How water-proof/resistant is green pb ?

[mointainwalker]

Hello there, would be grateful for your thoughts on this question.

I want to install two wet-rooms in my renovation and in both cases the walls will be stud and it was my intention to use water-resistant pb. I checked out the "cement-based" boards which were about four times more expensive, hence my decision to go with the pb before my concerns arose.

I intend to take a loose plastic membrane ( DPC sheet which is sealed to drain by rubber gasket ) up behind the pb to a height of about 2m with fibre-glass insulation behind this..

Since reading comments about the permeability of this pb , I have become concerned, because if the amount of water involved is considerable, then it is going to sit in an open plastic pocket and when it evaporates will presumably soak my (proposed ) fibre-glass insulation causing problems.

Showers will only be used couple of times per day, no power-showers and tiles probaby 20 x 20 i.e. nothing small.

Thanks in advance.

 

[Richard C]

Except for expensive epoxy products, waterproof tile adhesive & grout is only waterproof in the sense it wont break down when wet, it is permeable & will absorb moisture which can eventually find it’s way into un-tanked PB; your waterproof membrane must be in front of the PB not behind it!

Moisture Resistant PB is impregnated with silicone to give it additional water resistance over standard wallboard which has virtually no resistance at all; the mess that un-tanked PB (including MR) can end up in behind the tiles can be gruesome & it stinks. I will only ever use MR PB in bath/shower rooms but would never use it in “wet” areas unless tanked. Given the choice I always use tile backer boards here & would certainly advise nothing less in a wet room; it’s more expensive but not much so when you factor in the tanking kit you would (should) otherwise need.

My advice is to use only the best, quality trade materials if you want it to last; more expensive initially but not if you have to rip it out & do it again in 3 years or so, do it right & you'll only have to do it once.

 

[Chukka63]

why not use merlin board ( i think its called) instead of tiles.