How firm is compacted sub base?

onionsa · 25 Mar 2019

So I’ve whackered my MOT1 sub base for the patio and some bits are lovely and firm. Others where there are large stones mainly seem loose on the top later. It’s firm under foot but just these big stones seem to be loose. Is that normal just because they don’t have a good mix in that area? Does it need rectifying or ok to lay the mortar mix on it?

Thanks.

williamglossop · 25 Mar 2019

It's fine - it's just because the finer grade is a bit lacking in those areas. U can throw some Sharpe sand over the areas and whack it again - but once the patio is laid, it won't make any difference

onionsa · 25 Mar 2019

williamglossop said:
It's fine - it's just because the finer grade is a bit lacking in those areas. U can throw some Sharpe sand over the areas and whack it again - but once the patio is laid, it won't make any difference

Great thanks for confirming. I think where it’s dried out the dust has just lifted out as it’s mainly where we’ve been walking. I’ve dampened and thrown a bit of small stuff on it and it’s looking a load better.

John D v2.0 · 25 Mar 2019

the main thing about whacking it is to avoid any voids and gaps causing settling, if the main body is whacked properly and thick enough it won't settle more even if the top layer is a bit loose. We had the same with the drive base and by the time the later layers are on you can't tell.

Millwright · 25 Mar 2019

The big stones on the top will be lose as there's nothing interlocking them. The rest of it will be compacted nicely and interlocked together during the compaction which is why the lower layers feel very firm.

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How firm is compacted sub base?

onionsa

williamglossop

onionsa

John D v2.0

Millwright

DIYnot Local

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