tiling on WPB ply - problems

[dudley_rob]

a cowboy did a poor job tiling my plywood shelf next to the bath and it started to crack and leak. No flexible grout was used and it wasn't primed or PVA'd!!

I removed the tiles and the soaked/wrecked grout and have dried the wood. I can't get some of the old adhesive off (unibond all purpose adhesive & Grout non flex) the wood and I somehow got to removing the first (top) layer of the ply with much stuck on adhesive. Then I stopped as it felt wrong.

Can I continue to remove the top layer of ply fully and then prime (solvent based) and PVA then re-tile. Or should I remove the ply shelf all together and start from scratch? Or is there something else I can do?

I am stuck and don't really know what is possible and what will work at this point.

Thanks,
Rob

 

[breezer]

start from scratch, sounds like the ply is too wet and "de layering"

 

[dudley_rob]

the top layer has half come off. Does that mean I definatley can't prime the second layer and then PVA etc.. will the second layer not take well to solvent based primer and pva and then the tiles?

Start from scratch? You mean remove the entire wooden shelf? oh no!
Thanks

 

[big-all]

i agree with breezer on this one

if it means a majoy rebuild to replace try this

if its thicker ply [12 or 18mm] you could always drill several largish [12mm ish ]holes to have a look at the dammage to the ply
look closely at what the drill churns out [being carefull of pipes and wires]
also take a screwdriver and prod at the different layers in the hole to see how bad the delamination is and prod the ply all over to see how soft it is

hope this helps

 

[dudley_rob]

big all,
thanks but I don't thinkits as bad as that. Thewpb is 18mm and very thick. I built it myself from a timber frame and screwed it onto the wall and floor (concrete).

Stupidly I didn't overlap the top piece over the front panel so the top of the shelf has an exposed cross section as well as a section of ply. does thi smake sense?

Anyway when the tiles began to crack I knew they were leaking down through the tiles and into the wood so I took all the tiles off and the grout/adhesive on the top of the shelf. but I had problems getting the grout/adhesive off the front panel.

I decided I would remove the top layer of the ply wood myself. When I did this it was not coming away on its own and was not de-layering nor defective in anyway. I removed the first layer to get down to a complete new layer of wood with no old grout/adhesive stuck to it. If you have an email address I could always send you a photo.

My question is after priming and PVA-ing the wooden shelf minus the top layer of ply can I tile on it successfully without cracking and so on. I actually want to know if the second layer down will still have the same properties as the original top layer.

Will the primier seal the wood properly? will the PVA create a good bond between grout/adhesive and wood?

I would rather not remove it cause that means re-adjusting the bath amd a whole new can of worms will need to be opened including a hole in my wallet! but I can do if it needs to.

anyway appreciate the replies, they are definatley useful.

Still appreciative ...
Rob

 

[big-all]

the top layer missing wont make much difference apart from about 20% reduction in strength[over engeneered any way ]the top and bottom layers are normaly more continuous [no lots of bits and space]but the glues the same
so personaly if youve had to"force"the top layer off i personaly think it will be ok as long as the wood is fully sealed

now dont ask me about sealing for tyling ect as i am not very shure about tileing on ply

e mails in my profile rob where abouts in surrey you from redhill is my present part off the world

good luck

 

[dudley_rob]

big-all
Ok, thanks for your reply. I'll continue to remove the top layer. As you rightly say it is a continuos layer covering the joins below.

If I remove the top layer to reveal a clean sheet of wood (no bloody adhesive stuck on it!) seal it a couple of time with solvent based primer and then pva I should be ok.

I'm in Kingston. if you ping my email I'll send you a picture. its very interesting!!!!!! I've no idea how to see your profile! [email protected]

 

[big-all]

if you actualy go back to forum and click on "big all" where ever you see it on the side[last poster on a subject]there must an other way i havent found it

and they dont like personal e mail addresses on the posts here

 

[stevedo]

FYI, I have some new ply to tile onto. I'm using BAL adhesives and when I phoned their technical helpline last week they said to NOT seal new ply or plaster. The only preparation they recommended was to ensure that the surface was completely dust free.