potential problems so they can be monitored. Medium to Long-term you should aim to replace the cement render with an authentic lime render which will allow the cob to breathe hence avoiding any of the problems associated with damp in cob buildings. Another factor which you may wish to explore is whether a damp proof course (dpc) has been installed in the floor of the property. If the original floor has been removed and replaced with a modern floor with dpc this may lead to any moisture in the ground migrating to the exterior walls rather than evaporating through the joints of its former stone floor. Obviously, I'm unable to comment on the effectiveness of your injection dpc, but if it has not been undertaken correctly, which is particularly difficult to achieve in a non-homogenous stone plinth, then moisture may become focused in one area where the dpc is ineffective. For further information contact the Peter Child at the Devon Earth Building Association on 01392 382 261.



SUBJECT: Paint-stripping plaster coving
FROM: Jackie Needham (Somerset) and similar question from Vince Vitulli (Essex)
I have recently purchased an apartment in a Georgian Manor House which needs to be taken back to its former glory. I am trying to find out what product I can purchase to strip back the original plaster coving which has been overpainted so many times that it has lost its definition.

Jackie Needham

Jackie and Vince, contact Strippers of Sudbury on 01787 371 524 or Palace Chemicals Ltd (Speke, Liverpool) on 0151 4866101. Both companies supply products which will help you remove both modern day paints, limewash and distempers before you re-decorate the plaster coving and walls with a 'breathable paint'. Please also bear in mind it is important to test an area first, to take care to protect the substrate during stripping and keep a keen eye out for any original decorative paintings or original wallpaper which may exist below the layers of paint being removed.

Finally, Vince on the subject of removing cement render from brickwork it is a case of find a inconspicuous area and trying to get behind the render to see if it can be levered off slowly in small sections. If the cement is firmly fixed to the brickwork due to the rough nature of the brick and any attempt to remove the hard render damages the faces of the brickwork your ultimate aim would be to ensure the render does not bridge the slate damp proof course.


SUBJECT: Sealing an unglazed tiled floor
FROM: Eileen Chandler (Malpas, Cheshire)
Since moving in a year ago, we have had a damproof membrane inserted in the outside walls and a chemical injected into the interior walls. Two of the rooms have no damproofing under the floors which are of unglazed tiles. If we seal these, without taking them up and laying a damproof membrane, what problems might we be provoking?

Eileen Chandler

You have already changed the way moisture moves through the property and by inserting damp proof courses and membranes in the walls you have prevented moisture rising and evaporating naturally through the wall surface. I am doubtful if there was really a true rising damp problem and I would not normally recommend retrospective insertion of a damp proof course. Many of the damp problems I inspect in historic buildings are best resolved by straightforward building works rather than 'specialist' works. I cannot comment on the work undertaken in this instance. Nevertheless, the result of the work undertaken is that around the perimeters of the two floors in question there is likely to be more ground moisture than previously. If you simply seal these floors the moisture will become trapped and the pressure of moisture will eventually cause damage to the tiles, which may even lift under the pressure of ground moisture. I do not believe that sealing them would serve any useful purpose and is likely to lead to additional problems.

The alternative of taking up and laying a damp proof membrane would provide a solution, but it then involves completely changing how the building functions and copes with dampness. If you have already undertaken extensive damp proofing work elsewhere, this may be the only sensible option left open for you. However, if it is necessary or you are determined to damp proof this floor you must ensure that there is continuity in the damp proofing throughout the building. This is a major failing when damp proofing an old building that was not built with damp proof membranes/courses originally. If there is any break or gap in the new damp proofing moisture will find its way through (even if it is only a hairline crack). Where damp proof courses are inserted into buildings at the time of construction it is easy to ensure that the damp proofing is continuous and that there are no breaks in it. When inserting damp proof coursing or membranes into a building retrospectively, one cannot be so certain of continuity. This is one reason why retrospective insertion of damp proofing is now frowned upon by many of us dealing with historic buildings, as we recognise the difficulty of ensuring that it works properly. In fact, in my experience the retrospective insertion of damp proof courses, etc. usually leads in the longer term to additional problems, rather than resolving them.

Returning to the question of your particular floor, if the floor shows no sign of a problem at present I would be inclined to leave it alone.

