New floor bounce

[23vc]

Hi
On my extension I used 6x2 C24 treated for the first floor joists - 400mm centres, clear span is 2.8m
Pretty sure the span is just about OK for that size unless I've c*cked up horrendously, but maybe I should have gone for 8x2, as the first floor does feel a bit bouncy - not a big problem for the bedroom but the ensuite floor I am going to tile. Floor detail is:

- joists hung off bearer plate of 6x2, bolted to existing house wall with 150mm bolts at 700ish mm centres (maybe I need more of these?) all nail holes on hangers used, 35mm square twist nails
- other end is built into blockwork and sat on a block (not on a mortar bed) so I think that's as it should be
- running along the middle is struts of the same 6x2, with 2x80mm screws skewed at each end to fix
- new bathroom floor is 18mm ply, with extra noggins along the board joins, screwed at 20mm centres with 5x80 screws

I'd really appreciate a quick sanity check of the above and any area which I've fallen short - my only worry is tile grout cracks on the new floor - possible option to screw 6mm hardibacker down on top of the ply to give it more strength?

Cheers
John

 

[Notch7]

I suppose you have gone too far to sister the joists to make them more stiff?

 

[23vc]

Yep notch, wouldn’t be easy . But not even sure what I’ve done wrong anyway to be fair , if anything

 

[garyo]

I'm surprised given that you included some nogs mid span - that normally makes a massive difference.

 

[23vc]

Yeah, correction to above the noggins are done offset every other one so I could get a couple of screws in square off the joist, rather than skewing them

Couple of pics attached, am wondering if it just needs more bolts on the bearer

 

[^woody^]

The ends need noggins near the hangers, and bearings.

 

[^woody^]

At what stage of construction is it?

 

[tony1851]

Is the decking down yet? if not, that will stiffen it as it helps to spread the load between joists.
6x2 C24 over 2.8m span seems reasonable.

 

[23vc]

Woody Upstairs is finished and a nice warm bedroom, just the ensuite to do

 

[23vc]

Woody is that standard practice then, or more if the joists are only just big enough as mine might be

 

[23vc]

Is the decking down yet? if not, that will stiffen it as it helps to spread the load between joists.
6x2 C24 over 2.8m span seems reasonable.

Yep bedroom chipboard is down and carpet. Just the bathroom that I’m a bit worried about flex and tiles

 

[Doggit]

Well, you're either going to lift the floor (or drop the ceiling below), and put in the extra nogins, or you're going to lay vinyl rather than tiles - your choice.

 

[23vc]

Well, you're either going to lift the floor (or drop the ceiling below), and put in the extra nogins, or you're going to lay vinyl rather than tiles - your choice.

Easy choice as the ceiling below isn’t up yet.

Where am I putting extra noggins, along both of the ends of the joists just off the walls, which I think is what woody said? Or mid span between existing centre noggins and walls?

Cheers

 

[John D v2.0]

It could feel bouncy if the resonance is wrong, the limit on deflection is to stop the plaster board cracking not to stop it feeling bouncy. We added herring bone struts to a bouncy floor that was cracking the plaster, and screwed 18mm ply boards lengthways above and it helped a lot. Of you screw them below too it'd help more.

 

[Notch7]

Easy choice as the ceiling below isn’t up yet.

Where am I putting extra noggins, along both of the ends of the joists just off the walls, which I think is what woody said? Or mid span between existing centre noggins and walls?

Cheers

Since the joists are exposed, I would think about doubling up the joists. Theres no need for the ends to be supported, just sister each joist, then noggin.