6mm insulation board fixing (wedi) - Tile Advice

[117ws]

hi all,

I need to fix my 6mm wedi over my ply subfloor ahead of installing UFH and tiles.

As well as mechanically fixing the boards with screws / wedi washers do I need to use tile adhesive or can I use the wedi adhesive / sealant?

I spoke to wedi who said their sealant can be used as an adhesive to fix the boards but was unsure if the presence of UFH will be an issue? As I say they’ll be mechanically fixed every 250-300mm also....

Any ideas?

 

[Flintstone]

The tile adhesive is mainly there to fill any voids and create a solid base, I think the sealant might struggle to acheive that, why don't you want to use adhesive ?

 

[Dumbo]

As above and it's probably cheaper

 

[Waluigi]

I also prefer to use Tile adhesive.

When I last spoke to Wedi, their advise was as follows:-

“Prime the ply with a suitable primer and then bond the wedi building board to the existing substrate using a flexible cement based adhesive as well as mechanically fixing this through the existing”

If you’d like the BBA Certificate then PM me and I can mail it over. This is the manufacture recomended installation instructions.

 

[117ws]

I’ve read a lot more about using flexible adhesive than I have sealant it just got me wondering after I spoke to wedi and they were talking about their sealant as an adhesive, mind you the subfloor is pretty flat!

What size notched trowel for the adhesive? (Sorry for the bone question I’m a plasterer not tiler)

 

[On one]

If the floor is pretty flat a 6mm notch will do,in conjunction with screws and galvanised washers.

 

[Old Mod]

Wedi didn’t know if ufh effects their sealant/adhesive?

That’s incredible.

 

[117ws]

Any preference on primer for priming a timber subfloor ahead of using flexible adhesive to fix the wedi?

 

[Unused Account 1]

All the advice from different products ,use tile addy you know it works

 

[Waluigi]

Any preference on primer for priming a timber subfloor ahead of using flexible adhesive to fix the wedi?

Generally it depends on which brand of adhesive you are using. In an ideal world you should use the same brand of primer as your adhesive and follow the instructions for that primer including dilution rates and number of coats required.

 

[Old Mod]

Two schools of thought on priming ply, personally I do.
As a spread I’m sure you’ve some sbr knocking about, mix 4/5-1 and prime.
If you haven’t, buy tile specific primer to match adhesive.
Do not use pva.
Use 6mm trowel and keep the troweling constant, lay in the boards in a broken bond fashion.
Tape joints on timber floor. Alkali resistant.
Mechanically Fix Wedi boards with appropriate length screws and Wedi washers.
Prime Wedi boards.
Install ufh cables, follow manufacturers instructions closely.
Do not cross wires, this includes heat probe.
Use glue gun to stick down any loose cable that may float up when latexed.
Apply expanding foam or similar to perimeter of room and any holes where latex could run away.
Apply 3-5mm latex over top of ufh system.
The latex will not only protect the ufh system when you tile, but it will ensure allthecables are completely encased and allow for better heat transference to the tiled floor.
Prime latex
Tile.

 

[Time's Ran Out]

@3_fall - lunchtime?

 

[Old Mod]

@3_fall - lunchtime?

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