Groundworks (Oversite) and Footings - Logistics Query

[VDubDan]

Hey all, I'm building a dwarf wall greenhouse which is going to be surrounded by a new patio. I've settled on traditional strip footings because I don't really want a concrete slab on show, and think I'll get a much cleaner finish by building it with footings and then a separate solid floor.

Area is about 30sqm, so fairly chunky project (for me), and it looks like I'm going to have dig out a lot more than I hoped because there's a lot of top soil/made up ground (it seems I may have found the 1930s rubbish pile from the build)

As it stands, the whole area is level(ish..) at about 200mm below "Finished Floor", but it's dirt still and I'm going to have to excavate further to find good ground for both the patio and the greenhouse before then backfilling with, uh, lot of hardcore or whatever.

Basically, what's the logistically sensible approach. Would you dig the footings now, with the soil in place - or can I just clear the entire oversite down to sand and, uh, somehow go from there, before backfilling everything. Is it acceptable to shutter strip foundations, and then backfill everything? Or am I dreaming?

 

[noseall]

Hey all, I'm building a dwarf wall greenhouse which is going to be surrounded by a new patio. I've settled on traditional strip footings because I don't really want a concrete slab on show, and think I'll get a much cleaner finish by building it with footings and then a separate solid floor.

Area is about 30sqm, so fairly chunky project (for me), and it looks like I'm going to have dig out a lot more than I hoped because there's a lot of top soil/made up ground (it seems I may have found the 1930s rubbish pile from the build)

As it stands, the whole area is level(ish..) at about 200mm below "Finished Floor", but it's dirt still and I'm going to have to excavate further to find good ground for both the patio and the greenhouse before then backfilling with, uh, lot of hardcore or whatever.

Basically, what's the logistically sensible approach. Would you dig the footings now, with the soil in place - or can I just clear the entire oversite down to sand and, uh, somehow go from there, before backfilling everything. Is it acceptable to shutter strip foundations, and then backfill everything? Or am I dreaming?

We dig the oversite, the trenches and a 1200mm margin around the construction area, at the same time (machine excavator). However, a premium is placed on having the ground level for the machine, at all times, so the dig is planned and deliberate. We set up the digger for the first trench pull, and begin excavating furthest from the exit point. Dig the first foundation trench, then scrape off the oversite, whilst that material is still in reach and are still positioned to remove the fall-in spoil from out of the trench.

If drains need digging, we do them after the concrete is poured (and set), so that the drains dig doesn't interfere with the foundation trenches.

 

[VDubDan]

Thanks @noseall - how much do you leave - do you dig to the top of where the concrete woould be, or do you leave more?

 

[noseall]

Thanks @noseall - how much do you leave - do you dig to the top of where the concrete woould be, or do you leave more?

We end up digging off about 450mm (below DPC), for the oversite detail. And about 150mm around the exterior building perimeter.