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 (www.periodproperty.co.uk).

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...

Go back to the top
SUBJECT:
What moisture management approach to use for a damp half cellar?
FROM:
Joanna Boult
(Kent)

My end-of-terrace Victorian Town House built in 1872 has been built into the top of a hill. The front of the house has steps to the side leading up a path to the front (side) door.

The house has a half cellar, where for many years, I ran a Hairdressing and Beauty Salon.

The Half Cellar is divided into three areas. A room to the front, a middle passage with stairs and two brick arches which lie under the path to the side front door and a room to the rear. The room to the front has two earth retaining walls which are half below ground level, the wall to the front has high windows looking out onto ground level with a front paved garden and the other wall to the side has the path leading to the front door running up the side outside. This wall has a chimney breast.

Twenty years ago my brother used foil backed plasterboard attached to tannelized battens with a DPC behind each batten to line the room. He took the plasterboard only three quarters of the way up with an architrave attached along the top to make it look like a picture rail, this was to allow some ventilation behind the plasterboard. Above the plasterboard was painted plaster.

It worked very well for 20 years. A few years ago a big damp patch appeared on the plaster to the top of one wall and damp spots appeared on the ceiling around the chimney breast. The dry lining had become damaged in some places due to shelving etc. and I decided to take the dry lining down, to see what was behind it, what could be causing the damp patches and to replace with new dry lining but this time all the way up.

Once the old dry lining had been taken down, we found that the walls had a one-inch-thick cement render applied to them. Before I had chance to discuss the best course of action with my builder he had attached new battens all around the walls saying it was probably better to cover it up again. My builder dry lined the whole room and then over boarded the ceiling with normal plasterboard.

Unfortunately, he put the foil backed dry lining sheets up horizontally leaving horizontal joins which were not sealed, so when we had the first lot of heavy rainfall, condensation found its way into the gap in the join and left horizontal damp patches along the plastered walls. Also the damp patches are coming through the ceiling again, around the chimney breast. I eventually managed to get him to come back again to take the dry lining down on one wall to do again.

This time I have had a chance to take a good look at the cement render on the walls. I wonder, if this is the wrong kind of cement to use on the walls and its not allowing the moisture to come though the brick and evaporate, could it be forcing the moisture up wards causing damp around the chimney breast on the ceiling?

I have had the Chimney re-pointed, flaunched and all the flashings checked, gutters repaired, walls repointed etc. I have had the patio to the front above this wall re-done properly, sloping away, before it was just paving laid directly on mud allowing the rain to go straight down between the paving into the soil next to the building. I've had the steps re paved and any gaps filled. I believe the cement render on the inside of this wall could well be the cause of the big damp patches on the plaster and the damp patches on the ceiling around the chimney breast. I think removing this cement render to the inside of the walls would be the right thing to do but I'm really worried about what I may find underneath it, after all whoever did it had a reason for it, there is no render on the walls in the other areas of the basement. I could be opening a rather nasty big can of worms.

Joanna Boult

In short there is a very real risk of opening a can of worms. However, to resolve the problem you face I suspect that this is unavoidable.

With any building there are two basic methods of dealing with moisture. The modern approach is moisture exclusion whereby various barriers, materials and the building fabric are used to keep moisture out. Historically, moisture was dealt with partly by design to ensure that moisture did not enter, but also by management. It is unusual to find historic buildings with anything that might resemble a barrier to moisture. Traditional materials tend to be permeable and lend themselves to the moisture management approach.

Your property was built at a time when barriers were starting to be used to try to prevent moisture getting into buildings. However, the use of damp proof courses and other forms of barrier were not uniformly used and there was much that we might regard as experimentation. Furthermore, at that time traditional materials were still very prevalent in the fabric itself allowed quite a degree of permeability.

Without knowing what your seller was originally used for, my suspicion is that in the mid to late part of the 20th century its use meant that the owners or occupiers required a dry space and were no longer willing to adopt the moisture management approach. It is likely that this resulted in a cement based tanking render being applied to the walls, which I suspect is what you describe. Such a tanking render would have prevented moisture coming through the wall, or at least appearing on the internal surfaces.

