Lowering timber floor by 20mm

[phatboy]

We are trying to keep the entire house floors flush throughout. The bathrooms are all going to be tiled, and so a tiler has recommended allowing 20mm for this.

Current floor beams are 125x50mm rough sawn, span between sleeper walls is 2.2m. I am keen to avoid having to reduce the sleeper walls, and am thinking of replacing the existing timber with 95x74mm timber, at 400mm centres, and plenty of noggins.

Is this reasonable? This size doesn't appear on any span tables I can find. I would then fit wooden or lead packers to bring it up a little, and even it out.

Any other ideas welcomed, also!

Thank you

 

[phatboy]

Added span info, oops! 2.2m

 

[cdbe]

Is it the bathrooms you want to lower? An old trick is to fix battens to the sides of the joists, down the thickness of your flooring (eg 22mm) and drop strips of flooring in. For a tile finish you'd glue/screw cement boards on top. You can hide a reasonable difference in levels at the threshold.

 

[phatboy]

Is it the bathrooms you want to lower? An old trick is to fix battens to the sides of the joists, down the thickness of your flooring (eg 22mm) and drop strips of flooring in. For a tile finish you'd glue/screw cement boards on top. You can hide a reasonable difference in levels at the threshold.

es, the bathrooms are to be lowered.

Nice trick, and I'd never have thought of it! As it happens, I need to remove the floor, anyway. I need to run the 110mm drainage underneath, and lifting the joists seems like an easier method to do that. The joists only serve this space, so lifting them up will be pretty straight forward.

I'd be all for hiding it at the threshold, but SWMBO has different ideas

 

[phatboy]

Doing this job next week.

Is 4x2 with noggins every 600mm and the ends going to be sufficient and bounce-free? It's half the price of 4x3, unsurprisingly.

Thanks

 

[yorksbuilder]

Probably will be sufficient yes

 

[yorksbuilder]

Just FYI, you can use No more ply TG4, which is a strong 18mm or 22mm cement floorboard meaning you don't need to batten out the floor and drop in new floorboards between the joists....

Of course, if you do drop the floorboards down between the joists and use a 6mm thick cement backer board for the tiles, the buildup will be less

 

[Deluks]

Take no chances with a tiled floor, it really needs to be solid.
If you haven't bought it yet, use 6x2 timber, notched at the ends so it sits at the required height, it will be stiffer, and the notch won't be near where the bending stresses are.

If you have 4x2 consider reducing the centres or double them up.

Don't forget to insulate!

Run everything by your tiler, if you allow for tile backer board and so has he, then you'll be too low, which could cost you in time and materials.

 

[Dereekoo]

Assuming c16 timber, standard 1.5kN/m2 live loading and dead loading not exceeding 0.25kn/m2, max deflection will be just under the allowable 6.5mm limit and bending moment at 85% of allowable. Noggins do not add anything to the overall strength they just stop the joists canting over slightly and reducing their design capabilities (imagine turning a 4 x 2 by 90 degrees so its a 2 x4?)

 

[phatboy]

Take no chances with a tiled floor, it really needs to be solid.
If you haven't bought it yet, use 6x2 timber, notched at the ends so it sits at the required height, it will be stiffer, and the notch won't be near where the bending stresses are.

If you have 4x2 consider reducing the centres or double them up.

Don't forget to insulate!

Run everything by your tiler, if you allow for tile backer board and so has he, then you'll be too low, which could cost you in time and materials.

I think I'll do this... I definitely don't want cracked tiles and a complete tear out to resolve it. Will take some extra time, but hopefully make things worry free!

100mm of PIR going in between

No tiler appointed yet, and the wife adds this week that we need UFH, so that's nice! Once we appoint a tiler Ill go through the backer board, and we can use the size that works, accounting for the electric UFH too.

Thanks!

 

[Dereekoo]

I think I'll do this... I definitely don't want cracked tiles and a complete tear out to resolve it. Will take some extra time, but hopefully make things worry free!

100mm of PIR going in between

No tiler appointed yet, and the wife adds this week that we need UFH, so that's nice! Once we appoint a tiler Ill go through the backer board, and we can use the size that works, accounting for the electric UFH too.

Thanks!

Now you are down to a 2.2mm deflection calc

 

[phatboy]

Now you are down to a 2.2mm deflection calc

Wasn’t I at that anyway? But now it’s 2.2m with 150mmx47mm ?

 

[Dereekoo]

Wasn’t I at that anyway? But now it’s 2.2m with 150mmx47mm ?

See post 9

 

[phatboy]

See post 9

Sorry, was a bit too technical for me.

The span before was 2.2m, and it still is. But with deepeer timbers?

 

[Dereekoo]

Sorry, was a bit too technical for me.

The span before was 2.2m, and it still is. But with deepeer timbers?

2.2mm deflection as opposed to 6.5