preparation of ground for workshop

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Established Member
13 Nov 2018
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Hi all, just starting to dig out base for new workshop, will post photos as i go along.
Building is 7m x 4m, pedestrian door to front elevation and double doors to the left hand elevation when viewed from the front.
My initial issue is with the base level. i have set a datum for the height of the concrete slab that is at exactly the same level as a small workshop i have to the side of the new workshop. The idea is that when viewed from the front the slabs for both buildings are level with each other. This will require a 150mm dig out, as going 50mm of hardcore/ blindings etc and then 100mm of concrete. However due to the uneveness of the area where the workshop will be erected, i have a drop of 125mm over the 7m's. Hence i will have 25mm of hardcore in the ground and the finished slab will be 125mm out of the ground (inc 25mm hardcore and 100mm concrete) on the left and 150mm in the ground on the right. any suggestions as to what i should do. i cant make up the ground to the left.
Just to add to your problems, 100mm is too thin a slab for the size building you are proposing. It should be at least 25mm thicker than that.

As to your level issues.......why are you proposing to have the slab at the same level as that of the neighbouring building? If the ground steps down, then it might make more sense to step the new building down with it.
Hi mike thanks for coming back
understand re thickness, would you stay with the 50mm and then 125mm.
on the step down, as i am hand digging this all out myself, i was also trying to limit the amount of soil i would need to dig and dispose of. If i do step it down, the right hand side would below ground level as with the original post it is just about flush as is the existing building to the side. would you suggest i do a gravel soakaway around the slab to stop water ingress
Where the slab would be out of the ground: make the concrete thicker at the edge to take it below the ground, still with hardcore underneath, or use something like kerbstones, or concrete slabs on edge, on the outside of the slab to finish it off.
hi so in essence a retention block around the hardcore to stop it from shifting and also hide it from view. Thanks happy hacker
Around the back corner ramp the edge of the crush down at the edge with a trench dug along the edge and shuttering from the bottom oft the to the finished slab height
Quite often for garages and the like this will will be done round the whole perimeter and is called the thickened slab but usually with much deeper type 1 than you suggest