Taking up ply floor

BarraOG

I’m trying to figure out how I’m going to tile an upstairs bathroom and one piece of advice I recieved was to take up the existing 18mm ply floor and replace it with 9mm ply and 6mm cement board. This is because the existing floor is in a number of pieces. The problem is that the studded walls are sitting on the existing floor. The floor is surrounded on three sides by attic space so the ply floor stops under the stud. So the base plate is sitting along a joist for the long wall you can see in the picture. Is taking up the floor still an option and would you just cut it up against the edge of the base plates? How far apart should the extra noggins I add be along the edge of the room? How would attach the noggins to the joint so that they don’t budge?

https://us.v-cdn.net/6034073/uploads/NPU8GOERLZXO/img-6353.jpg

Rows Grower

I'd leave existing ply, remove all ware and fit marine ply over old ply making sure to overlap the joints. If you want to use cement board on top of new ply you could but it wouldn't be vital. Use good flexible tile adhesive and grout and you're good to go.

GreeBo

Id cut around the room as close to the walls as you can and then just add noggins to cover the joints.

Lumen

In the US they use a toe-kick saw for this job. Not available in Europe AFAIK, either because studs shouldn't bear on subfloor or because the kickback is lethal 😀 You could always buy one on eBay if you can deal with the 110V.

You could hire a jamb/undercut saw and use it rotated.

Or use an oscillating multitool or maybe if there's clearance under the ply a hand flush-cut saw, but it's not going to be fun.

BarraOG

https://www.boards.ie/discussion/comment/120473047#Comment_120473047

What about cement board direct on the old ply if it’s too awkward to remove?

Rows Grower

https://www.boards.ie/discussion/comment/120476732#Comment_120476732

That's another option I forgot to mention.