Anyone Any Good At Damp Problems?

[kme]

Our house is a 1930`s brick built, with cavity, and 1 metre sub-floor.

We were told years ago NOT to have cavity wall insulation, as the house had been designed to "breathe" through the cavity - and filling them would cause big problems.

So we didn`t.

We`re currently painting in the lounge - alcoves either side of the fireplace have bubbled up the paint - looks a bit like its had a heat gun on it; or the inside of an aero............ rubbed `em back and filled them - they`re not drying; just sort of sweating moisture.

So I lifted some floorboards to have a look............

The joists are predominantly dry, except around the area where the airbricks are in the outer skin - at that point they`re dripping wet. Not rotted at all - but wet. The skirting board had droplets of water on, as though it was sweating too. Plus there was a little patch of mould, on the floorboards, under the carpet.

Anyone got ANY ideas? Missus wants me to lay wooden flooring in that room ( already bought), so I need to make sure I`m not "sealing in" a problem for the future...........

Thank you in advance.

KME

 

[ProDave]

Check your damp proof course. That's quite likely where the trouble is.

Our previous house was a 1930's semi, but with 9" solid walls. When I bought it there was a damp issue in one corner.  Investigation showed the original rendering was bridging the DPC.  Hacking off the render just above the DPC and terminating it with a bell cast, and leaving the bottom few rows of brick bare completely cured the problem.

So have a good look outside and make sure there's no rendering issue, or the ground level is not too high. Check also for leaking downpipes or broken drains causing the ground to be saturated.

Sort the damp, let the joists dry, then treat them, else sooner or later you will have wet, or even worse dry rot.

 

[revjames]

My son had a similar problem and the previous owner had paved all round the house and it was higher than the DPC. Only solution was to take a grinder to the slabs and dig out all round and put gravel in the trench.

 

[OnOff]

A recent thread on a similar vein:

http://www.talk.electricianforum.co.uk/topic/21792-floor-socket-full-with-water/?hl=%2Bfrench+%2Bdrain

Don't forget that older, say terraced houses would have air bricks front and BACK of a house. Natural air flow would "wick" away moisture. It happens occasionally that someone builds say a modern extension on the back of the house and blocks the air bricks at the rear................then not enough ventilation. You can of course get "cold bridging" whereby you have a "hot" room above and "cold" under floor space below. At the interface moisture develops and is seen as condensation. 

 

[kme]

You may have summat there mate.......

And this is occuring in the room with a recently installed air source heat pump

 

[OnOff]

I wonder.................is the ventilated (from outside, thus cold) under floor space effectively insulated from the warm room above?

Some of those shiny foam backed carpet underlays DON'T breath and it'll be the same/worse with vinyl. They provide little insulation. Laminate floor might be different as that's sometimes installed on 10mm insulation boards for instance - whether it's enough is a different story.

This was never a problem in the "old days", draughty doors and windows, no central heating with people "putting another jumper on" if they were cold. What we see now are these halfway houses (excuse the pun) with folk whacking in double glazing into old properties and blocking off vents. In effect we're making warm boxes that are not properly sealed against the nasty outside cold. You can do this but need effective ventilation to cope with the guaranteed condensation that will occur. Go the whole hog and you're into Grand Designs territory where you can't even have a cat flap or it upsets the system! Alcoves and corners are to some extent areas of "dead" air where it doesn't move.

TBH EVEN if you are getting condensation then you can improve/increase ventilation to sort it or INSULATE against any cold bridging effect........... or both.

Just found this, might be worth a newbie question on there:

http://www.plasteringforums.co.uk/plastering-forum/719-cold-alcove-walls-creating-damp-batten-dot-dab.html

 

[OnOff]

If you do go on the plastering forum I wouldn't mention you're an electrician......................... :lol:

 

[revjames]

We get a lot of damp where I work, with it being a port...... A passenger asked me (during a heavy rainstorm) will de boat still be sailing? I replied "as far as I'm aware all our ships are equipped to deal with water"....

 

[KNB]

Has the room got a bay window? Sometimes the damp can be a result of a leak somewhere else or ineffective guttering. May not be the case but worth discounting.

 

[binky]

Might be worth installing additional air bricks to increase air-flow and allow damp timbers to dry out. Given a 1m void though it sounds more like penetrating damp through the walls. We occasionally get a small damp patch in our living room (single skin bick and rendered construction) have concluded the only possible point of entry is the bracket holding the guttering down pipe to front of house. Fresh cost of paint seems to have sorted it out (hopefully). Would also be worth checking higher up walls for for cracks or other possible entry points, as the way water runs down cavities can be quite random. Had a call out over xmas for flat on second floor that was effectively flooded. Cuase of water was blocked guttering, but it ran past top floor flat before jumping cavity into kitchen lights of the affected flat.

