shallow re-inforced found?

[climber101]

Hi,

For a large and in some places double storey raised decking structure I am building I am wanting good founds for concrete support pillars.

To avoid having to reroute various pipes and services the most sensible approach is to do 3 strips of shallow founds which the support pillars will be set into (effectively like 3 sets of floating founds).

So I’m thinking to do shallow trenches approx 600mm wide and fill with about 50mm concrete, put a 50mm approx. steel reinforcement ‘lattice’ on top and concrete on top of that.

I will get structural engineer calcs etc, but before I do was after some practical advice on how to construct this kind of shallow steel reinforced found,; for example I’m thinking a 50mm ‘mattress’ of steel mesh but how would I build that - can you buy prefab sections? Also if there is any common ways of creating a shallow steel reinforced found, what might be common overall depth of such a found, and any idea how strong it could be..

Thanks in advance for help

 

[RedHerring]

I can't give any opinion to your idea on the shallow foundations, etc.
I can only show you how I created the steel to go into some cast in-situ lintels we did a couple of years ago.

I think, if I can remember properly, the bottom steel (main bars) were 12mm dia., the tops (erection bars) 10mm dia. and the stirrups were 8mm. You'll also need to ensure the steel is covered by at least 25mm concrete.
I don't know if it's possible to buy ready made mattress like this.
It's quite a time consuming process. I made six in total and it was at least a couple of days work.
Some more info' here
http://www.autonopedia.org.uk/buildings_and_shelter/Rural_Building/Lintels.html
Incidentally, the bar diameter is defined by the stresses in the lintels. Your installation may not be subject to the same stresses as a lintel, so you'll need to identify the direction (torsional) force in order to determine which diameter steel goes where.

 

[climber101]

thanks for taking the time, very helpful I've started sketching up how design of mattresses might look (to help price up) before talking to a structural engineer