Don Wrote:
Due to possible bad ground conditions, I may have to use a raft
foundation
in my 25sq M, single storey, flat roof extension. I was wondering
whether I
could tackle the steel reinforcement which involves having a 400mm x
6M
long, sq box made out of A142 mesh and marrying it with sheets of A142
mesh
and various lengths of 12mm ms bars. I' ve seen guys on building sites
twisting thin wire around steel mesh etc, but how do you bend the bars
and
what kind of overlaps are required? Anyone have any experience or
advice to
impart?

I refer to the following site:
http://tinyurl.com/c9y96 No2 Raft Foundation


Cheers
Don

You would have to get the steel ( re-bar) from a specialist steel
merchant who can easily supply what you need, but would normally work
to a steel schedule which will specify each different type of
re-inforcement including bar size, lengths, shape code (ie bending
recquired) and number of bars.
Having said that, if you have to go for a raft then the local council
Building Control peeps will definately recquire engineers drawingg,
calcs and specs and the engineer would then normally supply you with
this schedule as part of the design.
The "steel fixing" itself is not too difficult as long as you take your
time and make sure everything is in the right place, you can set the
re-bar on small moulded plastic blocks (or concrete (ie broken paving
slabs) to get the right "cover" of concrete below. The building control
bods will check it all.
You will need "soft annealled tying wire" but the re-bar supplier can
get you this, theres a bit of a knack to tying it but as long as you
get it tight its OK.
Get a pair of cutters like these
http://tinyurl.com/74ehr
You loop the wire round the bars in a figure 8, grip the ends, twist a
few times then snip, easy.
One good tip is to allow plenty of time to get the steel in place
BEFORE the readymix trucks arrive, thats a big mistake to make !

If you have to do it then good luck mate.


--
Nick H