 

[apprentice87]

Hi all,

Now, i am no authority on building construction, but here are my thoughts!!

What if you could physically cut a brick out under the floor and have a look in the cavity?? I had a similar problem around a bay window in my house. I removed a few bricks and made a scraper and got all the stuff out the cavity. Now, the cavity wall of my house, extends into next doors...They are not separate. After i had done this, a few months later i asked the people next door if they had damp around their bay. They said they used to, but it had gone away a few months back!! Definitely agree with what you say about cavity wall insulation, as it happens i have a book here somewhere written by the "building research establishment" a government backed thing i think, but anyway, they say about cavity insulation, and that it can cause TERRIBLE problems, and that often, the only cure is to demolish the entire outer skin of brickwork and rebuild......

I think they have the "condensation" idea all back to front too. They all go on about cold air from outside, this is all back to front....

What actually happens is this.. The council come along one day, and they insulate every roof in their 1000 house estate [at vast expense] The poor householder now find that the WARM damp air from outside [just like wot we will have in a few days] is pulled into their now insulated and freezing cold roof space, the air cools, the water condenses out of it, and all the roof timbers rot. It is usually the case that when you look inside the roof space, it is the first 1/3 of the felt that is wet..Well, it would be, the WARM damp air came in at the eaves, dropped its load of water, and then went out the nice vents at the ridge that the council thoughtfully fitted at the same time!!..john

 

[binky]

was taking to an insulation installer a few weeks ago, Apparently you can fit cavity insualtion to 'difficult to treat' cavities, but it has to be the right stuff to avoid the transfer of moisture. Even then though, buildings in exposed locations can't be done.

Interesting point about roof insulation causing rot. Not seen it myself, but if you stuff loads of fibre up against eaves, it is clearly going to trap moisture and cause problems.

 

[revjames]

I have a chimney stack at the back of my house on a gable end. It is rendered and pebbledashed with a concrete top and a couple of chimney pots. Stack is made of stone and there is evidence of damp quite bad on the bedroom wall and also downstairs in a couple of places. No sign of any cracks or places where water can get in and flashing seems OK. A builder once told me the render has gone porous and the only answer is to hack the lot off and re render. Not totally convinced. There is also a bricked up fireplace in the bedroom where its damp?

Any ideas?

Apologies for jumping in

 

[batty]

All I will say Rev is get a roofer to look at it  preferably one who has been in the business for quite a few years they will probably be able to diagnose better than a builder.

 

[apprentice87]

Hi RevJames,

Yep, tell you exactly.. NO four inch wall is waterproof, i think it would have to be about 16" or thereabouts.. Anyway, when it rains water penetrates the outer leaf of a cavity wall, and then, the air circulating in the cavity dries it out. Now, your chimney.... the water seeps through the brick work, but now there is no circulating air to dry it out, and that is assuming that the pots have covers on them, if not you have foot diameter holes that the rain will drop in!!

Assuming the pots do have lids on them, what you should have, is some sort of air vent where the old fire place was, so air can go up the stack, out the top, and dry the thing out.

If the pots are still on there, it is very likely that water will seek in round where they are fitted anyway, so the best thing to do would be to remove the pots altogether, fit a concrete slab on there instead, but remember to fit a few air bricks under the slab so the old stack is ventilated.

john...

 

[binky]

Just to really help things Rev, old soot in chimney tends to absord water and if you are really unlucky leaches through wall to stain your walls. John is totally correct - must ventilate chimney, even better put a fire in!!

 

[revjames]

Thanks John and Binky, actually there is a woodburner and the flue only goes up a couple of metres, there was a prob before we put it in. The chimney is made of stone as is the whole house, gable end walls on main house are 3' thick! so Its probably render do you think? Is there a waterproof coating I could just spray it all with?

Apologies to OP for a slight hijack

 

[kme]

Rev:

Our next door neighbour was told the same thing about porous render. They had the whole lot hacked off & redone......their damp is now worse than ours!!!!!

Chimneys were dropped years ago, on the roof. The actual chimney still exists internally - as to whether its vented.........dunno!!!!

 

[revjames]

There is a bricked up fireplace in the bedroom on the gable end and no airbrick. I was thinking of putting one in and seeing if that helped.

 

[apprentice87]

Hi There, you could try painting the entire thing with "Thompsons water seal" or similar, that should water proof the stone work, but you still need air vents!!

As for render, this often makes it worse. No render is water proof, it all cracks as it shrinks and the building moves due to temperature changes. Once you render it, the water seeps in the cracks, but now it it sealed in and cannot evaporate once it stops raining, so now, the only escape route for the water is in to the house!!

john...