Patio slabs not sticking to the cement underneath

[lukewarmbath]

Despite careful preparation and sticking to the "rules" my stone slabs, bedded on 50mm of 7:1 sand cement mix, have not "stuck" down. They can mostly be lifted. Fortunately they are bedded on a continuous pad of cement so they don't rock and remain nicely level. My question is: should I rely on the pointing in the cracks to lock them in place or should I think about an adhesive on the undersurface?

Thanks for any thoughts

lukewarmbath

 

[joe-90]

They don't need to stick. Gravity and friction will do the job.

BTW I knew someone named Luke Warm.

 

[lukewarmbath]

Thanks Joe - that's a relief. It seems no big deal as they just "sit" there but I was a bit alarmed when I found they simply lifted off! (Apologies for posting on the wrong forum- I hadn't noticed the "garden" one.

As for luke warm - we actually knew someone on our staff list with that name

lukewarmbath

 

[r896neo]

Just make sure any free edges are stuck, might be worth relaying them to stop lateral spreading which can happen if you scuff your feet along them.

If the bed is smooth and sound rapidset stone tile cement is a nice easy way to do it as it goes down so thin and sticks like hell.

 

[^woody^]

The other method of laying slabs, on a dry sand bed and I would say used for at least 50% of the time, involves the slabs not being stuck down either, but relying on good old gravity ... and they don't move either

 

[r896neo]

They dont move if they are restrained by a kerb but can spread depending on the slab size if not.

 

[lukewarmbath]

The other method of laying slabs, on a dry sand bed and I would say used for at least 50% of the time, involves the slabs not being stuck down either, but relying on good old gravity ... and they don't move either

I think a sand bed is mainly for brick-sized pavers. The larger stone slabs need a continuos cement support.

lukewarmbath

 

[roberta1000]

I think a sand bed is mainly for brick-sized pavers. The larger stone slabs need a continuos cement support.

That's a bit of a sweeping statement. I have a largish slabbed area in my back garden (and several slabbed paths) which are laid on nothing but sand and have been there for over 30 years. Mixture of 3'x2' and 2'x2' and don't seem to be going anywhere.

 

[r896neo]

In my experience a compacted and screeded grit sand bed is used for block paving and generally any flag up to 450. It can also be used for larger concrete slabs as they are strong.

It's less suitable for softer materials like modern natural stone.