Replacing block paving with slabs - Replacing block paved patio with slabs

[glenne_n]

Hi Folks,

I have a patio constructed from block paving around 20 years ago. I need a change now and want to replace the stones with paving slabs, maybe 450mm.

If I carefully remove the block paving, the soft sand they were whacked in with is fairly flat and I toyed with the idea of just laying the slabs on that.

The problem, however, is that as the new slabs will not be as thick as the original blocks, the finished surface will be below the current edging stones.

Do I need to remove the bedding sand and build up the original hard core base or can I add something on top of the sand to build up the height so the finished surface is around the current height.

[lemoncurd1702]

You may get away with it if your using heavy 50mm thick council type slabs. Other than that, remove the sand top up sub-base and bed your slabs on a sand and cement mix.
The sand you excavate may be to contaminated with dirt after 20 years and may not be suitable to use with cement.

[glenne_n]

No, just the type you get from Wickes, B&Q and the likes (30-35mm, I think).

I have 1 ton of sharp sand unused from another aborted project, anything I can do with some of that.

[lutonlagerlout]

mix with cement and water and lay your slabs on it
LLL

[glenne_n]

That's what I had in mind but not sure if I can lay on top of the existing compacted sand (from block paving) or if I have to remove the old sand first.

Would a dry mix of sharp sand and cement do the job (then just hose over).
The patio is not meant to be permanent as I intend to turn the area into a conservatory or extension to wile away my days after retirement in a few years. Hence why I'm trying to see if I can do the job without removing any of the existing sand.

[r896neo]

You should remove the sand. Only you can judge the extra work to do it right versus the risk of it not lasting terribly well.

If i had to guess i would say it would probably be stable enough for a couple of years but the pointing may well fail quite quickly.

[glenne_n]

Yeah, guess you are right, I thought I'd found the perfect way to get rid of a 1 tonne bag of sharp in the middle of my back garden from an earlier abandoned project.

Doing the job correctly will mean ending up with a 1 tonne bag of soft sand instead, hey ho !!

Thanks for all the advice guys