Grout coming away from outdoor tiles - Tile Advice

[spooner68]

I have a client that has an outdoor area tiled with 20mm porcelain (600x600mm) where the grout is breaking out of the joints. It is on a very solid timber platform with (I’m assured) 25mm outdoor grade plywood as the top. It has been grouted with Kerakoll Fugalite Bio which now has come away from the tiles themselves leaving a hairline crack on some bits and lifting out completely in some others.
There is no obvious movement in the deck (a full glass of water didn’t spill or indeed wobble with the 16 stone client jumping up and down next to it) and he’s asking for a solution.
Any ideas of a product that could be used in place of the Fugabio?

 

[One Day]

No obvious movement you say - but there will be TONS of lateral movement with this heat.
There should have been an uncoupling membrane used.
Without one, there is no solution. The grout has cracked and de-bonded due to excessive lateral movement.
(based on your info given)

External tiling on ply is simply asking for a failure in my opinion anyway!

 

[spooner68]

The tiles seem well bonded but I’m sure if I put a bit of effort in they’d come away. Do you reckon a ditra cover and re-tile would solve it? Or maybe overlay with cement board, then ditra (or similar)? Just looking at options for them without trashing the whole area.

 

[One Day]

If it really is well-braced then I would have fixed Ditra drain 4 (as it's external) and this would have covered all bases.
I'm not a fan of cement boards because they hold water like sponges.
If the timber is sound and strong, clean it back, prime it, fix Ditra drain and you're good.
How big is the area? Does it need expansion joints?

 

[spooner68]

5x3.5m

 

[GoneGuy]

You will need ditra drain 8 for exterior, maybe ask @Schlüter-Systems Ltd for more info or for a rep to pop out and specifiy the job?