Bedding depth

[Avicena10]

[Absolutely brilliant site!!!]

I am planning a new patio in my backyard.

One of the builders invited for a quote explained his technology for laying slabs as follows:
1. Dig 6 inches from the current elevation.
2. Lay 4 cm thick Brett Westminster slabs on a sand and cement mixture bed only (no sub-base of MOT 1).

In my understanding this will bring the bedding to an excess of 10cm thickness.
I remember seeing somewhere in the “PavingExpert� main site a warning for the bedding in exceed of 5 cm.

Is this correct please? Is the whole suggested technology correct?

[Tony McC]

He's excavating 150mm and then laying a 40mm thick flag, giving a bed depth of 110mm, which is excessive. However, if it is all mortar/concrete, and he's willing to three times as much for that as it would cost for sub-base material, it's his lookout. Structurally, it's acceptable if a little OTT

Has he explained why he feels 110mm of mortar is necessary?

[Avicena10]

Dear Tony,

Thank you very much for your swift answer.

I will ask him tomorrow.

Anyway - the house is build in an old ex marsh area, the soil is a "fill in" and it is very unstable so after reading your web site for hours I feel that avoiding a MOT1 subbase is an odd choice.
(btw he is a Brett approved installer).

Best,

[Tony McC]

If it's made-up ground, that's all the more reason to use a sub-base rather than rely solely on a rigid laying course.