Laying concrete on tarmac/concrete

[Mentalguy2k8]

Hi

A friend of mine has roped me in to helping.... :( He owns a static burger van which is on a slope, he wants to level the area (about 10 feet long by

4-5 feet wide) at one end of it to install tables and chairs. It's quite a slope, probably 3-4 inches difference in height over about 10 feet. It's concrete underneath with a "council-type" tarmac on the top (looks like the cheap bubbly tarmac about half-inch thick that looks like it was laid like a roll of carpet)

So to level this off, should we rip up the tarmac? My opinion is that we need to get rid of it, then mess up the concrete underneath to give the new stuff something to grip, I have visions of a new slab of concrete simply sliding off down the road :) He thinks we can just build a wooden frame, then pour in concrete to form a wedge, let it dry, then remove the wood. No prep, nothing. What's general opinion on the best way forward ?

[Mentalguy2k8]

Also, as it's quite a slope and relatively a lot of concrete, could it be laid in 2 "layers"? If so, how do you prepare the first layer to take the second?? Thanks.

[robgraham]

I don't see why you need to disturb anything. The new concrete will grip the tarmac. All that might happen, over the years, is that the tarmac may soften in a hot summer (!) and the weight of the concrete make it ooze out of the side. But why worry about that? It's going to be a slow process.

Rob Graham

[Mentalguy2k8]

Hmm, more chance of it getting wet-rot than melting :)

Thanksd for the reply, I don't understand the physics of concrete, I just assumed it would just be resting on top of the tarmac and could possible slide off.

[robgraham]

If it shows any tendency to slide off, put half a dozen bolts through into the base concrete. I don't think it will, though, unless the tarmac gets very soft in the heat. I'm quite sure the concrete won't slide along the tarmac while it's reasonably solid.

Rob

[The Medway Handyman]

Build a timber deck over it. Up market burger van!