Tiling Questions - Porcelain tiles on PB/wood

This is a topic that pops up a lot & always gets a lot of input re thickness issues Kev, personally I would think that adding noggins etc would be sufficient for 18mm, securely fixed at 300mm centres. Check for movement once secured! T&G add's its own strength by itself being t&g spreading the load across the floor. Thing with any timber flooring/sub flooring is your always going to be susceptible to movement so my advice is secure thoroughly.

Sealing wise Kev, you only need to seal the underside & edges of the ply to stop moisture ingress from below, ply in itself is made by a laminating process using bonding agents. Use flexible power adhesive & flexible grout.

Seal the PB with an acrylic primer like BAL APD
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Thanks Paul for your advice - its greatly appreciated.

So for the ply, its the underside that I should seal, as well as edges - but not the top face that will see the adhesive? And seal with what? Not PVA - I see that is a dirty word on here!!

As WBP ply is bonded with water resistant glues (I thought) I guess it means I don't have to seal the face??

Can I use the same sealer on the PB as I can on the ply? I guess if I am sealing ALL of the PB then I don't really need to buy the green PB, just the standard stuff.
is the grout water proof or will the sealer do that for tile and grout area?
as well as sealing PB with BAL APD, I should also tank shower area with WP1? Is that right - i.e. do both?
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Just the underside kev

Marine ply is made use superior exterior grade bonding agents with many cross laminating sheets to withstand the elements, normal ply is made using interior grade bonding agents with less cross laminating but only for interior so not required

BAL SBR a good choice but lots of other manufacturers out there, we try to only use BAL as we feel its the best & a company that offers 25 yr guarantee on products speaks for itself, slightly dearer than most but you get what you pay for IMO

BAL APD for walls & standard PB, WP1 the shower area.

BAL grout is ideal for bathrooms, mixed & applied correctly will form a waterproof barrier. Its only a domestic bathroom so epoxy grout not needed unless its going to be immersed like a wetroom & such, don't need a separate grout sealer, just seal the tiles.
Sealing wise Kev, you only need to seal the underside & edges of the ply to stop moisture ingress from below,
:confused: Ingress from where/what?

As for replacing the boards 25mm has already been advised earlier in this topic,overboarding is advised at 15-18mm by british standards so replacing with only 18mm is not advised.
anywhere below floor level, upstairs & downstairs, crawl spaces, between floors etc, not a perfect waterproof barrier but helps nonetheless. Its a practice we've carried out for many years & lots of other pro tilers too

i know about the thickness issue...trying to help someone out who doesnt want a huge step.
Sorry to be a pain again, but... I seal the PB with APD, I tank the shower PB with WP1 - correct?

For the floor (ply) I can leave and put adhesive on directly, for ply on walls, do I need to seal face (I remember about edges) or again can I just put adhesive on directly (won't be in a wet area!).

My mind is going..... :eek:
....also, as only the shower area is the section getting wet, do I need to seal all the plasterboard or just tank the shower area?

I am not sure if the sealing is to stop water penetration or to stop the adhesive going off too quick or seaping into PB quickly.

You can usually tile straight onto plasterboard without priming. Read the instructions on the adhesive to make sure.

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