The problem with applying moisture exclusion methods to a building where moisture management applied is trying to ensure 100% continuity. Without such continuity of the damp proofing systems there is always the risk that dampness will eventually find a way through. In any event, tanking renders tend to fail over time.

The application of an internal plastic sheet and the dry lining clearly provided you with a dry internal surface for some years, but even so that eventually failed hence the problems that you now face.

The works you describe as having been undertaken externally may well have assisted in trying to prevent some of the water ingress. Without seeing the building I cannot comment on whether those works were appropriate and necessary, or indeed whether they might have helped to solve the problem or exacerbated. My suspicion is that they would have gone some way to help.

Without sight of the problem I cannot provide a definitive solution. However, from what you describe my suspicion is that you will need to strip out the area completely to get back to the wall. You may have to expose the junctions of the floor with the wall and floor to ceiling so that the whole of the structure can be assessed properly. The sort of method that I believe might be appropriate would be a modern membrane system such as those produced by Delta and Newton lath, although there are several other products on the market.

The membrane would be fixed to the wall. The idea of the membrane is that it provides a dry surface internally onto which you can apply whatever finishes you want, but allows a gap behind it for moisture to continue to move through the structure.

This means that the moisture is not necessarily diverted elsewhere and can move through the building without hindrance. The main problem is what to deal with the moisture that builds up behind this membrane. In most cellars the solution is to provide a sump and drainage system in the floor and in some instances the membrane system has to be taken across the floor as well.

The situation you describe is not one whereby chemical treatment of the wall is likely to be successful. You could simply remove the tanking render and apply tanking render again. This might remain satisfactory for a number of years, perhaps even decades, but it will eventually fail and could move moisture elsewhere and cause problems in other areas. My preferred method in situations such as this would be to consider the use of a modern membrane system. My suggestion is that you seek advice from a suitable specialist that deals with this type of system and can advise properly on whether it is suitable in your situation and how it might be fitted.

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

The Whitworth Co-Partnership LLP - Chartered Architects and Surveyors

Go back to the top
SUBJECT:
Is it safe to put a hard cover over an old septic tank?
FROM:
Wendy Taylor
(Gloucestershire)

I have uncovered an old septic tank or cess pool opening in the garden of my old cottage. The opening is 45cm diameter metal pipe level going down with a diamond shape metal outer casing but no lid. The property was connected to the main sewerage about 3 years ago before I moved in. Is it safe to put a hard cover over the opening and use the surrounding area to walk on?

Wendy Taylor

I have seen many properties where the septic tank has become redundant and has therefore been covered over. The simple answer is that it should be possible to cover over this and make it safe to walk over. However, you will need to find someone who can advise more specifically on the situation. It will need an inspection and you will need to ensure that whatever cover is installed is sufficiently strong for the area it is laid over and can take appropriate loads above it. You need to bear in mind that if you cover in this way it may become a forgotten feature in future and could theoretically become a hazard if that cover were ever to deteriorate or fail in some way.

In most situations I have seen, the septic tank is infilled with rubble, et cetera and is often then brought into use as a soakaway. In any event, by filling it the risk of a serious injury is reduced should the cover fail in any way.

It would probably be sensible to have an engineer look at the situation and provide some advice about covering the opening.

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

The Whitworth Co-Partnership LLP - Chartered Architects and Surveyors

Go back to the top
SUBJECT:
Water runs down our sandstone mullions
FROM:
Gary Roberts
Lancashire

I live in a converted barn with sandstone mullions, when it's cold outside and hot inside the mullions get wet through and the water runs down them and stains the inside of the mullions. Is there anything that can be done to prevent this and cure the problem? It’s worse, as you would expect, in the kitchen and bathrooms where it gets hotter inside.

Gary Roberts

The problem you describe could be due to external water ingress finding a way in and/or condensation. What you describe sounds more like condensation, but I would not exclude the possibility of some water ingress.

Depending on the precise nature of the stone, it could be quite permeable and therefore absorb moisture. Any fabric that is wet tends to be colder than a dry material. However, even if you suspect water penetration through the stone I would not recommend trying to seal the external surface because this can exacerbate problems or lead to other issues.

