More Greenroof questions..... substrate?

[Rick O Shea]

Green roof questions... OK the roof is on,  I wonder if some one could advice on  what sort of substrate is recommended, I have a book called 'Greenroofs' but  while there are lots of nice photographs..........there is not much information on the substrate.

The roof is 10m x 5m so a fair size.  The roof timbers are 225.75 at 350mm centres, and the covering is 18mm osb.

Should I put a couple of layers of standard roofing felt on first, then the 'carpet' then the pond liner?

I have had a quote today for three layers of felt, first layer cold tacked  the next two bonded hot for £2250...............when I got up from the floor  I was told  I was told prices have risen recently.....................

Mike         

[clockmanFR]

If you have that 1.10mm thick rubber pond liner, its mighty strong and very hard wearing.

I have been using my offcuts for building work, like covering up masonry work for the winter etc, its very durable. I used that proper liner polyfelt thick stuff as the carpet, but it is hell to cut straight.

I suspect that moisture will gather under the liner, but i am no expert.

Good luck.

[AlanM]

try safeguard chemicals, for Oldroyd xV membrane. Thats what i use for all my turf roofs, comes 2x20 rolls, polypropylene. Have done over a dozen ranging from over 500m2 down to wee ones of 20m2. Under it, use either roofing felt (22f), or some breathing papery thing, roofshield etc. It has a dimpled surface to help roots to stay on roof and also creates a 5mm air gap for drainage.

Alan

[Rick O Shea]

Thanks Alan  for that, I will have a butchers crook.