Covering for tunnels and hoop houses
 

I've got my hoops in place--1/2" PVC anchored onto 2' rebar, 1' sunk into ground--and am ready for the covering. I have some 4 mil white plastic sheeting, but saw a product at a building site near my house that might possibly be better. It's 6 mil reinforced poly (Dura-Skrim) with diamond-shaped webbing (looks like thick floss); supposed to be very strong, tear-resistant, etc. What I'm most curious about: the plastic sheeting is white (can't see inside) the Dura-Skrim more translucent (can see inside, sort of).

My sense is the more translucent would be better for growing plants, even if it might require shading on hot days (these hoop things will mostly serve in early spring to extend my zone 4 season and will come off in late May or so in any case). Which do you think would serve better? Not a lot of experience here. Thanks. Gary

The best would be the clear and I would suggest 6mil greenhouse quality plastic. It is a bit expensive but last longer because it has UV protection. I buy a 20' x 20' piece for about 60 dollars. The white will allow for light but not as much as you would need really vigorous tomatoes.

We have used clear plastic, but it just does not hold up very well (maybe 1 season). since we have put up a couple of smallish( but real) greenhouses we have advanced to using klerks plastic (just one of the greenhouse brands available). this is just a much better product for light transmission to the plants, it is also very durable( it has a 4 year lifespan). If you could also grow enough to sell a few, it would off set the investment of the greenhouse grade plastic. The price range for this can be wide, depending on where you can buy it. We have an amish supplier close, so it is very reasonable there, Check around at greenhouses where you see polyhouses and ask where they get theirs or ask if they have any extra they can sell you. Have you thought about installing a permanent hightunnel? you can extend your growing season by a month or 2 maybe even more. It doesn't have to be a new frame. We have bought several off craigs list very reasonable. We are zone 5 and we planted 30 tomatoes today in one. We protect them with wall o waters for the first month and then take those off and put cages around them when the forecast looks as if it isn't going to freeze anymore. Then we expect to harvest in there until at least Oct.

If I had easy access to greenhouse plastic, I would use that. But none is available here locally, and paying shipping costs for a large roll is not cost effective for what is just a temporary bed. My plastic gets used maybe two months in the spring, and two months in the fall. In between it is rolled up and stored in the shade, or garage. I have re-used the same Home depot construction type heavy plastic for at least four years. I'm sure if you left it up all year it wouldn't last that long, and southern locations would have more intense sun damage. In October and November, the sun has little power left here. :mrgreen:

They've got that heavy (20 gauge) clear plastic at Jo-Ann Fabrics. I got some to make a wee greenhouse out of a plastic shelf unit. Usually Jo-Ann's has a monthly mailer with specials and coupons, but I don't get it, so I asked at the register if there were any specials on, and the guy gave me 50% off; it came out to ~$4/yard, at 54" wide.

If you use of the plastic is short term then I would suggest buying a roll of construction plastic used for barriers in home construction. Usually on the inside of the exterior wall to keep the insulation in before the drywall is attached. It is cheaper and you can get the heavier guage. Home Depot or Lowes should have it.

For greenhouse grade plastic, since you are in the Minn area, check out carlinsales.com

There are a greenhouse supplier that has a branch in your area. They aren't always the cheapest, but you don't have the shipping if you can pick it up. Ask if they have anything they are looking to get rid of too. They often have odd ball and discontinued stuff they just want to get rid of.

Carol

Thanks for the good suggestions. How important, for my purposes, is the UV resistance/protection? I assume most of the ones mentioned don't have that.

I had (have) some pieces of what sounds like Dura-Skrim (matches
the description, anyway) that was sitting in a "take what you want
before we haul it away to the dump" pile of industrial debris (pallets,
etc) at an industrial site. I made a cold-frame one year of 2x4s with
a layer of that stuff inside and out. It is translucent, but seedlings inside
it grew as if they were not getting enough light (tall and sparse). It did
keep them from freezing, down to about 30F, with nothing more than
a light bulb inside.

It was around 4 feet tall, and I ended up converting it to a compost bin,
where the toughness of the Dura-Skrim came in handy and the low light
transmission was not an issue.

You can get stuff like this from Home Depot, Lowe's, Ace Hardware,
and so on: [url]http://www.homedepot.com/buy/paint/drop-cloths-sheeting-tarps/husky/6-mil-10-ft-x-100-ft-clear-polyethylene-sheeting-roll-54904.html[/url]
Light transmission probably varies from one brand to another, and it is
usually not UV-protected. (You can compare light transmission between
candidate coverings with a photographer's light meter.)

One would pay about the same amount for a 20 feet by 20 foot piece
of UV-shielded, non-woven greenhouse plastic. Light transmission usually
ranges from around 80-85% for woven and infrared reflecting non-woven
types up to what clear glass lets through for non-woven,
non-infrared-trapping products. The woven types are more resistant
to physical damage from wind, but they cost about twice as much per
foot and still only list a 4-yr lifetime (which seems to be determined
mainly by UV exposure).

6 mil greenhouse plastic is fairly stiff. It will last longer if you roll it when
not in use than if you fold it for storage (folds create stress points where
it will physically break down fastest).

These are all great suggestions, many thanks. I'll be experimenting with two different types of cover, both 6 mil, one with the webbing, the other not. I was able to find both in 12' widths, which seems just right for what I'm doing. Will see how it goes!

Duraskrim is very tough. The sides on that compost bin are still holding
together after 6 years. If I needed to cover a big hole where a storm
tore off a piece of roof until it could be re-roofed, that would be a
reasonable choice for a temporary cover. It is easily as tough as the
cheap vinyl tarps that a lot of roofers use, and it is lighter to haul up
and down ladders.

Duraskrim is UV-stabilized, and it comes in varying thicknesses. 6mil and
10mil are probably standard thicknesses, but they make it down to 2mil,
too, which would probably let more light through. It is the sort of product
that an "industrial supply" would probably list (although they need to sell
stuff in wholesale quantities to make a profit and may be underwhelmed
by requests for a couple of hundred feet of something).

I've been using Klerk K-50 for about four years - year around. It has lost some transparency, but is indestructible even in our high wind and strong sunlight. It is also IR and anticondensate.
You can get odd remnants cheaply. I think I got mine originally from Grower's Supply.