How level does a base have to be under the DPM?

f0rmula · 7 Nov 2014

I'm laying sand in my garage base before laying a DPM. I've not got enough sand to fill it until it's completely level, and I can't get any more until after I've given the compactor back. I can level it out around the old base, but that'll leave a step of about 50mm.

Untitled

f0rmula
7 Nov 2014
1

Untitled

f0rmula
7 Nov 2014
1

1. Am I going to be able get the DPM to lay flat-ish onto this step?
2. How flat to the base does it need to be?
3. If I do have to get the base completely level, if I get more sand and don't compact it, is that doing to be a disaster?

Cheers for any replies.

freddiemercurystwin · 7 Nov 2014

Whilst its only a garage you may get some movement in the sand causing the dpm to tear at the slab edge. Why can't you get some more sand. That would seem logical.

f0rmula · 7 Nov 2014

freddymercurystwin said:
Whilst its only a garage you may get some movement in the sand causing the dpm to tear at the slab edge. Why can't you get some more sand. That would seem logical.

Compactor has to go back on Monday morning. No-one seems to be able to deliver me any sand before then

jay679 · 8 Nov 2014

Several trips to a diy shed for bagged sand then?

Jay

f0rmula · 8 Nov 2014

Would need too many trips to get small bags from a shed, but my neighbour has a whole bag of soft sand he's not using! Will that do? Was using sharp to start with.

catlad · 8 Nov 2014

Just mix it in with the rest.

theprinceofdarkness · 9 Nov 2014

I thought sand was used to "blind" hardcore, i.e. to take the sharpness off. I don't think that such a thick layer of sand will be stable. I can see the base sliding " downhill" over the general slope of the hardcore, or trying to, cracking and pushing the wall out.
Frank

f0rmula · 10 Nov 2014

Yeah, this is my first DIY attempt, so in hind-sight I should have bought more hardcore and used less sand. But it’s done now, and if it cracks it’s not going to be the end of my world

There’s no slope underneath the slab, just a little step. Even my neighbours bag of sand wasn’t quite enough to get it perfectly level.

Cheers for the replies.

diynot

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How level does a base have to be under the DPM?

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