Tiling on 25mm Plywood - Prep + adh ?? for Granite tiles

[SproutsDad]

To refresh this is a small cloakroom, suspended floor with granite tiles 1.5m2.
=============================================
Previous topic was on plywood vs. chipboard - plenty of advice on that; thanks - I am definitely fitting plywood! I have started this topic new as it relates to adhesive etc., but follows on from the other one.

Lots of family catastrophes means I haven't done this job yet but am about to put down this piece of very robust 25mm marine ply that I picked up as a cheap offcut from timber merchant - perfect!?

Despite having spoken to BAL tech helpline (closed today Sat 23-Mar), and Topps previously, and purchased based on their advice; I just called Topps to check and the manager now says I have the wrong adhesive, but was his suggestion in the first place.
That was when he had persuaded me to have Hardiebacker over my MR chipboard - which somebody else had persuaded me to buy. I returned the Hardiebacker as I now have 25mm ply and was told the BAL Rapidset flexible would be Ok!!

Now he is confusing me saying the ply needs priming even on the adhesive surface, the opposite to BAL and advice from here. Oh, and he says to NOT prime the under surface according to him!? He recommended the BAL acrylic primer as good as SBR but cheaper. But I have the primer so want to now use it.

>>!! Once I have learned enough from you guys, I can tell the others where to get off!! Confusing and conflicting or what?? But it's opinions - everyone's got one - some based on knowledge and experience - unfortunately too many are not!

Summary I have the following materials .....
25mm plywood, Black granite tiles, BAL Micromax grout (flexi), BAL Rapidset flexible grey 10kg, BAL primer. I prefer to use them if possible as late returns are always a battle.

I want to fix the ply down now then get on with the job.My network of joists and noggins supoports at least every 250mm apart.
My Questions – your answers please
Q1 > Do I prime the back face (the one on the joists) and edges - but not the top adh face - with BAL primer?
Q2 > Do I screw down at very close intervals 150 to 200mm intervals
Q3 > Should I also glue it down – gripfill / NoNails etc? There are a few undulations as ply has a very slight bow, but will pull down with screws?
Q4 > Should I leave the top ply surface UNTREATED - just sanded?
Q5 > Can I use the Rapidset flex adh direct on ply? - Topps manager says no, it will absorb adh too rapidly and to use the BAL primer. He also says that now I don't have Hardibacker it should be a single part flex adh? - that only comes in 20kg ££lots
Q6 > Which adhesive and do I prime ply or not?

I will have other questions I am sure, but this is ample for now.
Any confirmation of the above would be much appreciated so I can get on with it.
Many thanks.

 

[jctilingservices]

To refresh this is a small cloakroom, suspended floor with granite tiles 1.5m2.
=============================================
Previous topic was on plywood vs. chipboard - plenty of advice on that; thanks - I am definitely fitting plywood! I have started this topic new as it relates to adhesive etc., but follows on from the other one.

Lots of family catastrophes means I haven't done this job yet but am about to put down this piece of very robust 25mm marine ply that I picked up as a cheap offcut from timber merchant - perfect!?

Despite having spoken to BAL tech helpline (closed today Sat 23-Mar), and Topps previously, and purchased based on their advice; I just called Topps to check and the manager now says I have the wrong adhesive, but was his suggestion in the first place.
That was when he had persuaded me to have Hardiebacker over my MR chipboard - which somebody else had persuaded me to buy. I returned the Hardiebacker as I now have 25mm ply and was told the BAL Rapidset flexible would be Ok!!

Now he is confusing me saying the ply needs priming even on the adhesive surface, the opposite to BAL and advice from here. Oh, and he says to NOT prime the under surface according to him!? He recommended the BAL acrylic primer as good as SBR but cheaper. But I have the primer so want to now use it.

>>!! Once I have learned enough from you guys, I can tell the others where to get off!! Confusing and conflicting or what?? But it's opinions - everyone's got one - some based on knowledge and experience - unfortunately too many are not!

Summary I have the following materials .....
25mm plywood, Black granite tiles, BAL Micromax grout (flexi), BAL Rapidset flexible grey 10kg, BAL primer. I prefer to use them if possible as late returns are always a battle.

