Is there such thing as too many substrate layers?

[Julian C]

Hi I have been browsing these forums for a while and have picked up lot of useful advice.

There will be 7 layers to my floor (not including Adhesives, seems like a lot!)

Joists/Noggins

18mm Ply

6mm Hardie Backer

10mm Warmup

Electric UFH

SLC

Ditra Mat

Tiles

I’m a Diy’er tiling my first floor but have done lots of research trying to get it right.

It’s a small upstairs bathroom in a Victorian Terrence.

I ripped up the floor boards as they had large gaps etc.

The beams are 400mm centres, I put in 3 rows of noggins at 610mm centres where the board join.

I laid 18mm Plywood (DIY stores didn’t do 24mm). Sealed back and edges, Glued and screwed to beams / noggins.

6mm Hardie backer board fixed with Mapei Kerquick S1 (Hardie recommended non flexible but my local screwfix was out of stock so used S1) and screwed at 150mm all over, fibre taped and adhesive over the joins.

This is as far as I have got so far (the floor feels nice a stiff when I jump on it) ... but the plan is:

10 mm Warmup boards stuck down with Mapei S1 and screwed with large washers. ( I got these boards for free or I might not have bothered).

Nass board underfloor heating kit (Laid by myself multimeter testing as I go and terminated by an electrician)

Bostik Cempolatex Flexible self-levelling compound (mainly to protect the wires from my bad trowelling)

Mapei S1

Schluter Ditra mat (Because I’m scared the gout will crack if I don’t, will it?)

Mapei S1 with Latex added

200mm X 200mm Ceramic tile with a 3 mm grout line Bal grout with Latex added. (Also using vitrex LASH system to hopeful get 0 lippage on my first try at tiling) going to be cutting with a wet tile saw.

I’m doing all the Adhesive will a 6mm square notched trowel, is this ok?

Is there anything obvious I have done wrong?

Will all these different layers interact to cause any kind of weakness or should I be ok??

 

[Boggs]

You could have saved a few quid and just glued and screwed the 10mm warmup boards to the ply floor, thin coat of slc and then tile.

Personally I would put heating on the Hardie and slc over and tile.

I would take the Vitrex lash clips back they are not the best and will probably cause more problems than they solve imho.

 

[J Sid]

as above and would need Ditra with them tiles

 

[Flintstone]

I wouldn't fit ceramic tiles over underfloor heating personally.

 

[WetSaw]

You shouldn't need Ditra. I don't like ceramic tiles on the floor, porcelain are much stronger especially on ufh and clips with that size tile will be more trouble than they're worth.

 

[Julian C]

I just checked and they are porcelain tiles not ceramic!

these: Brasserie Porcelain Paix Tiles | Artisans of Devizes - https://artisansofdevizes.com/product-collections/exterior-stone-porcelain/brasserie-paix-porcelain/

So should be fine with ufh then. Few
(I wasn't planning ufh when I bought the Hardie backer but added it in last minute as a nice luxury for only £70)

I will try the tiling without the Virtex clips and only use them if I struggle to get them level then, £20 worth of returns possibly, I just want to get it perfect after putting so much time and money in!

Thanks for the advice/reassurance guys.

 

[Dumbo]

Don't use the vitrex clips use something else vitrex clips have a strong curve in the base which will probably lift your tiles from the adhesive

 

[Boggs]

I hope those tiles are not as “sizey” as they are in the picture!

If you want to use levelling clips then buy some from Pro Tiler, down there, or eBay.
You want ones with a thin flat bottom.
I would suggest buying the 1mm versions as they break easier when removing and using normal spacers for grout width.

When you knock the clips out kick them along the grout lines otherwise you run the risk of chipping a tile.

 

[Julian C]

I hope those tiles are not as “sizey” as they are in the picture!

It took me a minute to figure out what you meant but, Yes!
I just noticed they look awfully laid in that picture. Hopefully they were just in a big rush to shoot the photo!