Correct block for patio retaining wall

[Tryer01]

Looking for some advice on the best blocks and best way of laying them for a 1/2Mtr high retaining wall with one separate 2Mtr long section retaining to 1/2Mtr but built to 1.8Mtr high?

I've read a lot of very similar forum posts but there seems to be many different methods used, the purpose of the wall is construct a raised patio area at the back of our house the taller section bridging the gab between our house and garage with a gate to close off the garden.

I've dug the founds 300x450 for the 1/2Mtr section and 450x600 for the 1.8Mtr section.

From other posts there seems to differing opinion as to the best size and strength of block and how to best lay them to achieve this?

Hope someone can help

 

[Cindysotherhalf]

Best to lay them down flat thus giving you a 9 inch wall. Use concrete blocks of medium to high density, not airated or Thermalites.

 

[noseall]

The lower retaining section would be best built from 7n dense concrete blocks. These can be bonded with a double flat course if you wish.

The upper part may be better being built from say fibolites/hemelites etc, if they are to be rendered.

 

[tony1851]

if they are to be rendered.

Is it wise to render a retaining- or free-standing wall? Just wondering about retention of damp and possible frost damage etc.