Browse Forums Paving & Concreting 1 May 19, 2013 3:50 am THE PROJECT (Victoria) Farm shed, 18m x 7.6m x 3m. 5 Bays, roller doors. Piers: 450mm, 1.5m deep (elevated soil), gently sloping site. Footings: Set in concrete. Nearly all do-it-myself job. BACKGROUND Ripped out tree roots and elevated the site (over 1m on the low side) using clay soil of the same type (from where I have been digging a big pond). Then it rained lots resulting in a year delay before drilling the holes for the piers (18 holes, each 1.5m to within solid soil). Shed frame construction has been completed and is ready for roofing and wall sheets. I am now ready to arrange for concreting the slab (for the entire area) but it's been raining again plenty and the clay is very wet and soft on the surface. I have just laid stone dust (supply calculated for a 50mm height but the actual height will be less after compacting. I estimate the slab will be 120mm thick. The slab will rest on the piers (no stone dust between slab and piers). MY CONCERN My concern is the wet clay. If the slab is poured when the clay is wet, it will shrink over time perhaps resulting in space between the slab and the soil (it will rest on the piers). If the slab is poured when the clay is dry (may have to wait with pouring until summer...), the clay will expand in winter (rains) perhaps lifting the slab and cracking it. It's unlike to lift the shed due to the footings design. Should I call the concreters now (wet soil) or wait until next summer (dry soil)? Building permit expires in June but may be able to pass it without completing the slab). Re: Concrete slab on piers (18m x 7.6m, wet clay soil) 2May 19, 2013 10:13 am I don't think the wet clay should have an impact. The whole reason for having the piers is so the slab won't sink. I so go for it now. I has the same issue when I poured my slab last May, a very wet May. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ I had trouble walking on it without sinking. The slab and pier design takes into account the clay soil. Apart from the issues of getting concrete trucks to the site, you shouldn't have issues pouring while its wet. Re: Concrete slab on piers (18m x 7.6m, wet clay soil) 3May 19, 2013 5:53 pm Thanks for your response, JB1. Sure looks like one hell of a clay mess What kind of structure went on the slab? Re: Concrete slab on piers (18m x 7.6m, wet clay soil) 4May 19, 2013 10:57 pm An older photo, haven't taken a recent one outside. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ I had about 16 piers, some 2000mm down some 1500mm. I think the engineers went overboard but better to be safe than sorry. I spoke to the engineer, he said after all the piers I shouldn't need a footpath around the house to protect the slab. I had to use about 40 tonnes of crush rock for the 30m driveway and around the house so I could get trucks up near the house. Then I had to pay someone to remove dirt and crushed rock after I dug the trenches and cut the driveway for concreting. An expensive, fruitless but unavoidable exercise. I've dug some footings to embed a post anchor into. My holes are around 450mm deep which I'll put a 200mm stirrup into. The bottom of these holes seem firm enough. … 0 3312 How good is Simeon?! Always taking time to help others out! Wish we were building in NSW and could work together. Thanks for all that you do! 7 6562 DIY, Home Maintenance & Repair That’s very helpful information. Will find out more from there. Much appreciated. 11 13446 |