Breathable water resistant underlay?

Hi all, I'm looking for some advice on protecting sub-flooring from moisture.

I'm having completely new flooring put in upstairs (subfloor, carpets and underlay) and I want to ensure that I'm making the best possible choices to protect the new subfloor.

I'm having 18mm structural plywood put down for the subfloor and this stuff is costing a fair bit of money, so I want to protect it from moisture as much as possible (mainly stuff like spillages or leaky radiators etc, as the house has decent enough ventilation).

I'll be putting carpet and underlay down on top of it and I was initially looking for waterproof underlay, but then I read that this will stop the floor from "breathing", so moisture could build up and get trapped between the underlay and subfloor.

Can anyone suggest a solution that will protect my subfloor from spillages but will still allow the floor to breathe?

Thanks,
Andy

 

Perhaps I could put down ramboard permanently between the carpet and the underlay?

 

Thanks Spacey, I was going to use the 18mm structural premium hardwood core plywood from MP Moran (it won't let me paste the link in here), do you think that stuff looks ok?

 

Hi ,
18mm t&g Caber deck would normally need joists with 400mm centres , 22mm for 600mm . Is there a reason for using 18mm ply ?

 

Hi Alban, the distance between the 3 joists that I can see are 417mm on one side (between joists 1 and 2) and 365mm on the other side (between joists 2 and 3). The reason for going for 18mm ply is that 18mm chipboard was down before but moisture has obviously gotten to it over time, probably due to the previous owners of the house not installing any extractor fans in the bathroom or kitchen. I figured if poor quality 18mm chipboard was put down before, then some decent 18mm structural plywood should be fine and would also mean not having to trim the skirting boards too. I went the plywood route after doing loads of research on OSB vs Plywood vs floorboards etc...

 

Good choice. Chipboard is like weetabix and shouldn’t be anywhere near a bathroom


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Hi ,

The ply will be an exterior grade support around the perimeter and screw or use D4 adhesive to fix to joists. Probably worth taking a picture of any pipework before laying .

Ta