Garden Woodworking

Cold Frame

There is something very satisfying in salvaging wood, and seeing it go into new things.

As I was saying in the previous post, in 2006 I tried to move a shed from outside our kitchen to a new location at the bottom of the garden. We were working on remodelling our kitchen, which included adding a new window (someday I will figure out how to write about that remodelling work.) Moving the shed would improve the light and make the kitchen much nicer to work in. Unfortunately, as I mentioned, the shed was old and didn’t survive the move. I bought a new shed, but kept as much of the old shed as I could.

Incidentally, I managed to find a picture of that old shed …

It doesn’t look too bad in the picture, but the floor was bad, and the bushes and trees had grown into the back corner and somewhat shredded it.

I decided to use the bits to make a cold frame. I used the shed windows to make the lid, attached with the shed’s door hinges so it could be lifted up. I took the gable ends from the shed to form a slope for the lid to let water drain off. I used the shed’s wall pillars and slats to make sides for the cold frame, and I salvaged enough of the shed’s floor to make a complete floor for the new construction. The whole thing was propped up on spare paving slabs that gave a semblance of a foundation. It looked very good!

And so far, I have failed to find a picture of this cold frame in good use. Sorry about that.

That cold frame did suffer from a few design flaws. Chiefly it was too deep. The idea was that we could put boxes inside to raise the heights of seed trays and so forth, but it was still too deep, and it took a lot of bending over to reach in and deal with things. The second problem was that the window unit was big and very heavy. It was three panes of glass, and really should’ve been split into three separate liftable lids. That would’ve required a lot of effort, and more skill than I possessed at the time, so we put up with the heavy and bulky unit over the years.

…until last autumn, when it was pretty clear that that cold frame would not survive the winter. Sure enough, a spell of bad weather caused the lid to fall off, breaking one of the panes of glass and opening up the insides to the rain. By spring, it wasn’t a pretty sight.

Right. That’s all the old stuff taken apart, the good stuff reclaimed and the rotten stuff discarded. Time to build a new and much better cold frame. I shall once again, use as many good bits of that old shed as I can, but this time I will put some more thought into the design and make a better, more functional thing.

I started to make a plan. I would use the remaining two panes of glass to form lids, and would make a smaller (and less deep) box as a result. This time though I would make two new, separate window frames for the glass. I would buy new wood for these window frames, to ensure they would fit well, protect the glass and last longer than the rest of the cold frame – I could replace any of the other frame bits as time went on.

All the rest of the wood would come from my reclaimed stash. So, what bits do I have? I have the remains of the cold frame; enough, I reckon, to make new sides and ends. I have a few strips of treated wood that I could use where necessary. I took down some fitted wardrobes a few years ago to make my son’s room bigger (I will write about that someday), and from that I gained some floorboards that had been used for shelves. Oh, and I had a trellis, against which a fig tree was growing – until the fence posts rotted through at the bottom and it fell down. I have a new trellis and new fence posts in place now, but the old bits still have bits that will be useable. Now for a design.

Since I had lost one of the panes of glass, the new unit would be narrower than the old. I could reuse that space by adding a table onto the side of the frame – somewhere to do the potting. With a bit more thought I could make the table an extension of the base of the box. I could be clever and avoid sawing the floorboards up – some of the boards were over 2 metres long. I could make one gigantic table, and put the frame on top.

And if I’m making a table, those two broken fence posts would make excellent table legs!

I was not going to cut the panes of glass, so these would determine the overall size of the cold frame. For some strange reason, the old shed’s windowpanes were not all the same size. The middle one was slightly larger than the other two. One of the end panes had broken, which meant I had two  different sized pieces to deal with. One was 61x61cm, the other 53x61cm.

Access to wood was tricky at this point due to the lockdown, though I found my local DIY superstore would let me click and collect some 2.4m long plain sawn strips of 4x3cm section. That seemed to be my only choice, so it would have to do. I bought a pack of 4 lengths of this wood. While I had the opportunity to do so I also ordered some Glass Bead Moulding that would be used to hold the glass in place.

To keep things simple, I decided to cut the wood square, and screw through the top and bottom strips into the ends of the side strips. A quick PowerPoint sketch shows this arrangement and tells me how long each piece needs to be.

Now it was time for some maths. My wood was 4cm thick. Given there needs to be a recess all the way around, the strips across the top and bottom of the frame would need to overhang the glass by this recess thickness on either end. E.g. if I assume a 2cm recess at the sides then the top and bottom strips need to be 4cm longer than the widths of the glass. So that meant 2 strips 57cm long and 2 strips 65cm long.

Conversely, the strips at the side would have to be shorter than the length of the glass by twice the recess depth. So that meant the four side strips would be 4cm less than the 61cm length of the glass; or 57cm long.

As it happens, 57 + 57 + 65 + 57 = 236cm So I can get the four side strips and the two pairs of end strips out of two 240cm lengths of wood. That’s good!

In the end I decided to use the spare 4cm by making the side pieces a little longer – 59cm each. This allowed me to reduce the depth of the recess at the top and bottom, keeping the wood thicker and perhaps a little stronger on these two pieces. I thought this might be useful for the top pieces in particular, which would need to bear the weight of the windows on the hinges.

And so, I have the basic bits for two window frames.

A quick check with the glass shows that I should have just enough room all round to hold the glass in place.

Anyway, this post has gone on long enough. Next time, I shall dig out the router, chisel and wood preserve, then get that beading cut to size.

By nickcnickcnickc

I spend my working life staring at computer screens, so in my spare time I look for things to do with my hands, preferably involving wood. It's a little ironic then that I've now starting writing a blog about my woodworking, and thus introducing computer screens to my main hobby..!

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