I'm about to tile in the extension where concrete base level was between 1 to 2 inches lower than the house floor. In order to level the floors the owner ordered asphalt floor to be laid down on top of sand packing. The asphalt is probably around 20mm thick. The floor seems solid. Can I tile on it? If yes how to tackle it?

at 20mm deep I would think you need to be wary. You can tile into Asphalt but you would probably need to overlay it first. There are a few options for this. You could use a gypsum based levelling compound. You could use a cement SBR slurry or you could use an epoxy sealer. Most people I know who have done this (not that many to be fair as it is not a common domestic substrate) have gone for the SBR cement slurry option. I would also use an uncoupling membrane to be on the safe side and to prevent any possibility of migration of the bitumenous oils which could stain your tiles long term

Others may have other options availbe

I think Alan has it covered here.

Is that kind of structure solid enough though? As they've put some sand beneath the asphalt.

The sand is basicly an uncoupler.. i would have liked it to be a thicker pour than you have but if sound then it should be fine.

They've also put membrane on top of the sand. Don't know what kind of membrane it is and what is it for, but probably is there for good reason. So what kind of levelling compound? Is there flexi one? The price range is quite huge. And what kind of adhesive? SPF?

Oh. And also regarding cement SBR slurry? What is it and is it difficult to do? Thanks

SBR is a liquid much like PVA to look at but dont think you can use PVA insead as you will come unstuck (please excuse the punn :-)
You mix it with neat portland cement and paint it onto the ashphelt then apply your adhesive for your tiles or decoupling membrane while it is still tacky so its fairly straight forward.
Good luck

Terry
On The Tiles (Hillingdon) Ltd
On The Tiles - Professional Tiling Service - High Quality Tiling London

Tradetiler Tilers Silicone and tools mixed with cement and using an old brush just worked into the surface

So it does seem straight forward. Do I use SPF on top of that slurry? And also any views on levelling compounds? Thanks in advance

Its SBR not SPF (wouldnt want you using the wrong stuff :-)
Sorry I missed the question about the leveling compound: what was it again?
Terry

The membrane under the asphalt on top of the sand is most likely a simple DPM. Common practice with screeds. As for the levelling compound I would suggest this simply to give you a flat level surface on which to tile. If you use the SBR/Cement Slurry you would need to use a cement based levelling compound. Go for a flexible one because the asphalt will expand and contract more than would a solid concrete fore example.

Originally Posted by terrygrant

Its SBR not SPF (wouldnt want you using the wrong stuff :-)
Sorry I missed the question about the leveling compound: what was it again?
Terry

I know it's SBR for the slurry. But is it Single Part Flexible(SPF) that I'm suppose to use on that asphalt(with the slurry as bonding agent)?

Originally Posted by Ajax123

The membrane under the asphalt on top of the sand is most likely a simple DPM. Common practice with screeds. As for the levelling compound I would suggest this simply to give you a flat level surface on which to tile. If you use the SBR/Cement Slurry you would need to use a cement based levelling compound. Go for a flexible one because the asphalt will expand and contract more than would a solid concrete fore example.

I'm gonna use either slurry or levelling compound. But thanks for advice regarding compliance(not sure if correct word) of slurry with SLC(that it need to be cement base), good for the future. I'm more likely to use the slurry.
By stating go for a flexible, you meant flexible adhesive or compound? I assume you meant adhesive.

Originally Posted by terrygrant

Its SBR not SPF (wouldnt want you using the wrong stuff :-)
Sorry I missed the question about the leveling compound: what was it again?
Terry

And about levelling compound I was asking if flexible one exist and what particular type I should use on asphalt. As I know nothing about SLC. Thanks

Use a two part slc

In my opinion the best Self Leveling compound I have ever used is Mira X-Plan. It is a polymer modified latex but what seems to make its performance superb is that it has fibre reinforcement. It can be built upto 50mm in one pour as well. However it is expensive and likley to cost around £25 per bag in small quantities but you can get down to about £15 if you a buy a palette and haggle(all ex vat)

Available from Trimline

Terry

Sorry that should say it a polymer modified single part leveling compound not latex.