Warm air can hold moisture whereas cold air does not. Therefore, the warm air created internally during cooking bathing or simply by having the heating on will mean that it will absorb moisture in the form of vapour. When this meets a cold surface it can no longer hold the moisture as a vapour and releases it. This is when it becomes visible moisture on the surface that we call condensation.

The situation you describe may not be an easy matter to resolve. In some instances raising the temperature of the material on which condensation occurs can resolve the problem. This can sometimes mean insulating the surface. In other situations improved air flow by ventilation can help. It may be that opening the window to allow moisture to escape quickly before the condensation forms will help. In particular, it is important to try and ensure that the areas where you create moisture such as the kitchen and bathrooms are areas where you need to get the moisture out quickly. Ideally kitchens and bathrooms ought to have some form of mechanical extractor fan to assist in moving the moisture laden air out of the property as quickly as possible.

In the past there have been studies looking at condensation in houses and there are some buildings and building materials that are far more prone to condensation problems than others. However, a major factor is the lifestyle of occupants. This is not necessarily because there is anything terrible about their lifestyle, but for some reason they create more moisture, or do not sufficiently and frequently ventilate the property. Therefore the moisture is kept within the building rather than allowing it to escape.

There is not necessarily an easy solution. It may be that you need to gradually change things and it is quite likely that you will need to seek further advice from a surveyor locally who can inspect and assess matters in more detail. You need to find someone who is experienced in dealing with such problems.

In the short term, the way to avoid the stains is to remove the moisture from the surfaces as soon as it appears. This is often impractical, but there is no reason why you cannot go around the property on a regular basis with an old towel or something similar and wipe down surfaces to ensure that the moisture does not build up.

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

The Whitworth Co-Partnership LLP - Chartered Architects and Surveyors

Go back to the top
SUBJECT:
How best to treat a wall before re-introducing a road surface above the DPC level
FROM:
David Isherwood
(Yorkshire)

The level of the single track lane abutting my gable end has been lifted by the highways contractors maybe over 30 years ago resulting in the highway covering the air brick that was likely installed over 100 years ago and breaching the damp course / internal floor level contributing to extreme dampness. The council have been very slow to assist in resolving this problem that I believe they are responsible for.

They are allowing me to have contractors dig a 12" wide trench down approximately 13" to the original level so I can suitably treat the property but then they want to re-introduce the material directly against my wall once again above the original DPC level.

Assuming that is fair / legal for them to do, what is the best way to treat the gable end before re-introducing the road surface and what product would cause least problems when laid against my property?

David Isherwood

I am aware that there have been legal cases about highways and the height of paths and roadways against buildings. This is something that would need to be researched to find out if case law exists.

Ideally the wall should be left with a slight channel alongside it. This could be finished with a suitable grating along the top. The idea of an open channel is that any moisture in the wall can escape from the surface and evaporate away. If moisture gets into the channel it will often drain away over time and is unlikely to pose a problem. At least the open channel means that there will be no lateral moisture penetration into the wall. I would start by trying to persuade the highways authority to allow a channel to be formed rather than insisting that the surface be right up against the property. After all we are only talking about a channel of perhaps 4 inches wide. Of course, there would need to be a small wall built parallel to the building 4 inches out against which the roadway will then backup. You would need to ensure that the roadway does not discharge water towards the building and into the channel, or a suitable kerb could be formed to prevent direct water run-off into the channel. I have used such channels alongside buildings quite successfully on many occasions where the ground level is high against the building.

If the highways authority refused to allow this and insist the roadway being taken right up to the building you will need to consider a modern damp proofing application against the wall surface as a form of external tanking. Traditionally slate was often used, but this can lead to gaps and eventually water penetration. There are a number of modern tanking systems and renders that should be suitable. The important thing in this instance is to try to ensure continuity of the system so that there are no gaps through which moisture could eventually penetrate.

The one thing that needs to be carefully considered is whether the application of an external tanking system could create other associated damp problems to neighbouring walls and areas. My advice is that you should seek professional assistance from a suitably experienced surveyor locally. In view of the fact that the highways authority is causing these problems I would like to think that they would at least pay for the services of a surveyor to advise you.

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

The Whitworth Co-Partnership LLP - Chartered Architects and Surveyors