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Insulating an external 9" solid brick wall on a 1900s terraced house.

Postby Eddie3625 » Sun Oct 11, 2020 6:00 am

In my kitchen off shoot I have a solid 9" external brick wall. The kitchen has been totally stripped back exposing the brickwork and the roof void above the area.

I have looked at the options for insulating it on DIY Doctor and for various reasons I have opted to create cavity wall by installing a stud wall 50mm from the exposed brick.

I have installed a couple of airbricks above floor level in the brick wall to ventilate the cavity and will use rockwooI (left over from a previous job) to insulate between the stud timbers. I will then use visqueen as a vapour barrier (again I have some left over) between the insulation and plaster board.

I have a number of queries that I hope can be clarified by your good selves as:

1. Do I need to install a breathable membrane between the exposed brick surface and rear of the timer stud wall. If so can I use Croma Vent 3 (again left over from another job) that is used on roofs between the batton's and tiles. If yes is it installed the same way as on a roof i.e. printed side facing outward.

2. Would the breathable membrane be attached to the brick wall or the rear of the stud frame.

3. When insulating the roof void above the stud wall, would the insulation go right up to the brickwork or would it be left 50mm short to maintain an airflow between the cavity and the roof void which has roof vents installed.

Hopefully I've explained clearly what I'm hoping to achieve.
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Simply Build It

Postby stoneyboy » Tue Oct 13, 2020 9:35 pm

Hi eddie3625
Suggest the breathable membrane is fixed to the back of the stud wall with printed side facing the cavity. Probably wise to leave a clear ventilation path at the top of the cavity.
There may be times when condensation runs down the printed side of the breathable membrane so if you are not installing a suspended floor you need to lap the bottom against the outer wall.
Regards S
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Postby Eddie3625 » Wed Oct 14, 2020 5:26 am

Cheers, I've ended up doing that plus installing a couple of air bricks
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