Gaps between slabs

[Sufyaan]

Hello all,

Bit confused on the space I'm going to need inbetween my slabs. I've opted for 45cm x 45cm paving slabs. Any idea what size gap I should leave?

Also, what are the risks of leaving no space and all and laying the slabs next to each other/touching?

As for the piping, would a 3:1 mix of sand and cement do the trick if brushed in?


Many thanks,

Sufyaan

[mnlad743]

I'd recommend a 10mm gap between slabs.

As for leaving a gap - it all depends on the edge style of the slabs. If they have an edge designed to mimic a natural stone product (uneven) then you'll need to go with the pointed gap.
If however, they have a hard edge which allows the slabs to be butted straight up against each other - then you have the option.

With regards to pointing - a 3:1 should be fine if you plan to use a sand/cement mortar. Just be careful as the slabs need to be completely dry - any residual moisture will attract powdered cement - if that occurs you will have staining. You can add a cement pigment to the mortar, but again be careful of any moisture being present. I would also strongly recommend using a pointing tool to push the mortar mixture into the joints as allwing it to self-compact rarely results in a good, strong mortar joint. You would be better off 'wet-pointing' the joints if you want a strong, long-lasting joint.

A good alternative would be a product such as EasiPoint (this seems to be the preffered brand of the pro's) which comes in a good selection of colours - it is however much more expensive than a sand/cement mortar mix.

[Carberry]

Need to know what type of slab and what kind of look you are going for eg: contemporary look has much smaller pointing gaps

[Bec@LondonStone]

Hi Sufyaan, are the slabs cast concrete or a natural stone? Natural stone paving (either the handcut or sawn varieties) will always have a cutting tolerance, ours is around +/- 2mm which as far as I'm aware is pretty standard across the board. This tolerance means it's not a good idea to butt joint, you will not manage to keep all the slabs in line over a large area. We always recommend a minimum 5mm joint. I'm not too hot on concrete slabs but I [/I]think they can be close jointed as they don't have the same tolerance. On the main site the advice is to close joint (1-3mm gap) rather than butt joint (slabs touching) to avoid problems caused by movement. Good luck!

[Sufyaan]

The slabs I'm going for are called Riven duo and it'll either be 450 x 450 or 600 x 600. They have a flat 90 degree edge. Hope that makes sense.

So a 10ml gap is a must then? Or can I also place them right next to each other with no gap at all? Would it cause any issues with expansion or movement (slabs lifting) later on?

I wonder if I can find some sort of spacers to help. Off to search on the net.....

Thanks again for the advice guys.

[Carberry]

roughly 10mm, given or take 2mm because of variations in the size of slabs.

They will look silly butted up against each other, could cause the faces to spall and they are smaller flags which makes them easier to move about so you need decent size and strength pointing.

Don't brush in the pointing.

For spacers, gapfast do a product that some guys on here tested I believe.

[DNgroundworks]

If they are pre-cast concrete flags with a square arrissed edge then butt them up (like you would council greys) pointing flags like these IMO looks naff.

[Sufyaan]

Hello all,

Quick update... eventually butted the slabs up tightly and its looking good. However, we're now coming to the part where we need to lay the slabs near the back door, kitchen, etc. I have a slight damp issue, so if I butt the slabs up, would this cause water to soak down the minute gaps and make the ground damp? Would a small gap and pointing prevent water making it way under the slabs?

Thanks

[London Stone Paving]

In the damp area point the slabs up and also make sure the fall iss good enought to take away any surface water