NogbadtheCool wrote:
bit late for this year I suppose, but I have a thermostat and a length
of plastic wired with heating cable which I keep meaning to make into
a proper heated seedbed. Does anyone have any advice / plans for doing
this properly? Many thanks
Make a 6 inch deep frame with an OSB or WBP ply base (threequarter inch
thick base because it will have to support a few kg of sand). Put a
layer of polystyrene or kingspan insulation in the bottom. Line with
thick plastic sheet. Follow the instructions for your soil warming
cable - generally 1 inch sharp sand, then the cable, then another inch
or two of sand. You can drill through the sides for the cable and
thermostat. Make sure that the legs are sturdy and braced if it is not
wedged in place

I built one like this a number of years ago and sized it so that an
aluminium cold frame would fit on top. This gives growing height and
when shut down at night can be cobered with bubble plastic to help with
insulation. Mine is in an unheated greenhouse and the air temp has
never gone below 5C.

Malcolm