Holding down greenhouse plastic in backyard greenhouses is a relatively simple thing without resorting to expensive commercial hold-down systems. Commercial systems can easily cost several dollars a running foot (one foot long) and if your greenhouse is twenty feet long (and you have four sides) then you’re looking at several hundred dollars just to hold down the plastic.
Using this system, you need enough 2×4’s to go around the perimeter once and 1×2’s to go around twice. Much cheaper!
Attach a 2×4 board securely to the base of your greenhouse structure – at ground level. It is critically important that this structure is very firmly attached to the supports and that it will not move.
At the top of the 2×4, attach a length of 1×2 board securely. Run this the entire length of the greenhouse as well and screw it to the 2×4 rather than a nail for added strength.
A second run of 1×2 will be attached to the bottom of the 2×4 to hold down the plastic as in the diagram below. The plastic is over the top of the upper 1×2 and below the bottom 1×2.
This means the pressure of the wind and plastic shifting is taken up by the edge of the 1×2 rather than by individual fasteners. Individual fasteners such as staples rip the plastic; this system does not.
I’ve used this simple system for years. The bottom 1×2 is replaced every few years when you change the plastic as it will rot out. The 2×4 and top 1×2 are not in contact with water and they will outlast the bottom piece.
I’ve used this to cover greenhouses as well as set up tarps to cover woodpiles and other areas where I didn’t want the covering to rip or tear. It works like a charm to hold down greenhouse plastic or any other covering.