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Depth of foudations for a 7ft wall.

what depth to dig for a 7ft wall and how deep should the concrete be before you start to lay the bricks. Should the concrete be level wiith the ground?
My bricklayer has laid foundations of 300mm, he has gone down to sold clay ground.
I am concerned that the concrete is at ground level, will this be a weakness in the wall. Other work i have had done there is at least 2 courses below ground level.

6 Answers from MyBuilder Bricklayers

Best Answer

I wouldn't build a 7' high wall on 200mm foundations. The concrete should be at least 450mm x 450mm and you should allow 4 courses(300mm) of brick underground (2 for leveling,2 to adjust the bond(space between Bricks) So a minimum dig depth of 750mm. Increase the depth of concrete for bad ground/tree roots. For this height the wall it should be a minimum of 215mm wide, and will require piers at exposed ends and 4-6m intervals. Expansion joints are required every 10m in Brickwork, 6m in Blockwork. Increasing the width of the wall to 330mm will allow greater spacing between piers, similarly if the wall is curved it is more stable, so in some cases they may be omitted(dependent on the length).


Answered 26th Aug 2011

.600 deep x .450 wide,I tend to lay the foundation 75mm below ground level so I can hide concrete with soil etc,if you have clay keep diging down until you hit solid ground


Answered 3rd Sep 2011


The foundations for such a wall would depend upon the ground type and surrounding areas,ie trees,marsh ground etc
but in a traditional dry ground type a foundation depth of 200mm -300mm of brickwork below ground would be sufficient for the same.The foundations would depned as above on the ground type and proximity of trees,drains etc.A normal house extension foundation depth is approx 300 - 450mm of concrete.How ever this is based upon a cavity wall construction and thus a detail of the type of wall and bonding required would also be needed prior to pouring of any foundations.


Answered 26th Aug 2011

your bricklayer has done a good job 300mm of concrete is loads for a seven foot wall i have seen 300 mm going in to build houses on every thing will be fine


Answered 12th Sep 2011

I wouldnt build a 7ft high wall on 200mm foundation, it will have to be at least 225mm thick wall that height, you will need to dig down about 900mm to a metre deep and 600mm wide.
How long is the wall, you may need expansion joints and pillars.

Edit to your extra info.
Regardless of weather the concrete finishes at ground level or below, 300mm depth is not good enough, I wouldnt build a 3ft high wall of that.
Theres no way he is down to solid ground, with a 7ft wall on a 300mm footing that wall and footing will fail.
I have already recomended the footing sizes required, as has Bricky 1


Answered 26th Aug 2011


The fact that the concrete is at ground level is not a problem as long as it wont be seen.Ideally it should be lower but the issue is the depth of the footing, it should be at least 500mm deep in my opinion and 450mm wide, filled with concrete. The wall itself needs piers for strength and needs to be double skin at that height. As others have suggested, it may also need an expansion joint dependant on its length.



Answered 30th Aug 2011

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