Damp halfway up external wall!

[Dustyy]

Bit of a curious problem here....
I've just had a single storey extension built adjoining to my galley kitchen, thus opening the area into a family room (if you can visualise that).
Where the back door was at the end of the kitchen has now been replaced with a window, with the space where the door was been bricked up to the new window level, and the external wall across the whole thing being rebricked to match the whole of the extension.
A problem has arisen at the external corner of the existing galley wall and new extension wall where the whole of the corner appears damp, two foot in at chest height and then tapering to the corner at the highest (where meets roof) and lowest point (where meets the ground).
The damp now seems to be penetrating through to the internal plaster at the corner.
The extension has been up a few months now and has only just started happening - is it linked to the colder weather?
I've checked the guttering and roof line and all seems ok.
Builder intends to look into it but has said he's no damp expert!
So I'd like to get an idea myself.
Anyone any ideas on the problem.
Sorry to ramble but wanted to fully explain the problem.

Cheers, Nick

 

[foxhole]

What type of roof? any pics?

 

[NickStone]

Builder intends to look into it but has said he's no damp expert!

Sounds as though he's not a building expert, either. Does he wear spurs and a large hat?

 

[JohnD]

are you saying that the wall is damp at about the point a flat roof meets it?

 

[Dustyy]

No spurs and hat but he does use a battered old white workhorse called Transit!

He's a genuine fella who's honest when he says he's no expert in damp - can't knock him for that.

I'll post some pics on as soon as i can.

JohnD - the roof isn't flat, its about 22 degress. The damp does come up to the roof line but only just, it tapers out as you go down the wall and then tapers in again as you reach the base. Pictures will probably paint a thousand words i think!

Cheers

Nick

 

[JohnD]

The damp does come up to the roof line

I think the damp starts at the roof line and goes down. Damp doesn't go upwards (much)

Sounds to me like something wrong with the flashing or the join of roof to wall. there are very detailed drawings available of different ways to make such a join as water leaks are common. You may do better to consult a roofer.

 

[Dustyy]

Hi all,
Managed to get some photos of the damp. The links below should get you to them. I've put them on photobucket and you can access the other pics from there.

http://s266.photobucket.com/albums/ii266/dustyroads_01/?action=view&current=IMG_1682.jpg" target="_blank"><img src="http://i266.photobucket.com/albums/ii266/dustyroads_01/IMG_1682.jpg" border="0" alt="external corner"></a>

The internal damp patches come and go, they often appear in the evening and then disappear by the morning!!
The external damp is always there and feels particularly damp behind the downpipe, but i have checked the joint to the gutter and all seems watertight.

The only other thing I can think of is that the cavity at the corner is very narrow, poss as low as 1 cm or so. Could moisture be getting across? but if so where is the moisture source?

Hope someone can shed some light on this!!

Cheers,

Nick

 

[masona]

The only other thing I can think of is that the cavity at the corner is very narrow, poss as low as 1 cm or so. Could moisture be getting across? but if so where is the moisture source?

Are you sure it's 1 cm?

 

[Dustyy]

Hi,
Yep, its certainly in that region.
The new part of the external wall extension was to be done in reclaimed brick, but then obviously wanting it all to match, the decision was made to re-do the external brick by the window (which was the old back door) in the same brick.
It then became apparent that the original extension had no cavity at the end part, thus there was little space to provide one with the new reclaimed brick skin. Hope that makes sense.
In hindsight i'm thinking that the internal wall should have been redone as well? But i am where i am, so what could be a solution?
What i still can't figure is what is making the external part of the wall so wet?

 

[JohnD]

the cavity is less than half an inch?

 

[Dustyy]

i didn't measure it, but its of that order.
As I say, the original construction (dating back to 1937) seems a bit wayward!

 

[Nige F]

the cavity is less than half an inch?

and those bricks look old/porous well, it`s up now so....check out the plastic covers at the edge of the roof ....it`s called a Dry Verge System ..and I`ve seen them incorrectly installed ...but then I`ve seen many things incorrectly installed in 36 years . Can`t understand why the brickwork wasn`t taken up to an undercloak and tiles mortared in ..........but then I can`t see the type of tiles in the pic ....and it`s a shallow roof

 

[Dustyy]

The bricks are reclaimed, and the same across the whole back face but this is the only spot where the damp appears
The tiles are the completely flat type that link together, as opposed to the wavy ones (sorry not very technical). May be called Marley?
How do i check the dry verge system? If this was responsible wouldn't i get damp from the top?
The roof is shallow, about 22 degrees i think, but all designed by architect and approved by Building Control.