Sticking tiles - what to use?

[Ham]

I'm making a frame to hold a frieze of tiles for my niece, to go on an outside wall. I've welded up the frame from 3mm steel and I'm going to inset a foam tile backing board, then the tiles. I'm thinking to use external white silicone throughout to stick and seal, but never having done this before I thought I'd enquire of a load of other people who have never done it before. Can you think of anything better to use?

Here it is, with the first coat of Hamerite (using that always makes me smile)

[Von Broad]

Nice.

Personally I'd use a roofing-type sealant, bit thicker [make sure the tube is nice and warm before you use it], but will do the job no probs.

[Poly Hive]

I would use Araldite myself.

PH

[Gattopardo]

Why not just use exterior tile adhesive?

Is that backing board water proof?  Sikaflex ebt is a favourite at the mo sticks and seals.

[Ham]

I reckoned tile adhesive would not have enough flexibility, given that the frame was steel. The external silicone seems to have done a decent job. I managed to get the frame tolerance +- 1mm, so happy with the overall finish. If it had been for myself, I suppose powder coating would have been better.