A new Polytunnel - oh my!

Of course, I don’t know your specific needs. I recently saw a high tunnel  where the lower edge of the covering rested in a piece of guttering. The gutter was slightly sloped to feed into a 55 gallon drum on either side of the tunnel. Of course, it does not rain inside a high tunnel, so the drums provided a source of water for the plants inside.

That's sort of my plan for the upper side of the tunnel John - I have gravity on my side there! I can collect the water run off in guttering and lead it into the tunnel into a barrel for storage and overflow (hopefully) into my raised wicking bed and overflow from there into the main growing space. I may add more barrels (if I can get hold of nice ones easily) to add more storage, as I expect still to need to water transplants and seedlings.

We've had a good spell of weather since the new year (all our rain went down South) so I've managed to get quite a bit done. Mainly I've been working on the firewood supply, but I have now switched back to the tunnel and started getting the irrigation channels sorted. I made grooves leading in from the East (downhill) side and from a spreader channel adjacent to the wicking beds into grooves in between these. There is also a channel from the NorthWest corner in case that water source becomes useful (otherwise that corner will be a bit dry). A bit difficult to describe, but I took a picture. They're a bit deeper than I anticipated. I have tried to ensure that they are level or slightly sloping down to encourage water flow. The spreader channel from the wicking beds will need to be larger to help the flow too. It's all a bit experimental!

irrigation channel layout from South end

I'm collecting together twiggy bits from the birch that I've cut - these make nice straight twigs so will make good wicking channels. I have some willow cut from last year that is probably still good enough to use (and won't grow!). I may need to use some alder twigs too - not so good, as the twigs are more wiggly, I'll see how it looks when I have everything laid out.

bundles of birch twigs for stick irrigation

My plan at the moment is to lay a layer of green spruce twigs over the broken rock, then maybe a layer of sheep fleece like a soil barrier. Put the stick drains in where the channels are and wrap those with fleece too, then cover the whole lot with the excavated soil. I did a sketch for my sheet hugel thread. This was before I thought of using the fleece as well....

stick irrigation concept

At the moment I'm gathering the materials together. I still need to get up on tall ladders to check the anti-hotspot tape on the ridge at each hoop, and put some on the crop bar brackets. It will be a lot easier to do this before the soil goes back into the tunnel, but I want to leave it as long as possible so that the scrappy bits are exposed to the weather for the shortest possible time as they do have a tendency to come back off in the wind...I will need to get back up again to put the high level vents in - but that will be after the cover is on, so that can't be helped.

Nancy, I just want you to know how I enjoy seeing the progress in the pictures that you post on this project.  

And to honor that day (which will be soon, I hope)  I have been working on a special herbal tea blend of Hibiscus, Chamomile and Mint, and saving a jar of Goldenrod honey, to toast you when I see the photos of the poly being pull across this new to you tunnel.  Seeing the end walls being closed in will be cool too, but the top cover going on will be the big thingy for me !!!

Peace/Heddwch

is plastic a necessary evil in building a greenhouse? trying to recycle plastic for a greenhouse iS probably a non starter. ive been wanting to build a greenhouse for years now but it is slow going accumulating  enough window glass to put it together

bruce Fine wrote:is plastic a necessary evil in building a greenhouse? trying to recycle plastic for a greenhouse iS probably a non starter. ive been wanting to build a greenhouse for years now but it is slow going accumulating  enough window glass to put it together

Nope, it definitely is not. Plastic has only started being used in the last few years, glass has been used for at minimum of 150 years, probably more. 150 year old glass greenhouse is just something I have been in and can prove :D

Glass does break easily, especially with weather events. I tested, and will use, expanded metal lathe mounted on the exterior at least 4 inches off the glass, to stop most hail damage. Won't stop softball sized, I'm sure, but it definitely stops 1 inch. Might help with other random things that break glass too.

bruce Fine wrote:ive been wanting to build a greenhouse for years now but it is slow going accumulating  enough window glass to put it together

Yes, depending on where you are sourcing secondhand windows can be tricky - I guess getting to know window installers might be worthwhile! There are some good ideas on this thread too about designs and sourcing glass.

Deane - I'm hoping the cover will go on towards the end of March/ start of April. That's when we tend to get some settled still, sunny weather (hoping!!!) I've got some offers of helping hands, and am intending to get all covered in a short spell of time - a partically covered tunnel is very vulnerable to bad weather.
I'm honoured by your special brew!

So the weather has been a bit more 'normal' (wet and windy) so I haven't got one quite as quickly as I'd hoped, but progress has been made with the irrigation channels and more.

