Help with damp diagnosis please

[john.andrews1]

Help - I'm struggling with a damp problem.

The damp is quite localised, stretching about 7ft along a 10ft wall.

From 12 inches above the skirting down it's as if you've just

dragged a sopping wet sponge across the wall. The wall is a brick cavity wall on the end of a 1970's chalet style bungalow. I'm trying to look at all the possible causes.

1 is that there is a problem with roof, guttering or downpipe, especially since damp is slightly worse in corner of room, where there is a downpipe outside. I've ruled this out (gutter and downpipe clear, been in the eaves, everything looks ok). 2 is that it's condensation forming at this spot. This seems very unlikely as the problem is so localised, but I'm checking with the glass tumbler test. 3 is rising damp. I can't see anything wrong with the DPC on the outside, but who am I kidding, I have no idea how to tell! I might have a go at lifting the floorboards (which are fine) to see if I can see anything on the inside. Maybe the cavity is full of rubbish from when the loft conversion was done. 4 is penetrating damp. Outside wall is bare brick, so bridged cavity could be causing the damp maybe. There are some repair patches on the outside walls (maybe some sort of vent was there before) which might have been badly done

One of my main options is opening the wall up to have a look at the cavity. Has anyone out there done this successfully, can you really inspect and rake out debris with only a few bricks removed?

5 is that the upper part of the outside wall, which has decorative wood cladding, is hiding something nasty e.g. wall is single thickness up there.

Any hints or tips very warmly welcomed! Cheers

[Cordless Crazy]

Whats the glass tumbler test

-- Cordless Crazy

[Stuart Noble]

With that much water it could be a plumbing leak.

[Weatherlawyer]

It sounds more like a leaking window but I am averse to reading such badly written essays.

I might come back to it if I get really bored.

[Phil L]

All these are possibilities, although considering it's only 30 years old, i'd guess it's not much chance of it being the DPC failing, I'd say that it's almost certainly the cavity being blocked causing this damp.

To get at it, you will need to either open up several holes just above dpc and rake the cavity out on each side towards the holes, the drawback with this is that you will lose a lot of skin and also you can only reach about

18 inches to each side, meaning you'll need several holes to clear a 10ft wall, other than that there is a much easier way and that's to make one hole in the face of the wall, again about dpc height and another at the corner...the one at the corner will allow you to poke down a long steel rake (any steel less than 50mm thick) and knock any snots towards the hole furthest away.

What you will need: sds drill with chisel. long rake.(over 8ft if possible) lump hammer and long chisel. bricklaying tools to make good. sand/cement

HTH

[john.andrews1]

Thanks for your response. I've looked at all the plumbing I can get at more or less easily and it's ok. Plumbing leak actually inside the cavity is always a possibility I suppose.

[john.andrews1]

Something I picked up from this newsgroup. Seal a glass tumbler or similar to the wall, with plasticine say. Glass gets damp on outside means condensation, on the inside means damp is coming through the wall.

My glass gets damp on the inside.

[john.andrews1]

Thanks a lot for your response. I like the sound of the two-holes option, something to look forward to in the Christmas holidays.

[Phil L]

You already know it's damp, you can see it's a visible line, 7ft long, condensation rarely follows any particular pattern

[Phil L]

Christmas Holidays? - if you go and hire an SDS drill tomorrow morning, it'll be finished for dinnertime. :-p

[Tony Williams]

Are you on a hill by any chance?

My Nan had a horizontal damp patch along an external wall in her ground floor flat. When I punched a hole into the cavity from outside a stream of water poured out. Took several minutes before it stopped. I thought maybe ground water had filled up the cavity, but left the rest of the problem to the council.