Uneven floor joists in bathroom

BarraOG

I'm renovating a bathroom and I want to tile the new floor. I took up the subfloor and installed lots of noggins. I used angled brackets at the double joists and coach screws. I used 100mm screws otherwise. I used a meter long spirit level and ensured that the noggins were flush with the adjacent joists. It feels very solid.

The joists run parallel with the door. There is a double joist at the door, 3 joists, a double joist, a joist and then a double joist at the far wall. The depth of the room is 2400mm which corresponds to a length of the plywood that I will be using.

I cut a piece of 7x2 of the same length and placed it over the joists and levelled it with spacers. Unfortunately, at the far wall, the spacer is 10mm. The spacers increase in thickness from around the middle of the room towards that far wall.

My understanding is that the most important thing at this point is that I create as solid a floor as possible, where I get plenty of screws down into the joists and noggins. Therefore I believe I am right to address the uneven floor after I get the subfloor down. Does that make sense or am I making a mistake now that I will regret later?

Thanks!

Rows Grower

If you don't use spacers will the 7x2 touch all the joists and noggins it is place over?

BarraOG

https://www.boards.ie/discussion/comment/121723748#Comment_121723748

If I stand at the door and place the 7x2 along the length of the room, it doesn't touch the first and last two joists. The gap is a mil or two. If I move the 7x2 parallel towards the adjective wall, it will rock slightly as it balances on the centre joists, as I apply pressure to the 7x2, off centre. It's really only sitting on the two centre joists in that case, one of which is a double joist.

Rows Grower

Pictures would help but if the biggest gap without using the spacers under the 7x2 is 2mm then that's not a big deal. You might want to plane the couple of mm off the centre joists before fitting your new sub floor or if your using plywood 12mm or more you should be able to make up any imperfections with adhesive.

BarraOG

https://www.boards.ie/discussion/comment/121724074#Comment_121724074

Thanks! The biggest gaps are 2mm or under at the door, slightly larger at the far adjecent wall. The ply I'm using is 18mm. I'll investigate the idea of planing the centre joists at that adjective wall. I think it makes sense to start screwing along the centre joists since the plywood spans the full length of the room and ensure that I'm applying enough weight to push the floor down fully when I get to the edges.

Rows Grower

You should be grand using 18mm plywood.

I don't know if you've used these before when tiling but they are a great help to achieve a beautiful finish, plenty of different places to buy them and loads of help on YouTube on how to use them.

https://www.screwfix.ie/p/no-nonsense-lspc-2-set-tile-levelling-system-kit-201-pieces/609pg

GreeBo

If it was me I would just screw to the floor, flat is more important than level with tiles.

You can make up 2mm with tile adhesive.

rob316

You could but a bit of leveling compound in the shallow spots over the plywood subfloor if you are determined for it to be level, you would need to seal all gaps and edges.

Honestly though I'd just tile away and use a tile levellers.

SteelyDanJalapeno

Sounds fine, any chance the 7x2 is not completely straight?

BarraOG

https://www.boards.ie/discussion/comment/121724182#Comment_121724182

Thanks, I'll consider using these!