Help with moisture in attic

Hi,

Mid-terraced wooden framed, standard construction house, built c. 2006.

Noticed a small stain on bathroom ceiling in corner near window (see [broken link removed]) a few days ago. Bathroom is ventilated through wall extractor and no problem with mould or mildew.

I went into the attic above the area where the stain has appeared, which is right at edge of roof just before eaves. When I pulled up the insulation I noticed a small amount of condensation/moisture trapped underneath the plastic covering the plasterboard ceiling, just above the area with the damp patch.

There are no signs of leaks or condensation in the attic (apart from the above) and no condensation or dampness on underside of roof.

What's strange is that the moisture is only underneath the plastic covering the plasterboard and not on top of it, meaning that the moisture seems to be coming from below (i.e from the bathroom) and not from above (roof).

Is this moisture/condensation likely to be a sign of something more serious or could it just be the result of the extremely cold winter we’ve just had?

I'd appreciate if someone could take a look at the attached photos and give a suggestion on what the problem might be. My 5-year Homebond cover for water ingress will be expiring over the next few months so I want to start the claims process if this turns out to be a structural or other serious problem.

[broken link removed]

[broken link removed]

Thanks.

is the plastic only covering the plasterboard slab or is it all along the gap between the joists..

the use off a dehumidifier might be of use to you to help with this issue they are now widely available from most builder providers or good electrical stores

jab1 said:

is the plastic only covering the plasterboard slab or is it all along the gap between the joists..

Click to expand...

Thanks for the reply.

As far as I can tell, the plastic seems to be almost shrink wrapped right around the plasterboard so I presume it goes under the joists as well.

It just seems odd that there's no other sign of condensation or moisture in the attic space.

have no idea why plastic would be anywhere near the plasterboard.the roof should be well vented from the vents in the soffit.. so no reason why moisture should be in the attic. i have seen on a few occasions where the extractor fan from the bathroom is vented in to the attic,whuch is a big no no and that caused moisture up there... buti would recommend getting either a roofer/carpenter to have a look at it,just to be on the safe side,a dehumidifier is only masking the problem not solving it.

rebeller said:

[What's strange is that the moisture is only underneath the plastic covering the plasterboard and not on top of it, meaning that the moisture seems to be coming from below (i.e from the bathroom) and not from above (roof).

Click to expand...

Not really that strange if theres a shower in the bathroom. Most shower extractor fans do a fairly dismal job at removing steam from a bathroom. If you have plastic over the plasterboard the moisture cannot pass into the attic and be removed by natural ventilation. The attic will be colder than the bathroom causing the water vapour in the bathroom to condense on the underside of this plastic sheet.

I do not see the point in having plastic over the plasterboard to begin with. It serves no useful purpose. You do not require a vapour barrier in a ventilated attic.

I agree with jab1 about the dehumidifer. In any case you are not supposed to use a dehumidifier in a room with a shower and you will not have an electrical socket in the bathroom.

Despite many different attempts to solve the problem of condensation in the bathroom the only one that we find that works properly is to leave the window open.

Modern plaster board has a foil bonded to it which acts a a vapour barrier, possibly they tried to do it with plastic sheet which is not the same.

I have a similar leak which is coming from the chimney area (flashing) ... water seeps down and runs inside the felt, and escapes through a tear onto the floor of the attic.

The dehumidifier is a good stopgap suggestion. It's possible to run a pipe out of it for continual drainage if you can find a suitable exit for it.