Insulating a new cavity wall

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Hi

Just been doing some reading and wondering if anyone can confirm my approach. I’m bricking the front of my garage up (half height with a window above it) for my garage conversion. It’ll be brick on the outside block on the inside with a 100mm gap.

Plan is to completely cover the inner wall (inside the cavity) with 70mm PIR and leave a 30mm gap between the PIR and the outer wall.

Do I need to leave a gap where the Pir meets the wall running perpendicular to the wall being made? How do you work Pir round wall ties?

The new wall will be about 2.1 metres wide.

Appreciate any advice.

Many thanks.
 
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You use 450mm wide stuff to go between the ties. You don't need a gap - Ideally you should continue the cavity.

Thermalite type blocks on the inside for extra insulation..
 
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You use 450mm wide stuff to go between the ties. You don't need a gap - Ideally you should continue the cavity.

Thermalite type blocks on the inside for extra insulation..
I was going to get the big sheets of it so I guess I can just cut it to size. its only brick and block on the facing wall. The other external wall is single skin and i've not got the width to have another block built up so I'm battening it and insulating it.

Whats the best way of attaching the PIR to the inner wall to maintain a gap to the exterior wall and prevent moisture transfer?
 
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I was going to get the big sheets of it so I guess I can just cut it to size. its only brick and block on the facing wall. The other external wall is single skin and i've not got the width to have another block built up so I'm battening it and insulating it.

Whats the best way of attaching the PIR to the inner wall to maintain a gap to the exterior wall and prevent moisture transfer?
Probably fine as long as you can match up the cut edges? Or can cut a very straight edge.
I would probably foil tape the joints too if its accessible.
 
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Probably fine as long as you can match up the cut edges? Or can cut a very straight edge.
I would probably foil tape the joints too if its accessible.
Yeah I’ve got some foil tape ready to go. Should be fine as we’ve built the block wall and will be doing brick from the front so should work well.
 
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With board insulation, spacing the ties is more critical, otherwise the boards can stick out all over the place.

We would space the ties to correspond with the end and middle of the board, so that's every 600, and if the end one is not spot on, you need two close together - one for each board ... likewise on the DPC.

The alternative is knocking nails in with a clip to hold the board, but sometimes the nail don't hold.
 
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With board insulation, spacing the ties is more critical, otherwise the boards can stick out all over the place.

We would space the ties to correspond with the end and middle of the board, so that's every 600, and if the end one is not spot on, you need two close together - one for each board ... likewise on the DPC.

The alternative is knocking nails in with a clip to hold the board, but sometimes the nail don't hold.
Thanks. I’ve just ordered 2.4x1.2m kingspan 70mm. Assume that’s fine to cut down and use instead of boards?
 

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