Tips on digging and pouring footings

[carryoncamping]

My Plans:

Just got a quote of £60,000 for a 30m2 ground floor + 10.5m2 upstairs
extension, which I think is a bit steep! I'll get more quotes but even
so I've decided to dig my own foundations by hand and lay the concrete,
to save money.

My existing house is built in the bottom of a former limestone quarry.
The top-soil/clay is relatively shallow approximately 500mm, below that
you hit solid limestone bedrock. So it's quite good for building solid
foundations on.


Digging the trench I think will be relatively straight forward
(architect's plan state strip foundation 600mm x 200mm)


I have a number of questions and concerns:-
My biggest concern is making sure the concrete will be level and
uniformly at the same depth (digging the trench to a uniform depth is
relatively easy). I've read about knocking wooden pegs in to the
trench bottom so you can easily gauge concrete levels. But won't they
weaken the foundation if left in which I'm told you do? How about
using Steel pins, where do you purchase them, are they the ones used
for steel reinforcing?

-How do you tamp the concrete easily without sideboards do you use a
"vibrating poker"?

There is a 4" soil pipe that will run through the rear extension wall. Do I simply run footing either side of the pipe and then lintel over, Or should the foundations be continous under the pipe and then lintel over the top?


- Should I measure concrete depth to coincide with brick/block
measurements, so that the once the bricks are built up to ground level
they coincide with the existing house brick level?


Any tips websites, books that can give me a full insight into what is
required would be most appreciated.

 

[noseall]

wooden pegs every 2m or so is fine.

get readymix with some freeflow additive, and it will practically level itself.

if you're having it pumped, (freeflow's not an option) then fill to the top of the pegs and it will tamp with a board easily enough.

no need for a vibrating poker.

if the pipe running through the trench is near the bottom then you will need to shutter either side and lintel over.
if its midway or near the top then wrap it in compressible material such as fibreglass insulation.

if you are building in metric brickwork below d.p.c then set your trench pegs at 75mm intervals down from the damp.
depending on ground conditions you would normally allow a course of blocks and four courses of bricks. 525mm in total.
if the ground levels vary then you need to show more brick work accordingly.