Damp problems again!!!

[Martin]

Hi All,

More damp questions - apologies for boring anyone.

The background - my living room has damp problems mainly on two walls

- it rises up to within a foot of the coving. 1870s house solid walls. I've done all the usual checks. It's not condensation and there is evidence it's been a problem before. Ground level is below both the slate dpc and the silicon DPC. Room 25ft by 10ft.

Recently had a quote by a damp company (~£3K) to do the following;

- Inject DPC (already has a silicon one and a slate one)

- Strip plaster on two walls (total 35ft inc 3 windows and frenchdoors)

- Treat the two walls with some sort of waterproofing "stuff"

- Replaster two walls

- Remove bottom 6" of external render and rerender with bellcast.

- Repoint two courses of bricks (35ft) below the DPC.

My plan is to get them to do the DPC (and wall treatment???) and I'll do the rest. I appreciate the injected DPCs are not trusted by many but I want to give this work every chance of fixing the problem.

For the internal walls;

- Should I plaster or use plasterboard with a skim? Damp Company didn't like the idea of plasterboarding as it causes problem with the wall treatment.

- If I plaster, what type(s) of plaster should I use? I would get someone in to do this.

- If I plasterboard it presumably celotex could be used to aid insulation?

- Could I "dot 'n dab" plasterboard direct to the wall?

- Should I treat the bare brick in any way prior to this?

- Do I need to give the walls time to dry out?

- If so roughly how long?

For the external walls;

-What mix of render?

-Any tips with the bellcast beading? How far above the DPCs should it be?

-What mix for repointing below the DPC?

-What mix for repointing above the DPC?

Incidentally, I am getting a few more quotes!!

All experiences/advice welcome...

Cheers,

Martin.

[Mike]

If it has a slate DPC (which usually works or can be made to work) why does it need an injected one (which doesn't) ?

[Jeff]

am i right in believing that this is more or less floor to ceiling ? I was always led to believe that rising damp gets about 2 foot up the wall and hacking off to a metre high is the done thing. I would suspect penetrating damp more than rising - are both walls exterior and rendered ?

Regards Jeff

[Andrew Gabriel]

By what means have you deduced it's not condensation? Damp up near the ceiling is either condensation or penetrating damp.

You have to accurately identify the cause of the damp before thinking of ways to fix it. If you've done that, you haven't said here, and it's necessary to know before advising how to fix it and how to replaster afterwards.

That starts by correctly identifying the cause.

[Richard Faulkner]

In message , Martin writes

If your wall is damp above about 3ft, IT IS NOT RISING DAMP, and a DPC has nothing to do with it.

They obviously dont know what they are doing and are relying on your ignorance to RIP YOU OFF!!!

The damp could be falling from within a foot of the coving, which suggests that it is coming from above. It could be Gutters, Overflow Pipe, Rotten Window, Shower/Sink/Bath/Central Heating etc. Leaking, and so on - but it is not rising damp!!!

Unless your covings are only 4 ft from the floor/ground level.

[Chris Bacon]

Check your rendering. Check it again. Look for cracks, tap it to see whether it sounds hollow. See if there are cracks around cills where water could be getting in. Is the render painted? I've had a few similar problems in the past.

[andrewd909]

The age of your house suggests that it has solid 9'' walls, was the outside rendered to try to cure the problem ? does the damp worsen after bad weather? old or blocked guttering may be overflowing on to the wall side and getting behind the render, we had a simmilar problem with water getting behind paint, once the paint was stripped away there was a damp patch of about 8 square meters on the outside wall, its just about dried out now ,about 7 months later

[Pete C]

Hi,

A few q's, what sort of % humidity do you get inside at room temperatures? Is the render bridging the DPC? Is the render made from a breathable mortar, and is it painted? What sort of windows and heating is there? Did the damp company suggest taking samples from the wall and having them analysed for salts?

Why not put in a dehumidifier with a humidistat to gain some time while you investigate the whole thing more fully? Just about everything you need to know is in the archives of this group and the forums at 'Period Property'

Bear in mind in the old days the fireplace and draughty windows would keep the place nice and dry.

cheers, Pete.

[Dave Plowman (News)]

I assume this is a brick built house? If so, the very first thing to do is to check the pointing. And not just visually - for a long way round the effected area 'tap' it to see if it's loose. And I'll bet you'll find problems. Rake out and replace using a lime mortar. Don't be tempted to use a more common sand and cement mix - this will simply crack due to movement.

