Damp Solum

[Anonymous]

We have recently bought a 1910 Arts and Crafts house that needs quite a bit of work.

Should we seal our solum sub-floor area?

When the house was surveyed (in June) the survey showed up some slight damp problems so we had a more detailed damp survey (by a timber specialist company) this showed one wall that had a damp problem. Now we have moved in and are looking to do the work, so we got another company out to give us a quote (October). This time the meter readings suggested that all of the walls required damp treatment. Our survey also recommended sealing the solum under the timber floor, as this is currently unsealed and feels damp to the touch - when I have been exploring the underfloor area it is definitely damp.

We have decided to do some preventative maintenance, before putting in a damp course. We will lower the ground level next to the house and putting in french drains. We'll check the damp readings next year and see if we need to put in a full damp course or not.

However, we don't know what to do about the solum. We are a bit concerned that by sealing the solum floor we may be creating more problems for ourselves. We would be particulalry interested in people's opinions on the solum, as there seems to be some debate on the forum.

 

[Anonymous]

I don't know about the floor - poss more info needed but if your house was built in 1910 I am pretty certain it will already have a damp proof course, and if the 'damp specialists' who stuck a meter in the walls and decreed damp all over weren't from a reputable company which has real professional expertise in damp and timber problems, witha range of solutions to match, and is one which also doles out chemical injection and cement render as 'solutions' to every perceived damp problem, then I'd carefully consider before parting with any cash to them.

Have you any idea what may be causing damp which you can feel? Have you cosnidered trying to solve the problem by tracing the source of the damp and trying to deal with that?

 

[Anonymous]

The building definitely has a damp course, we have seen it below the render on the building, and the company that gave us the quote have been highly recommended and are a reputable firm.

We are trying to deal with the source of the damp in the sub-floor area, by installing the French drains and removing the soil from edge of the building, but we are keen to know if we should seal the sub-floor or solum area as well. Any advice ?

 

[Anonymous]

Could you first describe exactly what you mean by the word 'solum'.

You will then probably find that the answer is 'no'.
One of the problems with sealing anything is that it doesn't make stuff dry, it just stops water moving from one place to another. You need to be sure where the water is moving from and to. You might find that sealing surfaces puts you on the wet side. Which is why polythene clothes are not a good idea except very briefly when it is raining hard.

 

[Anonymous]

By solum I mean the ventilated subfloor area. When I climb under the floorboards there is a soil sub-floor area and this is damp.

We are putting in preventative treatments like french drains round the house, and were advised to get the subfloor area sealed, but exactly as you point out, we are a bit worried about sealing it, in case we give ourselves more damp problems by forcing the water into other areas.

 

[Anonymous]

Hang on though - highly recommended by whom, and how do you know they are reputable? Are they independant of chemical injection sales, for example?

Also - diagnosing damp by sticking a damp meter in a wall isn't a very reliable method, and if you already have a physical DPC, why on earth do you need another? What did the company say about that?

Have you considered that any damp which may be there is possibly through the building not breathing properly, through damp trapped by render, through condensation or blocked underfloor vents? The usual suspects?

If ground levels are high, then reducing those and seeing if that has some effect is a good first step. French drains may be required, but they should be carefully designed or they can simply form a 'moat' and make things worse.

 

[Anonymous]

Damp under floor is quite normal, and does not in itself indicate a problem. This is why it is vented.

High meter readings on walls do not indicate a damp problem. They dont even indicate damp, they merely show some electrical conductivity, damp being only one possible cause. Do you have specific signs of a damp problem?

The contradicting readings and interpretation may tell you something about the companies concerned.

Sealing old buildings is often recommended as part of inappropriate works. Many old buildings have only been made damper as a result. Victorian buildings do not handle damp the way modern builds do.

NT

 

[Anonymous]

Something to check however - are there sufficient vents under floor to ensure adequate ventilation to dissipate any damp in the ground? If external levels have been raised then the vents may have been blocked, or even (personal experience!) now being used as a means of conducting water into the soil under the house when it rains. If the ground is very wet, and there isn't adequate ventilation and a means of evaporation under the damp course (lime mortar) then the moisture may well be causing condensation on the inner walls as it dries.

Again, I have had experience of this. The wallpaper was soggy, and came off in sheets. It was diagnosed by one firm as 'rising' damp' which it wasn't.

The cure - stop water seeping in, unblock vents etc.

I seriously would not waste money and have a vast amount of mess and disruption here having an injection damp proof course of dubious value. I'd lower ground levels first, check vents, etc. then I'd allow walls to dry out thoroughly before trying anything else.

If there is no obvious sign of damp internally, spoiled wallcoverings etc, then I'd be wary of damp meter reading diagnosis in inexpert hands.

