A reader's Roofs and roofing question: Slab on blockwork?

David P.   from   Brisbane, Australia   had this Slab on blockwork question.

Hi Bill,
When using modular concrete blocks to support a suspended concrete slab, if a gap exists between the top of the block wall and the soffit of the slab is it acceptable to close this off with an inner form and pour a type of minor ring beam onto the wall? David

Bill's answer

Hi David,
Yes it's common. You could have a case where say the slab is 150 thick, but you need the top to be 200 higher than the top course of blocks.

You don't pour a separate 50 strip around the top of the blocks, that's extra work, you incorporate it into the slab pour.

You pour you corefill to the top of the last block normally. Then form up inside and outside and pour the slab.

When you strip from the outside it looks like a 200 thick slab but it is only 150 really. So the slab itself looks as though it has a 50 thick reverse kerb around the perimeter.

If you are using "E" blocks then it is just the inside that gets the extra form to make the correct depth for the slab.


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