Porcelain floor tiles on plywood

[Raz]

Hi,

I'm looking to get commercial premises tiled with porcelain. The building is currently a shell with new flooring to go in. I have been advised to go with 22mm chipboard with 15mm plywood on top. In terms of primer and adhesive I have been advised that the plywood should be primed on the underside and the edges with Mapei primer g and Mapei keraquick should be used as adhesive.

Can someone please clarify if the above is the best solution for an area of approx 400 sq.m.

Also can Mapei keraquick be used on plywood?

 

[Old Mod]

Welcome to the forum!
Ply should never be your first choice of substrate, if you are going To over board, then use an inert tile backer board like Hardi for example.

http://www.jameshardie.co.uk/images...«_cement_backerboard_technical_data_sheet.pdf

Keraquick is just like it says on the tin quick!

http://www.mapei.com/public/COM/products/103_keraquick_gb.pdf

 

[AliGage]

Pretty much as above. But i wouldn't waste my time with the chipboard. Nit if you're prepared to overboard with ply.

Replace the chipboard with 25mm ply, overboard with 6mm hardie.

 

[Raz]

Many thanks for the advice.

Aligage, if I was to go without the chipboard will the floor not creak?
The flooring needs to be suitable for heavy traffic.

Is hardie applied down with adhesive?

 

[AliGage]

A timber floor would never creak of its well supported and fixed securely.

 

[Alan.P]

As Aligage says, especially in a heavy traffic area as you say you'll have, the floor needs zero deflection ( bounce ) otherwise you'll have tiles popping / cracking and grout coming out of the joints. What is the substrate at the moment, how high is the floor to be raised prior to tiling.

 

[Raz]

Currently the floor was made of plywood (I think) with linoleum on top.
The floor is 700mm high from ground floor level.
What's the downside of applying tiles onto ply?

 

[Alan.P]

The downside is that the floor could / will fail due to ingress of moisture causing the ply to de-laminate, excessive movement due to expansion and or contraction or deflection ( bounce ) witch will cause tile and grout failure.

YES, we used to tile to ply and YES it worked, not always though, there are horror stories on these forums that will attest to that, if your going to do the job right, and it sounds as if you want to, then listen to the guys, they are some of the best fixers in the country

 

[Old Mod]

........and he ain't none too shabby either! ⬆️⬆️⬆️⬆️⬆️

 

[Raz]

In terms of hardie, can you apply it with screws only also what do you guys think of applying hardie straight onto 22mm chipboard and will 6mm hardie be sufficient.

 

[kevsalt]

as long as its dense chip board i would screw it every 150mm with 4x20 quality screws then prime it with acrylic or sbr

 

[p4ulo]

Also, make sure you put a spread of tile adhesive under the boards to assist in firming the whole lot up!!

 

[Alan.P]

In terms of hardie, can you apply it with screws only also what do you guys think of applying hardie straight onto 22mm chipboard and will 6mm hardie be sufficient.

Hardibacker recommend fixing with adhesive and screwed down.

Here is a google link top listing will download a pdf for you to read.http://www.google.co.uk/url?sa=t&rc...Q2Ffb--iH6gpC4g&bvm=bv.99556055,d.ZGU&cad=rja

 

[Old Mod]

In terms of hardie, can you apply it with screws only

The reason for using adhesive under the Hardie is to take out any irregularities in the substrate, so that the Hardie has complete contact with the floor.
It's not used to fix it down, the screws do that job.
Note....use an alternative screw not the Hardie ones. Turbo Gold from Screwfix are popular.

will 6mm hardie be sufficient.

The thickness of Hardie on the floor is irrelevant.
All it's designed to do is give u an inert substrate to tile to, that is to say,
one that will not expand and contract due to temperature change and or moisture ingress.
6mm is completely fine. It has pre marked screw positions and they will need countersinking.

what do you guys think of applying hardie straight onto 22mm chipboard

Having that we have now established this is a high traffic area, as has been said by @AliGage and @Alan.P a heavier ply would be more suitable.

 

[Raz]

Many thanks for the detailed explanation.

 

[AliGage]

Just to add, I might be wrong in my thinking, but if the few alternative questions you've asked above are cost related. The difference between the two is approximately £3.50-4psm. Assuming you would also glue the Ply Overlay in your option.

Small price to pay in comparison to a failed floor if incorrectly prepared.

 

[AliGage]

@Raz out of interest have you had any survey the premises and spec the floor from a tiling perspective.
400sqm is quite an area. Your timber construction would still require expansion consideration imo. Your tiled surface would require expansion joints not just ditra. Why is this structure 700mm off the floor? What's going to be under it? How will the structure be supported? Rather than sqm what is the length and width of the floor Space? Presuming it's a square of course.

It's one thing to ask how to correctly prep a timber substrate but it becomes a bit more complex when the scale is as big as yours.

 

[Rizzle from the Portizzle]

ok you have suspended floor pree 1930 would be my guess the joist shoud have surport pillars over long spans open up a few spaces so you can get under the floor and check these are still holding now consider the wieght loading going on top now check the distance between them if the are more than 3.5 lm bridge the middle with another surport now thats done using 8x4 ply work out the midlle of there joints and nogging out with 4x2 now lay and screw down 12,5 mm 5 ply now soak that in wood glue then cross ply with 12.5mm ply screw down when the glue drys it should be as hard as nails .get you self a glass of waterhalf full place in around the floor and walk past all ways checking for defletion the more the water move the higher the deflection now if you have no movement you have got it right now heavy traffic will require a none conpresive over lay iso matt will do the trick or hardie backer its your choice

 

[AliGage]

Superb post @Ray TT @ Porcel-Thin