Period Property UK would like to thank Stephen Boniface from Boniface Associates for answering this question.


SUBJECT: Underpinning
FROM: Ritu Kapoor (Kingston Upon Thames, Surrey)
Dear Malcolm, we are considering buying an Edwardian property about 100 years old. This property was underpinned 3 years ago and is guaranteed for 13 years. Can you please explain what it means and what are the things that we should look out for. The house is also in need of total refurbishment. Is it wise to knock down two or three internal walls to make the house more open and spacious?

Ritu Kapoor

At its basic form underpinning means that the original foundations or footings were found to be inadequate movement occurred to the building and to prevent further movement and problems arising the foundations have been strengthened. This usually involves excavating a hole under the building (usually in sections to avoid total collapse of the building!) and filling the hole with concrete. In some instances piles might be driven under the building and there are of course other methods of underpinning. However, underpinning is basically where the existing foundations have been strengthened in some way.

When buying a building that has been underpinned you need to ask for as much information as possible. You should establish precisely what damage originally arose, what investigation, monitoring, etc. took place and if possible you should obtain copies of the original engineer's report. The matter would normally have been overseen by an engineer or building surveyor. Often, such work is carried out as the subject of an insurance claim and therefore records will be held by an insurance company.

There are differing views on the need for underpinning and the extent of underpinning required. Present thinking is that underpinning should be regarded as the last resort and in some cases partial underpinning is frowned upon as it can lead to differential movement (between the parts underpinned and those that are not). However, the most important issue with a property already underpinned is to establish whether the underpinning has been successful and whether there is any evidence of ongoing movement. It is therefore imperative that the building be inspected by an engineer or building surveyor experienced in the type of property and such problems. Re-inspection by the original engineer might also be a possibility.

Period Property UK would like to thank Stephen Boniface from Boniface Associates for answering this question.


SUBJECT: Replacing high windows
FROM: Paul Marsh (Bury, Lancs)
We have recently moved into an 18th century block of Weavers cottages spread over six levels. The front windows need replacing but are up to 60 feet above a main road, with very little pavement. Where can I find a reputable window installer who is prepared to take on the task?

Paul Marsh

Paul, visit which contains the names of the UK's leading companies concerned with period property conservation and their renovation. The site is predominantly used as a trade site for council conservation officers, architects and surveyors working in the field of conservation. Look under the Directory section and click on products and services, then click on either builders or window manufacturers. The companies appearing in the directory are leaders in their field and if one of them was unable to undertake the work in question I'm sure they would be able to put you in contact with another reputable window manufacturer and installer who may meet your requirements.


SUBJECT: Vandalous pebbledash
FROM: Maureen Wilkinson (Norfolk)
Thank you so much for your reply to my query about damp and how to diagnose its cause. Your answer leads me to suspect that the cause of the damp may be the pebbledash that some vandal applied over the Edwardian bricks. I don't suppose you know of any way of getting rid of it?

Maureen Wilkinson

Maureen, if you look at the bottom left hand margin on the home page of you will find a search function. Simply type in the word 'pebbledash' and all content on the site relating to this subject will appear. You will find the answer to a previous 'Agony Uncle' question listed concerning the removal of pebbledash/render from the exterior walls.


SUBJECT: Improving a loose flagstone surface
FROM: Chris Wallis (Beaminster, Dorset)
We are restoring a 16th century farmhouse. The living room is floored with large blue lias flagstones. While most are not bad, some are delaminating and flaking badly. We aren't too worried about the evenness of the floor, but the loose surface is a nuisance. Do you have any ideas for improving it? Sealing? Grinding?

Chris Wallis

Chris, you mention that the floor is uneven and the original surfaces of the flagstones are exposed. This suggests you still have the original floor intact, with the stones laid directly onto earth floor below. Because of the natural state of the floor any move to seal the flagstones and the surrounding joints would be unwise because it would lead to moisture, which at this point is evaporating naturally into property, being trapped. Once trapped there is a tendency for it to migrate sideways to the exterior walls where it will adversely affect the moisture content at the base of previously dry walls, partitions and chimney breasts.

