Concrete on weeds - ok?

[pauljygrant]

Hi All,
I'm about to have a 70sqm rural shed erected on virgin land, currently a selection of weeds and grass - regularly whipper snipped, but not yet removed.
One shed erecter has suggested that they are willing to build the shed prior to any earth works allowing me to sort out the base at my own pace, etc - they would leave around 100mm for the concrete. The site is fairly level.
Given that I am prepared to spread say 50mm of rubble over the land prior to having a contractor pour the slab, is it necessary to scrape the vegetation and top soil? (if the consensus is that its okay to leave, then I would weed kill completely prior to adding the 20mm road base rubble).
All comments appreciated.
Cheers, Paul

ps - if anyone wishes to recommend shed erectors / concrete contractors in the McLaren Vale area of Adelaide, that would also be appreciated.

[Brikky]

As long as the ground is flat and compacted and the granos pour on plastic it should be all good.

[woodchip]

Personally I would remove the weeds & topsoil.
especially in your rural location, with most likely access to a tractor with bucket & somewhere to dump the spoil...too easy.
A concretor told me weeds, grass etc takes about 7 yrs to decompose under slab, its then problems may occur as the soil subsides under the slab, causing cracking etc.

cheers

[johnc]

Remove the vegetation, chip or scrape taking a small amount of top soil will do.

[pauljygrant]

Okay - 2 out of 3 recommend removing the vegetation - that was my gut feeling also, but was hoping for the consensus to be the easy / lazy one!
I phoned Kennards Hire today to get prices for hiring a machine to remove the vegetation etc and initially asked about a 1tonne mini excavator - they guy suggested I might be better using a small bobcat or even a dingo. I know that a Dingo is not designed to 'dig' but can anyone offer any advice on the most suitable machine (especially for me who has not used any of them , but willing to give anything a go....I do have a forklift and scissor lift ticket, so consider myself reasonable at getting to grips with new machines).
Cheers, Paul

[Master Splinter]

Unless the ground is really loose and soft, you are probably expecting too much of a Dingo to scrape it off; anyway, with the daily hire rates for them, it's cheaper to call a guy with a bobcat as he'll have it done in less time than it takes to drive off the truck.

[pauljygrant]

, it's cheaper to call a guy with a bobcat as he'll have it done in less time than it takes to drive off the truck.

Agree with you on that one...however you are then relying on someone else to turn up when they say they will and do what you want. At least doing it yourself you gain experience and although the total cost may be around the same, as long as you are willing to 'write off' a day of your life,you have the same outcome.

[Bloss]

Take the top layer off - and out to around 1m or so past the area of the shed. Unless you are in a hurry this can be chipped off with a sharp shovel over a few days (couple of hours each day) - but machinery in under two hours. Gotta get the machinery there though. I'd be paying someone or just doing it by hand - it's not a big area - effectively removing turf (but harder, yes).