London (change)
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25/01/2014 at 18:15

Hi all, over the next couple of weekends I'm building a heated propagator from various bits of wood etc which I have left over from other projects around the house and garden and will post photos as I go.  Feel free to ask any questions if this sort of thing interests you.  

Today I made the base from left-over decking boards and some outdoor-grade plywood I happened to have:

Screwed together using stainless steel screws and painted with clear wood preserver before being put into the greenhouse overnight to dry.


25/01/2014 at 19:03

I wish I had some of those skills Bob. Anything I build is never quite parallel and the screws always protrude on one side because they went in crooked.

I shall follow your project with envy


25/01/2014 at 19:38

I,m interested to know how you will heat it.Or is that a silly sod presumption that you have already got it sorted.Personally I have a good generator in me shed.Hope it works well for you Bob the Gardener.Regards Brian.

26/01/2014 at 07:02

Brian this is what you would heat a propagator with

I have bought one and shall be building my next weekend


26/01/2014 at 07:03
29/01/2014 at 08:37

Brumbull I would think your sealer has dried by now any chance of a up date


29/01/2014 at 10:25
CluelessGardener wrote (see)

Brumbull I would think your sealer has dried by now any chance of a up date


Clueless do you mean BobTheGardener who started this thread?

29/01/2014 at 12:10
Hi Bob a cracking idea matey ,now can you price up the things you cant make and have to buy, it would be a big help, Brum seems to be on the ball as well thats a good looking one he,s got, were all sat here like Sat matinee waiting for the next episode go for it,
29/01/2014 at 18:17

Hi Alan, I have already bought the soil warming cable and thermostat but progress will have to wait until the weekend as it's dark when I get home from work.

29/01/2014 at 19:33

yes sorry it was bob I was trying to poke




29/01/2014 at 19:36

OK what is the difference between and hot bed and a heated propagator

I will be making mine this weekend with the heater cables and thermostat I bought early January


30/01/2014 at 09:44
Hi Brum can i ask where do you get the hotbed gubbins ,which r u using ,iv not done this before and i like the sound of helping cuttings to grow.
30/01/2014 at 12:03

i am simply doing this as iv been trying to get  a smiley box and its just happened i think Daniels got his wand out hope it stays on mipostbox 

30/01/2014 at 15:29

Alan - it looks like you can get them from pretty much anywhere! For instance looking on eBay I find photographs exactly the same as the ones Brum has posted earlier.

01/02/2014 at 12:52

cheers for all that info ,im onto it 

01/02/2014 at 21:53

Hi all, before I post pics of all the latest work done today, here's one of how I decided on the exact size of base to make.  I originally wanted it to be roughly 4ft x 2 ft to fit the space available in my shed but decided to make it an exact fit to multiples of standard seed trays by laying them out on the plywood I used for the bottom then adding 2 x the thickness of the decking boards used for the sides.  This is how it turned out:


01/02/2014 at 22:01



I worked out that it would take 4 x 25kg bags of sharp sand to fill it to the required depth (4 inches: 2 inches below the heating cable and 2 inches on top.)  As that meant the whole thing would weigh over 100kg, very sturdy support would be needed!  I used 50x50mm (2x2 inch) timber to make a frame and used steel legs from an old office desk I found in a skip:

Pic below is it in place on top of the frame:

01/02/2014 at 22:10

Next would be to line it with insulation so that the heat would be retained.  I had a roll of polystyrene insulation which was left over after fitting a laminated wooden floor in my conservatory (which has a concrete floor.)  This stuff is very cheap and ideal for the job:

First layer stapled in place:

Second layer now stapled (with galvanised 12mm staples) and trimmed:


01/02/2014 at 22:21

I used a 6m long Parasene soil heating cable as this is the recommended length for a 4'x2' propagator and is rated at 150W:

it needed feeding through 13mm a hole (there is a blue seal on the end of the cable which needs to go through the hole) in the side which was made 2" (50mm) from the bottom of the propagator:

01/02/2014 at 22:34

Next was a 2" layer of sharp sand:

Now for the tricky part!  Somehow the cable needed laying evenly so it covered the whole area without any loop touching another loop or any crossing cables as these would cause hot-spots.  The trick here was to plug the cable in for 10 minutes to let it warm up, making it more flexible.  However, it wouldn't stay in place even if I patted it into the damp sand, so I came up with an idea - use pieces of decking to temporarily hold it in place - these will be removed later:

Clever, eh?!   Now I filled the gaps between the bits of wood with more sharp sand which would hold the cable in place:

removing the wood left it like this, ready for adding the rest of the sand:

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