 

[Anonymous]

If the humid air from outside will come under your cold floor, it will condensate. And if you cannot give temperature in the construction, it will moisture up.

Any sealing and DPC will make situation worse. A lot of helpful information what to do with damp buildings you will find in the link.

Good luck!



Dampness in Buildings

 

[Anonymous]

Hang on - wooden joists, wooden floors - some air movement is needed or you are liable to get rot!

 

[Anonymous]

The underside of the wood floor will be a little above outdoor air temp, so there should be no condensation occur there.

The earth under the house floor will be shaded from the sun but also slightly warmed by the house...

Exterior temp will be higher in the day and colder at night...

I had the same thing a fair while ago as Evelyn, where water was flooding under the floor due to blocked exterior drains. Under the house was flooded upto the level of the airbricks. The problem turned out to be the drain grate, which was cast iron with only some tiny holes. It blocked readily with leaves. The solution was to fit a modern plastic open grille one.

NT

 

[Anonymous]

Steady there.

A lack of ventilation might raise the timber moisture content to the point where insect infestation becomes a problem, but initiate fungal decay- not enough water for that from condensation alone usually.

Matt Green
-my experience, my opinion, not that of..etc, etc-

 

[Anonymous]

So all this loft ventilation isn't required either, and we can block off the underfloor ventilation as it's draughty?

Too many contradictions really... I think a large glass of something alcoholic is the answer.

 

[Anonymous]

Woah there.

It's still a good thing to keep timber dry through ventilation. I was only quibbling about what might happen if you didn't. Which, generally, is an increase in the suseptibility to insect attack not usually decay fungus.

And yes, mine's a pint please.

<IMG SRC="http://www.periodproperty.co.uk/discussing/smileys/wink.gif" BORDER=0 ALT="">

Matt

 

[Anonymous]

It doesnt seem to sit with what I've seen personally, but I'm no damp expert. Have seen several cases where damp resulted in fungal decay.

NT

 

[derekmclay]

I have a similar issue with a timber framed 1920's house re-clad in synthetic stone. I have had 3 quotes from 3 different local companies - all want to lay a DPC and pump 'lightweight' concrete onto the solum. Cutting out and replacement of decayed timber of the internal and timber frame walls including sole plates etc and replacing any flooring and joists as required.
The external vents are too close to the ground and the ground requires lowering.
It may be that these companies have a standard stunt that they all play, however they have been doing this for years and the work carries a 30yr guarantee - and their work is mortgageable (in Scotland anyway).
I have seen and heard excellent reports of this practice and I am forming the opinion that it is the way to go.
If your period property allows concrete capping of the solum, then maybe its for you also.
I would welcome any suggestions on this matter as I will be carrying out repairs in August.
Cheers.

 

[Mark]

I understand that flooding the solum with a couple of inches of concrete is standard practice in new houses these days. But as has been pointed out, modern buildings are not like old buildings. It may well be that you would be ok to do this is a 20's building. I wouldnt do it in my house.

I would be asking what is around the property? Is there lots of concrete already ? paths? patios? etc? Assuming it isnt the ground water level or a leaking water pipe or drain which is causing damp then something is preventing moisture from escaping elsewhere.

The modern materials and approach is to make a waterproof shell, sounds like that is what they want to do to your house. Fine as long as the materials can take it and it stays waterproof and all the moisture is only on the other side. Biffs plastic coat analogy is v.good. If the timber frame is rotting I would be concerned about that rather than damp soil in a solum. As a first and much cheaper step I would be sorting out sub floor ventilation.

 

[derekmclay]

Thanks.
Yip, the ground around the house is a pebble path and is humped with a run towards the walls - and lo and behold, the vents are right at ground level in places. Obvious really, but once this is sorted out I think I should still cap the solum. The previous owner was a very old lady who never opened the windows so this will have added to the problem.
From related posts, it appears that the general consensus is to let the solum breathe and create good airflow - this must be a prerequisite, however I would be happier if the bare earth is capped as from all accounts the ground will never totally dry out.
Or will it? I will be taking the plunge soon and if the concrete/DPC works are uneccessary and the woodwork only is carried out it could mean the difference between £5K and £10K of work.
Cheers,
Derek.

 

[biffvernon]

Concrete, made with Ordinary Portland cement, is seriously evil stuff and should be banned from all period properties, if not the whole planet. There is always a better method and material.

 

[Moo]

"I would be happier if the bare earth is capped as from all accounts the ground will never totally dry out."

But you don't really know for sure, do you? Only time, and some sensitive (and cheap) remedial work will tell.

And do you really want it to totally dry out? My uneducated guess is that a small amount of moisture in the soil may well be a good thing. You just don't want the structural wood sitting in a puddle.

Comments from them what knows about these things, please.