Damp or mould

dahac

That's what I think its to do with the gas pipe allowing water through. I'm going to get rentokil to have a look as they will look at it for free and give me some heads up on it.

Am I right in thinking that the outside damp course is ok but it must be something in the cavity that's causing it as we only get it in the corner,

cyclonebri1

dahac wrote: »

That's what I think its to do with the gas pipe allowing water through. I'm going to get rentokil to have a look as they will look at it for free and give me some heads up on it.

Am I right in thinking that the outside damp course is ok but it must be something in the cavity that's causing it as we only get it in the corner,

More or less, but you haven't answered the question as to whether there is any other form of dpc other than chemical injection?

Plus it's difficult to judge if chemical DPC is totally intact/correctly done, apart from if it doesn't work.

Damp in the outside skin would most likely show itself as efflorescence(sp) on the bricks, the white furry stuff that is formed by water dissolving salt in the bricks.

It is perfectly possible that the os dpc is fine, but water may be bridging the pipe or dropping onto the joists or any rubbish in the cavity.

Personal exp;

17 years ago I bought a 1930's bungalow, blue brick damp course, but a large damp patch under the dining room window.
Now the house had been changed around in the previous 60 years or so, the window wasn't originally there, that was the clue.

I removed 4 bricks from the inner skin under said window. Now I'm not exaggerating here, I removed a wheel barrow full of rubble, sand, wood, mortar and brick ends from in the cavity:eek::eek:

Rebuilt and problem solved, no issues since.

dahac

I dont think there is any other dpc as the street level is the same as inside floor and all I can see from outside is the chemical injection. We do have water marks on the outside wall but no salts or anything? I did have ago at cleaning the cavity out before where the gas pipe comes in i did remove abit which was blocking a outside air brick. I wasn't sure how far to go down, should I go down until I hit the something solid?

cyclonebri1

Yes, you should go down as far as possible to ensure you are below the dpc, which it seems you may not have anyway.
This is why in my example I had to remove 4 bricks, to get my elbow in.

Also, the air brick should be sleeved through the wall, not just into the open cavity.

But you need to realise that this was done 100 years ago, cavity walls were virtually unknown back then, certainly not perfected.

You must have an example of 1 of the earliest cavity wall systems in Britain, a quick look suggests they didn't start to be widely used until the '20s

dahac

Ok I will have to remove some more bricks to get to the correct depth. Had a damp meter at its saying between 16% and 20% moisture levels in the affected area. The un affected are is about 7%