Laying garden slabs

[InvictusBob]

I have to lay some slabs for a garden seating area - about 3.5 x 4m - and I would appreciate some advice on how to go about it. So far I have at least 50mm of scalpings whacked down over a weed suppressing fabric. There will be very little traffic so the plan is to lay the slabs on screeding sand with no cement - the local builders merchants suggestion. Being weed-phobic my wife wants a second layer of fabric beneath the slabs and the design calls for 50-100mm gaps between the slabs, filled with shingle. The slabs vary in thickness over a small range and will be arranged in a psuedo random design. To start off I plan to lay a thin layer of sand to obtain a smooth base then put down the fabric and another thin layer. I'm not sure how to go from there. Should I try to start with all the thickest slabs regardless of position or start in one corner adding sand for the thinner slabs? Or would I be better with no sand above the fabric except as required for the thinner slabs - this would have the advantage of avoiding having shingle mixing with sand between most of the slabs, but I guess the slabs wouldn't be so stable.
Sorry if this sounds like a trivial job to be asking so much about!

 

[toptec]

Bob. I can't see how this will work. As your slabs will have nothing holding them in position, the shingle doesn't count, they will be unstable and slide after a short while.

Your idea to lay a second layer of fabric will also prevent the slabs from bedding down into the sand. The principle of bedding on sand is fine for paviours, they are fixed at their edges either by kerbing or cement.

Also, although your have 50mm of wacked scalpings the first layer of fabric will prevent it bedding down into the sub-base which is what provides the firm surface.

If you have a firm surface it would be much better to lay the slabs onto cement directly onto the scalpings. Forget fabric under the slabs, between maybe the shingle will cover that.

 

[^woody^]

Whack the hardcore, and then cover the top with screed sand to fill any voids and whack again to leave a smooth, firm, level base. Lay your fabric.

Then I'd suggest spotting the slabs with five dabs of mortar to allow you to get them level and to hold them in place.

Laying on a sand bed risks the sand being washed away, or becoming wet and allowing uneven compression (ie the slab tips) with this design of gravel between the slabs

 

[Thermo]

thats going to end up a total mess.

there is no need for any fabric under any properly laid slabs. your builders merchant is that, a builders merchant, not someone who lays paving for a living. Lay them on a full bed of wet mortar, not 5 spots as they will rock over time. If they are laid on a full bed they will not move.

With regards the weeds, they will not grow through paving. they will grow in the shingle as tehy will quite happily seed themselves in there. no amount of fabric will stop that as they are not coming up from below but growing actually in the shingle. if your wife doesnt like weeds then go for a diffent design.

 

[InvictusBob]

Thank you all very much. It sounds as if we had better rethink this.

Thanks again.

 

[K-Rod]

Listen to Thermo, I'm so glad I did!!!