I want to fix the ply down now then get on with the job.My network of joists and noggins supoports at least every 250mm apart.
My Questions – your answers please
Q1 > Do I prime the back face (the one on the joists) and edges - but not the top adh face - with BAL primer?
Q2 > Do I screw down at very close intervals 150 to 200mm intervals
Q3 > Should I also glue it down – gripfill / NoNails etc? There are a few undulations as ply has a very slight bow, but will pull down with screws?
Q4 > Should I leave the top ply surface UNTREATED - just sanded?
Q5 > Can I use the Rapidset flex adh direct on ply? - Topps manager says no, it will absorb adh too rapidly and to use the BAL primer. He also says that now I don't have Hardibacker it should be a single part flex adh? - that only comes in 20kg ££lots
Q6 > Which adhesive and do I prime ply or not?

I will have other questions I am sure, but this is ample for now.
Any confirmation of the above would be much appreciated so I can get on with it.
Many thanks.

1, prime all sides and underside ( side facing joists )

2, screw down at 150 mm centres,

3, no glue or anything else

4, i would seal / prime it

5, yes you can use rapid set flexi directly onto ply

6, bal rapid set flexible adhesive ( single or 2 part ) yes prime the ply

 

[SproutsDad]

JCT - Many thanks
That has clarified all those Q1 to Q6, great.
Q7 > I also have a joint in the plywood, suppoorted by a joist at that point. Should I prime all faces and edges and have the joint 'dry' or should I gripfill/glue the joint edge - along it's edges and push together then screw both down at 15omm? Glue or leave dry?

Q8> Tiling under the Doorway?? - Because the cloakroom door is outward opening, the granite tiling will go into the doorway/reveal until it meets the threshold strip on the other side adjoining the hallway carpet. But the new 25mm plywood stops on the inside of the doorway and buts up against the joist and hallway T&G floor boards which will be under the tiling within the doorway for about 100mm and sits 3mm lower than the marine ply.

I have to make up the height and secure the whole lot firmly. The T&G is fully supported by joist timbers underneath and I have put loads of 60mm screws to pull it down, no movement at all - 2 fat men test. I now plan to use 3 mm ply bonded/screwed to the T&G for just that 100mm to finish and level it up. Will that work just for that small area as long as it is all tight and fully held down with screws and glue?

If it will help I can take and send a photo.

Thanks again.

 

[jctilingservices]

JCT - Many thanks
That has clarified all those Q1 to Q6, great.
Q7 > I also have a joint in the plywood, suppoorted by a joist at that point. Should I prime all faces and edges and have the joint 'dry' or should I gripfill/glue the joint edge - along it's edges and push together then screw both down at 15omm? Glue or leave dry?

Q8> Tiling under the Doorway?? - Because the cloakroom door is outward opening, the granite tiling will go into the doorway/reveal until it meets the threshold strip on the other side adjoining the hallway carpet. But the new 25mm plywood stops on the inside of the doorway and buts up against the joist and hallway T&G floor boards which will be under the tiling within the doorway for about 100mm and sits 3mm lower than the marine ply.

I have to make up the height and secure the whole lot firmly. The T&G is fully supported by joist timbers underneath and I have put loads of 60mm screws to pull it down, no movement at all - 2 fat men test. I now plan to use 3 mm ply bonded/screwed to the T&G for just that 100mm to finish and level it up. Will that work just for that small area as long as it is all tight and fully held down with screws and glue?

If it will help I can take and send a photo.

Thanks again.

7, just as before prime / seal all four edges and the underside, no need to glue, just butt together and screw down well

8, yes that will work, prime both mating faces of the boards and that will act as a glue, just make sure it is screwed down securely at 150mm centres

 

[SproutsDad]

Thanks again JCT.
Just to clarify about priming/sealing if you don't mind please.
I have obviously sealed all edges and the underside and the 25mm ply is now well screwed down.
But the top face - the one which the adhesive will go on, should it be sealed? I have the BAL acrylic primer.!!
I ask this because in a previous post on here I had specific advice from one of the advisers to NOT seal the top face. Remember I am using BAL Rapidset flexible!
The advice then was ........
"You only seal the edges and underside of the ply. This is to stop it absorbing moisture. Do not seal the face you will be applying the tiles to."

It is confusing for me. I can do either, but can't unseal it once done.
Hope you can help. Thanks

 

[jctilingservices]

Thanks again JCT.
Just to clarify about priming/sealing if you don't mind please.
I have obviously sealed all edges and the underside and the 25mm ply is now well screwed down.
But the top face - the one which the adhesive will go on, should it be sealed? I have the BAL acrylic primer.!!
I ask this because in a previous post on here I had specific advice from one of the advisers to NOT seal the top face. Remember I am using BAL Rapidset flexible!
The advice then was ........
"You only seal the edges and underside of the ply. This is to stop it absorbing moisture. Do not seal the face you will be applying the tiles to."

