Digging and pouring padstone and foundations

[iwanttodiy]

Hi

I’ve attached the site drawings of an extension i am planning to get built. The red lines are the anticipated beams. C1 and F1 are the columns and padstones. Padstone size is 1200x950x500). Purple dotted line (F2) is the new standard depth foundations (60cm wide and 100cm deep). These are the specs from my SE for the job.

Ive attached a picture of the trial hole showing existing foundations. They are 70cm from ground level, 20cm thick. Therefore, I assume the job would be, to create a pad on top of the existing foundations which will make the top of the pads ground level (Thus not necessarily underpinning)

Now the question: having separate ground workers to provide a quote for the padstones. (This part I am not comfortable to even attempt myself and the builders to do the beams are not comfortable with doing the padstones.)

If I had the foundations F2 dug out ready for filling, and the ground workers lined up to dig out the padstones, is it not possible for the ground worker to fill it all in one go? Considering the Concrete is the same spec (C35)? This would save cash in terms of only needing a single ready mix truck at 9-10sqC of concrete instead of one for the pads and another one for the foundations?

I may be missing something, but doing them as 2 separate jobs seem to be quite ineffective. (Unless I’m being told this due to pricing calculations I.e, the ground workers wanting to dig the footings as well at £200 per meter, and thus £2400 just to dig the footing, would be cheaper to rent a digger.

Any thoughts on my predicaments? Unfortunately I am struggling to get ground workers to do partial jobs as they generally want the full ground works when they see my situation.

 

[Footsoldier888]

I am not an expert in any way but the fundamental rule about groundworks is to get the best guys you can and don't worry over small costs. This is an expert field and mistakes can be hugely expensive to rectify.

If you are in London with this build you especially want to get your trenches filled the minute you stop digging, weather permitting. It might not be possible to use a digger anyway if your are near neighbours foundations, party walls etc etc. Get a reputable firm and leave it to them is what I would do, get a recommendation and do your research. I would leave all the details to them.

As for the lorries you can get a mix on site lorry for a small batch so it won't be a problem if it is in two stages. This is the most critical part of your build so you need to get good people in who won't make a mistake.