ADVISE NEEDED - Mastic Asphalt roofing grade situation

[SquareEyes]

HI everyone, I'm hoping someone out there will have some insider knowledge on how to deal with roofing grade Mastic Asphalt.

I am preparing to tile a roof terrace and have just been told that the substrate (the roof) has been waterproofed with Mastic Asphalt:yikes:.
I need to raise the floor up by 10-20mm so I was going to use Topcem pronto. Now that I know it's roofing grade mastic asphalt I do not know what to do. Mapei Technical say that roofing grade asphalt cant be tiled onto or screeded onto as it will "pull" up the asphalt. Every other company I call say the same thing - either to rip up the asphalt (not an option) or to sand cement screed it min 65mm (not an option).

Does anyone know how I can raise the roof terrace floor up by the needed amount, ready to receive tiles? Can Mastic Asphalt (roofing grade) be tiled onto whatsoever?

Would it be a matter of laying floor grade mastic asphalt?

Any help would be greatly appreciated!

Tiles - porcelain
Area - 20m x 2.5m (50m2)

 

[DHTiling]

You have been told which way to do it, we cannot advise you to do it any other way.. roofing grade is a no no..

 

[SquareEyes]

Im just confused with the types of mastic asphalt out there. I've called a few roofing companies which say their roofing mastic asphalt can be tiled onto, but this doesnt tally up with what the likes of Mapei or Bal say....

 

[Gazzer]

If the adhesive companies say no then think about it....they say that for a reason. Its not just about selling their product.

 

[SquareEyes]

Thanks, I realise they are there to give correct advise on using their products, but after having received conflicting advise I started doubting what was said - finally I feel more confident with good outcomes from 2 Technical departments...

Just spoke to a Mapei (again) and IKO (makers and distributors of Asphalt) technical guys and they said that as I long as I use 1200 gauge visqueen sheet laid over the top of the roofing grade mastic asphalt and a min of 35mm screed used there would be no problem with tiling over the top of that. Any thoughts on that guys?

Hopefully that might help someone in the future, but would certainly advise on checking any information given twice or three times.

 

[Dan]

If Mapei have said that, then go with that, if it's an option. Obviously use their gear so it's backed by them etc.