Block footings 300mm cavity

[2019]

425mmx210mmx100mm blocks and will have a 100mm cavity on top of concrete footings. Is it acceptable to have 2 block on top and one butted up beside it for block on flat 150mm below dpc rather than 2 block on flat crossed over with another 2 block on flat on top which brings me up to the 425mm same as block on edge.

Trying to save on the amount of block needed for the footings.

 

[^woody^]

You might know what you mean, but what I think you mean might not be what you mean if you know what I mean.

 

[2019]

You might know what you mean, but what I think you mean might not be what you mean if you know what I mean.

Sorry, was just in from a day with lots of drink. Reading it back, I canna even understand it either.


See pic. Will it be ok for this on the bottom courses then continue the blocks on edge on top 1 course up to DPC level. The blocks are 100mm thick, 100mm cavity. I know I will still have 25mm difference below but it'll never be seen because it'll be filled in.

 

[^woody^]

You mentioned wanting to save on blocks, and yet that uses 33% more than necessary.

Why can't you just build it in two leafs with a cavity as normal?

Or are you trying to do an actual footing strip in blocks with no concrete?

 

[tony1851]

Can't see that being much use as a foundation on its own, both in terms of the width and the lack of bonding.
Surely it's being built off a concrete strip? in which case - yes - just have separate skins.

 

[23vc]

I guess that would avoid the need to put the lean mix in as it’d be solid? I’m sure I’ve seen it done somewhere, not immediately obvious why tho.

 

[tony1851]

If the foundation isn't too deep, there's no need to put lean mix in anyway, as long as there are a reasonable number of ties.

 

[noseall]

Use trench-blocks.

 

[^woody^]

Just fill the trench with concrete

 

[2019]

I guess that would avoid the need to put the lean mix in as it’d be solid? I’m sure I’ve seen it done somewhere, not immediately obvious why tho.

I also forgot to mention this. It was to save going back and putting the lean mix concrete into the bottom courses.

 

[2019]

Use trench-blocks.

Here in donegal, we can't source them

 

[2019]

If the foundation isn't too deep, there's no need to put lean mix in anyway, as long as there are a reasonable number of ties.

It's 2 block high. The concrete if I remember right has to up to 150mm from dpc level

 

[Leofric]

I think the cavity should be clear for 225mm below the dpc.