Mouldy gap near window frame

[6ply]

I'm looking for collective opinion on what to do with this problem. If you look at the photos you'll see there is a gap between the UPVC window frame and plasterboard. On windy days there is a significant draught through this gap and as you can see it is prone to developing mould. The wall construction is insulated timber frame with brick cladding.

One of the previous owners built the patio level up way too high but I've reduced that to almost 2 bricks below DPC. I would have liked to have gone further but other levels prevented that. Further away from the window it is at least 3 bricks below DPC. I also re-pointed some brickwork around / under the window as it had either crumbled away or was never done properly in the first place. I also added some sealant externally in the hope it would reduce wind / damp air entering the cavity. It does seem drier.

I checked moisture in the plasterboard today (and it has been VERY wet and windy all week) and it seemed good - just 15%

Before filling any gaps with sealant / expanding foam / other suggestions, do you think I should remove some plasterboard to check for more significant problems? e.g. rot in the timber frame. Or should I remove a small square of plasterboard, fill any void behind (with what?) and make good? My past experience of using sealant at this junction has not been good - it has gone mouldy and failed. However, that was prior to reducing the patio height and filling external gaps, so that may have solved a problem. I would not want to completely fill the void between external brick cladding and internal plasterboard as that could act as a bridge for moisture to travel across. So what would be considered best practice?

Thanks.

 

[voipio]

A look with a thermal imaging camera would show that corners of plasterboard walls, with outside facing wall behind, are generally the coolest parts of internal walls, and window/patio door surrounds also tend to be cooler. During the recent gusty weather, I checked the indoor barometer, and saw it repeatedly fluctuating by about a millibar, which seems quite a lot. The outside pressure would be varying by more than that. In situations like this, the house would be "breathing" in and out through all the gaps. As the house breathes in, outside air enters, cooling the surfaces it encounters, and as it breathes out, warm humid air from the house goes past those surfaces, condensing the moisture out if conditions dictate. Sealing the gap between wall and frame with a flexible sealant will probably be sufficient to reduce, or even stop the condensation, and the resulting mould.

 

[6ply]

A look with a thermal imaging camera would show that corners of plasterboard walls, with outside facing wall behind, are generally the coolest parts of internal walls, and window/patio door surrounds also tend to be cooler. During the recent gusty weather, I checked the indoor barometer, and saw it repeatedly fluctuating by about a millibar, which seems quite a lot. The outside pressure would be varying by more than that. In situations like this, the house would be "breathing" in and out through all the gaps. As the house breathes in, outside air enters, cooling the surfaces it encounters, and as it breathes out, warm humid air from the house goes past those surfaces, condensing the moisture out if conditions dictate. Sealing the gap between wall and frame with a flexible sealant will probably be sufficient to reduce, or even stop the condensation, and the resulting mould.

I tried that in the past (albeit before I addressed the problem of pointing and patio level) and the dampness persisted. Maybe I should try it again.

 

[Welderpaul]

Neatly cut the plasterboard off and give yourself chance to see what the problem is behind.

It could be anything really, bridged/no vertical DPC, cold bridge, rising damp, failed silicone, water tracking off the end of the cill, or just condensation.

The black marks on the inside just above the timber cill is probably the true entry point?


I ripped out a yard yesterday, the yard surface was slightly higher than floor level inside, and sloped towards the house, so everytime it rained the floor and walls become damp. The skirtings and laminate could be rolled up and put in a bin bag
The original Victorian yard surface was still underneath. A load of work to deal with someones lazy bodge but the house was cheap

 

[6ply]

Neatly cut the plasterboard off and give yourself chance to see what the problem is behind.

It could be anything really, bridged/no vertical DPC, cold bridge, rising damp, failed silicone, water tracking off the end of the cill, or just condensation.

The black marks on the inside just above the timber cill is probably the true entry point?

This may be overkill but would at least give me peace of mind. Thanks for the suggestion.

 

[voipio]

Are there any weep holes, or weep vents, in the brick course above the damp course, to allow the runoff of any water that gets behind the brick wall?

The vents above our back door were dripping well during the recent heavy rain, which was being blown directly onto the wall above. The vents above the damp course were also showing signs of water coming out of them.

Having a close look using a good light, at the inside wall and patio door surrounds after heavy rain, might show up water that might be getting in. Look in particular at the channel that sits next to, or on top of the inner wooden sill.

 

[6ply]

Are there any weep holes, or weep vents, in the brick course above the damp course, to allow the runoff of any water that gets behind the brick wall?

The vents above our back door were dripping well during the recent heavy rain, which was being blown directly onto the wall above. The vents above the damp course were also showing signs of water coming out of them.

Having a close look using a good light, at the inside wall and patio door surrounds after heavy rain, might show up water that might be getting in. Look in particular at the channel that sits next to, or on top of the inner wooden sill.

Now you mention it, no there aren't any weep holes. It wouldn't be difficult to fit a couple of perp-end ventilators if that's what it needs.

 

[6ply]

Interesting, as I don't have a single one in the whole house (bungalow).

 

[6ply]

Also found these. About as unobtrusive as they could get.

 

[500e]

Drain holes in door frame channels

 

[voipio]

Now you mention it, no there aren't any weep holes. It wouldn't be difficult to fit a couple of perp-end ventilators if that's what it needs.

Drill a hole to the depth of the brick, in the vertical mortar (perp joint) between the bricks, just above the damp course, and it'll soon be evident if there's water behind there. Maybe insert something like a pipe cleaner, or a rolled up piece of paper into the hole, and see if it comes out damp.

 

[rtcosic]

I had that symptom in the same place in my previous house - traditional cavity construction.

As @voipio suggests I am sure my issue was caused by lack of weep holes at DPC level and also lack of weep holes above the lintel. I removed sopping plaster and chased water ingress around the frame several times without solving the issue.

The weep holes weren't a BC requirement in 1989/90 when the house was built and was made worse by retrofitted cavity insulation.

 

[6ply]

Mine was built sometime in the 80s. I'll try the weep holes when it's not raining all day long!

 

[6ply]

I drilled a test hole outside, just above dpc. No water in cavity.

 

[voipio]

Might need to wait until it's chucking it down against the wall to do a proper check. The weep holes here soon stop when the rain stops.

 

[6ply]

Might need to wait until it's chucking it down against the wall to do a proper check. The weep holes here soon stop when the rain stops.

Thanks. I'll bear that in mind.

I've now removed some of the plasterboard and internal sealant around the bottom of the window frame. It looks much better than I had anticipated. There's no rot - it's basically dry - and it looks like you were probably right about air being sucked in/out and condensing in this area.

 

[6ply]

If you look at this photo you'll see the end of some coat hanger wire entering the gap. I can poke this wire straight down below DPC level.

Do I need to leave a channel of some sort to allow any condensation / ingress to drip down into this void?

 

[6ply]

Would it be a good idea to get some sealant into this gap (marked red) before replacing the plasterboard?

I will also need to seal this gap (green). Can anyone recommend suitable sealant? It will have to be mould resistant - unlike the previous one.

 

[roofman]

Must be gap free so your not introducing cold air into that corner, i would fill the void with expanding foam myself.

 

[6ply]

Must be gap free so your not introducing cold air into that corner, i would fill the void with expanding foam myself.

Thanks for your suggestion. I'll see what I can do, but I won't be emptying the whole can down there.