Laying tiles on wooden floor with G-flex

[scoobysnax]

Hi, looking for advice on laying ceramic floor tiles in our wooden floored bathroom. The area to be tiled is 1500mm x 1300mm, and is currently covered with a 4mm layer of hardboard to which is attached self-adhesive vinyl tiles. We now want to lift this, and lay 600mm x 295mm ceramic floor tiles.

We paid a visit to our local tile centre yesterday, and were shown this new product called 'G-flex' (£28 per sq.m) which apparently replaces the need to lay thick plywood prior to tiling. It is a self-adhesive backed plastic mesh, approximately 5mm deep onto which you lay the new tiles. We were told that the hardboard could be left in place but would need to be screwed down onto the floor boards (currently panel pinned) before applying the G-flex. I was wondering if anybody has used G-flex, and how successfull a process it is?

The reason I mention the area to be tiled is that as I feel it is such a small bathroom, there is less area to be prone to 'bounce'. Please correct me on this if I am wrong! This is the first time I have ever tackled floor tiling, though I have tiled several walls. Just want to be sure that the G-flex is up to the job before starting.

Any and all advice greatly appreciated.

 

[Gazzer]

5mm ???
Genesis APS International Ltd - Products - G-Flex -

Nope never used it.

 

[Rob Z]

Hi

There have been several products on the market here in North America that were similar to the product you are listing. To my knowledge, all are off the market or not really selling anymore because of scores of failures.

The concern about how much "flex" is in your bathroom floor is a good one to have, but it's not the size of the room but instead the length of the unsupported span of the joists. The joists likely span a longer distance (unsupported) than just the bathroom. Is it finished space beneath the bathroom?

 

[scoobysnax]

Hi. Sorry, not sure what you mean by 'finished space beneath the bathroom'?

 

[metereater]

if i was you id remove the vinyle, make sure the hard board is in good shape not rotted or cracked, prime it and tile it. If it is in bad shape replace it with 6mm h/b
Floor boards will always move abit hence why the hardboard is on top, its a solid plattform.
FLEXY sticky isnt much to shout about if you give a solid floor movment it will crack, especially in your joints.

 

[Rob Z]

Hi. Sorry, not sure what you mean by 'finished space beneath the bathroom'?

Is the bathroom over a basement (unfinished space, where maybe you can see the floor framing exposed).

Do you have any way of piecing together how large the joists are, what their span is, spacing, etc. If everything is covered below with plaster, drywall, etc, then it's harder to figure out what you have in floor.

 

[Gazzer]

if i was you id remove the vinyle, make sure the hard board is in good shape not rotted or cracked, prime it and tile it. If it is in bad shape replace it with 6mm h/b
Floor boards will always move abit hence why the hardboard is on top, its a solid plattform.
FLEXY sticky isnt much to shout about if you give a solid floor movment it will crack, especially in your joints.

Tile on HARDBOARD ???? You are having a laugh !

 

[scoobysnax]

Sorry...clicked wrong button!!

 

[scoobysnax]

The bathroom sits above our kitchen, so there are no exposed joists. We had new heating fitted throughout the house last year, and from what I can remember, the joists are approx. 70mm wide x 200mm deep, spaced approx. 300mm apart.

[FONT=&quot]Thanks for taking an interest in this![/FONT]

 

[Stef]

NEVER EVER tile on to hardboard

 

[scoobysnax]

Just another quick question about something that has just occurred to me. With the tiles being 600mm x 295mm, would it make any more sense, and less chance of cracking etc if I were to lay the tiles in the same direction as the joists, or wouldn't that make any difference?

 

[Rob Z]

The bathroom sits above our kitchen, so there are no exposed joists. We had new heating fitted throughout the house last year, and from what I can remember, the joists are approx. 70mm wide x 200mm deep, spaced approx. 300mm apart.

