On 21/08/2013 19:53, Phil L wrote:
I'd build centre walls for added strength if it were mine - you can use
shorter beams and there's less stress on the outer walls.

I was expecting to do this anyway since I am spanning 5m and that a big
ol' chunk of concrete to lug round the back of the house.

Don't forget, pre-stressed beams usually have a camber and you'll have to
factor this into your final levels WRT drainage etc

Ah, useful to know. Thanks.