Joists Spacing

[OBBob]

Hi There

In the old standard construction the two joists under a load bearing wall had a gap between them. This allows them to protrude each side of the wall so that the flooring can be supported at the edges.

However, when using a complete layer of yellow tongue prior to the walls being stood on top ... is there any advantage or disadvantage to having that gap? Or should the two joists be nail laminated together? What would be the norm these days?

Thanks in advance.

[journeyman Mick]

Don't know about non-cyclonic areas, but up here there's always a gap between double joists, saves having to drill holes for the cyclone rods. Handy for electrical, phone and water too.

Mick

[Sigidi]

OB Bob,

when using a complete layer of yellow tongue, you have used what it is termed 'platform' construction. In this type of construction, you space all your joists evenly either 450mm or 600mm depending upon thickness of structaflor (some structaflor 22mm thick can be used over joists @ 600mm crs but this is red tongue, I think the colour is right) this spacing is NOT dependant upon internal walls.

This type of construction is now favoured over 'traditional' construction for a few reasons;
1) less piers are required over the footprint of the building.
2) less joists are required
3) it provides a working 'platform' which aids in construction
4) speeds up the build process as a whole
5) increases site safety as no-one is walking across top of joists all day, but walking on a solid platform.

Hope it helps

[silentC]

Sigidi. I almost responded with the same but then, I had to stop and think: normally when we are building platforms, you assume internal walls are not load-bearing - roof is trussed. In my place, we have two internal load-bearing walls and these are directly over footings which run right through the building. We have joists that sit directly over the top and walls sit on top of that. I don't know enough about it, but something tells me you don't want a load-bearing wall sitting between joists on chipboard flooring. Maybe blocking is all that is required?

[OBBob]

Yeah, sorry guy's I should have explained that they are loadbearing walls. However I'm not intenting to put the walls between the joists just to have a 40mm gap between the double joist under the wall.

I'm fairly convinced now that this is the way to go as there will still be plenty of bearing capacity on the joists and it allows a gap that may be useful if any wiring / plumbing etc. ever needs to go through there in the future.

[silentC]

I should have explained that they are loadbearing walls

You did:

In the old standard construction the two joists under a load bearing wall had a gap between them.