Damp coming in, trying to find source

[phatboy]

Hi, this is a bit complex so ill try and keep it brief!

- Wall had obviously suffered damp when we moved in 2 years ago
- Since then we have had the house externally insulated, new windows installed (pushed to edge of walls), and room re-skimmed.
- Ground level outside the affected area is about 3ft below internal floor level
- House is solid 9" masonry, with no cavity

Unfortunately there is one fairly large damp patch, and also where the fixing points for the old radiator was the paint has lifted, as well as a couple of other areas underneath the window.

Everything to the sides and above the window is dry.

My theory so far is it is a roof defect, and water is getting in and then running down the outside wall of the house (pebble dash) behind the external insulation, and stopping where the old base rail height was, and from there it is coming through the wall.

I have had a roofer out, but I am far convinced he was any good, and the water ingress continues.

I am finding it harder to explain why the spots where old fixings underneath the window into the wall have had the paint lift, through a new layer of plaster.

And advice greatly appreciated, as I am really lost on this one!

 

[KenGMac]

phatboy, good evening.

Have you considered rising damp?

Ken

 

[phatboy]

Thanks Ken,

I knew I'd forget to mention something! There is a damp course present - the house was built in 1959. So I don't think rising damp is likely, but do correct me if I am incorrect....

 

[^woody^]

It's less likely to be roof related if the problem area is below a cill.

It's more likely related to the frame/cill or render below it, or is an issue with internal humidity as is common with external insulation placed over external render.

Does this appear or get worse after rain?

 

[phatboy]

Thanks Woody,

The room shouldn't be very humid as nobody currently sleeps in there and we don't dry washing inside. In fact I have been de-humidifying the room to try and control the big damp patch.

It most definitely gets worse after rain - it only began just before Christmas when there was heavy rain and very strong westerly wind. Since then both have continued, as has the problem.

I've just had a good look around the window from the outside, which has a plastic cill, and everything is very neatly sealed (I used a Mastic Man company), with the only gap being window - cill join.

Please see photo from outside attached. To the left is a small flat-roofed extension, and to the right is the garage.

Thanks again for all the guidance!

 

[John D v2.0]

Got to be the window if it's not the roof, Windows have drainage holes, are you sure they come to outside? It's not uncommon for them to be siliconed up causing the water to fill up and overflow somewhere it shouldn't.

 

[phatboy]

Got to be the window if it's not the roof, Windows have drainage holes, are you sure they come to outside? It's not uncommon for them to be siliconed up causing the water to fill up and overflow somewhere it shouldn't.

I guess they are by far the 2 most likely.... do you think I will need to get the window de-glazed to be checked? Then pour water into the frame and see if it all comes out via the front drainage holes. The window has only been in about 7 months so I'll talk nicely with the supplier as a next step.

Thanks again, and any more experienced view welcome!

 

[phatboy]

Just poured water into the frame of the opening side. There is a visible drainage hole in it, and the water did exit via both of the front facing drainage holes. Could there be more to look at... maybe a screw through the drainage channel or something?

Frustrating!!

 

[nebjamin]

Looks more like you have a drainage channel on that window (rather than specific holes like on the window in the LHS of the pic).

Do the oversills go right to the back of the drainage channel? Is there any chance that water from the drainage holes could be going underneath the oversill (in between the oversill and the existing sill)?

If it has happened more frequently during a strong wind it could be that the wind is blowing water on the sill back into the drainage slot and then going under the oversill, to the edges of the existing sill, then off into the wall?

I had external insulation fitted a few years ago, and was concerned about this exact problem (the fitters just shoved plastic oversills into the drainage channels). In the end I had a separate company replace them all with aluminium oversills (which were much thinner), stuck down with CT-1, and sealed at the edges. Still not ideal - the only 'real' solution IMO is for them to have fitted undersills instead of oversills.

EDIT: This only applies if you have had oversills fitted of course. If the original window sill was long enough to project over the insulation, then perhaps check the edges of the sill when it's raining. Wind could be pushing the water to the edges, where it's entering the wall.

 

[^woody^]

If the center of that damp patch lines up with the widow jamb, then that's a suspect.

 

[phatboy]

If the center of that damp patch lines up with the widow jamb, then that's a suspect.

it certainly is, directly in line on fact. The window company have been to take a look, and wonder if they forgot to silicone the join between the sill and the window.

In answer to nebjamin, the sill is the proper one for the window - the windows were in fact fitted after the insulation (lack of budget before insulating), but your point is similar to the possible issue.

So when the window company come back, they are going to seal the gap between the sill and window. The window is face drained so they think this will be fine.

And then we see if the wall dries out.....!

 

[crank39]

Unless it's been both face drained and had concealed drain slots drilled first by mistake and they weren't sealed up at the factory or on site, it's been known!

The fitters wouldn't of checked for concealed drain holes if they saw it was face drained and just fitted the window, add the fact that they then didn't seal the window to the sill, with rain and wind it's quite possible water is tracking backwards and to the ends but you would see damp patches at each end.

I think it's worth taking the window and sill out, you can inspect the cavity as well

 

[phatboy]

Udd the fact that they then didn't seal the window to the sill, with rain and wind it's quite possible water is tracking backwards and to the ends but you would see damp patches at each end.

I think it's worth taking the window and sill out, you can inspect the cavity as well

That was my thought, it started to happen when there was extremely heavy rain and strong wind against it for a prolonged period.

A couple of months ago i silicone sealed the sill to the window at the front. If there was base drainage then I've created a worse issue, but if there wasn't will that be OK as a solution? It would be a massive pain to remove the window if what I have already done is likely fine.