prob a silly question about polytunnels

[cooltrikerchick]

was just wondering for future ref ( ok if we ever manage to buy some land...lol...)

could you put up a poytunnel on ground which is hard gravel standing...? and put raised beds inside

or could you only put a large greenhouse on it?

[oldjerry]

Perfectly plausible,take out holes for frame with powered auger(cheap dayhire),and if you dont have one of the non burying type everyone else really rates,take out a trench with a pick to bury the sides.The majority of tunnels on commercial nurseries are constructed on this sort of surface.

[Thurston Garden]

Absoultely as oldjerry says, hire a post hole auger and bore out the tube holes. Fix a couple of exhaust brackets to the tubes so they are under the ground and concrete the tubes in. The brackets will give the concrete something to grip to.

The only way to go in my opinion is with a timber base rail. No trenching for me please.

[Odsox]

The only way to go in my opinion is with a timber base rail. No trenching for me please.

You obviously don't have couch grass, bracken, sheep sorrel or buttercup near your tunnel then, or you like weeding.
Of course that wouldn't apply with a gravel/concrete surround, so maybe that's what you have.

[Thurston Garden]

Tony, I certainly dislike weeding like most other folk. The trick with the timber base rail method (especially if you are putting in raised beds) is to carpet the whole of the interior of the tunnel with weed suppressing fabric. Take this fabric out under the timber base rail by about a foot or so and peg it into the ground outside the tunnel. Then, when you install your raised beds, do so over the fabric and then cut the fabric out of the centre of the raised bed, but leave enough on the inside of each edge so you can fold it up the inside of the raised bed wall and staple it in place. Weed free tunnel interior for several years in addition to be able to strim around the outside of the tunnel without the danger of strimming through the polythene (unless you are really crap at strimming!).

Worked for me anyhow.

[grahamhobbs]

Odsox, I like the timber rail method, fixed about a foot off the ground to which the polythene is fixed but then flaps down over the remaining foot. When clipped up this flap provides good variable ventilation, as well as ease of fitting and replacement of the polythene. But I also bury a strip of Mypek about a foot deep vertically, fixed to a similar timber rail at ground level - this keeps the weeds out. In one of my polytunnels I have also covered the 1 ft ventilation gap inside with scaffolders netting, this allows good ventilation but prevents strong winds blasting the plants at ground level.
As my polytunnels are on my allotment I can't get to them every day, let alone morning and evening to adjust the vantilation, so I prefer to err on the well ventilated side as more damage is done by short periods of over-heating. The above system however does provide great flexibility in ventilation.

[Odsox]

Fine on that Graham, just goes to show that different people have different needs.
I am here all the time and ventilation is not a problem most of the time, this close to the sea there is pretty much always a breeze from some direction, plus the tunnels are on a slight end to end slope which causes it's own air movement.
Also I have double doors either end which can either be angled as air scoops or baffles.

I like the buried method mostly because of the added security in stormy weather, having the polythene secured all the way round with soft heavy soil seems to me to be preferable to being secured with screws or nails albeit with a timber batten.
Anyway, it's all academic as that's how my tunnels are and that's the way they will have to stay.

[grahamhobbs]

Odsox, yes it's horses for courses - in London I'm in a relatively sheltered spot, no worries about the thing being blown away, more the reverse of ensuring sufficient ventilation.
In the past I've replaced the polythene on a big polytunnel where the polythene was buried, it was not that difficult or time consuming, although I think the rail method makes tightening the polythene that bit easier.
So in exposed situations burying the polythene must be the preferred solution, more sheltered situations and although it is a bit more expensive I'd go for the rail system.