Tiled patio

[PuPPeT]

Hi.
I need a bit of advice about a 95m2 patio I'm due to do in 1200x600 porcelain tiles.
The issue is with the substrate. It has drainage channels all around the walls which to me isn't needed as the substrate falls away from the house and only needed channels at the bottom end.
Long story short.
The substrate is 25mm to 40mm below the channels in places. Any advice on what I could use to build this up to a suitable height.
The company I'm doing it for was told to use a cement fibre board which I was told wasn't suitable for exterior use. I keep getting told different things and I'm rather confused now, so some advice would be great.

 

[Old Mod]

Both Bal and Ardex have exterior SLC's but both have limit of 20mm
BAL Acrybase | Tiling Products | BAL Adhesives - http://www.bal-adhesives.co.uk/products/acrybase[COLOR=rgba(0, 0, 0, 0.701961)]
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[COLOR=rgba(0, 0, 0, 0.701961)]ARDEX K 301 - http://www.ardex.co.uk/ProductDetail.aspx?ProductID=23&CatID=17

Bal's stone PTB on top goes 25mm suitable for porcs and exterior.
Broken Link Removed

These products would work, wouldn't be surprised if there was a more cost effective way tho.


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[Russell brown]

What is the substrate?

 

[PuPPeT]

its a concrete substrate with a 4 inch screed on top.

 

[Russell brown]

You can go down to 25mm depth with a bonded sand and cement screed. Not sure how it'll work on top of anther screed though?.

 

[Spare Tool]

I,d go for a 50/50 mix of ardex k301 and grano for the first 20-30mm then k301 to level it off for tiling, unless you wanna go the s&c route and wait a month..

 

[PuPPeT]

The customer has been waiting since October last year due to being busy, the weather and fall in temperatures. I doubt she will wait any longer :lol:. I will look into the ardex k301 thow.

 

[Old Mod]

The link for the k301 is above. Recommends a max of 20mm even with more than one coat