Insulating my extension roof as a DIY-er. Joists are 150mm at 400mm centres.
Couple of questions:
1. Spec suggests Kingspan Kooltherm 150mm between the rafters. If the joists are only 150mm deep shouldn't this be an absolute max of 100mm?
2. Total build up is 190mm insulation (seems significant). Would you add 50mm x 50mm batons in line with the rafters allowing 150mm to be fitted (between the rafters) and then add 40mm insulated plaster board on top? Or, to build up the remainder would you use 102.5mm insulated plasterboard? - I imagine these would be massively heavy??
3. Kingspan Kooltherm is around £100 per sheet, other brands are around £40/£50 per sheet, I know the R value is lower (4.5 vs 5.25). However is that difference really significant and something building control will query?
4. Gapotape - I know people use sprayfoam but I am not convinced I would achieve a great finish. Has anyone created DIY Gapotape using UFH edging strip and strengthened foil tape? - https://www.screwfix.com/p/jg-under...5m/340ty#product_additional_details_container
Couple of questions:
1. Spec suggests Kingspan Kooltherm 150mm between the rafters. If the joists are only 150mm deep shouldn't this be an absolute max of 100mm?
2. Total build up is 190mm insulation (seems significant). Would you add 50mm x 50mm batons in line with the rafters allowing 150mm to be fitted (between the rafters) and then add 40mm insulated plaster board on top? Or, to build up the remainder would you use 102.5mm insulated plasterboard? - I imagine these would be massively heavy??
3. Kingspan Kooltherm is around £100 per sheet, other brands are around £40/£50 per sheet, I know the R value is lower (4.5 vs 5.25). However is that difference really significant and something building control will query?
4. Gapotape - I know people use sprayfoam but I am not convinced I would achieve a great finish. Has anyone created DIY Gapotape using UFH edging strip and strengthened foil tape? - https://www.screwfix.com/p/jg-under...5m/340ty#product_additional_details_container
