Gap between plasterboard and breeze block at the loft

[SidDIYer]

Hi All,

My exterior walls have plasterboard dot & dabbed to breeze block, however the gap between the plasterboard and breeze block is open where it reaches the loft.

This means that any heat in this gap escapes into the loft. This can't be good for insulation I'm guessing. Should this gap be filled at the top and if so, what with?

I hope the above is clear! All answers appreciated.

Many thanks,

Sid

 

[mointainwalker]

So what insulation is there in the breeze block ? If the answer is none, then stop worrying, you are going to lose heat either way

 

[SidDIYer]

Surely air-sealing is as important as insulation.

There may not be much in the breeze block, but there is no point having an open gap between the plasterboard and the breeze block. Air from inside the house will find its way out through electrical sockets etc and into the roof space.

Sid

 

[freddiemercurystwin]

In theory there should be a continuous dab of adhesive at the top although that's not all that likely given the standard of building. Its possible the ceilings were boarded first so the wall plasterboard does not go any higher than the ceiling board anyway. You raise a relevant point though that there will be air leakage through the sockets and everywhere else there is a penetration through the board and all of these should be well sealed before you go worrying about the top of the boards. You could block it off with some expanding foam if you can be bothered. That said in theory your loft insulation should be well packed into this area in the loft anyway.

 

[SidDIYer]

In theory there should be a continuous dab of adhesive at the top although that's not all that likely given the standard of building. Its possible the ceilings were boarded first so the wall plasterboard does not go any higher than the ceiling board anyway. You raise a relevant point though that there will be air leakage through the sockets and everywhere else there is a penetration through the board and all of these should be well sealed before you go worrying about the top of the boards. You could block it off with some expanding foam if you can be bothered. That said in theory your loft insulation should be well packed into this area in the loft anyway.

There isn't a continuous dab of adhesive and the wall-board goes all the way into the loft.

I noticed the gap when running cable from sockets in the wall up to the loft where they terminate at a switch. The gap was useful for feeding the cable through!

There's no insulation of top of the gap either, so I will probably fill it with expanding foam once I'm done with the cabling.

Thanks.

 

[mointainwalker]

Surely air-sealing is as important as insulation.

Certainly not in the case of the very small gap you are talking about where the air is not moving.

 

[freddiemercurystwin]

Surely air-sealing is as important as insulation.

Certainly not in the case of the very small gap you are talking about where the air is not moving.

To be fair that's a bone of contention MW, were it a new build built to today's standards every joint and possible gap throughout the whole dwelling would be (or should be in theory) sealed up to minimize air movement through the external envelope. You can feel breezes and air movement all over existing dwellings around junctions here there and everywhere.

I would acknowledge there is little point worrying about it in an existing house built in yesteryear unless the OP attacks air movement everywhere.

 

[SidDIYer]

The house was built in 1996 so I'm surprised it wasn't better insulated & sealed. I have found a few areas that need to be tidied up such as where the toilet downpipe punches through the ceiling.

Not sure if there's any insulation between the breeze block and external wall; if not I will get some cavity wall insulation added.

Thanks.

 

[freddiemercurystwin]

In 1996 the Regs didn't give a hoot about air leakage.

 

[stevethejoiner]

Doubt there is much, if any, air movement rising behind the plasterboard going into the loft. But I agree with FreddyM you can drill a few holes and foam it up.
I am all for air tightness in a new dwelling but in an older property I think drafts are good. The 1996 regs probably don't worry about it because natural air leakage is good for our older houses but now we know its bad for CO2 emissions we can do something about it with new builds.