How hard to dig foundations?

neneromanova

Looking at the cost of things for a two storey extension, one of the biggest costs is digging the foundations (Please correct me if I'm wrong).

Now I don't mind doing a bit of digging, but how hard is it to dig the foundations out? And how do you know how deep to dig them?

Does anyone have anything online somewhere that I could have a look at to help me?

Thanks very much

Gloomendoom

It depends on what you are digging, how deep, and what with.

Other variables such the weather, time available and your physical condition etc. may also play a part.

warmhands.coldheart

neneromanova wrote: »

Looking at the cost of things for a two storey extension, one of the biggest costs is digging the foundations (Please correct me if I'm wrong).

Now I don't mind doing a bit of digging, but how hard is it to dig the foundations out? And how do you know how deep to dig them?

Does anyone have anything online somewhere that I could have a look at to help me?

Thanks very much

All I would say is they are NOT something to get wrong so I would suggest leaving it to the experts or at least get an expert to advise, not the sort of thing I'd get Joe Public to advise on..

All I do know is it depends a LOT on the soil type you are on and what the subsoil consists off..... If you're site is shallow topsoil over a hard stoney suboil you may not need to go down far, on the other hand if you are on deep soil or sand with little subsoil structure you may have to go down meters or even have it piled !!

27col

When I built my first house I dug the foundations by hand. Very hard work It took me and a friend several weeks. But it make me a lot fitter ready for the rest of the self build project. The biggest problem is getting rid of the spoil. In my case, I had a hollow in the corner of the site.
When I did my second house I got a JCB and a lorry in. But I still had to fill several skips by hand. On balance I wish that I had got it done professionally. But at the time we were on an extremely tight budget.

zaax

Its not difficult to hand dig just very physically, and your going to need somewhere to put it. Mini digger hire is best.

arbrighton

We had a structural engineer to do the calculations for ours (no I didn't dig them- several of the builders did, with a mini digger and by hand over a couple of weeks). Unfortunately he didn't really take account of the hawthorn hedge so they had to be made deeper (we're talking about 6 foot down) and as it's right by a road, dug in sections, inspected and filled the same day.

The spoil has been used to back fill and help level the sloping garden a bit

neneromanova

I can get a digger which i guess would help. So the person to go to would be a structual engineer and they could help? I guess that wouldn't be cheap though.

I guess the first thing to do is go for planning permission to see if we could actually build the extension first.

teneighty

You will not need a structural engineer unless the ground conditions are poor and you need a special reinforced concrete foundation.


To be honest it is not something you will save a lot of money on by doing it yourself. It is a ground worker/labourer's trade so only £100 to £150 per day per man (probably2 men 2 days max.) plus hire of mini digger and skips or muck away, then cost of concrete. It can be hard back breaking work even just barrowing the spoil out so be prepared.


If you phone the Building Control Dept. at your local council they should have a pretty good idea what the ground conditions are like in your area and give you an idea how deep you are likely to need to dig. More than likely 1 metre. Obviously you need to be aware of underground services such as drains, cables etc.

force_ten

the depth of footings required will vary greatly by soil type and site conditions, footings of 1000mm deep by 600mm wide in perfect soil conditions would be hard work to dig, but in certain soil types footing may be required to go down 2000mm or six foot deep in old money now that would be some real hard work

societys_child

When I've dug foundations, the building inspector is informed, he turns up and says yeah or neigh **
The concrete is then poured and the inspector returns again to give his approval.
Next step is to build up to DPC level and the inspector comes back once again to tell you how happy (and impressed) he is with your efforts . . . :j

** In one case needed to dig down 8 feet (just one 6 ft section) to get him to smile

Always managed to have good relationship with building inspectors, but they do drink a lot of coffee . . .

kaya

Go to your local town hall and talk to building services inspector, show them your plans or intentions and they should inform you of how deep you are required to go (may take a few weeks for them to turn up). It is a good idea to dig a test hole so they can see what type of soil you have if there aren't lots of extensions build locally. I would advise against hiring a digger as a diy job if you are unfamiliar with the equipment, you also need to contact building services or planning to find out about any services (drains, electrical etc) that may be under where you plan to build , hit one of accidentally those with your hired digger and it can cost you a lot more than paying someone else to dig the foundations for you
My friend had to go down 3 meters for his extension, not something you would want to do by hand