Customer has had a shed base laid (not by me, I turned the job down) which has turned into a bit of a disaster. Its off level by about an 1" in both directions and the surface looks like a roller coaster for mice.
They want a metal shed erected on top, but there is no way thats going to work until the base is sorted.
Initial thoughts are to erect level formwork & top the base with a little more concrete.
Is it going to bond OK to the exciting base, especially where it 'feathers'.? Would PVA help?
But if you do end up fixing it, I wouldn't put more concrete on top, because unless you are expecting to put about >3" thickness all over you'll liable to end up with a weak layer that may crack off.
What you could do is screed it (ie sharp sand, cement, forget the pebbles). As long as that goes on > about 30mm all over (so 50mm in the off level bit) it would probably be fine and it would look dead smooth.
Keep whatever you do covered for a few days by polythene in this sun or it will fall off if it dries out without setting.
Lots of water/cement slurry on the existing concrete to assist with the bond.
You could go all the way to an SBR screed regime as mentioned recently then you could repair it down to 10mm minimum depth. Maybe the cost of the SBR will balance the saving in the materials???
Don't know what the original monkeys were doing. I can get raw concrete good to
I wouldn't use concrete that feathers because thin concrete will always crack, no matter what you put in it.
If the out of level is only an inch, I would erect the shed level using steel packers where the base is low, then fill the gap between the base angle and the concrete with expanding grout underpinning.
"Expanding" is a misnomer - the admixture is just enough to prevent it shrinking.
For the steel packers, go to any fabrication shop and ask for some offcuts in an assortment of thicknesses. Used in combination, these will give you packers in a range of different heights. For a small fee they will flame cut them to the size you want. For a slightly larger fee they will grind the edges flat.
Hardwood folding wedges would be an alternative.
For the expanding (non-shrink) grout, you can either buy it ready mixed in pourable or trowellable form, or use an admixture from a builder's merchant and add it to a 1:3 cement:sharp sand mix. Don't add too much admixture or it will really expand and bend the shed base!
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make the grout frost resistant, SBR would be ideal if you have some, but some waterproof PVA is a cheaper alternative. After all, it's only a shed.
More likely, I can't see how you can fup up so badly with a shed base unless they just dug a vauge hole and threw a couple of barrow loads in without any formwork at all.
Using some stuff already suggested - one course of bricks all round using variable depth mortar bed to bring the bricks level. Screed inside the bricks up level with the top. Put the shed on the bricks.
Interested as to why you turned the job down - were they not prepared to pay the price of a decent job?
I should have asked: is the base good enough as the exposed floor? It crossed my mind briefly whether to just sort of the bit that bears the metal frame, but the base sounded so bad I defaulted to "screed it"...
You can't feather concrete - you can lay a sand/cement screed, quite strong, bout 3:1 sharp sand and yes, unibond will help where it feathers to nothing
Simply because humping & mixing large amounts of concrete is bloody hard work. I can earn more doing simple jobs - like changing light bulbs, putting up borders, siliconing around baths etc.
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