Which blocks for garden wall

[Adam2]

Am replacing an above ground (not retaining any soil) block wall that was partially removed during our excavations to avoid it being a risk of falling down. The concrete footing is still there and some of the first course of blocks which are laid flat for 2 courses. I plan to have this now rebuilt - single skin blocks on edge to match existing and then render. Will put piers in to match previous as this section of wall is 6m long and 2m high.

 

Does it matter which blocks I use this for the main wall area? Was thinking lightweight 3.6N blocks

 

Should the blocks laid flat for 2 courses which will be below ground level by a denser block which looks less porous?

 

Is it necessary to put a DPC in? there isn't one in the rest of the wall, the soil is free draining and we're at the top of a hill so will stay pretty dry.

 

 

 

 

 

[PeterW]

Don’t use lightweights as they absorb water like a sponge.  Get the cheapest nastiest concrete blocks you can find - lay them all on flat unless you can get 150’s as single skin of 100mm at 2 metres high is very thin and will catch the wind. 

[MarkyP]

There's scope for confusion over the terms used for blocks but generally lightweights in trade speak are aggregate blocks and they are not that light! They are medium density and would be fine for this application. Dense concrete blocks are for foundation courses and very, very heavy. Aerated blocks are to be avoided here, these are lightweight, brittle and suck up water like a sponge. Personally would use 7n medium density aggregate, I.e. what the builders merchants call lightweights. 

 

Confused yet? ?

[Adam2]

Ha yes totally - but thanks ?

 

OK so the current wall is/was 100mm block - If I go with 140mm wide I could connect to the remains of the existing wall this with a straight cut using a wall starter kit rather than toothing the new part into the old.  This will be quicker and cheaper than laying flat. Will still add piers to match previous

 

Jewson have these at 140mm wide which are frost resistant so could use for the single skin but will need to use 100mm wide laid flat for the initial courses to keep the overall levels matching. These 140mm wide blocks are described as aerated :

 

Medium Dense Concrete Block 7N 440 x 215 x 140mm is manufactured from autoclaved aerated concrete with fine aggregates,& cement, and an expansion agent that causes the fresh mixture to rise. This product is sourced from several suppliers and may differ in appearance and texture due to regional variants.

Features & benefits

High thermal and sound insulation owing to its make

Frost resistant

CE Marked

 

But as frost resistant seems like they will do the trick.

 

cheers

[MarkyP]

Yes those are what your brickie would call lightweights.  The labourer would disagree!

Edited December 9, 2020 by MarkyP