Ready to hire?

Post your job in minutes, browse real reviews and choose who to speak to.Post a job

Need some tips or advice?

Bathroom Fitting

Method for buildling up new bathroom floor from joists and concrete?

Anonymous user 16/03/2024 - 2.36 PM

Am figuring out the correct floor build up for our small GF family bathroom (40 sq ft) in our flat. Have exposed the joists but 30% of floor area is old, thin concrete slab on raised earth, which is 20mm higher than the joists. My plan was (1) screw 18mm plywood to the joists, (2) tank the plywood using a kit (3) overboard the plywood AND concrete with 6mm cement board like Hardiebacker using flex adhesive (4) tile for final finish. The pipework comes up in the brick wall, so no need to cut out holes for piping that creates space for water to come through. So, should be pretty water tight. What do you think? Would you use marine plywood instead of general plywood? Anything I've missed or you would do differently? UPDATE (1): thx for feedback so far. now thinking will break through the small slab, remove the sub-soil and extended the timber suspended floor so it covers the whole area. assume need to consult building control. Can I put down PIR foam or mineral wool to insulate under the new (plywood) boards? Do I need a vapour barrier under the ply?

Are you a tradesperson and able to answer this question?

4 Answers

Anonymous user

id make it all a solid floor with a new dpc if its not to big all timber tends to move / flex / shrink leading to tiling grout joint failures later

Answered26 October 2020

Fairbrother Interiors

Rating: 5 out of 5

Nuneaton

I agree with the first answer, apart from, in my experience, if done properly with appropriate materials, tiling grout failures are rare on timber flooring, especially as you’re using cement boards too. If you do go with your original plan, you don’t need to spend on expensive marine ply, you can use BWP ply, which is much cheaper. Though, all in all, a new solid floor with insulation and a new DPM is the best way forward.

Answered9 November 2020

JKB Property Services

Rating: 5 out of 5

Milton Keynes

Ply it to make it level. You may have to put extra wood on joists to make the ply the same height. Then use durabase matting over the whole floor with flex adhesive. Will be solid and water tight. Or - ply on top of joists then use a flexible self levelling compound over the whole lot

Answered19 November 2020

Alton Fitter

Rating: 4.7 out of 5

Portsmouth

If you are doing this work because the old floor was damp then you really need to sort out the reasons it was damp, not use materials that will cope with damp conditions. Definitely remove the old concrete as this may be part of the problem Suggest it would be far better to get everything out and start again. Whether you use timber or concrete shouldn’t affect the end result if done properly. Remember to consult building regs re damp proofing, insulation and ventilation. Your local building control team should be helpful if you are doing this DIY.

Answered21 November 2020