8 Nov 2007
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United Kingdom
Should i fill this void with rockwool insulation or insulation board? (this is the front of the roof and the back of the facia board), I am putting in 150mm board insulation in between the rafters but don't think it will be easy to to slide down. its a non vented roof as I have a breathable membrane.

Also when I fit the first layer of insulation do I staple on my VCL over the rafters and then fit my second layer of insulation board over that or does it get stapled to the battens and then Plasterboard, Thanks

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Really your cavity insulation should meet your roof insulation.
Have you counter battened the joists?
Have you counter battened the joists?

The only battens fitted at present on the joists were for the roof tile.

Most of the top of that wall is made up of the steel lintels as I can fell the top of them and the gaps that i can put my had in i can feel the rockwool insulation but it does need topping up.
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Is it to be a vaulted ceiling then? Is it partial fill or full fill insulation assuming traditional cavity walls?
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Yes but you need a path for any water to run. If those are 150mm joists then ramming 150mm of insulation will mean it's tight against the battens.

Like this
The rafters are 195mm and the cavity wall is a 100mm with rockwool and the ceiling will be vaulted, its a non vented roof and in my specs it does not tell me if its a full or part fill, but they did mention using 165mm insulation so I guess a part fill is ok.
Think I will run a bit of the 100mm rockwool I have left in there so it meets the cavity insulation and level with the roof insulation.

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