concrete

i have to lay concrete over an existing slab , how thick should i lay the new section , 20mm more or less , ? it will be for a new kitchen floor

If you want to do it with a slab topping product, I think it needs to be about 50mm thick. You'll also need to scabble the surface of the existing slab with a scutching comb to expose the aggregate and apply some Bondcrete or similar just before you pour.

Best thing to do is get in touch with a cement products company like Ardex Building Products and see what they recommend. They'll give you info on how to do it too.

I wouldn't recommend you use ordinary concrete, unless you are going to make it at least 3" thick.

If you want to lay a thin layer over concrete then as Silent C said scabble the existing concrete, use a bonding agent and then grano which from memory is made from dust, sand and cement, they use this for topping stairs ect.

This may be your cheapest option, but you may need a concreter to lay it.

The problem with ordinary concrete is the aggregate is too large to finish in thin layers.


Daniel

Bunnies sell a self leveling compound that can be laid as thin a couple of mm, and as thick as you want it.
Great for unlevel floors.
Cheers, Allan

thanks for the help , i will report back on the success or failure of this project. once again thank`s .

The tile industry would be worth a serious look.
I have seen a number of products used.

1. my own on suite the tilers used a product to "render" the floor to provise accurate falls prior to tiling. went down very thin in parts.
2. saw a bloke do a whole sert of WWWide stairs in a caffe with a self leveling compound prior to tiling again very thin in places.