It has been four years since I built my greenhouse. All in all, I am very happy with it. This Spring we had some severe thunderstorms roll through (quite typical for central Oklahoma). One of them dumped a lot of hail about the diameter of a quarter. Many people in town got new roofs after the hail storm, but our new roof withstood the hail without any damage. The greenhouse didn’t fair so well.
Roof of greenhouse riddled with holes from hail damage
The roof and walls of the greenhouse are made of triple wall polycarbonate. There is one seam in the roof. Based on my damage assessment I’m guessing that one of the sides of the polycarbonate must be tougher and more resistant to damage than the other side. I had no idea when I installed the sheets. Nor did I realize I was putting different sides up on the two pieces. The repeated pounding of the hailstones punctured through the upper surface on one of the polycarbonate sheets and left the other sheet unharmed. I wish I had known this when I was building the greenhouse.
The panel on the left is completely without blemish while the panel on the right has hundreds of holes. You can also see where the panel has filled with water (top of the image).
At the time of damage I couldn’t just remove the sheet and replace it. For one, replacement material is expensive and difficult to procure. I had to buy a huge sheet (8′ x 36′) and cut it down to manageable sheets to get it home the first time around. It was also still getting down near freezing some nights at the time, so I couldn’t leave the greenhouse unprotected. Because I used triple wall polycarbonate the holes weren’t actually exposing the interior of the greenhouse to cold air from outside. There was still a layer of protection.
Seeds from our Sycamore tree and other junk has been washed off the roof, right into the channels of the polycarbonate panel.
I stalled and life was busy and in the meantime, the holes of the roof allowed all sorts of water and junk to get inside. Because the ends of the panel were sealed shut, the roof actually filled up with water, to the level of the lowest hole in each channel.
Water draining from one of the channels after I removed a screw attaching the panel to the frame.
What to do now? Well, I have removed the damaged sheet, which was very heavy with the added weight of the water. I drained the water and I am in the process of cleaning it out. This is a time consuming process and I’m afraid the final outcome will not be a clear panel. The walls and other roof panel of my greenhouse still look about as clear and clean as the day I installed them, but this roof panel will likely not be as pristine.
Typical hole punched by hail
Once the cleaning process is complete I will be patching the (hundreds of) holes with clear packing tape. I have patched some areas and then tried to shoot water through those channels to flush out the junk. That didn’t work as well as I had hoped, so I am going to try to use the holes to wash out the junk, and maybe also use a shop vac.
My patch job . Not the prettiest thing around, but hopefully it will do the job.
After the junk is out, I will do all of the patching, re-seal the ends of the panel, flip the panel so the repaired side is down, and then reattach it to the roof. With the repaired side facing down any “leaks” would just be allowing the warm air from the greenhouse into the cell, rather than cold outside air into the cell. Also, if it is true that the sides of the polycarbonate differ in strength then this puts the stronger side facing up to weather the next inevitable hail storm.
Stay tuned to see how the repair progresses.