Securing end joists of suspended timber floor

[oldbutnotdead]

Simplest is what you were doing- just add niceties like DPC on top of the dwarf walls, DPM on the earth (keep the moisture content down in the subfloor void, chuck some gravel on it to stop it floating/flapping), noggins (stiffens the floor up very nicely), insulation between the joists and off you go

Nice thing with the dwarf wall- all the support is being done by structure rather than fixings. The fixings (skew nails) are useful while you're putting the joists in (so they don't move around) but that's really all they're doing. Much easier to level with the dwarf wall as well- slate or shim to compensate for undersize timber.

 

[tony1851]

Why is that? What are the benefits of hangers, more secure?

Because it can cause splitting of the timber; hangers are a far better option as they have provision for correct nailing patterns.

 

[vinn]

OP,
I'm confused as to what exactly you now intend to do?

How about:
Given that you have brick ledges on opposite walls then if you lay fresh sill plates on the ledges on either side of the span,
and seat the joists on the sill plates then no hangers would be needed.
The plates would be levelled as necessary.
The joists would be pinned to the plates and firmed up with noggins.
A wrap of membrane would be laid below the plates and flopped up the wall to cover the joist cut ends.

Caution would be needed that all vents were left open, and that your FFL would flow into any adjoining rooms.

 

[Ian H]

Is 5x2 right for a 2.4mtr span?

 

[vinn]

Yes

 

[KatieMcMahon]

OP,
I'm confused as to what exactly you now intend to do?

How about:
Given that you have brick ledges on opposite walls then if you lay fresh sill plates on the ledges on either side of the span,
and seat the joists on the sill plates then no hangers would be needed.
The plates would be levelled as necessary.
The joists would be pinned to the plates and firmed up with noggins.
A wrap of membrane would be laid below the plates and flopped up the wall to cover the joist cut ends.

Caution would be needed that all vents were left open, and that your FFL would flow into any adjoining rooms.

Yes that's pretty much what we had planned. Although not the membrane on the floor, but we will do that now. I just got a bit thrown when tony1851 said nailing wouldn't be suitable so thought I better check out other options in case.

 

[tony1851]

The problem with skew-nailing is that it is very easy to split the timber; also, you will not get a firm fix against the face of the timber wall plate.
It works better if you notch- and house the joist ends.
The BS code on timber construction does not recommend skew-nailing except in very specific circumstances, which do not apply here.
The joist-ends will eventually work loose; joist hangers are the way to go.

 

[KatieMcMahon]

Would they work loose even with noggins/bracing?

 

[tony1851]

Would they work loose even with noggins/bracing?

TBH it's anyone's guess because you won't know how much, if any, the timber has split. Any weakness may show itself over time
as the floor is walked on.
Not worth risking IMO when the bendy tin joist hanhgers are so cheap.

 

[vinn]

The short 2.4m span joists are seated on a sill plate there's no "wall plate" involved.

Doing timber framing structures we shoot the skew nails into all joists and blocking that sits on the plates. Same with truss or rafter tails: shoot them into the plate on one side, and pin the ceiling joist and the rafter from the other side - all done to a nailing schedule.
A couple of skew nails will hold each joist in place but no harm in using: screwfix stretcher plates - about £2 for ten.