Heated propagation bench

It can get very cold in the polytunnel and to grow frost sensitive plants we needed some form of heat. We chose to build a heated bench. Not so much to germinate seeds (we do that elsewhere), but to protect seedlings from frost.

We use the 2400mm x 1200mm bench all the time to bring seedling on after germination. We planned to convert the chipboard table to a heated bench using insulation, a heated cable, and builders sand.

The centre of the bench has a new support to take the weight of the wet sand.

For the insulation we used 75mm Insulation board, Kingspan TP10. It spans the whole area beneath the chipboard and should provide a good heat insulation below. The heating cable is an Elixir Gardens 24meter 120W, giving us cables at 7.5cm spacing.

There is a sheet of thick plastic to water seal the top of the table. We used tape to keep the heating cable in place on the base.

We used 7 bags of building sand so we ended up with about 10cm depth of sand.

The thermostat is a Ketotek KT99 dual-way temperature controller, so we get a sand bed and ambient temperature readouts at the same time.

We have set the thermostat to 10 deg C so its really just to keep the edge off any frosts. If the forecast suggest a deep frost we will use fleece to cover the table.