Laying slabs - bed of sand or mortar?

[wolfie882]

Hi,

I recently queried guidance given on the website of a large landscaping products manufacturer which said its paving products should not be laid onto mortar but onto a sand bed. I queried this by email and received the following reply:

"Sometimes when flags get laid on a mortar bed, they can break away from the actual mortar if they take any weight. This then results in all the flags becoming loose throughout the area. Whereas with sand, if they take any pressure the flags will move with the sand base. A sand base will also provide sufficient drainage if any excess water gets through the joints on the flags."

This seems to contradict most advice I have seen (inc from other manufacturers) that mortar should be used. I am interested in reading the comments from learned users of this forum

Thanks

 

[Ennui]

For me, it would depend on the expected traffic on the slabs.
Pedestrian traffic only, even very light vehicular traffic, where the sand could not seep out and flags could not creep, at the edges, I'd be happy with a sand bed. If necessary, using a mortar bed around the edges to prevent sand loss and movement of flags. A brick edgeing would serve the same purpose.

For any vehicular traffic I'd use a full bed of mortar, which can be a weak mixture, say 1:6 or similar.

I think the sub-base and weed control are as important, or even more important than the sand/mortar bed.

 

[r896neo]

It very much depends on the flag and the area.

Any wet cast flag or natural stone should be laid on a rigid bed i.e mortar. Pressed concrete or small element paving 400x400 or less can be laid on sand.

Flags laid on sand can never be pointed succesfully so are only suitable for close jointing.