Insulating loft with 7cm joists

[Markjmj]

Hi

Can anyone suggest an insulating material that I can use under the floorboards in my loft that will meet building regs? The joists are only 7cm deep. I can increase this to 10cm but its only a small loft and I can no way get to the 27cm of glass wool required by the regs. (Well I can but there would be a tiny floor space left!)

thanks

 

[Static]

Lay the extra 200mm over the joists at 90' to the way they run.

 

[shenks]

under the floorboards in my loft

Does this mean you have boards directly on your ceiling joists? This would suggest you can't achieve building regs compliance even before you start thinking about insulation. The ceiling joists are there to hold the ceiling up - not to support a floor (dead load) and additional items (imposed load).

There are insulation materials available (e.g. Kingspan, Celotex) which are easier to work with and 'sometimes' less builky than rockwool but it all depends on the individual situation and you would need to consult BC.