By Popefrancis
United Kingdom 
Instead of using polystyrene as a base in making a soil warming cable bench would a piece of plasterboard with a reflective foil work just as well?
9 Jan, 2015
Answers
You don't need polystyrene either.
9 Jan, 2015
I lined my tray with recycled bits of polystyrene, then a layer of sand, then the cable, then another layer of sand. I topped mine off with perforated black plastic and the seed trays or pots sit directly on this. The sand is supposed to be kept damp.
9 Jan, 2015
If you must make a hot bed, and I'm not a fan of them because they can get quite heavy if it's a large bed,
then the base is lined with grit.
Then 2" of sharp sand, cable, 2" of sharp sand.
Permeable weed suppressant material is better than the plastic mentioned to go on the surface. Should you wish, a capillary mat can go on top of that.
I do have an 8 foot by 3 foot cable bed but it is at ground level, so weight isn't important.
9 Jan, 2015
no It wouldn't
9 Jan, 2015