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cold frames – a poor man’s greenhouse

November 11, 2012 Gotalottie, Tips 4 Comments

A quick look at the diary and we can see that we’re 18 weeks in, in our journey on Plot 36.

It doesn’t seem so long to be honest, given the volume of the weeds removed and compost and manure brought onto site. I mustn’t forget the pallets either. The site resembles a builders yard now, bricks, pallets and the mystery heaps covered with black plastic.

The actual act of growing vegetables was never going to be successful this year, there was simply too much to do and so little time to do it in! Despite this, our salad leaves, having sustained relentless attacks by the resident slug and snail population, have given us successions of ‘cut and come again’ harvesting and continue to do so, along with the spring onions and Pakchoi . Our leeks have pepped up and the cabbages are starting to crown up and pack on some weight. Vegetable growing it is not, but it’s allowed us to focus in 2 directions and not just clearing a plot for next year.

There has been a casualty – our late spuds. They were never going to make it through. They were late arriving, late in the ground and yet – made terrific progress and put on a lot of growth. They were attacked by frosts in the middle of October, they were protected by fleece but this wasn’t enough; there was a week of windy days and cold rain and even sleet and snow at the end of the month and this has been their demise. One morning the fleece was blown off and the potatoes had been covered in sleet and hail, all coming on a hard Northerly wind. I just cannot be at the plot every day to keep an eye on things and so - Mother Nature has had her way.

There just wasn’t enough time to prepare for such things, this is the North East, plants need protection, but next year will be very different.

We’re fortunate to have a plot which is well protected on one side by a 1.2m fence, that’s the freshly stained brown thing that features a lot in all photographs of our plot. It runs East-West and the sunny side - the South side - protects our plot. On a sunny day, it feels so much warmer as a result, we plan to harness this feature.

We’ve been building some compost bins along this fence, there are now 15 planned, each will sit in the protection of the fence and each will face the sun. I can hear you ask ’15 compost bins?’.. why so many?

Our modular, compost bin, cold frame, hot frame setup

Our modular, compost bin, cold frame, hot frame setup

They’re not just compost bins, they’re being laid out in such a way as to double up as cold frames; also we’re going to utilise a technique known as ‘Hot-Bedding’, so that we can have some successes with tomatoes, cucumbers and the like and the rest of this post describes what we’re doing, how we’re doing it and the plans for next year.

Our compost bins are all being assembled in a straight continuous line, nothing fancy in their construction, other than the fact that they need to be raised up every couple of metres, as our plot has a gentle slope; you can see this from the angle of the fence in the photo above.

compost bin, cold frame or hot bed? These frames are interchangeable.

compost bin, cold frame or hot bed? These frames are interchangeable.

The core of the construction is the humble pallet, available in green, blue and natural; we selected the natural and after receiving some minor revisions to width, they were given a quick colour stain to match our fence. For the first compost bin, three pallets were assembled creating a final internal space of 1.2m x 0.9m. It wasn’t possible to use a full pallet for the depth as this would encroach on the path too much and would also create some problems for the cold frame modules – the glazing.

Each subsequent module only requires 2 pallets, a full width unit for the back and another - in our case, adjusted unit – for the next side panel.

By building the bins in an exact way, it is possible to alternate between glazed or unglazed at will and to switch these later with very little effort.

The glazing elements:

We have acquired a large amount of double glazed wooden sash windows, without their frames. These were removed from a fairly new housing development and are readily available. Most modern windows come in modular sizes, with widths of 0.9m and 1.2m being the most common. There are 2 common heights for modern sash windows and these are 1.2m and 1.05m for ground floor and first floor respectively. We have a mix of double glazed sashes from window frames of 1.2m  width and of both common heights.

How do the glazed units fit?

It’s very simple, two glazed units fit into the space between the end panels and it’s a simple task to fit them. The detail at the bottom of the opening will depend on whether we’re fitting tall glazed units or the shorter version. The tall units require a soul plate to rest on, as the photo below:

Tall glazed unit resting on wooden sole plate

Tall glazed unit resting on wooden sole plate

The shorter units rest on a raised soul plate and this is made from a section of pallet of 1.2m width and screwed to the side panels.

Shorter glazed unit resting on raised sole plate and plinth

Shorter glazed unit resting on raised sole plate and plinth

The framing between glazed units and the side panels consist of 25mmx50mm battening screwed to the side panels according to the angle of the glazed unit.

angled battening completes the glazing framing

angled battening completes the glazing framing

We are filling the void inside each pallet with sheets of cardboard tightly packed in, this will stop cold air passing through.

In essence that’s it. The compost bins are filled and covered with thick card to keep the elements out. The cold frames are covered at the base with sharp chippings to deter slugs. The hot frames will be filled to a depth of 25-30cms with fresh horse manure and topped with compost. The hot frames will serve to protect some delicate seedlings during the winter months and add a little warmth to help them on their way.

Of course in the middle of the year, our planned tomatoes and cucumbers will need more space in which to grow. There is another element to this modular system that’s not been described yet and that’s a simple revision to the top, allowing us to fix the existing glazed panels vertically and add more light. This can wait for another post – nearer the time.

It might seem like a lot of effort, we don’t think so. We’re simply trying to maximise the benefits of a good sunny location on a plot which can be exposed to some pretty bad weather at times.

In reality, the planned 15 compost bins might not be enough, but we can think about that later. In the middle of the row, we’ll be adding an interesting feature, an insect hotel and a little bit of lockable storage space also.

Hopefully more than just a poor man’s greenhouse.

Currently there are "4 comments" on this Article:

  1. Kathryn says:

    Envy you all those double glazed windows – much better than single. When you run out of fresh horse manure you will find half and half leafy veg waste and weeds/carbon such as straw gives nice steady heat for a good long time. Just make sure you keep it nice and damp for a long burn. I keep a thirty foot run heating in stages all year without having to buy in manure (I do have half a dozen chickens bedded on straw and wood chips).
    Watch out for rats using the spaces in the pallets as a predator free run into the bottom of the beds – they got a lot of my early spuds like that this year
    Enjoy – you deserve to with all that hard work

    • royw says:

      Hi Kathryn

      the wooden double glazed windows were quite easy to find, we just approached a couple of replacement window fitters in the area. They were glad to get rid of as they only get charged for tippage.
      Hopefully with the way that we’ve aligned the pallets, there won’t be any possibility for vermin to get through but on the other side of that fence is a public park, dog walking and all so it should never be a problem.

  2. taylor says:

    looks great, i’ll be adding a coldframe to my veg patch this year with the same materials. its getting late so i’d better get started! i really like the blog/project your working on, im putting it on my blog roll.

  3. royw says:

    Thanks for the encouraging comments. Good luck with your coldframe too!

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