Hi, we are building our flat roof extension with web joists. The structure is a cold roof with 150mm pir then a minimum of 50mm insulation with insulated plasterboard (25mm)under the joists.
The architect has said that pir should infill the gaps in the web joists as much as possible up to the level of the main insulation. Makes sense to me but our builder thinks not needed, I don't think they fancy the fiddle job it will be. He has suggested putting rockwall in there instead. Its not going to be perfect as there still going to be gaps for the thickness of the metal section but every bit of insulation counts with gas prices.
I don't think we want full fill as the web is going to give some cross-area ventilations.
Has anyone done similar or got any suggestions please? Any advice at all would be really appreciated.
The architect has said that pir should infill the gaps in the web joists as much as possible up to the level of the main insulation. Makes sense to me but our builder thinks not needed, I don't think they fancy the fiddle job it will be. He has suggested putting rockwall in there instead. Its not going to be perfect as there still going to be gaps for the thickness of the metal section but every bit of insulation counts with gas prices.
I don't think we want full fill as the web is going to give some cross-area ventilations.
Has anyone done similar or got any suggestions please? Any advice at all would be really appreciated.