It is confusing for me. I can do either, but can't unseal it once done.
Hope you can help. Thanks

if I am correct, your previous advice would have came from Richard or davie ( tictic) and that advise is spot on, However if it was me using granite tiles then I would prime the floor before tiling,thats just my preferential way of doing it, it cannot harm the floor by priming

 

[SproutsDad]

jct thanks very much.
I appreciate that two professionals can have different methods, neither of them wrong, but the advice to the novice can come across as confusing.
I think on balance I will prime/seal the top surface. BTW... The floor is like concrete, would take the two fat elephants test.
My quote was from advice given to my earlier topic .... ..
//www.diynot.com/forums/tiling/tiling-over-22mm-chipboard-mr.351320/
on 17 & 18 Jan.

Q8 > earlier/ above -
Ref my earlier query on making up the 3mm level with thin ply in the doorway, see below......

Q8> Tiling under the Doorway?? - Because the cloakroom door is outward opening, the granite tiling will go into the doorway/reveal until it meets the threshold strip on the other side adjoining the hallway carpet. But the new 25mm plywood stops on the inside of the doorway and buts up against the joist and hallway T&G floor boards which will be under the tiling within the doorway for about 100mm and sits 3mm lower than the marine ply.

I have to make up the height and secure the whole lot firmly. The T&G is fully supported by joist timbers underneath and I have put loads of 60mm screws to pull it down, no movement at all - 2 fat men test. I now plan to use 3 mm ply bonded/screwed to the T&G for just that 100mm to finish and level it up. Will that work just for that small area as long as it is all tight and fully held down with screws and glue?

Please confirm .....
I have read that such 'packing' should be done with the adhesive to be used for tiling (Rapidset Flex) + thin ply, not gripfill/ glue & screws? Which shall I do? As long as the thin ply is well bedded on an adhesive of the right type and is also screwed to the T&G boards, which are themselves pulled down tight with 2.5" screws into the joists - wouldn't that be fine?

Which do I do please? Perhaps Gripfill is too 'fluid' for the job, it doesn't set rock hard, always slightly flexible. Or maybe that's a plus?
Feedback as always much appreciated.
Thanks

 

[jctilingservices]

jct thanks very much.
I appreciate that two professionals can have different methods, neither of them wrong, but the advice to the novice can come across as confusing.
I think on balance I will prime/seal the top surface. BTW... The floor is like concrete, would take the two fat elephants test.
My quote was from advice given to my earlier topic .... ..
//www.diynot.com/forums/tiling/tiling-over-22mm-chipboard-mr.351320/
on 17 & 18 Jan.

Q8 > earlier/ above -
Ref my earlier query on making up the 3mm level with thin ply in the doorway, see below......

Q8> Tiling under the Doorway?? - Because the cloakroom door is outward opening, the granite tiling will go into the doorway/reveal until it meets the threshold strip on the other side adjoining the hallway carpet. But the new 25mm plywood stops on the inside of the doorway and buts up against the joist and hallway T&G floor boards which will be under the tiling within the doorway for about 100mm and sits 3mm lower than the marine ply.

I have to make up the height and secure the whole lot firmly. The T&G is fully supported by joist timbers underneath and I have put loads of 60mm screws to pull it down, no movement at all - 2 fat men test. I now plan to use 3 mm ply bonded/screwed to the T&G for just that 100mm to finish and level it up. Will that work just for that small area as long as it is all tight and fully held down with screws and glue?

Please confirm .....
I have read that such 'packing' should be done with the adhesive to be used for tiling (Rapidset Flex) + thin ply, not gripfill/ glue & screws? Which shall I do? As long as the thin ply is well bedded on an adhesive of the right type and is also screwed to the T&G boards, which are themselves pulled down tight with 2.5" screws into the joists - wouldn't that be fine?

Which do I do please? Perhaps Gripfill is too 'fluid' for the job, it doesn't set rock hard, always slightly flexible. Or maybe that's a plus?
Feedback as always much appreciated.
Thanks

2 options available, screw down 3mm wpb ply then tile over, OR make up the deficit in height by using slightly more adhesive, ie on the rest of your floor use a 6 mm trowel, on the last part which is lower, use a 10 mm trowel, this will bring tiles to approx. same height, just make sure you press the tiles in place using a twisting motion.