Of course, also check for things like failed gutters allowing the wall to get soaked.

Also, on an old house built in this way, if you've removed and sealed up all the fireplaces, and fitted double glazing, without adequate ventilation, and don't keep it warm, you'll get condensation.

[Chris Bacon]

Don't use gypsum plaster on anything that's likely to get damp, incidentally. It will not last.

[Martin]

Hi All,

Good replies and questions as usual. Apologies for this long reply!

Contrary to one reply I don't regard myself as ignorant!!

Here is what has been tried.....(deep breath)

- Render is good. No cracks and painted. No knowing if it was applied to try and cure the damp. The only problem I can see with the render is that it has no bellcast on the bottom. I've no experience of bellcasts but it makes sense to me.

-Gutter is good. Works with no blockages or leaks.

-No damp in the room immediately above the affected area. Recently took it back to plaster and it was bone dry.

-The only source of water above the affected area are some central heating pipes. I've had all the floorboards up and there is no evidence of previous leaks or current leaks. It's all dusty dry.

-No water tanks or pipes in the loft.

-No water pipes in the walls.

-Damp has been a problem for some time. Replaced with double-glazing approx one year ago. This has had no effect whatsoever. I've sealed it up very throughly. No evidence of damp immediately around window when I removed the old unit. Sash windows must have been fitted originally. The gaps where the weight boxes would have been have been replced with timber. These were bone dry and had no evidence of water damage.

-I've tried the old mirror trick and no condensate formed on the mirror.

-When I replaced the window some of the least accesible brickwork was noticeably damp.

-The metal inserts used to get a good corner on the plaster and a couple of socket back boxes are rusting as well which indicates to me that it's not condensation.

-I was told the same thing about rising damp being only able to get a few feet up the wall but it doesn't change the fact I have damp to approx 8ft.

-One builder and two damp companies have agreed the exterior render (painted by the way) is in good order.

-Wall are solid 9" with no cavaties. It used to be a commercial property but was converted to residential in 1988.

-Someone feel free to correct me, but I heard that slate dpcs fail after a time. This one is 135+ years old so I'm not expecting it to be that good.

-Both walls are exterior and rendered.

-Weather doesn't seem to affect the levels of damp - I experimented over the summer.

-There is some paint bubbling on the outside when it rains (approx the size of a dinner plate) but this approx 10ft from the worst affected area. The rest of the paint seems to be stuck fast as is the render.

So the question remains (one I've been trying to answer for some time) is it rising or penetrating damp. I see no way it could penetrate the walls so it has to be rising damp? The only weird thing is it's almost up to the ceiling.

I do have another couple of damp companies coming around to give me a quote - it's going to be interesting to hear what they advise.

Any advice suggestions would be most appreciated. Someone did suggest moving but that's not really possible at the moment!

Any experience of bellcasts on the render solving problems would be good to hear. It does sound logical that rain hits the wall, runs down and soaks in immediately above the silicon (and slate) dpc. A bellcast would prevent this and theoretically involve only a small outlay of time and expense to try.

Cheers,

Martin.

[Richard Faulkner]

In message , Martin writes

Make sure that they are members of the BWPDA,

Ask them how damp could rise above 3 ft, when all theory says it cant.

It may be worth paying for someone to take a core sample from the brickwork to see if it is damp in the wall, and not just on the surface.

Many damp companies dont know what they are doing, and tell you something needs doing when it doesnt.

Are you anywhere near Manchester?

[andrewd909]

-There is some paint bubbling on the outside when it rains (approx the

on our wall there were a few patches of bubbling paint the majority of it looked fine, once removed though the wall was damp over a large area which had been covered in 'good' paint. one of the problems was the previous owners had used a rubber based paint half way up the wall (to cure the damp) so the water couldn't evaporate once it had got behind the paint, as someone said earlier any paint used should be breathable. Could you scrape a patch of the bubbling paint away to see if the render is damp underneath any water can travel a fair distance before it finds its way in.

[nafuk]

Check pointing Is the floor dirt - my 1850s semi had carpet on tiles on sand/earth. so even though outside ground level was below the dpc the walls were still damp - this construction is ok but it's not designed to have carpet etc. on it, only bare tiles so that moisture can evaporate.

Check ventilation of chimney etc. - are you drying washing inside?

Has the house been unoccupied?

I put in a small French drain - dug down about 9-12" on outside walls, and about 9" away from walls, and filled the trench with pea shingle, and put old slate floor tiles as a border - looks good.

