which blocks?

[sudbrooke]

In my extension, I am planning on just one course of blocks for the inner skin to bring me level with the existing dpc.

Can I use aerated blocks BELOW dpc? I like the idea of aerated blocks which are lightweight and can be cut with a handsaw, when I think of all the cutting there will be with gable ends etc. Why use the heavy old type brize blocks?

And can the lightweight blocks support steel lintels?

Thanks

 

[noseall]

Regular (3.5n) aerated blocks are not really suitable for below dpc application.

However, Celcon, Tarmac etc do make a trench-block suitable for below dpc application that are denser than their 3.5n above dpc counterpart.

Lightweight blocks can support proprietary steel lintels yes. A typical lintel (standard duty) would need to bear onto the masonry 150mm at each end. For unusual loads an engineer may specify a greater end bearing coupled with a heavy duty spec' lintel.

Steel beams would need to sit on padstones directly beneath the beam.

 

[sudbrooke]

Thanks for the above answer...

When making the footings, is there any reason why I should not just pour ready-mix concrete into the trench, right up to ground level? That would leave just one block (inner skin) and three courses of bricks (outer skin) to get to DPC level. Seems simpler than trying to lay bricks and blocks below ground.
(more expensive in concrete, obviously)

 

[noseall]

Provided ground levels permit, it is possible to pour to within say three courses (225mm) of the dpc.

However, having the concrete this close to the surface does not allow for drainage gullies, unusual paving applications, frost cover (winter) etc.

The closest we ever set our concrete, where ground levels allow, is to within seven courses (525mm) of dpc.

 

[simonjay]

Thats what I did, 3 courses / 1 block up to ground level.

Note what noseall said about allowing for drainage gullies etc, I had to chisel out a bit of the foundation edge (ie. the 150mm outside the walls) in order to get a gully close enough to the wall. Not really a problem, but had I foreseen it ? Ummm ... !
Simon.

 

[simonjay]

Noseall, what do you mean by frost cover ?

Do you mean to cover the concrete whilst it is curing in winter ?
Simon.