"David Hearn" wrote in message
...
I'm planning on boarding out our loft so we can store some boxes up there
easily. The joists are 4"x2" with a 30cm gap between them. It's a 1930's
semi BTW. The joists appear to be half the length of the house, with them
meeting (and joined I assume) over the middle wall of the house. This has
a
(measured from outside wall to middle wall) 11' span at the front of the
house and a 13' span at the back of the house.

The way the loft and roof is layed out, there's a large centre part which
would be best for storage due to height of roof and ease of access into
the
loft. This centre of this area is over the middle wall.

Any idea what sort of loading may be possible? I would prefer not to have
to add anything extra to the joists if I can help it. It shouldn't be
used
for anything more than storage of boxes, and not terribly heavy ones at
that
(as I have to carry them up the ladder!).

I've heard that 3x2 flex a lot and therefore aren't really suitable for
boarding directly out onto, but does the extra 1" make much difference
with
my 4x2's? Obviously, thicker joists would allow for more insulation -
but
at the moment, I'm really looking for doing it with as minimal work (ie.
cost) as possible, and therefore really want to know about the loading of
what I've already got.

http://www.hmso.gov.uk/si/si2000/20002531.htm

This contains the tables which calculate acceptable loadings.

My loft has 4*2s on 14" (36cm) spacings and longest span of about 22' -
there is a stud wall under this but I don't know if it is load bearing at
all - certainly the lounge runs front to back without any load bearing wall.

There is a beam above the joists and at right angles but I don't know if
this is connected to each joist and carrying part of the load.

The house is 1930's and the loft was part boarded when we bought it.
I have added more boarding for more storage.

The loft seems fine with boards - no sign of the ceiling sagging etc. - but
on the other hand the next door neighbour had someone in to do engineering
drawings for a loft conversion and he had an attack of the "Never seen one
like that before - I suggest you move all your stuff round the edges to
reduce the loading."

I am pretty sure the beam sizes are well outside current building regs. for
flooring, but then again the regs. allow for cast iron baths etc.

Seems O.K. for us but then we could be lving on borrowed time.

As for increasing the thickness of the joists, I suspect you can't get the
extra thickness over the side walls and under the existing roof. This is why
loft conversions tend to install a new, independant load bearing structure.

I presume that if you halved the spacing i.e. inserted a 2*4 between each
current joist to go down to 15cm spacing you would be O.K. but this is a
very expensive option given the price of timber nowadays.

HTH

Dave R