Preventing airflow into cavity wall at wall plate

conor_mc

Had a thermal imaging survey last year and one major issue identified was air flowing into the cavity at the wall plate in the attic, and finding it's way down into the floor underneath skirting boards, etc. The advice given at the time was to look into foam insulation in the attic as the most effective way of dealing with it. However, this has turned out to be a bit pricey, so I'm wondering are there any alternative methods of ensuring the wall plate is somewhat airtight?

House is a detached 2-storey, built circa 1989, internally dry-lined back in 2010 I think (just before we bought the house).

Calahonda52

I don't buy the analysis which is suggesting that the air gets into the cavity in the wall and then finds its way out through a plastered/skimmed wall into the rooms.

Am open to be proven wrong

If you want to see exactly what is going on you need to strip off the first few rows of roof tiles for a small section and go look at the wall plate detail under the felt.

My guess is that the dry lining may be the problem : take off the cover off a room wall vent and post some pictures.Pm me when the pictures are posted as I don't follow stuff here

Lumen

I'd have thought you'd be better off sealing the wall floor junction where the air is getting out, cos surely there are other routes for air to get into your cavity.

conor_mc

Okay, opened up a wall vent, and this time stuck my hand in and turns out the wall is actually 9” hollow block.

Calahonda52

hard to tell from the pictures: is the dry lining flush against the inside face of the wall or is there a gap?

conor_mc

Calahonda52 wrote: »

hard to tell from the pictures: is the dry lining flush against the inside face of the wall or is there a gap?

Hard to tell, but I think there’s a gap of maybe 5-10mm. I can feel a plastic strip there too, could be some sort of spacer perhaps?

Calahonda52

well if there is a gap then the cold air is coming down between the wall and the dry/L because the vent is not ducted out to the outerface of the plaster board.
I have posted extensively about this problem, see below
https://www.boards.ie/vbulletin/showthread.php?t=2057697500&page=2

conor_mc

Calahonda52 wrote: »

well if there is a gap then the cold air is coming down between the wall and the dry/L because the vent is not ducted out to the outface of the plaster board.
I have posted expensively about this problem, see below
https://www.boards.ie/vbulletin/showthread.php?t=2057697500&page=2

Thanks Calahonda, that was one of the other problems mentioned in the survey, and I’m going to address that too with pipe and foam.

PerryB78

Hi All, Sorry to hear of your issues op and I can relate to them as I have similar problems aswell. Our house is 11/12 years old and has caused us nothing but grief and hassle. We had the front of the house pumped with expanding foam and the back and sides were externally insulated but we still have cold air coming in through certain areas and under the floorboards. The attic was spray foamed and the contractor told us that any gaps in the wall plate would be sealed. Unfortunately this is not the case and the problems remain. Our 4year old sleeps at the front of the house, which is north facing, and is suffering very badly with her chest and chronic colds due to this issue. I would be very grateful if someone on here could advise me on someone who I could contact in order to have this issue resolved. Thanks

BryanF

PerryB78 wrote: »

Hi All, Sorry to hear of your issues op and I can relate to them as I have similar problems aswell. Our house is 11/12 years old and has caused us nothing but grief and hassle. We had the front of the house pumped with expanding foam and the back and sides were externally insulated but we still have cold air coming in through certain areas and under the floorboards. The attic was spray foamed and the contractor told us that any gaps in the wall plate would be sealed. Unfortunately this is not the case and the problems remain. Our 4year old sleeps at the front of the house, which is north facing, and is suffering very badly with her chest and chronic colds due to this issue. I would be very grateful if someone on here could advise me on someone who I could contact in order to have this issue resolved. Thanks

What is the houses ventilation strategy?
Assuming it’s hole in wall are all vents open and cavity pipe sleeved?
Is there condensation on inside of windows in the morning?

PerryB78

Yep all have vents, they are all properly sleeved as they were inspected as one of the troubleshooting options years ago and found to be substandard. The problem is definitely with the wall plates as on windy days you can feel air gushing in at particular spots around the house. The windows were also changed and are air tight so its not from them. When the front wall was pumped there was foam coming out from the top of the wall and down from the eaves so this was a sign that the wall plates are non existant or poorly constructed. There is condensation in the bedrooms where people sleep and of high activity i.e the living room

Gumbo

PerryB78 wrote: »

Yep all have vents, they are all properly sleeved as they were inspected as one of the troubleshooting options years ago and found to be substandard. The problem is definitely with the wall plates as on windy days you can feel air gushing in at particular spots around the house. The windows were also changed and are air tight so its not from them. When the front wall was pumped there was foam coming out from the top of the wall and down from the eaves so this was a sign that the wall plates are non existant or poorly constructed. There is condensation in the bedrooms where people sleep and of high activity i.e the living room

Wall plates are for connecting the above joists/rafters. They are not there to close the cavity or stop any foam/insulation from protruding from the cavity.

PerryB78

I didn't know that was their purpose and was under the impression that they prevented air flow into the walls. Its worrying that you mentioned joists as a neighbour from the estate said in a forum that her joists will need replacing to a cost of 10,000 due to the same issue I'm having. Whatever is needed to prevent air from coming down through the walls is non-existant

Wartburg

I´m not long enough in this country to know all Irish building specs into the last detail, but the most existing houses, I surveyed, had a block-on-flat underneath the wall plate. Perfect for closing the cavity but unfortunately a thermal bridge. Houses built over the last few years do mostly have the cavity blocked with cavity closers.
There´s a permanent air circulation in the cavity at any time, doesn´t matter if you have it pumped or not. That´s not a problem, as long as the air won´t get access to the inside of the building. Your air tight layer is the inner leaf and if you have draughts underneath the skirting board, you should take of the skirting and seal the floor-to-wall junction.
In the most cases you´ll be looking to a plain concrete block behind the skirting, because the plasterer thought it would be perfect to finish his workmanship at least 2 inches above the floor level. He doesn´t like to go too far down because of his back, the cleanliness of his trowel and plenty of other creative excuses. And the skirting board will hide this bad job perfect as soon as the second fix is done.
The pitty is, that air infiltrates exactly through such messy details. I could do a complete exhibition with all the photos, I made about.

