ᐅ Base for Patio Slabs / Concrete vs. Gravel

Created on: 21 Jan 2021 13:30
M
Marius2016
M
Marius2016
21 Jan 2021 13:30
Hello,

Our terrace is going to be expanded soon and will receive a new surface. We have chosen the concrete slabs SIREO from the company KOLL. The slabs measure 60 x 40 x 4 cm (24 x 16 x 1.6 inches).

The contractor suggested installing the slabs in concrete, among other reasons because the slabs are quite thin at 4 cm (1.6 inches), and to prevent them from breaking if voids later form underneath. The terrace will not be driven on, but it would also be easier this way since the slabs cannot be compacted with a plate vibrator during installation (according to the installation instructions).

The installation instructions from KOLL, confirmed by inquiry, advise against firmly embedding concrete slabs outdoors in mortar, because the slabs’ surfaces can deteriorate due to potential trapped moisture in the mortar. A bonded installation method does not make sense for concrete slabs, as trapped moisture must always be avoided.

I would be interested in the assessment/recommendation of forum members, as honestly, I am unsure which option to choose.
H
hampshire
21 Jan 2021 14:53
Edge the concrete and place it on gravel.
xxsonicxx22 Jan 2021 13:30
We have the same dimensions. Edging with natural granite stone, then slabs laid on gravel.

Everything holds well. One slab is loose and will be repaired in spring. That’s it. Of course, if it’s just done carelessly, it will become less stable ;-)

I don’t see what could break—unless you drive over it with a tank. It even withstands our children ;-)