level a floor

[brizzo]

Hi all
i've got to level a floor. the old floor has sunk quite a bit in some places 25mm it was origanaly ruabon reds 150mm tiles but over the years its had various stuff put on top.

i have stripped the vinal tiles of but the stuff it was stuck down with is putting up a good fight, its a tar like substance. i've got as much as possible off, my real question is do i need to seal/prime the floor area with something before i use self leveling compound to get a good bond and in the deeper parts should i add sharp sand to the mix

 

[JerryM]

in the deeper parts should i add sharp sand to the mix

i would fill in the deeper voids up front with mortar. say sharp sand 5:1

1've got as much as possible off, my real question is do i need to seal/prime the floor area

difficult one. i would say no go straight on with the self leveller. make sure you use the latex or equivalent as it minimises hairline cracking. suggest 1st doing a trial to make sure by putting a spread of the mortar over a bad area and see how hard to pull up 24hrs on.

are the tiles damp at all as given the floor has sunk in places would expect no dpm. if so i don't really have any suggestions (i am able to use a tanking material from my trade) other than to search this site and try your local builders merchants.

also you need to be sure the sub floor is now stable otherwise the topping will unfortunately crack over time (4" of concrete and a proper spec is what's technically needed but a big job).