6mm insulation board fixing (wedi)

[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.