"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.


4"x2" and 30cm (assuming your mix of units is correct)

Maximum unsupported span for standard loading would be 1.98m .... so your
13' span already exceeds the loading that is allowed nowadays on joists.

OK .. your house is safe as dead load is probably just ceiling boards -
hopefully any water tanks have supports over a loadbearing wall.

But the joists ain't going to take any load from above.

Even boarding out with sheet material is high risk, the dead load of the
sheets would be too high.

If it were my place as the spacing is low at 300mm ... I would be happy to
deck out in t&g 18mm wheyrock, screwed at 150mm centres.
This would spread the load well enough for storage of light weight boxes.

A thought for you ... if joists are only 4" deep and you want to board over
what about the insulation ? presumably you still have the 1930's cold roof
construction and have rolled out insulation between joists - and this must
be no more than 4" (or you couldn't board)

This is VERY poor insulation, and you would be well advised to send your
money on increasing depth of that instead of boarding out.

I have 450mm depth in my place.


Rick