The 'gutter' along the lower edge of the tunnel was the first one I tackled. First I laid in some of the dag end fleeces I was given, to wrap the twigs in and act as a soil membrane. It actually took quite a long time to 'fluff' the dirty matted fleece out so that it would make a nice fabric once compressed between bindles and soil. It was pretty easy to lay the birch twigs in a continuous row though. As I needed to direct the water into the internal channels, I put half the twigs in the channel, then made bundles and inserted them in position, before placing the rest of the twigs in the gutter channel and tying the sausage up as tightly as possible. I've got through quite a bit of my 100% cotton string....

twigs laid loosely in gutter and first bundles in irrigation channels

Then more fleece was added to the top to make a thick, complete layer and wrapped around. It was fairly hard work to move the soil to cover the bundle, as it is rather wet through, so not a pleasant job at the moment. However, I have managed to cover the whole length of the gutter bundle with a thin layer of soil.

twig bundle in gutter channel, covered with fleece and then soil

Basically I then had to do the same for all the irrigation channels in the polytunnel footprint. Fluffing up the wool was probably the slowest part of the job, but somehow satisfying to do too. I've laid the bundles with a view that the water will flow from tips of the branches to the thicker parts, so I'm hoping this will match the tendency of the water to flow. On the part of the bundle that the water will flow to first when overflowing from the wicking beds, I have used willow rather than birch. These are longer straighter twigs, so I'm hoping that will help the water spread out more quickly at the start. So all the bundles are now laid in the channels and wrapped in wool.

stick irrigation channels laid out in polytunnel

I've made a pretty good start on cutting the spruce branches into flat sections and laying them in the areas between the irrigation channels, but haven't quite finished that as yet (no picture sorry).

In between, whilst the weather was rather wet to work outside, I made a start at assembling the additional high level vents using some of the wood from the old polytunnel. These have turned out rather stiffer than I'd expected and did not require any additional corner bracing.

new window vent frames

I also (fortuitously) was able to make a start this week on assembling the new Aluminium door frames. I say fortuitously, since I have spotted another mistake I  made with the tunnel frame. For some reason I had it in mind that the single door was the same width as the smaller of the two double doors (1.2m), but actually it is the same width as the wider door (1.7m). This means that the doorframe at the South end is narrower at the moment than it could be. I think it will be possible still to adjust the doorway width, so that is a job for the next nice day I have. I also need to increase the width of the door step infill plinth that I have contructed before I can finish off the spruce wicking layer.

Just a few more steps before I get the cover on...

Door frame width adjusted - the advantage of a bolt together frame:

altering door frame width

It didn't take too long to rebuild the door step - a few more stones required.

covering sheep wool with a layer of soil

I started covering the fleece with soil to stop the dogs messing with it. They can cause havoc pretty quickly.

Della investigating a bit of poo

The soil is rather mixed - the anaerobic layers where the water had been sitting are very visible in this photo:

mixed up layers of soil

There's not much I can do, so I've been breaking up any lumps as I go, and fishing out the creeping thistle, docken, couch grass and buttercups. There's bound to be a reservoir of seeds, so I expect them to grow back at least at the start, but if I can avoid the roots being in the bottom layer, it might save some heartache in future.

My husband helped yesterday with the digger - the large bucket just fitted between the hoops! He moved more soil in a couple of hours than I did in as many days....The digger isn't big enough (or the tunnel frame is too restricting) for him to spread the soil over the whole tunnel floor, so there is still quite a bit of work to do.

a tight fit...

We got rained off, but at least the fleece is protected now. Probably another afternoon between us will see enough soil actually in the tunnel, and the soil mounds outside roughly levelled off (for my new kitchen garden)

dog protection in place

I had a look through my offcuts from the old polytunnel cover, and I just about have enough to cover all my openers, which makes life a bit easier. I can cover all the frames before we do the main tunnel cover, so will be able to fill in the door/window holes fairly quickly. That means that we don't need to be so careful with the new cover positioning as I won't need the offcuts for specific jobs. However, if we can be frugal there should be enough plastic to redo the main doors, which will be helpful as the old plastic has seen better days.

sizing up

The sheets are all a bit muddy, so I've scrubbed them down with water and hope to get the frames covered this weekend. It didn't matter for this job that the rain showers were coming and going...

rinsing off

I'll need to do a dry fit first to get any holes drilled and work out the hardware....

At the moment the weather forecast is good for Monday and Tuesday next week, although still a bit unsettled. I need to alert my potential helpers and see which days suit them best.

So the countdown begins...

Very exciting! Looking so good!