Laying Patio - question about foundation

alirob12

Hello

I am just about to lay a patio in my veg garden. I wonder if anyone can advise in terms of the foundation. I previously laid a similar patio (40sq m) using 2ft x 2ft slabs on sand and put dry cement+ sand mix in the gaps. It turned out really well and 2 years on it is absolutely perfect.

Now I would like to do something similar, but I am wondering if I need the sand. Currently the ground I will be laying on is a mixture of dirt (gravel type thing) with stones? I am hoping to just rake it and lay slabs on top and then use the cement + sand mix to seal the gaps? Any idea anyone? It will only be walked on as it is to create a path between the veg patches + I will be using 1,5ft x 1,5 ft slabs

There is also an area 2 x 8 m which is hard/compressed soil. Once again – do I need the sand on top of it or can I just lay the slabs straight on that?

Thank you

rmg1

I would say use the sand as well.
It will help to level the slabs as well as for drainage.

alirob12

thank you. Will need ab a tonne of sand!! never mind. thank you

DCodd

The sand is to give a level surface to lay the slabs on, this distributes the weight evenly across the slab, reducing the chances of the slab cracking.

Note though, that if the ground you are laying on is an old vegetable patch, the ground will have been dug over constantly in the past and so will not be compacted. Depending on how compacted the soil is or not, you may need a subbase of say scalpings compacted with a vibrating plate to stop the patio from sinking.

Maybe check out the DIY part of the forum for advice.

alirob12

Thank you... I will actually be laying on a very compact base - so based on the above hopefully i can get away with just using sand to level it off. The 2nd bit where i will be paving is a path between the veg patches - which is again very compact and with dirt/gravel on top so very hard...
thank you

spud17

If only we could get away with this sort of (non) preparation in my line of work.

Our slabbing etc is expected to last considerably longer than 2 years.;)

Always start with the required finished level and calculate downwards.

Finished level, take away 40mm (?) for slab another 50mm for sand then 100mm compacted Type 1 (803) stone.
So you need around 200mm removed, more if still in topsoil which will contain organic matter, this decays causing settlement and uneveness.

grizzly1911

I would use a sand and dry cement mix as a minimum for the bed and joints.

As PPs have said the sand gives you an even bed, and a "hardcore" underbed should be used if you want it to last.

Just laying them on the "dirt" will make them difficult to level, they will move, crack etc.