PerryB78

Wartburg wrote: »

I´m not long enough in this country to know all Irish building specs into the last detail, but the most existing houses, I surveyed, had a block-on-flat underneath the wall plate. Perfect for closing the cavity but unfortunately a thermal bridge. Houses built over the last few years do mostly have the cavity blocked with cavity closers.
There´s a permanent air circulation in the cavity at any time, doesn´t matter if you have it pumped or not. That´s not a problem, as long as the air won´t get access to the inside of the building. Your air tight layer is the inner leaf and if you have draughts underneath the skirting board, you should take of the skirting and seal the floor-to-wall junction.
In the most cases you´ll be looking to a plain concrete block behind the skirting, because the plasterer thought it would be perfect to finish his workmanship at least 2 inches above the floor level. He doesn´t like to go too far down because of his back, the cleanliness of his trowel and plenty of other creative excuses. And the skirting board will hide this bad job perfect as soon as the second fix is done.
The pitty is, that air infiltrates exactly through such messy details. I could do a complete exhibition with all the photos, I made about.

Hi Wartburg, all the skirting boards were removed, spray foamed and sealed with air tightness tape but the air is still getting down into the house under the floor boards. When the wind is gusting outside, within a couple of seconds you can feel the draught coming in at various spots In the house. What is the best way to close the cavity off? And can anyone recommend someone who can do this?

Wartburg

PerryB78 wrote: »

Hi Wartburg, all the skirting boards were removed, spray foamed and sealed with air tightness tape but the air is still getting down into the house under the floor boards. When the wind is gusting outside, within a couple of seconds you can feel the draught coming in at various spots In the house. What is the best way to close the cavity off? And can anyone recommend someone who can do this?

When you say floor boards do you mean ground floor or first floor level?

PerryB78

Wartburg wrote: »

When you say floor boards do you mean ground floor or first floor level?

First floor level, there are no floorboards downstairs as the house is at ground level

Wartburg

I was expecting first floor level, but just wanted to be sure. You have the typicall weak detail for air tightness - timber joist ceiling and nobody took attention to make this part of the house air tight. Can you get access to the floor boards, e.g. by lifting carpet?

PerryB78

Wartburg wrote: »

I was expecting first floor level, but just wanted to be sure. You have the typicall weak detail for air tightness - timber joist ceiling and nobody took attention to make this part of the house air tight. Can you get access to the floor boards, e.g. by lifting carpet?

Yes I can lift the carpet and when I do I can feel some bad draughts coming through some of the gaps in the floorboards

Wartburg

PerryB78 wrote: »

Yes I can lift the carpet and when I do I can feel some bad draughts coming through some of the gaps in the floorboards

Option no.1 - tape all these joints between the floor boards with air tight tape. The air infiltration in the ceiling will continue and might appear through other gaps/ penetrations like recess lights downstairs or around heating pipes.

Option no.2 - lift the floor boards adjoining to the external walls and seal the area in between every floor joist. Bigger voids can be filled with air tight foam and a finishing air tight cover, e.g. by using air tight paint, prevents the access of draughts in this area for the future.

PerryB78

Would there be a way of stopping the air getting in at the top of the walls? Stopping it at source so to speak. Seems more doable than option 2

Gumbo

PerryB78 wrote: »

Would there be a way of stopping the air getting in at the top of the walls? Stopping it at source so to speak. Seems more doable than option 2

Close the cavity?
Could be extensive invasive works.

BryanF

PerryB78 wrote: »

Would there be a way of stopping the air getting in at the top of the walls? Stopping it at source so to speak. Seems more doable than option 2

Yes
Lift off bottom few rows of roof tiles/slates, remove battens, fold back felt, and close cavity as appropriate with suitable materials based on site assessment

Wartburg

PerryB78 wrote: »

Would there be a way of stopping the air getting in at the top of the walls? Stopping it at source so to speak. Seems more doable than option 2

No chance to stop it at source unless you find a way to eliminate the cavity completely, e.g. by pouring something into. But there´s no technology available as far as I know.
If you block the cavity on top, you still have to expect a continuing circulation of air within the cavity.

Bryan´s suggest would be the right way for a dormer, to prevent air infiltration through the crawl space by creating a wind tight barrier at the eve level of your roof structure.

PerryB78

BryanF wrote: »

Yes
Lift off bottom few rows of roof tiles/slates, remove battens, fold back felt, and close cavity as appropriate with suitable materials based on site assessment

What kind of tradesperson would be qualified for this type of work? Its seems to be the course of action that I would like to undertake. Alternatively, Could the fascia and soffit be removed to check where air is getting in?

BryanF

PerryB78 wrote: »

What kind of tradesperson would be qualified for this type of work? Its seems to be the course of action that I would like to undertake. Alternatively, Could the fascia and soffit be removed to check where air is getting in?

A carpenter and air-tightness tester

Just sort out the ventilation strategy at the same time

Who2

The tops of the cavity can be closed easily enough by foaming down into them from the crawl space. Most air getting into people’s cavitys are from around the windows . Be that along the sides and under the drips, other usual spots are in around vents that aren’t properly lined and around pipes that haven’t been filled out properly around.