Tiling over slate and flags: which adhesive?

[gasket]

hi folks.

I'm about to lay some metro wall tiles over two disused fire hearths, just to tidy them up.

Was just about to lay them and noticed the adhesive I was about to use (standard wall tile adhesive) says for porous substrates only. Common sense really, but wasn't thinking when I picked up a little tub or ready mixed adhesive.

Both hearths are made of simple flags - one is a fake polished granite/slate looking surface, the other is rougher - looks like a big standard patio flag.



Could someone advise on the best adhesive (no one will be standing on them), would it be standard non flexible floor tile adhesive? Don't want to have to lay hardie backer if I can avoid it. Cheers.

 

[vinn]

Best adhesive would be cementitious bagged powder but if you have a tub of mastic at hand then use it. Comb it on to the hearth surface and then back comb it on the tile - buttering gives you room to play with the fixing. Cut and dry fit everything before any adhesive is used.

 

[gasket]

Thanks very much vin. Bought the cement substrate adhesive you reccomended and tiled it all yesterday - went well with good adhesion.

 

[L95]

Best adhesive would be cementitious bagged powder but if you have a tub of mastic at hand then use it. Comb it on to the hearth surface and then back comb it on the tile - buttering gives you room to play with the fixing. Cut and dry fit everything before any adhesive is used.

Mastic? I hope your not referring to silicone as that would be borderline insane to use. Cement based adhesive is ideal for this kind of job but I'd suggest using a flexible based one such as BAL Max Flex or Mapei S2 depending on budget.

 

[vinn]

L95,
Ready mixed tile adhesive is known as "mastic" to distinguish it from powder - as any experienced tiler would know.
Why would I "refer to silicone" when I wrote mastic?
If you had read gasket's post's you would have noticed that he had already bought a tub of mastic. You would also have noticed that gasket actually used the cementitious powder that I had recommended.


Judging by your posts you seem a little confused about things?

 

[L95]

L95,
Ready mixed tile adhesive is known as "mastic" to distinguish it from powder - as any experienced tiler would know.
Why would I "refer to silicone" when I wrote mastic?
If you had read gasket's post's you would have noticed that he had already bought a tub of mastic. You would also have noticed that gasket actually used the cementitious powder that I had recommended.


Judging by your posts you seem a little confused about things?

Yes my good sir, I was rather confused. I read it as "tube" of mastic which is how a lot of people refer to silicone and no nails round these parts. And alas, yes I must admit that I didn't read Gasket's last post for some reason.

 

[Gteuk]

The only thing I would add to the post for people going to do this in the future is for both surfaces I would recommend something like Prime Plus (acrylic bond) the reasons are as follows.

The Flags can absorb a lot of moisture, on a warm say the flags can pull a lot of moisture out of the adhesive giving poor bonding as it will in areas turn to powder, it may look like you have good adhesion to start but over a short period of time it becomes evident that the bond was not that good.

The granite is less porous and therefore harder to adhere to,, the used of prime bond will enable better adhesion, alternatively you can use adhesive with the flexible additive in.

You can also add prime bond to the standard adhesive to give better adhesion, providing you are sure you want them to stay there forever.

I have tested using prime bond on substrate in adhesive and on the back of the tile,, and nothing short of an STS Chisel would lift them and it made a right mess.

The above was as a test in controlled conditions to see the suitability and capabilities before adding the products to the range.