new extention build

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hi, I'm going to be building my first ever extention HOORAY! A few points i need to run through, how many courses of bricks should i brick below external floor level? and should i use engineering brick below external ground level or just regular face bricks? Please advise

Im also wanting to tooth into a extisting extention any tips would be great.

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  • 3 weeks later...
Guest cannyfradock


The depth of your trench depends on the ground. Your strip foundation needs frost protection so the top of the concrete must be at least 450mm below ground level. The ground in our area is usually solid so I dig a trench 600mm wide (for a normal cavity wall with 100mm between the 2 walls) and 675mm below ground level. The min depth of concrete is 225mm so that will leave you with 450 mm from concrete to ground floor level....= 2 coarse concrete block to GFL then 2 coarse bricks to bring you to DPC or finished floor level.

Your local building control will tell you exactly what is required. In my area (Newport Gwent) the building inspectors are all very helpful.....which really helps. They will want to inspect the trench before you pour the concrete.

There is a diamond core drill available (about £8) which screwes into a 4" angle grinder and is brilliant for raking out joints for toothing.


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