Penetrating damp coming through brickwork (I think)

[Jim Walsh]

Dear All,

Might someone (or even, many people) advise me on a damp issue I have at my= 1950s detached, brick-built house? Specifically, it affects the internal w= alls at first-floor level, particularly on one side of the house.

In one room, where the radiator had been turned down low (the room is not o= ften used), there was visible moisture on the surface of the wall. This see= med not to be condensation but rather, the result of seepage through the wa= ll. Tearing off a strip of wall paper, the plaster underneath was sodden, t= oo.

In terms of the cause, I noticed that the outside wall on the side of the h= ouse most affected has a tinge of green in many places. In other words, it = seems to get wet enough often enough to promote algae growth. I also notice= d that the mortar is in pretty poor shape on much of this wall, being sandy= and quite crumbly. The gutters are fine and are not causing water to run d= own the walls (one obvious possibility that occurred to me). So, might it s= imply be excessively porous mortar, caused by sixty years' worth of weather= ing?

Is it possible that sandy, absorbent mortar could suck up enough rain water= to precipitate a damp problem? I'm thinking about having re-pointing done,= followed by a water repellent treatment (e.g. Thomson's Water Seal).=20

Thanks and best regards,

Jim.

[Phil L]

Rain tends to drive on one side of a building, and this appears to be what's happening here. It needs re-pointing sooner rather than later, but more than that, it seems to be tracking across the cavity somehow. When you say first floor level, at what height is the dampness showing in the walls? and more to the point, why isn't it happening at ground floor level?

[meow2222]

my 1950s detached, brick-built house? Specifically, it affects the internal= walls at first-floor level, particularly on one side of the house.

often used), there was visible moisture on the surface of the wall. This s= eemed not to be condensation but rather, the result of seepage through the = wall. Tearing off a strip of wall paper, the plaster underneath was sodden,= too.

It won't be condensation on an internal wall. I'd look at the usual sources= of water ingress: roof, guttering system etc, and plumbing leaks.

house most affected has a tinge of green in many places. In other words, i= t seems to get wet enough often enough to promote algae growth.=20

That's far too damp

ll, being sandy and quite crumbly.=20

Repointing is good, but do ensure the mortar's weaker than the bricks. Dama= ge can happen many years later otherwise.

obvious possibility that occurred to me). So, might it simply be excessive= ly porous mortar, caused by sixty years' worth of weathering?

Also check for missing slates, and defective roof detailing, eg cement flas= hing frequently fails

er to precipitate a damp problem? I'm=20

If the wall were very exposed and non-cavity, yes, but I'd expect more like= ly cavity construction from the 50s.

No, just fix the faults, don't apply things that end up blocking the brick = pores and causing troubles later.

NT

[harry]

my 1950s detached, brick-built house? Specifically, it affects the internal= walls at first-floor level, particularly on one side of the house.

often used), there was visible moisture on the surface of the wall. This s= eemed not to be condensation but rather, the result of seepage through the = wall. Tearing off a strip of wall paper, the plaster underneath was sodden,= too.

house most affected has a tinge of green in many places. In other words, i= t seems to get wet enough often enough to promote algae growth. I also noti= ced that the mortar is in pretty poor shape on much of this wall, being san= dy and quite crumbly. The gutters are fine and are not causing water to run= down the walls (one obvious possibility that occurred to me). So, might it= simply be excessively porous mortar, caused by sixty years' worth of weath= ering?

er to precipitate a damp problem? I'm thinking about having re-pointing don= e, followed by a water repellent treatment (e.g. Thomson's Water Seal).

Porousity in pointing and brickwork can cause this sort of thing however the water has to also cross the cavity as well. So there must be an additional problem. The cavity may be bridged or some of the "weepholes" may be blocked.

You usually find weepholes above cavity trays above windows and doors. Their function is to let out water that has accumulated on top of the tray (usually made of sheet lead.) Poke them out with a bit of wire. If there aren't any above the lead trays, this could be the problem. The weepholes may just be open perpends (vertical joints ) in the brickwork.

You also need to see if you have any cracked/broken slates/tiles immediately above the cavity. A leaking gutter alone doesn't usually cause this problem.

The tiles need to be examined closely, get up there with a ladder. Pay particular attention to the bits of tile hidden under the others.See if any are loose. If they are loose they may be broken & letting in water.

Check any lead flashings above the suspect area too.

Opening the cavity to fix any bridging is a last resort but might be neccesary in the end.

There were some real shit houses built in the 50's.

[Dave Liquorice]

How do you get penetrating damp on an internal wall as well? B-)

Is this damp below a window? Check the condition of the frames and sealing to the brickwork.

Also agree that an overall waterproofing sealant is not a good idea. Walls need to breath.

[charles]

everyone seems to be assuming a cavity wall - is there a cavity?

[Dave Liquorice]

I'm not but I agree most people are and to modern building standards, with cavity trays, weep holes etc.

[Man at B&Q]

MBQ

[charles]

since other people have mentioned windows, I assume the must be some involvement of the outside. If it is really a fully internal wall and not just the inner surface of an external wall, I'd be looking at a tiny hole or weeping joint in a water pipe, or one of the connections to the tank in the loft.

[Man at B&Q]

Reading the OP again, it seesm to be affecting both internal and external walls.

MBQ

[harry]

:

Well, leaking roof or plumbing if that is the case.

[Phil L]

He has damp on an internal wall, he mentions that it's green outside, which means it's the inside of an outside wall, not a seperating wall, he also mentions seepage.

It's 99% certain it's a cavity wall because almost all houses built since WW2 were built with cavities and quite a lot prior to that date as well

[The Natural Philosopher]

that is not strictly true.

MOST houses built since...but not ALL.

[dennis]

There were lots of system built houses built in the fifties that did not have cavity walls, whole estates full of them.

Smiths houses are an example of them and are faulty by design.

[robgraham]

There's a ruin that I know of in Fife that goes a long way back and was brick built with something like a 4 inch cavity and had long tie bricks holding the two leaves together. Judging by the decay and overgrown trees it must have been built in the 1920's or earlier.

[charles]

I think it all depends on the quality of the build and the cost. Our first house, built 1902 had cavity walls, our current one built 1911 does not.

[Dave Liquorice]

If there is any of the orginal building here, built in the early 1700's, it now has cavity walls as the rubble infill and lime mortar has degenerated and fallen out. Well perhaps not quite that bad but if you open a hole in one of the outer faces the infill falls out...

[meow2222]

its an internal wall

NT