I would actually do that using the 2 trowel method, not using the 3mm ply. but hey that's my preference, hope this helps mate. just remember when using rapid set, only mix what you can comfortably use otherwise it will just start setting in your bucket

 

[SproutsDad]

Yes, the slowest tiling job ever!! But I get lots of domestic diversions.

I am just about to lay the granite floor tiles, they cut easily using the wet diamond cutter, so that's great. The 25mm marine grade plywood floor, only 1.5m2 is all screwed down tight and sealed on back face and edge with BAL primer.

I have BAL Rapidset flex, bought ages ago so it can't go back, recommended for the job by Topps Tiles manager, likewise BAL primer instead of SBR. I went through this in earlier part of this thread and JCT advised that most of this would be fine.

So, with so much conflicting advice, not wanting to make a mistake and not convinced that bare wood is the best to put adhesive on I called the BAL helpline to confirm sealer or not on the top face?!

What a mistake!! Of late their tech Helpline has been manned by mostly women who admit they can only give limited advice. They are reading from a script and just quote 'no sealer', lay adhesive on bare wood. So I asked why, and they couldn't answer me I was transferred to a man who questioned absolutely everything I have done to date.
He challenged >>
> If 25mm ply was thick enough?
> Why was I using Rapidset and to take it back for single part flexible instead.
> He said primer wasn't suitable and it should have been SBR (very expensive). Too late! His colleague at BAL & Topps manager had earlier said it would be fine and I have used it on underside and edges.
> He said my 10mm x 20mm notched trowel was no good and to buy a special BAL flatbed trowel leaving a complete layer + notches.

Help please !!
Q1 - Shall I use primer on plywood, BAL say no and that the wood won't dry the adhesive too fast?? I don't know!
Q2 - Which trowel? Is my square notched 10 x 10 square notch or the half round one?
Q3 - Shall I stay with the Rapidset? I don't have option to return it.

Sorry, but I found the BAL helpline very OTT and quite negative.
Hope you can help.

 

[tpt]

In fairness the tech lines do often go over the top, but they have to follow the letter of the law.

First load off your mind can come from BALS data sheet for that adhesive
http://files.building-adhesives.com...C Technical Data Sheets/BAL_Rapidset_Flex.pdf

Suitable for ply - yes.

They do state to prime the face and all sides with SBR. if you want to follow the letter of the law, then do this but most other addy manufacturers state no sealer on the face.

25mm on the area your covering will be fine -you can test for deflection yourself, bounce up and down and you'll feel it.

 

[SproutsDad]

Thanks TPT, a very prompt reply and much appreciated.

> So Rapidset adhesive is Ok, thanks.
> The 25mm plywood is well screwed down & shows no movement at all when bounced on, Ok.
Q1 > Primer - mine is the ordinary BAL primer, not SBR - hope that is Ok? Topps manager said it was just as good as SBR.

Q2 > Sealing Plywood top face?
Sorry to question it but BAL themselves also say to only prime the underside (face against joist) and edges of ply and to NOT prime / SBR the top face. Therefore to put adhesive on bare ply. Is that what you mean? Tradesmen I have spoken with and others on this forum have mixed views 50/50 on priming the top (adhesive) ply face or not. As a layman I would have thought that by it's name Rapidset will go off quickly and that a dry, porous wood surface will draw the moisture and therefore make it cure even quicker - possibly too fast for workability. Your comment please, I will do whatever you feel is best.

Q3 > Trowel type and adhesive bed method?
What depth of solid adhesive bed am I looking to achieve once it is pressed down, and how do I achieve that - with what trowel and method?

I am very confused. My tiles are black granite, the back surface is as-cut, 30 x 30cm with a polished face.

Q4 > Should I be using a thick flatbed approach, where the surface gets a complete 3mm covering, PLUS the notched beads of adhesive on top of that? BAL have special notched trowels for that I think, if you can get hold of them. But do I need to go that route?

Q5 > Or do I use one of the trowels I already have which are a square 10 x 10mm notch or a half round notch of about 15mm diameter?

I read another post on "Floor tiles - notched OR flat bed ?" //www.diynot.com/forums/viewtopic.php?t=267554.

