Garage conversion - using Celotex GA4000

14 Jan 2011
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United Kingdom
Hey all,
I'm starting the walls in my garage conversion today. i've got Celotex GA4000 boards and I'm following the advice on the Celotex website (the pdf linked form here)
It says:
Upgrading existing walls: U-value requirement is 0.30 W/m²K
When insulating a 103mm brick wall, first fix a breather membrane against the wall, then fix Celotex GA4050 to the wall by over battening with 25mm x 50mm battens at
600mm centres. This is fixed through the battens and Celotex GA4055 into the wall using proprietary fixings. The joints of the insulation are then taped using Celotex Insulation Tape and the perimeter edges sealed with mastic, thereby providing a vapour control layer (VCL). Finally, fix 12.5mm plasterboard to the battens. The above installation will provide a U-value of
0.29 W/m²K.

Two quick questions:
Should the 25x50mm battens have the 25mm side or the 50mm side flat on the board?
Should the tape be on the side facing into the room or the side facing towards the wall?
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