Steel reinforcement in concrete ?

[Don]

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:

No2 Raft Foundation

Cheers Don

[Dr Wu]

No2 Raft Foundation

[somebody]

In message , Don writes

Hi,

If I understood and read it correctly, the link you gave (doc 2 - raft foundations) specifies the overlap at 450mm (point 11 at the bottom of the list).

Bending 12mm rebar - no idea :-) Hopefully someone else will have an answer for that. My only thoughts were Oxy Acetlyene to heat it enough to allow bending. That would be fine for 12mm rebar alone, but in a mesh I'm not sure.

Hth Someone

[Nick H]

You would have to get the steel ( re-bar) from a specialist stee merchant who can easily supply what you need, but would normally wor to a steel schedule which will specify each different type o re-inforcement including bar size, lengths, shape code (ie bendin recquired) and number of bars. Having said that, if you have to go for a raft then the local counci Building Control peeps will definately recquire engineers drawingg calcs and specs and the engineer would then normally supply you wit this schedule as part of the design. The "steel fixing" itself is not too difficult as long as you take you time and make sure everything is in the right place, you can set th re-bar on small moulded plastic blocks (or concrete (ie broken pavin slabs) to get the right "cover" of concrete below. The building contro bods will check it all. You will need "soft annealled tying wire" but the re-bar supplier ca get you this, theres a bit of a knack to tying it but as long as yo get it tight its OK. Get a pair of cutters like these

loop the wire round the bars in a figure 8, grip the ends, twist few times then snip, easy. One good tip is to allow plenty of time to get the steel in plac BEFORE the readymix trucks arrive, thats a big mistake to make !

If you have to do it then good luck mate

-- Nick H

[Rick]

No2 Raft Foundation

I did all my own steelwork.

You but the bars bent. Forget the builders merchant, find the local stockist of this stuff.

To tie them, you use potato sack ties, and a special twisting tool - easy peasy.

You also need to space the bars, again the stockist will have all the stuff you need.

Here are pictures of what I did. The main issue is the mesh comes in

8mx4m sheets, and you need two people.