Finding the cause of damp

pink_petal

Hi

Hopefully someone on here has some experience of this! About a year ago we noticed a really small damp area at the top of our bedroom wall. The wall is an internal wall between two bedrooms so we've been baffled as to why it was damp...the other bedroom wall isn't!

It kind of comes and goes so we ignored it but recently it seems to be constant and I think we need to do something about it...but we have no idea where it's coming from so don't know who to call out to look at it! We had a look in the loft and there was no damp at all. We left paper and cardboard over the area above where the damp is but when we checked it (even after very heavy rain) it was completely dry. Could the water be bypassing the loft somehow? We are thinking maybe a roof issue and the water could be coming down the wall cavity but we feel a bit daft in case it isn't!

Any ideas?

DRP

What do you mean by damp? Mould growing (probably condensation) or a damp stain?

What roof style / construction above the wall?

Can you get into the loft, move around, view all areas? i.e. is insulation in the way?

Any water pipes/tanks in the area?

THis time of year a leak in the loft will dry out really quickly - we're having trouble tracking down an intermittent leak in our loft due to this issue.

pink_petal

Hi

Thanks for replying!

No mould growing, just a damp stain which started really small but has now spread. It looks quite patchy so not one massive patch.

We have a tiled gable roof, not sure about the kind of tiles though.

We've been in the loft numerous times looking for a leak. We can move around and get into all areas. The only thing we've not done is lift any floorboards or start looking into cavities which is why we figure that must be where the problem is. There's an ancient water tank up there but it's not been in use for years and it's completely empty.

We're in Scotland so have had some pretty heavy rain and have checked the loft before, during and after having days of torrential rain, the loft really is completely dry.

After being baffled for months my dad suggested it could be coming in the roof/chimney and down a wall cavity but I just wanted to check if that was even possible or if there were any other possible causes before we pay an expensive call out charge for a roofer only to find it isn't that at all! We don't have a big enough ladder to get a good look at the roof ourselves!

Hoploz

It could be coming from a small gap not directly above it. Water will find its own way through and it may not be in straight lines, it can travel along horizontally along a joist, for example, before going down through a tiny gap into the wall.

Are there any air bricks / vents on the outside at the top by any chance?

What about guttering, there could be a blockage where a bit overflows and spills onto the wall behind it. This might happen when it rains heavily. Ut take time to seep through so it isn't noticeable when the rain actually happens

ariba10

Google" Condensation " and see if there are any similarities?

missprice

If it's any help, water rarely runs in straight lines.
We had a damp patch on a beam away from the bay window.
It's now fixed by lifting the bay roof covering fixing a channel that takes water away. The channel!was warped slightly. The water only ever came in when it not only rained but was also windy.
The water was pushed uphill with the wind and came out over the top of the beam ,several feet away from entry point, we looked for ages for a leak somewhere else in the roof 😗

pink_petal

Thanks everyone, lots to look into!

We actually do get a fair amount of condensation on our windows, despite opening the windows frequently and we also have vents which are open constantly. I didn't realise that condensation could actually affect a wall and that it didn't necessarily have to be all black and mouldy! Some of the pics do look a bit similar to what we have...although so do pics when I google other types of damp!

We're going to investigate the condensation option further and a builder we have in doing other work for us has said he'll bring his biggest ladder and have a look at the roof for us (free of charge) so hopefully we'll get to the root of it one way or another!

Thanks again for all the suggestions! Very helpful!

PP x

Grenage

Condensation is a bit unlikely on an internal wall, isn't it?

ariba10

Grenage wrote: »

Condensation is a bit unlikely on an internal wall, isn't it?

Why on earth not?

Hoploz

Damp patches don't always go mouldy. We had a leak from an upstairs flat bathroom, leaking a tiny amount for over four years and although our wall is clearly very wet it only showed signs of mould on one occasion (3 years in) and after I wiped it down it didn't go mouldy again.

(Finally the leak was found a couple of months ago - if only they had investigated properly earlier during the four years I was complaining!)

Grenage

ariba10 wrote: »

Why on earth not?

Well condensation normally occurs on colder surfaces, such as windows and external walls.