Concrete over old patio slabs

Idbatterim

Hi, parents place has a 17x12m courtyard, currently there are old concrete slabs laid down, if these were to be concreted over and a drainage channel laid in the middle, what depth would concrete have to be poured to on average? I have heard of 4 inch or so as a guide, in normal situations i.e no patio below, in this case over 20m3 would be required, making this option quite expensive...opinions?

mike65

Wouldn't do that myself, concrete has NO give, if the slabs move more than a fraction underneath you'll have a cracked concrete top. An overlay of asphalt would be wiser.

jj build

depends whats under the slabs and if its gone b driven on. u have to have expansion joints. u can also put steel mesh if u wanted . u could relay the slabs in sand and cement and clean them with a power washer

Idbatterim

was thinking of lifting slabs, putting weed proof membrane between the joints and then filling with sand or whatever is used, the size of the area means that come the spring / summer, the amount of stuff that grows up between the joints is unreal and keeping it weed free takes alot of effort and time... it wont be driven on, just walked on... under the slaps there is just hard compacted soil I reckon... this job was done in the late sixties...

jj build

if put hardcore down first then 50mm of sand and cement mix and bed the the slabs to the correct falls and then wet the joints and brush a semi dry mix into the joints you will have no problems , the way you where thinking of doing it will bring u back to square 1 u will still get weeds growing from the joints and the slabs will probably start rocking