Bathroom repair - and while I'm at it...

[Interloper]

I have to replace a cracked S-trap toilet in the bathroom.

It seems that the floor (circa 1960) around the toilet base and bath would benefit from repair. At the moment it is a traditional suspended pine tongue & groove wooden floor that is warped and slightly rotted in places.

The bathroom is quite small, and it wouldn't be much of a job to replace the whole floor while I'm at it. Initially I was considering using green, water-resistant chipboard flooring sheets, but I'm not convinced chipboard would be resilient enough if it gets wet.

I would like to finish the floor with a single fitted sheet of luxury vinyl cushion floor, or similar - something that will not let water through. If I stay with a repaired tongue & groove floor, I guess there's a good chance the joints between the boards will mark through the vinyl cushion floor over time and spoil it, so I will need to install some kind of overlay (hardboard?) on top of the T&G boards first.

Then, of course, if I'm taking up the whole floor, maybe I should consider installing underfloor insulation while I'm at it?

What is the best material to use for a suspended bathroom floor? 20 - 25mm waterproof plywood sheets, perhaps, or is the green, water-resistant chipboard OK?

Thanks,

[The Natural Philosopher]

It i9sn't, buy then that's why you tile or vinyl it...

yes, at which point really its best to rip up the existing crappy pine and slap down chip or ply.

is it ground floor? if so, yes, otherwise its a waste of time..unless its over e.g. an unheated garage..

either..

Both won't take soaking and will swell. The key is to try and seal any vinyl or tile edges to the walls with something like silicone. or some other flexible mastic.

The biggest danger is splashes that run to the edge of the waterproofing and then get under it..

[Interloper]

I wrote:

Bungalow, so yes, ground floor.

What is the best insulation to use? I would prefer something fairly rigid, like polystyrene or Rockwool sheet that will require less supporting between the joists.

Should I install a damp-proof membrane on top of the joists (warm side, above the insulation) before installing the new floor panels?

[Tim Watts]

On Wednesday 29 May 2013 12:42 Interloper wrote in uk.d-i-y:

celotex type boards. Easy to cut, can be wedged in (and held with a few squirts of PU foam for good measure), self extinguishing in the even of fire (though I suspect modern building polystyrenes are also made fire resistant??)

Your vinyl is going to effectively provide a DPM on the top - and if you do get a leak, you want it to be able to disperse rather than get totally trapped by another sheet.

[meow2222]

no.

very much

fibreboard, as used with laminate floors, adds a little spring/insulation t oo

certainly, for a suspended ground floor. It would be foolish to miss the op portunity

chip, ply, osb, wood boards, take your pick. Chip is least resilient. non-W BP ply is not going to be water surviving either, nor OSB2 & 1. OSB3 and WB P ply are. Wood boards are, especially if preservative treated. Or you can reuse what you have, just replace the few damaged ones.

any insulation works. Polystyrene is nasty in a fire. Rigid sheet is more w ork to fit. Fibreglass batts are cheap and easy to use, but iritating.

No, the vinyl will act as a vapour barrier. You want any leaks to disperse, not be trapped, as already said.

NT

[Interloper]

Thanks for the advice so far.

To pursue the installation of underfloor insulation - I've seen two installation methods suggested:

1. Fit the insulation towards the bottom of the gap between the floor joists (underside of insulation flush with underside of joists), leaving an air gap between the top of the insulation and the underside of the floor. Ensure that the insulation is touching the perimeter walls, so there are no gaps and consequently there is no air movement in the gap between the top of the insulation and the underside of the floor. This advice was in an insulation manufacturer's literature.

1. Fit the insulation towards the top of the gap between the floor joists (topside of insulation flush with top of joists), leaving no air gap between the top of the insulation and the underside of the floor. IIRC, this method was suggested on this ng a few years ago.

Which is the better method? And why?

Thanks,

[meow2222]

1. gives more airflow around the boards in case anything gets wet. But noticeably less insulation, as IRL there are always air leaks.

NT

[fred]

In article , Interloper writes

The greater the gap the greater the opportunity for air movement and leaks which reduce the effect of the insulation. In short place it as close to the boards as possible (option 2).

[harry]

There are grades of flooring chipboard that are water resistant. Glue the T&G joints with PVA if using. If you are laying vinyl on floorboards, the standard practice is to lay thin plywood first. Well fitted on any joints and nailed down. (Plenty of nails hammered in flush). If on first floor, pointless insulating underneath.

If on ground floor then important to insulate these days. Rigid foam is the best, there must be no air leaks. Thick as possible. The whole house should be done. I have 150mm under my house. Seal off any draughts around skirting/floor.

[F Murtz]

Compressed cement sheeting if you have it in UK.