My new new-build is watertight. After getting watertight, I have then installed a mid-floor wall plate and posi joists at 600mm centres myself, all specified. Has gone well so far - dry, flat, neat, tidy.

 

I'm planning to lay the entire upstairs sub-floor floor over the posi-joists and then partition the rooms on top.

 

I have just purchased and had delivered 22mm P5 T&G from Wickes (Caberdeck) to install over the posi-joists. https://www.wickes.co.uk/Wickes-P5-Tongue-and-Groove-Chipboard-Flooring---22-x-600-x-2400mm/p/164536

 

I am second guessing myself. Reading the T&G won't do well in the bathrooms over time (there are two, main and en-suite). Planning to lay Vinyl in the bathrooms, maybe Karndean or Amtico if I can afford.

 

Should I have gone for Structural Plywood CE2+ 18mm? https://www.wickes.co.uk/Wickes-Structural-Plywood-CE2%2B---18-X-1220-X-2440mm/p/252240

 

So the question is P5 vs Structural Ply? Will the P5 do a good job?

 

Prices are currently similar so that's not in question. I can exchange as only just purchased.

 

Opinion please, thanks.

Neither will ‘do well’ if getting routinely soaked / heavily wetted so just lay the P5 and tank it all if you’re expecting water to be getting to the subfloor with any frequency. 
The issue should be mitigated against at source, eg don’t install the bathroom with flaws.

If tanking, just check with the LVT fitter about compatibility of the glue vs tanking. 
FYI, with LVT you should be installing a thin plywood sheet atop the P5 and using a feathering compound to fill screw holes / perfect joints before the LVT goes down or you’ll see the P5 joints through the LVT. 

1 hour ago, Nickfromwales said:

Neither will ‘do well’ if getting routinely soaked / heavily wetted so just lay the P5 and tank it all if you’re expecting water to be getting to the subfloor with any frequency. 
The issue should be mitigated against at source, eg don’t install the bathroom with flaws.

If tanking, just check with the LVT fitter about compatibility of the glue vs tanking. 
FYI, with LVT you should be installing a thin plywood sheet atop the P5 and using a feathering compound to fill screw holes / perfect joints before the LVT goes down or you’ll see the P5 joints through the LVT. 

 

May I ask, what would you use to tank? Products / brands?

Thanks

 

18 hours ago, Johnny Jekyll said:

 

May I ask, what would you use to tank? Products / brands?

Thanks

 

Link

 

Theyre all much of a muchness tbh, and made from the same stuff. 
No need to spend mega bucks and I’ve been using these types of products for decades. 
Impey do a system, as do Roman etc, but that “liquid membrane” from Mapei is plenty good enough and had never let me down. 
 

 

Hand made this bespoke shower ‘tray’ ( 2700mm x 900mm ) falling to a centre drain. All tanked in the above product, walls and floor. 👌. 

@Nickfromwales thanks, can these be used on my 22mm P5 chipboard flooring and under vinyl tiles such as Karndean or lino?

Edited April 24, 20224 yr by Johnny Jekyll

8 hours ago, Johnny Jekyll said:

@Nickfromwales thanks, can these be used on my 22mm P5 chipboard flooring and under vinyl tiles such as Karndean or lino?

The tanking?

4 hours ago, Nickfromwales said:

The tanking?

 

Sorry yes? Basically I'm looking at what's best to protect the chipboard in the bathrooms. Some sort of DPM or tanking.

Plan for bathroom finished floor is luxury vinyl tiles. May need to latex below them to make it nice and flat. But I believe latex can't be laid directly onto chipboard.

Hence some sort of DPM or waterproof taking over the chipboard.

Hope this makes sense. I'm a flooring novice so just starting on this for my new build.

On 22/04/2022 at 07:29, Nickfromwales said:

If tanking, just check with the LVT fitter about compatibility of the glue vs tanking. 
FYI, with LVT you should be installing a thin plywood sheet atop the P5 and using a feathering compound to fill screw holes / perfect joints before the LVT goes down or you’ll see the P5 joints through the LVT.

 

You cannot use a DPM as they whole floor will need to be bonded. LVT cannot be floating in a bathroom for obvious reasons ( any gap will fill with water / damp by capillary action, even when bonded, so seal, seal and seal again! ). 

@Nickfromwales thanks for taking the time to help 👍