Footing Questions

[padstar]

After preparing myself for a weekend of digging i have found a local mini digger and driver for a very reasonable price. As i am sure there is no risk of this being more than a days work (max) i thought the money would be well spent and save me back at the same time.

I have roughly marked out where the footings will run and believe i am ready to go. I plan on doing the following;

1) Remove old porch slab
2) reduce full area by 300mm (mainly sand from the old paving)
3) Dig footings a further 1m

I believe we are sat on London Clay. On this basis am i likely to be safe with a 1.3m dig for the footings. The architects drawings show 1m from ground level. As i have the machine coming in a dont want to then end up digging more out myself after. Is there anyway of gauging what the BCO will look for?

Is 150mm each side of the new wall face the norm (600mm footing)?

 

[motorbiking]

1.3 is a good depth as long as there is no evidence of tree routes etc. Have you checked for supply pipes and cables (gas, electric, water)? Also have you worked out where the drain goes?

 

[padstar]

1.3 it is then subject to not finding any obstructions down there. Not many trees about so hopefully we will get lucky.

The 2 drainage gulleys in the photo run back to the main run where i am stood taking the photo. They will both come out during the dig and be made good.

There is gas water and electric running into the garage. I am borrowing a CAT scanner from work to help locate and i assume a careful dig in this area. The footing inst running across the garage door so hopefully they can be left undisturbed. What level should they be buried at if installed correctly?

 

[motorbiking]

Hopefully someone will post an answer - its beyond my knowledge.

 

[^woody^]

I can't see there being any difference to 1 or 1.3 metres in the same soil type - apart from 300mm that is.

 

[padstar]

I can't see there being any difference to 1 or 1.3 metres in the same soil type - apart from 300mm that is.

I just thought as i was taking 300 off the top throughout the 1m should then go from that level rather than ground level. If not i wont bother and just go down 1m from GF and save a bit on the concrete.

 

[^woody^]

1m from lowest ground surface level is the norm.

 

[padstar]

Will do. I was not going to dig that deep under the garage door 2.5m wide and doesnt need footings so will save on skip and concrete. Will this give the rickie issues in lining the front wall up as the footing wont run all the way through

 

[^woody^]

Will this give the rickie issues in lining the front wall up as the footing wont run all the way through

Not if Rickie is a brickie.

 

[padstar]

If Ricky is indeed a brickie would it make it tricky?

 

[^woody^]

If Ricky is indeed a brickie would it make it tricky?

Only if he's a complete dickie

 

[noseall]

After preparing myself for a weekend of digging

Your man will make a mess of anything and everything within a couple of meters of the intended dig. All the paviours surrounding the immediate dig will be churned up. We normally dig of the oversite at the same time as we dig the trenches. We always dig off a margin of 1.2m around our building perimeter and stone that too, once the stone arrives on site. You (the homeowner) will be responsible for pointing out where any underground services are, to the digger driver.

ALWAYS MAKE SURE THAT YOU CAN TURN THE STOP COCK OFF IN THE ROAD BEFORE DIGGING.

 

[padstar]

Had assumed that they will churn up around it. Thats not an issue. Thames Water stop cock is accessible at the end of the drive.

 

[padstar]

Footings have now been dug. Where the new trench hits an exsiting footing, should i dig underneath the existing and fill with concrete essentially underpinning it? Also should the new concrete be finished level with the existing footings so that the brick coursing aligns?

 

[noseall]

should i dig underneath the existing and fill with concrete

Yes, good practice.

Also should the new concrete be finished level with the existing footings so that the brick coursing aligns?

Not necessarily no*. Establish where DPC/floor level is and gauge down from there in 75mm or 225mm increments.

* It may be that your existing masonry is old 73mm gauge which would not align with metric equivalents.