Retaining wall for patio - Advised materials to use...

[samselbygarden]

Hi guys,
I'm on a project next week building a raised patio area coming out from a new extension.
We need to build up approx 450mm (H)
Will i be ok building up 2 courses in 6" concrete blocks? Or am i better off using 4" blocks laid flat to give a 9" wall thickness?
Alternatively, am i better off using hollow blocks and filling with concrete?
I have approx 30 tonne of sub base coming in to bring up to level and obviously i'll need to get the wacker on it so i want the wall to withstand this.

Many thanks in advance

[Pablo]

4" block on flat will be fine but I'd double the first 2 courses. The general rule is that the wall retains everything to an angle of 45deg ish so a wall 1m long x 450mm high plus a course or 2 below ground will be holding 280kg at most and all the stone in the centre has no impact on the pressure.