How to make a coldframe #4

Time to get back to my coldframe construction - it's been put on the back burner a little since all the blessed weeds started growing in about April. I'm currently juggling with a Heath Robinson construction of planks and old greenhouse glass next to my greenhouse as the home for my long-suffering seedlings (late-sown summer annuals, mostly) - I do wish I could get on and finish the deluxe model. At this rate it'll be just about ready for the first frosts...

Anyway, I think I left this just as the uprights were nicely battened and ready to clad. You start by doing the end uprights, the ones you put battens around the inside edges as well as at top, back, front and base. The reason for these inside battens will now become obvious: these are what you fix the cladding to.

This is a pretty easy process: you can either use thin planks, like I have, or following the Terence Conran design more closely, you can use overlapping cladding, which is kind of wedge shaped and widely available from DIY stores. I originally thought this would look a bit clunky (actually I still think that) but now I think it might be the better option - the above looks smart, but it does inevitably mean tiny gaps between the planks, as wood rather inconveniently tends to move as it gets soaked or dries out. Cladding, on the other hand, can move all it likes but it's still overlapping, so no draughts.

The only slightly tricky bit is cutting the top triangular wedges to size: the best way is to draw the shape of the upright onto the planks as a cutting guide before you actually nail them on to the battens. Or you can do it like me, and fiddle about cutting extra bits off here and there as you go along, thus doubling the time it takes you and making you swear in frustration.

No prizes for guessing that we'll be cladding the rest of it next time.

Previous bits of the series:

How to make a coldframe #1

How to make a coldframe #2

How to make a coldframe #3

How to make a coldframe #3

Right, now having blown your brain cutting impossibly shallow angles for the upright dividers (I hope it wasn't that bad - I "borrowed" my husband's professional shed-making machinery so I cheated)... now here's an easier bit of woodwork for you.

The battens you attach to the uprights are to hold the cladding in place, and should measure 25mm x 25mm, though I couldn't find that at my local branch of Wickes so settled for 25mm x 38mm. As you can see from the pic you only need them along the top edge and down the two vertical sides of the dividers - not along the bottom. You'll obviously need the battens on both sides of the two central dividers.

You do need to cut the top batten to shape at an angle, but it's a lot easier this time. Use the edge of a bit of cut-off batten wood as a spacer to work out how far down you need to attach the batten itself (if you're using 25x38mm wood, use the 25mm edge). Just line the spacer up with the top edge of the divider and draw a line underneath. This marks where the top edge of the batten will go.

Then cut the batten to about 10cm (4") too long at each end and nail it on so that it lines up with the mark. After that, it's just a matter of cutting the ends off flush with the divider.

The upright battens are far easier - unless you're a real perfectionist (or are borrowing your husband's shed-building machinery) you don't need to cut the ends at an angle as they go in pretty close anyway, certainly close enough to fix the cladding to. You do still need to do the thing with the spacer, though, or the cladding won't lie flush with the uprights.

After you've done all that, you'll also need to put in an extra bit of battening all around the inside edge of the two end dividers - the divider in the picture is an end divider, so you can see how I've done this if you look closely. This is so that you can attach the cladding across them to form the ends of the coldframe. Again, you don't need to be too exact - just cut the battens off straight and fit them in as snugly as you can.

I'll get on to cladding the ends next time, and all this will hopefully start to make a bit more sense.

In case you missed the previous bits of this inordinately long series, here they are:

How to make a coldframe #1

How to make a coldframe #2

How to make a cold frame #2

Hmm... photography never was my strong point, but bear with me here.

For my mega-coldframe I've adapted the design from Terence Conran's Garden DIY, a very handy little book which has lots of useful projects and explains things simply enough even for novices like me. I've made both my compost bins from a design in this book, and very successful they've been too (when I make the third, I'll put that on here too). So if anything in my description of how to make these doesn't make sense - get the book.

After getting the base right, it's time for some woodwork. This design centres around dividing frames, which are then held together using the cladding. I suspect it will have little structural strength in the long run - i.e. I won't be able to move it much - but that doesn't bother me: if it bothers you, you'll need to work in some stronger connecting pieces to hold the dividers together.

The dividers are made from 2x2 (5cmx5cm for the metrically-minded) treated timber. Measure the depth (front to back) and width (side to side) of the space you have available - the good thing about this particular design is that you can have as many or as few dividers as you like, so the coldframe can be whatever size you wish. Mine is made up of three sections, so I've made four dividers (two at each end, two in the middle), which will eventually be spaced a little over 2ft apart.

For each divider, cut a length to fit the depth, then two more for the uprights: one at 1ft (30cm) and one at 18" (45cm). Finally, cut the length that will slope across the top: it'll need to be the same length as the base, plus about 4" (10cm).

Nail the two uprights on to the base at each end, using 2 3" nails at each joint, driven in at an angle - this will mean the joint is much firmer and won't pull apart.

To set the top rail, lay it across the two uprights so that it rests lining up with their top surfaces, and mark off the angle it lies at. It'll only be a very slight slope. Saw this off so that the top surfaces of the two uprights are now at an angle (hopefully the same).

Nail the top rail across them, using the same angled-nail technique as before, and leaving a length of rail sticking out from each end. Finally, saw off the ends of the top rail so that they lie flush with the uprights.

Next: putting on support battens (you can see a couple in the picture above - sneak preview!)

How to make a cold frame #1

Just occasionally I'm not so much a gardener as a builder. When you're developing a garden, the first several stages involve an awful lot of digging, lugging stone around and construction - it all seems to take ages and hasn't got a great deal to do with plants. But if you have the patience to do it, it's worth it.

I've been struggling to manage in recent years without a decent coldframe, so this spring I've decided to bite the bullet and make myself a super-deluxe model, the entire length of my 8' greenhouse and about 3'6" from front to back. This is not small for a coldframe - but then my greenhouse is already groaning with seedlings and I've only just started early sowings, so I do need the extra space!

As you'll see in the picture, the first step, before I so much as banged in a nail, was to sort out the area where the coldframe was to go. There were two blackcurrant bushes here, which were always a bit close to the greenhouse for comfort, so I moved them to the allotment this winter. I had to hoick out a spare gooseberry bush, too - not such a well-thought-out manoevre as I hadn't anywhere to put it. Luckily I've got two more to the right of this area, so I'm not exactly going to go short.

Then I marked out the area and dug it down to half-a-spade's depth. This is a really useful depth for hard landscaping - it does for paths, patios... pretty much anything, really.

Next I edged the area with boards - I used 4" boards, but you can use standard gravel boards which are 6". These were attached to short stakes at the corners and checked for straightness with a spirit level.

I roughly levelled out the earth inside the boards, and then put down some weed-suppressing membrane, stapled to the boards on the inside to about 1/2" from the top (you can just about see the edges in the picture). And, finishing touch, about 9 bags of gravel from the local DIY store. This means you can level it easily, and the coldframe isn't resting on bare earth - which means it won't rot so quickly, either.

Next instalment... the start of the woodwork!