"Wordy" wrote in message
om...
Hi,

I am interested in boarding over part of my loft area, in order to
increase the
amount of storage space in our house. My question is concerning
insulation.
The joists on the floor of the loft are 3x2, thus if I put boarding
directly
on to them, I can only have a maximum of 3" of insulation (I think I
should have a lot more ?!) Should I screw some lengths of 3x2 or 4x2
at right angles to the joists, place extra insulation in the spaces.
and then board on top of these ? I know I will lose a small amount of
height, and it will cost a bit more, but the house is a 30's semi
(with no cavity walls) so I would like to get the loft fairly well
insulated.

Would I also need to put in some form of damp membrane ? The roof is
not felted, so there is quite a bit (!) of air flow through the roof
space. I was not going to board over the complete area, so would it be
ok to not put down a membrane on the warm side of the insualtion ?

Any comments appreciated..

Paul..

First comment is to check your floor loadings - 3 * 2 won't carry much
weight.
[By that I mean that it wouldn't carry the kind of load you would put on an
average floor - so if you plan to stack heavy things and walk on it as well
you could be in for a surprise]
The building regs. carry tables which show maximum load for cross section
and span and spacing for beams.

I don't know if additional beams at right angles will increase the load
bearing capacity by spreading any load, or just count as additional weight
on your original 3*2 beams/joists and reduce the amount you can store. I
assume that of you screw at every joist this may provide a more rigid
structure.

If you screw additional joists along the top of your existing ones (e.g. add
another 3*2 to make a nominal 6*2 joist) that may help but it won't be as
strong as a single 6*2 joist.

For loft conversions they put in a new load bearing structure - but this is
way OTT for a bit of extra storage :-)

Alternatives are to use more efficient insulation e.g. Celotex between your
3*2 joists but this is likely to be expensive.

All very imprecise, I am afraid.

Cheers
Dave R