Over boarding Chipboard floor with 6mm Marmox board

[richardbell81]

Hello all,

Following on from my last thread I wondered how you would suggest fixing 6mm Marmox board to 18mm chipboard flooring. I haven't been able to do anything about it since my last post as i've been away so just to re-cap...

I'm tiling a small bathroom floor (2.2 m2, pic attached) with large porcelain tiles (600x300x10mm). I removed the old damaged floorboards and replaced them with 18mm Tongue & Groove Waterproof Treated Chipboard Flooring 18mm. I would say the floor is solid with 'slight vibration'. I wanted to avoid adding any more height to the floor so I was planning to tile directly onto the chipboard with BAL spff... but thanks to all of yours advice I have decided to compromise and overboard with a 6mm tile backing board. I can't go any thicker than this which is why it's a compromise! I have decided to use Marmox/Wedi board as it will add that bit more strength to the floor, it's waterproof and is a much better substrate to tile on to. I realise I should go for a thicker backer board but I really can't add any more height to the floor due to the position of the soil pipe!

My plan was to...
- screw the Marmox board down (screws 150mm apart) with a 'sandwich' layer of adhesive in between. Was going to us either BAL spff (or Supercover rapid flex as I have a spare bag!).
- Tile onto the Marmox board using BAL Single Part Fastlex
- Grout Using BAL Wide Joint + GT1 additive

How does that sound?Your advice really is appreciated!

 

[nybor62]

have you got the screws washers and jointing tape, and as you removed the old floor i would have gone with 18mm wbp ply instead of the chip board, imo

 

[richardbell81]

have you got the screws washers and jointing tape, and as you removed the old floor i would have gone with 18mm wbp ply instead of the chip board, imo

Using 25m galvanised screws with 30mm washers. Part of the reason for over boarding is that I know chipboard isn't the best substrate but I can't take up now as it has been screwed down (and glued in places where it covers the old upstairs concrete fireplace hearth).

 

[nybor62]

ok you seem to have it all covered

 

[richardbell81]

Using 25m galvanised screws with 30mm washers. Part of the reason for over boarding is that I know chipboard isn't the best substrate but I can't take up now as it has been screwed down (and glued in places where it covers the old upstairs concrete fireplace hearth).

Really? That's the first time i've heard that! :smilewinkgrin:

 

[Perry]

only thing you may get away with IMO is 10mm never gone any thiner stuck down with something like fastflex or timberflex then spf with the tiles

 

[richardbell81]

Really? That's the first time i've heard that! :smilewinkgrin:

So confusing, I suppose it comes down to personal experience. In my last post I had quite a few suggesting 6mm tile backing board. Would using Hardiebacker make a big difference as opposed to Marmox?

 

[macten]

If I was only going to overboard at 6mm I would use NoMorePly stuck down with their megastrength glue and screws.
Minimal height increase as not using a layer of adhesive and this stuff really works well for what you are doing.

 

[richardbell81]

If I was only going to overboard at 6mm I would use NoMorePly stuck down with their megastrength glue and screws.
Minimal height increase as not using a layer of adhesive and this stuff really works well for what you are doing.

Thanks for the advice! What Adhesive and grout for tiling would you recommend with NMP? Would the BAL spff and wide joint + gt1 still be my best bet? I do have a spare bag of Super cover rapid flex which I bought before christmas but was warned this wouldn't be flexible enough?

 

[Andy Allen]

bal single part fast flex, bal wide joint grout with gt1 admix is about the most flexable combination ive come across..

 

[prceramics]

ditra mat ?

 

[richardbell81]

ditra mat ?

I have considered Durabase but I just thought that over boarding would add more strength and help any minor deflection in the floor. Although a thin un-coupling membrane is very tempting if it would do the job!

 

[Perry]

So confusing, I suppose it comes down to personal experience. In my last post I had quite a few suggesting 6mm tile backing board. Would using Hardiebacker make a big difference as opposed to Marmox?

yes it wouldn't be as good as marmox IMO must of laid close to a million mts of floor tiles I have a little experience lol

 

[richardbell81]

yes it wouldn't be as good as marmox IMO must of laid close to a million mts of floor tiles I have a little experience lol

Thats a hell of a lot of floor tiles! So your saying use Marmox/wedi? Or have i read that wrong?

 

[Perry]

Thats a hell of a lot of floor tiles! So your saying use Marmox/wedi? Or have i read that wrong?

No if your floor is solid no movement cement board is fine you said you was going to put 6 mm marmox down spf no good on chipboard IMO was trying to help the best way to do a bad job as such marmox is a little more sound with adhesive IMO than cement board

 

[richardbell81]

No if your floor is solid no movement cement board is fine you said you was going to put 6 mm marmox down spf no good on chipboard IMO was trying to help the best way to do a bad job as such marmox is a little more sound with adhesive IMO than cement board

yeh, thanks for your help and advice. That's interesting as i would have thought that cement board (hardi, nmp) glued and screwed would be more solid than Marmox + adhesive.

