"BigWallop" wrote in message
...

"David Hearn" wrote in message
...

"BigWallop" wrote in message
...

snipped
ventilated properly to prevent moisture from gathering and then
dripping
through. So to seal the loft space to tight will mean you are
actually
going to create more problems for yourself in the future.

So if I was boarding out 4" insulation, it may not be worth trying to
add
extra insulation (which would require adding extra timber to give the
height, either cross or on top of existing joists) as it would seal the
joists off.

I doubt I'll board it out right to the edges (its pitched on 3 sides,
which
limits access, plus these sides tend to be in the middle of joist spans,
which would be weakest). At the edges then I can just lay extra
insulation
on top.

Thanks

D



But access to the edges doesn't have to be any thicker than the thickness
of
the boards, because you'd slide the boards in to the edges of the space.
Then just fix them down where it is most convenient to do so. If you go
with a flooring grade chipboard system, then the tongue and groove around
the edges of the boards will be enough to hold them together in the short
distances you can't reach right under the eaves. So you'll still
literally
be able to board the loft right out to the edges and make the space
between
the ceiling and the new loft floor into a sealed unit with the existing
insulation still between it.

The reasoning for not boarding right to the edges is two fold. The boarding
is mainly for storage, and storage at the edges would be difficult to access
(plus loading may be an issue when its in the middle of the spans - not
boarding saves me thinking I can put things on it!). The edges form a
significant proportion of the loft area, which means I could do it quite
cheaply if I just boarded the area I would store in. Of course, if the area
I'm boarding is a small proportion, then the insulation benefits from it
wouldn't be so great.

Depending on the cost of the boarding, I may well board it all (or the vast
majority).

The small packs I have already (2 packs of 3) say they're designed for 45cm
spacings. As I've got 30cm gaps (which should work out to be 35cm centre
spacing), these would probably have to have a proportion trimmed off of
each, which would be wasted. I'm hoping to go for large boards and cut them
to an appropriate size for my spacing. This should be cheaper than using
pre-cut boards - shouldn't it? Any idea of the normal size of these boards,
and their relevant costs (18mm thickness - unless I can get away with less
as I'm using 35mm spacings rather than 45?)? I'll look at our new "The
Timber Store" which has recently opened in Guildford - hopefully that'll be
cheaper than B&Q etc.

I've got a jigsaw which I expect I could use to cut down these sheets
(probably using a bar to aid as a straight edge). The other option I have
is to invest in a circular saw - though I'd prefer to keep costs as low as
possible. Do you think a jigsaw would be up to it?

Thanks for everyone's advice - its been very useful!

D