My neighbour has a car port at the bottom of her garden next to the garage. In fact it is a corrugated plastic garage in reality. The plastic used for the roof sags between the beams and so lets water in. She wants to know what to replace it with so that it doesn't leak but does let the light in.

Now the car port is dual purpose. She, being a little old lady in her 80s pots flowers in it like a green house. I get to use the rest of it for building cars! I can take a hint and will happily do the roof for her but I don't know what will cover it without sagging or leaking. What do you recommend?

Additional supports, and corrugated sheet, or, the triple wall stuff used on consrvatory roofs.

You can't drill the latter, so more framing would be needed.

poly carbonate conservatory roof sheets.

twin wall poly carb sheets

Yes, some little wooden support struts in between the main beams

[Edited on 2/8/10 by Andi]

My car port is 10m long and 3m wide, corrugated plastic. No sag at all, but it has main joists evry 1200mm and cross peices every 1000mm. All good old 4x2 with extensive use of mini joist hangers. Not expensive to do. If you go twinwall the stuff is much pricier, and you need those expensive joining strips (mind a bit blank at the mo!) Bearing in mind it is only a carport..........