Insultation in the rafters. Is there an official guide?

[joewa]

I am beginning the first stages of insulating the loft at rafter level, with a view to converting the loft. This would also add an some extra insulation for the time being.

The loft is already insulated, although poorly, at joist level. When the floor is replaced with proper joist this insulation will be replaced.

I am looking at solid insulation like celotex to fit between the rafters. The rafters are only 85mm deep.

Question is how much ventilation space should I leave and can I get away with simply putting thin insulation in between the rafters. I have read that it has to be 100mm minimum.

I must stress that this will not be an official loft conversion, so the house will become a "2 + 1" bed house.

Any help would be much appreciated.

Thanks

 

[noseall]

I must stress that this will not be an official loft conversion, so the house will become a "2 + 1" bed house.

I'm afraid you need to clarify what a 2+1 bed house is? We ain't talking 2 seater sports cars here now. As far as building regulations are concerned, as soon as the stairs are fitted then regulations apply.

 

[joewa]

I won't be using a permanent staircase so it won't be an official room. Hence 2+1. A term estate agents use. I will be addressing means of escape though.