In my opinion to maintain the integrity of the old floor you have two choices. Firstly you could possibly reverse the flagstones. This is commonly done with brick floors which are then re-bedded down on a layer of sand. Because the existing substrate to the floor will have been well compacted over the centuries the use of sand may not be necessary. Alternatively you can overcome the problem of the laminations splitting along the bedding planes by using a technique called 'slurry grouting'. Simply make a slurry from lime putty and cottage cheese (for its casein content) and inject it into the problems areas once they have been cleaned by flushing out any voids with water. The slurry helps to re-adhere the laminations on top of the flagstones. Water content in the slurry should be kept to the minimum required to produce a pouring/flowing consistency. Well worth a try on a small trial area.


SUBJECT: Glue removal
FROM: David Flockhart (Kent)
I want to sand the existing floorboards in my old Victorian House. Carpet tiles were put down by the previous owner and it is very difficult to remove the remains of the glue used to stick them down. How can I remove the glue before sanding?

David Flockhart

David, removing glue can be a tricky process particularly over a large area. The use of solvents can mark the wood and/or turn the glue to an even more gluey mess which is even harder to remove. The degree of difficulty or messiness is dictated by how the glue has been applied e.g. spread all over the boards or just applied as spots. Secondly, sanding the floorboards can lead to problems if the property has been timber treated in the past. The sanding process simply results in some of the sawdust, which is contaminated with chemicals, becoming airborne for everyone to breath in.

One alternative you could consider is to simply lever the boards up individually and reverse them. Hopefully, they will be clean. They can be re-fixed using the original holes and nails and after a gentle wipe should be all set for waxing or varnishing. I've never tried this technique before. Therefore I would be interested to find out how it worked out if you decided to try. Finally. take care to gently lever the boards up using a bolster chisel and then push the handle of a hammer under the width of the board. This sends a shock wave along the whole length of the board helping to loosen the nails. Continue the process by using the hammer handle to gently lever the board up before attempting to flip it over. Taking care with the lifting process will help to protect the board edges and prevent splitting.


SUBJECT: Removing pebbledash rendering
FROM: David Weisfeld (Hertfordshire)
I noted your reply to George Omerod on the subject of removing pebbledash rendering. I have the same problem. I want to remove the pebbledash from the front facia of a small 1860 terraced cottage in Watford to expose the original brickwork. I have heard that there are specialist companies that can do this by soft blasting. Do you know anything about this process and any companies that can provide the service? Also if the brickwork needs coating afterwards to improve water resistance what would you recommend?

David Weisfeld

With any form of pebbledash, render, etc. there will be areas of poor adhesion and those of far greater adhesion. Random tapping of the surfaces should reveal hollow areas of poor adhesion. However, whatever system is used the forceful removal of such material from areas of strong adhesion will result in damage to the sub-structure (whether this be brick, stone, etc.). The only situation in which this might not be the case is where the surface material (i.e. the render) is on a backing material (such as expanded metal lath). In such cases the surface may be forced away with the backing material, leaving relatively undamaged sub-structures. The only damage in such instances might be where the backing material has been fixed. Initially it might be difficult to assess whether the render is fixed directly to the brick or stone, or whether it is fixed on to expanded metal lath or a similar material.

If you are determined to remove the surface material (or for some reason have to remove it), I suggest using a variety of methods in a relatively hidden area. These trial areas should help determine the method best suited to removing the material and yet least damaging to the structure beneath.

Turning to what to do after the removal, this will really depend upon what condition the surface is in. In some instances the condition is such that the elevation has to be re-rendered. If this is the case a suitable material should be used that is of a style and nature more in keeping with the type of property. With older buildings this will most often be a lime render. However, such re-rendering should only be necessary if the condition of brick or stone is left in particularly poor condition. Sometimes if only a few bricks are damaged, it might be possible to cut out and either turn them around or replace them.

Old brickwork is by its very nature porous. The application of sealants is usually a waste of time and money. The best advice is to let the building breath. Applying sealants, can lead to accelerated decay. If a surface is particularly prone to extreme weathering, water penetration, etc. then it might be more suitable to provide an appropriate render or other form of cladding (such as hung tiling) to provide weathering protection.

Period Property UK would like to thank Stephen Boniface from Boniface Associates for answering this question.