Damp problem

[John]

Okay - you people have always given me good advice (not necessarily advice I want to hear but good all the same) so try this one

3 years ago we had an extension built. A single storey extension which lean to the front of the house and has a normal /\ type roof at the side of the house. When the weather is damp/humid there's a smell of damp in the house particularly in the new bits. What could be causing this?

To give more information. The flashing on the extension looks okay but what do I know... On the front it goes into the wall as normal between bricks. On the side of the house though the builder used a power tool to cut a line in the bricks and then put the flashing in there. I wasn't worried about this at the time as I'd seen it in lots of other houses around here. However now I'm not so sure. Where the extension joins on the side there is definitely a leak as small marks have appeared on the beam separating the house from the new part. However there is no sign of water damage at the front of the house although it still smells and a dehumidifier on for a few hours gets rid of the smell.

Any ideas folks?

Thanks

[TMC]

Presumably its worse when its pi**ing down although you do not mention this?

Have you checked if there is damage to the flashing?

Is there movement of the extension away from the house?

What sort of beam is it (could the marks be caused by condensation on it)?

Is there adequate ventilation in the room at all times?

Tony

[Tanner-'op]

John,

It is possible that the lead flashing is pushed deep enough into the mortar joint and and not properly wedged and sealed (and is certain that there are no cavity trays fitted see link

) which means water could be permeating down the external of the house into the now internal wall of the extension (if you can picture what I am trying to say) and causing the musty smell and staining.

This is just a guess having not seen the problem.

Tanner-'op

[Tanner-'op]

John,

Correction to:

"It is possible that the lead flashing is pushed deep enough".

That should read "is *NOT* pushed deep enough... (damn fingers again)!

Tanner-'op

[meow2222]

Sounds like you need a good look round to see where water's getting in. Hope youve got access to the loft.

NT

[John]

If only - the ceiling at the front part of the house slopes with the roof so no way in there. The side part of the extension is a flat ceiling with no access. Both the architect and the builders "persuaded" me I didn't need access as it would spoil the look of the thing. I'm tempted to put a hatch in there anyway - extra storage and find out where the water's coming through

[John]

Thanks - I know nothing about lead flashing - except that I've not had a problem with it before. I can only assume it's the flashing causing the problem as it's most likely to be where the house joins on to the original.

Can't see on that site. What are cavity trays? Is it possible they're missing so water is dripping down through the cavity into the extension.

[John]

Actually no - the smell is worse when the weather is humid. The damp patches are only visible in a small part of the extension towards the lower part of the roof

it looks okay - no cracks/holes. Whether it's fitted properly or not I'm not totally sure of what I'm looking for there so may be not.

no

it was a dirty great metal thing that I couldn't even lift one end of

We tend to have windows open most of the time. Plus at the moment we haven't got a door fitted to that room - it's on the list of things to do...

[meow2222]

Adding a hatch is not too hard, but is one of those jobs that takes longer than it should considering the result obtained. You should get in ok without altering the ceiling timberwork, but a full size loft hatch generally requires cutting a joist and resupporting it with 2 cross pieces.

NT