Odd sized joists...

[irrelevant]

I'm trying to sort out a loft floor that was put in by a cowboy a few years ago.

He put in new joists, 95x70mm, sideways (so they are only 70mm deep), across a 3M span vaguely attached to the purlins either side. There's a supporting wall about 2/3 of the way across which they are sort of braced to. (Small scraps of wood screwed to the side going down to the wall, they are not sat on it.)

All of the tables I've been able to find have assumed that joists will be placed with the longest side vertical, which is obviously the strongest orientation, and it's an odd size too anyway which I've not found yet.

Is there any way I can find out if these are good enough for their usage? If not, would they be OK if I turn them around and/or drop them to sit on the wall or put spacers between them and it?

 

[tony1851]

The 4x3s you refer to are not 'normal' sized floor joists, nor are they laid in the conventional way (ie with 4" side vertical).
However, if they are at the normal 400 centes, and are PROPERLY supported on the wall below (assuming THAT wall is substantial enough), it could be that the joists, although small, are OK. This is because they are acting as 'continuous' joists over the support, and this reduces the bending stress and deflection. If you can support them properly on the wall below, and they do not 'bounce' unduly when walked on, they could well be satisfactory.
(if this is to be a compliant loft, there are of course other considerations).

 

[irrelevant]

Thank you; that pretty much confirms what I thought.


They are at 400mm centres, pretty much the only thing he did right. The wall underneath is solid all the way to the ground, and is used to support the floor joists on the floors below, and the ceiling rafters here, so I'd think it would be OK. By "Properly supported" what would you recommend? My thought is to fit further lengths of timber to fit between the ceiling joists on top of the wall plate, effectively increasing it's height to meet the new floor joists, obviously all secured firmly. Would that be OK? I've got a fair bit of weight to put back up there, albeit spread out, hence my worry about this!