DIY Doctor UK DIY Forums

Hiya

Not a builder but here we go anyway.

Nearly finished building a 1.2 metre high, 10 metre long 2 skin concrete block wall. Bricklayer is laying blocks although I have done the foundation and reinforcement, cavity fill etc (ie. all the less skilled bits as instructed by him).

Front and back skin of walls built using 440x215x140 blocks. Front skin is 140 wide as is back skin and there is a 4 or 5 inch cavity between them with vertical rebar, 8mm mesh, wall ties, and filled with concrete except for bottom 4 inches which is 20mm washed gravel to allow for weep hole drainage from back of wall to front.

100mm perforated drainpipe wrapped in Geofabric behind wall set in 2-3 inches of 20mm washed gravel, the gravel extending to just below full height of wall.

My question is regarding the top of the wall. Due to the width of both skins and the 5 inch cavity the coping required to cover and overhang both skins would be really wide and would probably have to be some kind of cut paving.

I was thinking of just laying coping on the front skin of the wall and backfilling over the back skin and cavity with soil. That way the wall looks like a nice slim wall but with the added strength of the back skin and central reinforced cavity.

Is it ok to do this or must I cover both skins with coping.

Thanks in advance.

Barry

Hi watsonb01
Suggest you fit a DPM partly under the front coping and extend back to behind the back wall. This will reduce - but not stop degradation of the steel in the cavity fill.
Regards S

Thanks Stoneyboy.

The rebar and mesh are totally covered in concrete so does that not provide suitable protection. But DPM sounds a good thing to do anyway.

Hi watsonb01
Use some epdm damp proof course wide enough to cover cavity and inner wall. Even if the rebar is encased in concrete the less water getting to the better.
Regards S

Thanks Stoneyboy.

Do you happen to know if it goes against building regs in anyway.

Cheers

Barry

Hi watsonb01
Short answer - no a retaining wall is nothing to do with BRegs. If it is part of building a domestic property then it may well be part of the whole application.
Regards S

Thanks Stoneyboy for your help. Appreciated.

Barry