Concrete block retaining walls - what size block?

[macman]

Having looked at the possibility of using sleepers for the retaining walls we want to build, we now are thinking about using concrete blocks, rendered and capped.

We have a main retaining wall approx 14.5m wide down near the house/patio that will be 4 blocks high with a brick capping and will have a set of steps built in up to a levelled lawn area. Then at the sides the walls will be 6m long to the back of the garden, where the rear wall will be 3 blocks high and 12m wide

As the garden is being levelled due to it's sloping nature upwards and away from the house, the soil removed from the rear will be dragged to the front where the main retaining wall must be built first to pile the excess soil behind.

So.... I'm told that: the sides and rear wall will only need to be single skinned, while the front wall, being the main one near the house, will need to be a double skin wall with ties as it's taller - 4 blocks high.

The point of this rambling diatribe about my landscaping nightmare is that I don't know what size blocks to use. 100mm, 140mm or the hollow block. Can anyone offer any advice please?

Then I want to install low-level lighting in the wall, which will no doubt add insult to injury as I strive manfully to achieve something resembling a garden! On the plus side we have a mini digger and driver arranged to level the garden.

Thanks in advance...

 

[^woody^]

You can do this with 100mm dense concrete (7N) solid blocks as a single skin.

 

[r896neo]

Ditto on the dense concrete block. But in my opinion a 3 foot retaining wall needs to be a little more stout than just 4 inch blockwork. I would advise you to build the higher one in 9 inch, a simple block on the flat wall would suffice.

You should also be aware of the potential staining problems associated with retaining walls that are to be rendered. The saturation caused by water can make render blow over time and/or leave staining on the wall.

Consider either synthapruf or similar under the render or a lot cheaper is to put dpm between the wall and the soil. Obviously if you take this route the drainage needs to be sorted well.

 

[macman]

Ditto on the dense concrete block. But in my opinion a 3 foot retaining wall needs to be a little more stout than just 4 inch blockwork. I would advise you to build the higher one in 9 inch, a simple block on the flat wall would suffice.

You should also be aware of the potential staining problems associated with retaining walls that are to be rendered. The saturation caused by water can make render blow over time and/or leave staining on the wall.

Consider either synthapruf or similar under the render or a lot cheaper is to put dpm between the wall and the soil. Obviously if you take this route the drainage needs to be sorted well.

Much appreciated. I think we might be getting people in to quote on this job - I can do some of the work, but I'd rather someone eminently more qualified than me did the retaining wall - it will be safer in the long run!