- - - - - - - - - - - - - - - - - -
zappastix wrote:
"Does it work like this: I use the correct notched trowel, and when slight pressure is applied to the floor tiles the "notches of adhesive" push/join together to form a 'solid bed"

To that Richard C replied ..........
"Yes; the type of notch trowel you use dictates the adhesive bed. Push down firmly & use a very slight side to side twisting motion the bed & level the tile; same technique for wall tiles. TBH, you will be OK with the smaller 10mm deep notch trowel which is all I use unless the tiles are like paving slabs!"
- - - - - - - - - - - - - - - - - -

And..... in all this I need to remember that this is a cloakroom of 1.2m2, with about a 0.4m2 traffic area !!

Thanks, your help is much appreciated.

 

[jctilingservices]

sproutsdad,
your ply will be absolutely fine, the primer you have used will be fine, you can use either the notched 10mm 0r 20mm trowel. Don't be put off by what the tech guys tell you, they are NOT tilers, mostly they are reading from computer screens and giving you the jargon. Rapid set flexible adhesive, yes it will set failry quick, therefore only mix as much as you fee you can comfortably use at any one time.

Priming your floor before tiling is entirely your choice, if it was me and I had primer with me then I would prime, if didn't have it with me then I would tile without using it,

you have primer so just use it, then tile. everything you have done and all the materials you have are entirely suitable for fixing granite.

Just waiting to hear back from you as to how you got on, best of luck mate

 

[SproutsDad]

JCTiling,
Thanks very much, I will crack on with it tonight. Just a couple of other small queries if you wouldn't mind please..............

Q1 > Tile spacers / gap -
I have some 3mm tile spacers which, for this small area seem plenty. I also have some larger ones about 5mm but that gap seems massive and in such a small space looks out of place. Although it may be snug, it is still wider than wall spacers I think? Anyway, it looks more correct in the small area of this cloakroom. Shall I go for the 3mm ones?

Q2 > Granite Sealer -
I have a sealer and was told to guard against staining the tiles - black granite - from either adhesive or grout. I was advised by Topps & BAL to put one coat of sealer on before grouting to protect from the grout - I am using BAL Micromax flexi grout gunmetal colour - then will seal the lot once grouted and cleaned up. How does that sound?

Q3 > Adhesive Thickness and Bedding Tiles
I presume that the resulting adhesive bed will be around 3mm thick once the notches have spread out to join together. Do I just place and slightly twist the tiles and tap lightly with rubber mallet and spirit level to align?

Your valued comments please, then I'll press on with the job - at last!!

 

[jctilingservices]

JCTiling,
Thanks very much, I will crack on with it tonight. Just a couple of other small queries if you wouldn't mind please..............

Q1 > Tile spacers / gap -
I have some 3mm tile spacers which, for this small area seem plenty. I also have some larger ones about 5mm but that gap seems massive and in such a small space looks out of place. Although it may be snug, it is still wider than wall spacers I think? Anyway, it looks more correct in the small area of this cloakroom. Shall I go for the 3mm ones?

Q2 > Granite Sealer -
I have a sealer and was told to guard against staining the tiles - black granite - from either adhesive or grout. I was advised by Topps & BAL to put one coat of sealer on before grouting to protect from the grout - I am using BAL Micromax flexi grout gunmetal colour - then will seal the lot once grouted and cleaned up. How does that sound?

Q3 > Adhesive Thickness and Bedding Tiles
I presume that the resulting adhesive bed will be around 3mm thick once the notches have spread out to join together. Do I just place and slightly twist the tiles and tap lightly with rubber mallet and spirit level to align?

Your valued comments please, then I'll press on with the job - at last!!

1, because of the small area I personally would opt for either 1 or 2mm spacers, 3 would be at a push

2, seal before grouting, then after washing off grout let the floor dry, if there is a slight haze on he tiles, polish it off using a soft, clean lint free cloth, then seal again

3, Spread out your adhesive, try to keep the trowel at a constant angle, and thoroughly comb the adhesive, lay your tile into position and give a slight twist, just repeat this for every tile, making sure you check that all edges are level, or you may have to press the tile deeper into your addy or even add a touch more depending if a tile is high or low, yes keep checking with a level, although sometimes a floor is flat but not level, keep a check. hope this gives you the help you need

 

[SproutsDad]

JCT - Thanks very much, what a thorough and incredibly fast reply to both queries. With that support it can only go well - I hope. The thinner spacers sound best.

I will report back on progress.

Thanks again. BTW - Sprout is the 3-legged cat, otherwise known as Tripod !! Dodgy heart, bit missing from his ear and a leg gone, but otherwise healthy, climbs trees and keeps the dog in line.
Thanks for everything.