[FONT=&quot]Thanks for taking an interest in this![/FONT]

Hi again, I had to break out the calculator so I could think in metric . Those joists are likely fairly stout, and are closely spaced together, but really the thing to determine is the unsupported span. Based on the direction the joists are running, can you hazard a guess how bearing walls below sit relative to the joist span?

 

[scoobysnax]

Give me a minute Rob Z, i'm going to try to prepare a drawing for you. Thanks so much for your help. Be back in 15minutes!

 

[Rob Z]

Here's a diagram that shows you what you need to determine.

The bearing walls carry the load of the joists down to the foundation. The wall in the middle of this house is a bearing wall, because it transfers the load to the stell beam below.

The wall in the room on the second floor isn't supported by anything other than the joists, and so if your bathroom is situated in your house in this way, you will need to consider how far the joists span (and not just the small size of your bathroom).

Let me know if this makes sense, and what you can determine about your house.

 

[scoobysnax]

This is how our walls are laid out. The orange wall is a supporting wall below the bathroom, but I don't believe the wall between the bathroom and the bedroom is a supporting wall. I think it is like the one in your diagram Rob Z.

 

[metereater]

yea sorry brain dead moment, i ment plywood idealy marine plywood costs a bit more but has already been treated, screwing it down every 300ml not just around the sides but threw the entire floor.

sorry for confusion.

 

[Rob Z]

Hello again, nice diagram!

It looks like the unsupported span of the joists is only about 6.5 feet, and with the size and spacing of the joists that should be a solid floor.

I'm not familiar with the product that you mentioned in your first post, but a product such as Schluter Ditra would be perfectly fine in this application, installed directly over the subfloor (just the plywood, not the hardboard).

BTW, how thick is the plywood on the joists? We would use 5/8" tonge and groove minimum here. 3/4" would be better.

 

[DHTiling]

G-flex is basicly plastic ply.. IMO it does not add strength and will not directly replace plywood..


BS5385 minimum for a plywood sub-floor overboard is 15mm, this is not only for deflection but also for moisture ingression stability .

There are better products on the market if the floor is solid and i would be inclined to use hardibacker.. never use hardboard or thin ply..

 

[scoobysnax]

Sounds like good news then. There isn't any plywood down on the floor though. Not sure if I explained myself correctly, but there is the joists, to which is screwed the tongue and groove floor boards, which are I believe 3/4". A few years back, I put down the hardboard onto which I applied the self-adhesive vinyl 'planks'. Basically they are made to look and feel like real wood planks.

My plan is to lift the vinyl planks and hardboard before applying the G-flex directly to the tongue and groove boards.

This Schluter Ditra stuff, do you lay the floor tiles straight on top of it?

 

[Rob Z]

Hello again,

Yes, Ditra is a membrane with is bonded directly to the substrate, and then tile is set directly over the Ditra.

I missed the part about the T&G flooring. In my opinion, it would be a superior installation with 3/4" plywood on the joists, rather than T&G flooring.

I'm not sure that Schluter allows for Ditra to be installed over T&G flooring.

 

[DHTiling]

Sounds like good news then. There isn't any plywood down on the floor though. Not sure if I explained myself correctly, but there is the joists, to which is screwed the tongue and groove floor boards, which are I believe 3/4". A few years back, I put down the hardboard onto which I applied the self-adhesive vinyl 'planks'. Basically they are made to look and feel like real wood planks.

My plan is to lift the vinyl planks and hardboard before applying the G-flex directly to the tongue and groove boards.

This Schluter Ditra stuff, do you lay the floor tiles straight on top of it?

Again, not something i would advise..

 

[CJ CERAMICS]

just been shown this g mat in my suppliers it states that it is for newly laid floors and will prevent cracking etc etc CANT see how it is going to work as there is no solidity at all in the product........

 

[grumpygrouter]

just been shown this g mat in my suppliers it states that it is for newly laid floors and will prevent cracking etc etc CANT see how it is going to work as there is no solidity at all in the product........

As far as I can see it is nothing more than a decoupling memebrane and will only work for lateral movement. Not something I would consider using myself.