# Correct amount of trench blocks

Discussion in 'Building' started by shabbaranks, 1 Feb 2021.

1. ### shabbaranks

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Hi,
Posting here because all of the online calculators seem to want me to have a height of 1 meter minimum - which is too high.

Can I just check Im not being thick.... Although anything is possible

I have a total height from the top of the footings to meet the top of the existing slab of 890mm

I have taken away 100mm for Celotex 155mm for the block and beam height leaving me 635mm for trench blocks (I might need to reduce the 100mm of Celotex to compensate for the screed over the block and beam plus the floor finish).

Trench blocks are 215mm in height which gives me just under 3 courses of block required. At a total "L" shaped length of 8.2 meters I will need 19 blocks a course * 3 = 60 Trencheroos in total?

Does this sound right?

Thanks and sorry for the stupid question

3. ### ^woody^

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Measure the total length of the walls = 8.2m
Deduct the corner overlap (block width) -300mm = 7.9m
Multiply by the height (3 courses) - 0.675m = 5.33m2
Multiple by 10 blocks per m2 = 54 blocks
Add 10% wastage = 60 blocks

You may want to adjust the height of the concrete to get block courses of 675mm, not 635mm and loads of cuts

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4. ### shabbaranks

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Thanks - or reduce the finished height and increase the Celotex\screed for floor finishing I guess. Thanks again!

5. ### Notch7

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I've heard some SE's don't like trench blocks below BB, they prefer hi density concrete blocks

6. ### shabbaranks

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Hi - is this something I should check with BC? The builder I have doing the work hasn't said anything just asked me to order the trench blocks... Cheers

8. ### ^woody^

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You need to check with the floor beam supplier. It's nothing to do with SEs or building inspector.

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9. ### shabbaranks

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@^woody^ is there anything you dont know?

10. ### ^woody^

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Lottery numbers

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11. ### shabbaranks

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Ah well I can help you there - the numbers run from 1 to 59

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