 

[Perry]

yeh, thanks for your help and advice. That's interesting as i would have thought that cement board (hardi, nmp) glued and screwed would be more solid than Marmox + adhesive.

Have you phoned Marmox and Hardi ? if not try and see what they both say

 

[richardbell81]

Have you phoned Marmox and Hardi ? if not try and see what they both say

I'l give them a try although i've phoned a few manufacturers (Ditra, Durabase, BAL, Marmox) and they all think that their product is suitable... which i'm not doubting but I just need to find the best possible solution considering my constraints.

If i'm honest, i'd quite happily pay a pro to come and have a look and give me his opinion but i'm not sure if many tilers around sheffield offer a consultancy service!

 

[Stewart]

yeh, thanks for your help and advice. That's interesting as i would have thought that cement board (hardi, nmp) glued and screwed would be more solid than Marmox + adhesive.

All the products mentioned above are designed to give you the best substrate to tile to and not "strengthen" or make more solid" The substrate that these boards need to be fixed to, must be solid and deflection free before installation on floors commences!.

 

[richardbell81]

All the products mentioned above are designed to give you the best substrate to tile to and not "strengthen" or make more solid" The substrate that these boards need to be fixed to, must be solid and deflection free before installation on floors commences!.

The floor is as deflection free as it can be considering the joists are over hundred years old and not specced up to modern standards. I've done the glass full of water test and as I said, there is some minor 'vibration' when walking on the chipboard flooring but it's screwed down solid. I realise there will be some natural movement over time but i'm assuming over boarding makes a more stable substrate to tile onto.

2 Layers made up of 18mm Flooring + 6mm Boards glued and screwed is surely 'stronger' (in one sense) as it's 24mm of support as opposed to a single layer of 18mm woodchip? That's why I can't get my head round how a de-coupling membrane would help in my case other than being a better surface to tile on and protect against any moisture affecting the chipboard even though it's the water proof treated stuff... and yes I know, chipboard can't be waterproof.

I should have just chucked down laminate over the bloody thing!!! :mad2:

 

[izzi1]

I would definately use No more ply 6mm glued with mega strength adhesive and screwed with no more ply screws. I have used this method in both bathrooms in my own home over chipboard flooring and the tiled floors are solid as a rock with no movement or cracking of grout lines. Its very good stuff, easy to use and quick. Tiletown are a cheap reliable supplier and make sure you buy the cutting tool.
Single part fastflex is very expensive, I always use Mapei Keraflex maxi.

 

[richardbell81]

I would definately use No more ply 6mm glued with mega strength adhesive and screwed with no more ply screws. I have used this method in both bathrooms in my own home over chipboard flooring and the tiled floors are solid as a rock with no movement or cracking of grout lines. Its very good stuff, easy to use and quick. Tiletown are a cheap reliable supplier and make sure you buy the cutting tool.
Single part fastflex is very expensive, I always use Mapei Keraflex maxi.

That is music to my ears! I've just ordered Some no more ply 6mm, adhesive and screws! Although I didn't order the cutting tool... is their anything else I can use instead? I also ordered a 'solid bed tipped trowel' for use with the BAL spff a;though I will look into the mapei stuff if you say it's much cheaper! Do you know what trowel would be best with the keraflex?

 

[richardbell81]

That is music to my ears! I've just ordered Some no more ply 6mm, adhesive and screws! Although I didn't order the cutting tool... is their anything else I can use instead? I also ordered a 'solid bed tipped trowel' for use with the BAL spff a;though I will look into the mapei stuff if you say it's much cheaper! Do you know what trowel would be best with the keraflex?

Also, did you prime the NMP before fixing the tiles?

 

[izzi1]

Dont bother buying the primer you dont need it, always use a solid bed trowel for floors, i would seriously advise you to buy the cutter, the boards are dense cement board so if you think you can use a stanley knife or a saw you will be tearing your hair out. Use the cutter with a straight edge, scribe firmly and snap over a batten laid under the full length of the cut. Follow the instructions on the NPM website and you will be fine. Also do the whole job in one session, dont glue them down then screw hours later or the next day, the reason i say this is that the glue expands while curing, so you want the whole lot glued and screwed in 1 go.
Dont know how much you are paying for BAL but Kerraflex maxi can be bought for aboout £** from tile giant (they price match).

 

[richardbell81]

Dont bother buying the primer you dont need it, always use a solid bed trowel for floors, i would seriously advise you to buy the cutter, the boards are dense cement board so if you think you can use a stanley knife or a saw you will be tearing your hair out. Use the cutter with a straight edge, scribe firmly and snap over a batten laid under the full length of the cut. Follow the instructions on the NPM website and you will be fine. Also do the whole job in one session, dont glue them down then screw hours later or the next day, the reason i say this is that the glue expands while curing, so you want the whole lot glued and screwed in 1 go.
Dont know how much you are paying for BAL but Kerraflex maxi can be bought for aboout £** from tile giant (they price match).

ok that's great, i'm guessing the solid bed tipped trowel with do the job then!

One last thing, what flexible grout would you recomend with the keraflex maxi?

Thanks again, rich