Attic Conversion

Triangle

We recently had our Attic converted and I was just wondering if the insulation was done properly.

1) on the ceiling (between rafters) the builder put rock wool/Mineral wool between the rafters and then put up plasterboard to cover. Should there be some breathable layer or gap between the insulation and felt/plasterboard?
I'd been reading a few websites and the exact way this should be done is a bit confusing......

2) the walls of the conversion are vertical. The insulation has been put between the trusses and string has been tied across the backs of the trusses to keep the rock wool/mineral wool in place.(Plasterboard has been put up on the front of the trusses). Is this standard? it doesn't seem like a very good way of insulating side walls.

Thanks in advance,
Trig

sundula

is the string running along the back of 'walls' on the perimeter of the attic ?

gsxr1

there should be 300mm of fiberglass insulation (or equivalent in kingspan) with a 50mm gap between the insulation and roofing felt. The 50mm gap is very important as it prevents condensation . If you have not got the depth in your rafter to accomadate all that insulation you would screw up PU board and foil tape the joints.

Between the plasterboard there should be a vapour barrier. Basically a plastic sheet with all joints taped up. This would have been stapled to the rafter before the plasterboard went up.

If he used foil back plasterboard you might get away without the plastic.. Dont quote me on that. Its best to have both.

You must also have a 4 " vent in the room.


If the string keeps the insulation in place then I guess it works. I would hammer 4" wire nails into the sides of the studs to catch the insulation .

Triangle

Sundula,
Yeah, behind the walls, in the crawl space. The string 'kind off' keeps the insulation in place, but it's not 100% against the walls. gravity seems to be taking it's toll on it.

gsxr1,
The rafters are about 150mm and seem to be packed top to bottom with insulation (i.e.no gap) should I be (more) worried? get an engineer to check?
is the condensation a big issue?
The plasterboard was foil backed though.....

thanks for the replies so far,
Trig

Freeranger33

Sounds Very Shody

Best Way to Convert and attic is

100mm insulation between the Rafters with an air gap of 50mm Base on 150mm Rafters
if rafters smaller decrease the Insulation size to leave a 50mm air gap
Then When Slabbing use a 30mm Composite Board it has 21mm inslation on the Back of the plasterbaord.
or the other option is Super ten from U Value

Question is your house a Bunglow or a 2 storey house
AS after this work odes it meet fore regs ?

Triangle

It's a two story, and the work did not meet regs but we knew this before going ahead with it.

Tbh, it sounds like the builder just did an old fashioned job of it without worrying about the best way to do it.

I'm happy enough just knowing that my roof isn't going to warp - after that i can live with it.