Damp FAQ

[bournonite]

Wouldnt this be FAR better served by putting a few decent pages on the website? You cant really do this in a forum - why not have a damp section (the mind boggles...) on the website itself, which can carry photos and diagrams, and be edited by Rob/Simon with input from all those who wish to contribute. If not, I'll happily put one together on our site and link to it - we have loads of relevant photos.. I know its a lot of work, but a forum isnt really the way to inform people - not quick and visual the way it should be... The forum has the advantage of geting loads of different inputs - but if they were collected and edited to produce some really good web pages, I think the overall benefit to the general public would be much greater...

I'll copy onto the other threads..

Pete

 

[charlie-ia]

http://www.oldhousejournal.com/notebook/npsbriefs/brief39.shtml

http://www.webvucms.co.uk/showcase.php?id=128

 

[chuckey]

An intermediate wall type of typical thickness 12 - 24" is the rock and rubble type. Here an outer and inner skin of dressed or partially dressed stone is used, with the cavity filled with rubble and often dirt. To add stability to the walls "through" stones are used either randomly or in courses. These go right the throught the walls. Often the outer layer of blocks are "weather or water shot". The stones are laid tilted forward so any rain penetrating runs outwards.
Rain penetration around windows and door opening is often caused by the lack of weather shooting from the side (slope is from in to out, no slope from side to side around openings)
Throughs may be badly set or porous.
Because of all the rubbish in the cavity any water ingress through the outer skin may cause random penetration to the inner skin.

Thought I would add this.
Frank

 

[Nemesis]

In my experience the cause of this is defective mortar. Repointing (lime!) is the answer.

 

[chuckey]

Not in my case.
frank

 

[Nemesis]

Mostly.

Trad buildings do tend to respond to trad repairs best.

 

[Matt Green]

Seems pretty fair to me. Through stones and bricks bridging early cavity walls have been found to transmit water to the internal surface. Adding that to the damp FAQ doens't seem like a crime. It might be something to consider.

Frank isn't recommending what to do about it, so the traditional repair comment seems misplaced.

Clearing out blocked cavities at the base of walls, whilst a little invasive, can be a reasonable route to take if the problem warrants it. Fallen debris effectively turns a cavity wall into a solid one, and you could argue that reducing ground levels would reduce the risk of ground water ingress into the base of the wall I suppose.

:?:


Matt

 

[Nemesis]

No - it's just Frank is very fond of cement... :? so hope he isn't recommending that as a solution...

 

[MdB]

An interesting article that MDE found.
http://www.greensteps.co.uk/tmp/assets/1163178050906.pdf

 

[Nemesis]

Read the caveat on page ten, consider that 'lime' is many things.

 

[Rebecca]

I am buying a middle terrace, stone house built in 1890. The exterior has a cement render. There is damp in the property and I have been advised to inject a DPC into the walls. I think that the reason for the damp is because the walls can't breathe because of the cement. Does anyone think it is a good idea to take the cement render of the exterior wall? Is this extremely costly because I am on quite a tight budget? Would it be worth it?

I am also taking up the floor slabs because there is no damp proof course underneath and was thinking of putting in instead, a limecrete floor. Does this sound like a good option? Again, is it extremely expensive? Would it be worth it?

Rebecca

 

[MdB]

Rebecca, before you do anything, work out where your damp is and why it is getting there.

A injected DPC (if it worked) will only stop damp going up from the ground into the base of your wall. It won't stop damp coming through the walls, up through the floor, condensation and other damp problems. I don't think you will find anyone here that thinks injected DPCs for old properties are a good idea and most will say that all they do is damage perfectly good walls.

Why are you taking the floor slabs up? Because the floor is damp? You should ask yourself why the floor is damp before going any further. My guess would be that your outside ground levels are higher than your internal ground levels. If you sort this out, I bet a lot of your damp problems will be solved. Very rough round figures for flooring a 3 bed house £1k to £2k for concrete, £2k to £4k for lime - materials only labour extra.

Removing cement from your walls is probably a good idea but may not be necessary. If its in poor condition with rain getting through cracks in the surface then you want it removed. If its in good condition and the inside of the walls can breath and are well ventilated then it might be a job that could be left. Removing it is either an easy job if its delaminated from the stone (like in my house ) or a long horrible job if its still stuck. I don't know costs for replacing it.

 

[Rebecca]

Thanks for your reply MdB.

I had a damp report done which stated there was rising damp in the property and recommended that the affected walls should be injected with DPC. It also stated that the floors had been constructed without a DPM so that seems to be the reason for laying a new floor down (this is all on recommendation from my builder!)

I'm not actually sure whether the floor is damp. The report just stated that moisture meter readings indicated rising damp. However, the neighbouring property has got a higher internal floor level because the terrace is on a steep hill. If the outside ground levels are higher than the internal ground levels, could you solve this with a raised floor?

The cement on the walls on the whole seems to be in good condition, so maybe its better just left alone.

 

[Moo]

Just a guess, but I reckon it went a bit like this:

- Building Society requires a survey.

- Surveyor sticks his little damp-meter probe in a wall or two and gets a 'reading'.

- Sucks in through his teeth and says you should call in a specialist.

- 'Specialist' (aka salesman) comes along, sticks his meter probe in the wall and prescribes (aka sells) all the expensive treatments you have described.

 

[Matt Green]

The cement on the walls on the whole seems to be in good condition, so maybe its better just left alone.

It's a funny thing: 'damp specialists' don't sell a product called Leave It Alone, so they rarely recommend it.

 

[Nemesis]

1890. Should in all probability already have a physical DPC installed from new.

 

[Rebecca]

That's pretty much how it went Moo. The problem is now it is one of the conditions to getting the retention back from the mortgage lender.

 

[Moo]

I'm sure that this problem has been addressed here relatively recently. The solution seems to be (if I remember rightly) to get a report from a real specialist.

Someone here will have suggestions as to where to find one.

 

[Rebecca]

Thank you Moo.

I have just looked up specialists on this website and have had a good read of their websites. I think going with an independent specialist who has knowledge about preserving older buildings, is definitely the way to go.

 

[dave40]

I have lived in many period buildings and have never once heard from a damp proof company that didnt tell me to inject a damp proof course !This is death as you all know for many buildings and makes the problem much worse so you are right to see a specialist that deals with old buildings and knows about letting them breath etc.
On 2 of my properties a simple french drail cured the rising damp problem .The list given by "NT" in this thread is an excellent reference.