Some Advice For Tiling Kitchen - Tile Advice

[Swindiff]

Hi
1st time post, newbie tiler after some advise.

I am planning on tiling the whole of the downstairs in a 3 storey townhouse, total area is around 30 square meters, have ordered 33 square meters of this porcelain tile. The room is kitchen / diner / family room, with a cloakroom and hallway.

Surface White

There has clearly been some water issues in the kitchen area in the past, as far as I can tell the floor is a concrete base (assumed as I cant see it) there is then a layer of insulation (polystyrene sheet), a DPM (blue plastic sheeting), then 18mm T+G Chipboard and then plywood (maybe 6mm thick).

I am assuming where there has been a leak in the past the plywood was compromised as it has been cut away (actually looks like it has been gnawed by a beaver) where it could be accessed in the kitchen area, however the ply still remains underneath the kitchen cabinets and in the dining area. The chipboard is also rotten around the sink area.

My plan is to remove the remaining plywood from the dining area, and where the cabinets once were (the kitchen has been removed). I then need to cut out the rotten chipboard with a circular saw and replace it.

I am then planning on laying 6mm Hardie Backerboard, this seems to be the best price I can find.

HardieBacker EZ GRID 6mm for Floors (HardieBacker 250) | Dry Lining | Plasterboard | Specialist Board | | Insulation Express

I have read that this should be laid on non-flexible tile adhesive and screwed to the chipboard. As the chipboard is 18mm and the backerboard is 6mm, the standard Hardie Backerboard screws at 32mm will be too long and puncture the DPM and Insulation so I was planning on using these screws which are 20mm

http://www.NoLinksToThis/p/turbogold-woodscrews-double-self-countersunk-4-x-20mm-200-pack/11191

The joints then need to be taped and skimmed with the same non flexible adhesive

http://www.diy.com/departments/ceme...6414!&ef_id=U853pAAABQH6jUcU:20160607105713:s

The porcelain tiles are then laid with flexible adhesive.

Have I got anything spectacularly wrong here?

Are those screws suitable, they seem to make a big deal about using the right screws, but then I guess they want to sell their product.

What adhesives should I be using, flexible and non-flexible.

Many thanks for any advise you can give.

Cheers

 

[Ian]

What is the chipboard fixed to? Sounds like a floating floor from what you've described.

 

[Swindiff]

Hi Bri, yes as far as I can tell its just sat on the DPM and Insulation. I will know better when I come to cut the rotten portion of the chipboard out.

 

[Ian]

Have a search on the forum for, floating floors, it's a heavily discussed subject and 95% wouldn't even entertain tiling onto one without some serious prep work.

 

[Swindiff]

Oh crap

Whats the solution, get it screeded?

 

[Ian]

Oh crap

Whats the solution, get it screeded?

In a word. Yes. Using a 12mm cement board might work but, it's difficult to know without seeing just exactly how much deflection is in the chip board. Not something I'd be doing, once bitten and all that.

 

[Swindiff]

How thick would the screed need to be, just simple cement sand screed or something else? If I take the Chipboard and Ply up I am estimating that would be about 25-30mm. There are a couple of areas where there are partition walls e.g. cloakroom, is it ok to cut the chipboard out around them and screed upto them?

 

[Old Mod]

If u have a cross hair laser, put it on floor and walk around it, u'll soon see the amount of deflection u have and its a good visual aid to show customer the problem.
Failing that a brim full glass of water can have same visual effect.

 

[Swindiff]

OK I have been and had a better look, there is a concrete base, on top of that is 50mm of bog standard polystyrene sheet, layer of thin blue plastic (think this is to stop the chipboard squeaking on the polystyrene more than anything else), then 18mm T+G Chipboard then 9mm plywood.

So total of around 77mm. Could I replace the 50mm polystyrene with 25mm Celotex, than add a screed of around 50mm, this will bring me to the same level. I understand recommendation for screed is 70mm, but I am assuming 25mm celotex wont flex as much as 50mm polystyrene, also would it help if I had screed with fibres added?

Or I could possibly go to 70mm screed which would raise the floor level by about 20mm?

Opinions on the best way to go

Cheers

 

[Spare Tool]

I'd be looking at lifting floating floor and either getting it screeded to desired height, or fitting marmox boards, available from 6-60mm, to concrete base.
Most cost effective is screeding for sure but you'll then have to wait for at least two months before its dry enough to tile on.
Marmox boards can be tiled on straight away..

 

[Swindiff]

2 month wait is ok. Just want to check that this floor construction is adequate

Concrete base - 25mm Celotex - 50mm screed with fibres

Should there be a plastic sheet separating the Celotex and screed, or does the screed just go straight onto the Celotex, does it need to be prepped in any way?

 

[Swindiff]

I'd like to throw something else into the mix now, underfloor electric heating

I guess this would go on top of the screed and tiled directly onto?

 

[Tile Shop]

I'd be looking at lifting floating floor and either getting it screeded to desired height, or fitting marmox boards, available from 6-60mm, to concrete base.
Most cost effective is screeding for sure but you'll then have to wait for at least two months before its dry enough to tile on.
Marmox boards can be tiled on straight away..

I'd like to throw something else into the mix now, underfloor electric heating

I guess this would go on top of the screed and tiled directly onto?

BAL Quickset cement can be added in place of normal cement if you wanna fast-track it. Going onto a polythene layer then Celotex to build up the level, would mean the heat transferring down 65mm of screed (minimum thickness of screed on a floating layer) before bouncing off the insulation so it will use extra power on the initial heat up.

So my opinion would be, Polythene layer, 65mm cement/sand screed (1:4 mix), 10mm Marmox, UFH, SLC, Flexy adhesive, tile, grout, finish!

But there are guys on here with more experience than me, that may blow my theory out the water and have a more suitable suggestion

 

[J Sid]

I'd like to throw something else into the mix now, underfloor electric heating

I guess this would go on top of the screed and tiled directly onto?

underfloor heating in the screed

 

[Swindiff]

Either in the screed or on top, open to opinions. Is there a need for a SLC if on top of the screed, I can see how it would probably make laying the tiles easier.

If I screed first then put insulation on top, rather than the other way round, would it be better to have a thinner screed, say 50mm and a thicker insulation layer, 25mm as doing it this way the screed is laid directly onto the concrete, not on insulation.