Whilst doing the French drain I also repaired the pointing underground, which was very bad around the bay window (lots of movement that made cracks and the lime mortar had fallen out), and cleaned all the caked on clay from the bricks (which may assist the wicking-up of water into the walls).

Can't defiantely say but I think the French drain did quite a lot - it now means that damp wpould have to travel up an extra 12" before it gets inside.

I also replaced the floor with an insulated dpc protected concrete floor - diy it and it's quite cheap, and a good workout.

There is a side which says that rising damp is not a real problem and damp companies do nothing and are a waste of time. If you want to go down this route you can rent the solutions and pumps, drills etc. quite cheaply and do the whole thing in a weekend for about £100-150 (if you do this do rent/buy a good SDS drill and have a spare 10 mm bit).

I'd try the simple things first pointing (above and below ground), French drain, ventilation, put heating on, open a window when drying washing etc.

Good luck

[Martin]

Hi All,

Apologies for the lack of reply. Computer packed up but at least that was cheap DIY fix!!

Affected wall is painted and rendered. Below the silicon injections, the render does need repair. Still don't know if it's rising damp or penetrating damp.

Floor is good with the correct membrane.

There is also a draining channel against the wall - half full of shingle.

At the moment, I'm getting quite cheesed off with this damp problem. Another company have just paid me a visit. Their recommendation is to tank the walls at a cost of £4k+.

Now I'm really unsure of what to do. £4K+ seems *cough* excessive. DIY tanking?? The company's attitude was that on damp solid walls only tanking would fix it. So I assume he believes it's penetrating damp. However, he then went on about the temperature difference being greater which implies condensation so why should it need tanking? Hmmm...

A few answers to previous questions...

Q: Is the house occupied? A: Yep. For 15+ years

Q: Are the gutters ok? A: Perfect. No leaks, no overflowing. They work fine.

Q: Old house now sealed up causing condensation? A: Condensation is definetly not the issue. I ran a dehumidifer for 6 months+ and it made no difference. Plaster was still coming off the wall.

Q: What sort of % humidity? A: No idea. Dehumidifer was running and walls were still damp. I don't do anything daft liking drying washing in the house.

Q: Check ventilation? A: No obvious ventilation but dehumidifer made no diffence. Solid floor, no air bricks, no vents, no chimney. Strange for a house that used to be a Bakery but I've found no evidence of where a chimney used to be.

Any other suggestions? DIY tanking? I've another company paying me a visit on Monday - anyone care to take bets on their being a third different solution to the same problem?

Cheers,

Martin.

[andrewd909]

The best advice i received when we had our problems was from a painter and decorator, it was a medium sized company, the Boss came round,no reps, he said he sees it all the time, what did impress me was he didnt view it as a 'problem' it was just his job

[markzoom]

If the outside finish is waterproof (as opposed to water-repellant) then your walls can't dry from the outside. All they will eternally do is soak up moisture from the inside air by condensation, particularly if they are single thickness and always colder than the inside. How about stripping any waterproofing from the outside and relacing it with breathable water-repellant. M.K.

[Anna Kettle]

Like others I've had success with French drains. You could also make the inside of the wall breathable so the damp can evaporate into the room. Of course there is a limit to how much water can evaporate and if you have a stream erupting onto the wall, breathability is not going to help, though a French drain would

Breathability - remove gypsum plaster, cement render and modern paints from the inside of the ?bricks?. Do not add any tanking, PVA etc. Replaster with lime plaster and paint with limewash. It can't do any harm, is cheap if you do it yourself and might do a lot of good

Anna

~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[Jeff]

Martin wrote :-

If the render extends below the dampproof membrane then it is bridging the membrane - it needs removing to above the membrane

chemical injection is one thing but you also have to take care of the obvious ie make sure nothing can bridge the new DPC outside or inside - I had to remove render outside and have 7" skirting inside

What exactly is this ?

Regards Jeff

[Pete C]

Hi,

What sort of heating arrangements do you have? Eg how long is the room heated per day and to what temperature.

Also what sort of windows do you have? Eg double glazed or draughty sash etc

And does the render bridge the slate DPC in any way?

A dehumidifier won't necessarily remove the damp under any circumstances but it should at least contain the problem to some extent while it's investigated.

AFAIK one of the best ways of diagnosing damp is to send samples of the wall away for chemical analysis for hygroscopic salts.

Dry lining the wall might be another way forward.

cheers, Pete.