My hardcore was nice and compacted, and now it's not!

[maf20]

As the title suggests this is what's happened.

I had 4.5 inches of compacted hardcore all ready for a patio on top. It's rained a bit since the hardcore has gone down (which I was told by someone was a good thing as it helps it to bind???). Anyway, one corner of it seems to have gone quite spongy. Could this be: -

1. The fact that it's wet and this is common?
2. It's gotten too wet and the earth underneath is what's making it collapse almost?
3. Or is it nothing to worry about?

Also, I suppose I know the answer to this but. Can a natural stone patio (therefore using a mortar mix) be laid on wet hardcore?

Many thanks

 

[Thermo]

its sinking because you have voids under the area in question or you are on a clay soil etc. Compact it well in and if necessary top it up. It will staboilise when dry. i would always recomend covering the surface of the hardcore with MOT type 1 and compacting that down. It will allow you to get a good flat level firm surface ready to lay the paving on.

 

[WabbitPoo]

When you say "hardcore" do you mean old bricks and builders' rubble, or do you mean crushed stone from a builders' merchant? The latter should compact down very well as it has a mix of sizes - hardcore/rubble does not. Echo what Thermo says - don't consider laying on a layer that is not yet stable. Wet is OK, sponge-like is not.

 

[noseall]

mot stone that is rich in dust will react like sponge once completely saturated.

you tread on one place and another rises. you can not compress water so it will act like a water mattress. seen it done it.

once dried out the mot will react as normal.

 

[maf20]

Thanks for the replies guys.

Hardcore is the type delivered from the buiders merchants. Just couldn't workout how one minute it was solid and then the next it wasn't. Only in one corner though.

I'll have a look around for MOT stone then I gues, never heard of it before, but I'll find it. Quite a novice to all this stuff, but earning my stripes quickly!!!

 

[Thermo]

any builders merchants will do it for about £30-£40 a bulk bag. DOes have various names, scaplings, mot, road stone etc

 

[bhwh]

Sorry maf - I'm just gonna hijack your thread a second!

Related Q: My compacted mot has been down for several months, well compacted but I haven't yet manged to lay the slabs. What I've noticed is that the top surface has changed as the rain has washed the fine dust lower down. Still seems solid enough though. Is this a problem before I lay do you reckon?

 

[Thermo]

no problem at all.

 

[bhwh]

cheers

 

[noseall]

actually, the longer the stone is down the more it will 'settle'.

 

[maf20]

Folks

Since the hardcore was 'spongy', I haven't done anything to it and now it's solid as a rock. We've has hail, rain, snow, frost, the lot over the past week or so and it's solid. Does this mean it has settled ok now, or could there still be a problem with clay underneath?

just waiting for a b****y break in the weather and I won't need to ask anymore questions about the hardcore as it'll be covered with stone!

Cheers

 

[Thermo]

no its fine, the water has drained out and its stabilised. NOW GET ON WITH IT!

 

[noseall]

no its fine, the water has drained out and its stabilised. NOW GET ON WITH IT!