Trench Footings

[JoshRogan]

For trench fill footings, what depth should be left from the top of the footings to the ground level?

I understand for strip footings you usually leave enough for 2 or 3 courses of block work and then back fill, but whats the general procedure using trench fill?

Thanks.

 

[noseall]

you first need to determine the external finished ground level, usually 150mm below dpc.

if the ground conditions are fairly level around the building, then i guess you only need a maximum of three courses of engineering bricks and probably one course of blocks on top of the concrete.

in other words set the top of your concrete 450mm down from dpc.

if the ground level slopes to any degree, just make sure that no foundation concrete can be visible once the ground has been made up around the building and that only bricks and not blocks are visible when you do.

if any drains pass through into the building or if there are any gulleys sat against the outside brickwork, make sure the foundation concrete does not interfere.

 

[Static]

As nosealls says, but you may find 450mm from DPC level low for drainage to exit the building. If you have drainage passing over the footings work out what level it should be and try to put footing top below it. Remember if you are doing a suspended floor youll need to have a void below the floor 150mm-225mm depending on soil type.