600mm high retaining wall - very quick question!

[fryups]

Hi,

I know this question has been asked 100 times before but all situations are different!!?

Basically I'm building a retaining wall to excavate and lower the ground level around a house and garden.

The highest part of the wall will be approx 600mm above lower level with majority around the 400mm mark. Total run is about 12m next to house and furter 12m into garden area.

I will be excavating down to inline with the bottom course of the house - obviously no lower than the foundations and taking the 45 angle away from foundations as guide.


1- For a 600mm high block wall i'm planning a 150mm deep footing by 450mm wide?

2- Im trying to decide over using 100mm/ 140mm block and then wither to lay normally is enough or if they need to be layed on their side ie: a 215mm thick wall and not 140?

3- last question am also trying to decide between solid and hollow blocks? Hollow appears a cheaper alternative but then if i have to fill hollows with concrete and/or rebar i would assume its massively more expensive?

Am planning weepholes/ pipes every 1m or so, with granular backfill, not decided if it needs a drainage pipe as well behind the wall as will only be 600mm high?

Any thoughts would be appreciated!

Many thanks

Phil.

 

[themiddleagedun]

The footings sound Ok
I'd use 140 blocks, but 100's would probably do.
You should be alright without a perforated pipe as long as you use the granular backfill

 

[fryups]

Hi,

Thanks, so using 140 blocks on the 140 edge, no need to lay side face down then?

 

[RonnyRaygun]

Hi,

Thanks, so using 140 blocks on the 140 edge, no need to lay side face down then?

4d is the rule of thumb for retaining walls up to a metre or so, so 600/4=150mm.

Maybe lay the first couple of courses flat to be on the safe side.

 

[^woody^]

600mm is nothing, and a 100mm wall will be fine

 

[RonnyRaygun]

600mm is nothing, and a 100mm wall will be fine

Oh, here we go...I've seen several two foot retaining walls fail due to insufficient masonry, but you can build it 100mm thick if you like and wait...

 

[^woody^]

At 600mm high and soil to the top, its retaining a tiny bit of soil from 400mm down from the top and lets say a 45° angle upwards - not the whole amount of soil behind it

In addition, then OP is backfilling with granular fill, which will reduce the loading even further due to its lack of compactness and being recently added

These walls you have seen fail, did you investigate the cause of the failure?