Concrete on soft lawn

Hi i have got a section of lawn about 12ft square that will need concreting in the new year. The section has to be raised about 15 inchs but what worries me is that the lawn is very soft and boggy will this affect the concrete, what would be the best way to do this, i was thinking 8 inch hardcore and 7 inch concrete would that be a stable longlasting base.
Any ideas as wife nagging
thanks
Steve
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It rather depends on what you want to put on it. A well mixed and laid 7 inch slab 12 foot square >>should<< stay together and move as a unit, and if it's only a shed base will probably be ok BUT:- why is it boggy? is there some underlying drainage problem?
I would be tempted to investigate the boggy nature before laying a few tons of concrete - shame to find a cracked drain under it!
Before you lay you really should strip off the turf and top soil and get down to the underlying none-organic layers for best stability.
Also consider putting 6" h/d mesh in the base if it really is that boggy to re-inforce the slab and also possibly the wife under it if the nagging gets too much <g>
Andrew
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why is it boggy? is there

No there is no underlying problem, maybe boggy is the wrong word more squelchy and soft,
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Are you referring to clay type soil? I live in a clay soil area and that goes very 'squidgy' after a lot of rain.
If so, I would reccommend laying some of that iron grid reinforcing into the area you are going to fill with concrete. its cheap enough, about 15 for an 8ftx4ft sheet.
When i layed the base for my log cabin (14ftx13ft) I compacked 4 inches of hardcore, layed some of that gridding and poured 4 inches of concrete on top. Thats been down for 2 years and there have been no signs of breakage yet.
Hope that helps
Phil

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wrote:

http://www.pavingexpert.com/ specifically http://www.pavingexpert.com/concrete.htm
an excellent site.
--
Peter Parry.
http://www.wpp.ltd.uk/
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SJ wrote:

I'd say so.
I am on boulder clay, its veruy boogy, and what I have done so far in sorting out teh drive is to scrape off the brown dirt bit, down to where it looks pretty clayey, and lay abouut 4-6" of crushed limestone road base.
Thats as far as I have got, because laking a road rller, I have been letting the 20 tonners that have delivered varios things compact that down. In some places I have conctreted over that - nothing like as much concrete as you are envisaging - by using mixed stone and rubble and simpley pouring a tad of concrete on top.
The big problem that I see is that uneless you go really deep, there will be some subsoil movement as the clay dries out - or gets wetter - that is you WILL disturb soil water content one or another way, and that will lead to subsidence or heave. The two classic solutions to that are deep single point or line founations and then a block and beam platform over the top, and concrete to top off, or go deeper with the hardcore/limestone etc.
Or accept the odd crack. The mesh reinforcing will not prevent cracking on a thin layer, though it will stop sections breaking apart.
I think if it were me, I'd go down about a foot or so, and a tad more at the edges, then lay a concrete foundation strip all aroumnd the outside, shuttering up to nearly finished height, fill the inside with about a foot of smashed up hardcore and limestone, then a sand layer of an inch or two, then wire mesh and top off with about 4-6" of concrete. Remember to put a fall in the slab away from the house. And don't go up beyond a couple of brick courses below house damp course if it can be avoided, and if you have to, leave a gravel filled gap between slab and house.

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