I finally got going and I'm in the process of finishing up a greenhouse using a shed hardware kit. The wood is from the local big-box hardware. There is a materials list and cut list with the hardware kit. I eliminated the plywood (except for the floor). The cost of wood, screws, and the kit was around $150. I bought the kit online from Amazon, but I've seen it at retail too.
I'll be following up with a series of pictures showing progress and some of the details.
This is the start of the frame. The base is built with treated 2x4s then covered with 3/4" plywood. It might be possible to skip the base, but I didn't want to figure out how to brace & level the walls without the floor. Also, the floor gives the structure some weight for overall stability. I'll show later what I'm doing to still be able to move the weight.
(This is my brand-new son-in-law doing the work. At the time of the picture, he was still a finance.)
More assembly work. The frame is strictly 2x4 lumber with sheet metal connectors. The connectors fasten wall studs to the floor and also to each other at joints. I spent several hours with a power saw, measuring, labeling, and cutting the various lengths needed for assembly.
(This is the son-in-law again, with my daughter. Besides starting the shed, they also helped me plant several hundred onion sets from Dixondale.)
The walls and the initial roof structure. There are still more rafters to be added, but this was an excellent afternoon's work. The overall size, since I haven't mentioned that, is 7' x 8' and 8' high. The kits actually include instructions for 8' x 14' x 9' or 10' x 22 x 11. Each size requires an extra hardware kit and lots more lumber.
We had to stop early, since we were going to "Fogo de Chao", a Brazilian restaurant, for dinner. It was Sarah's 21st birthday!
This is the complete wood frame, with the extra rafters, end framing, and door framing. The wall frames and ceiling joists are on 32" centers. There is also an extra wall stud at 48". I think that is is primarily for nailing support for the exterior sheathing. I used it anyway, thinking that it might give the walls more rigidity. The weakness to this plan (without siding) is that there is very little end-to-end structure.
This was another good afternoon's work. This time my help was my other daughter and her husband. It seems that I didn't actually get pictures of them working--but they did. I couldn't have done it without their help.
This is a close-up of one of the framing joints. It is designed to use square cuts on the lumber. That is MUCH easier than a shed I built several years ago that had all the angles cut. I would guess that the brackets are not as strong as the shed would be if the boards were cut to have angled ends, but it seems to be strong enough. Every bracket has multiple screws in each board, so they are held pretty well. It is important to be sure the boards are placed correctly in the bracket and everything is tight. If not, the frame won't fit together...
The strips of duct tape are covering all the external joints, anywhere that the greenhouse plastic cover will touch. Hopefully that will reduce the chance of a sharp edge cutting or wearing through the film. Covering all the joints took a couple of hours, and almost an entire roll of duct tape!
This is the start of the outside cover. It is greenhouse film that I already had on hand after my hoop-house greenhouse project from a couple of years ago. I originally bought a 25' x 100' roll of 6 mil greenhouse plastic. I used less than 20' of the remaining roll for this project. Each end was part of an eight foot length and the sides were one full strip of the 25' width cut 8' long. The plastic is fastened to all the available wood at about a foot between staples. I started from the bottom, square, edge and worked my way up with the plastic. That way I could keep everything straight and even.
This is a closer view of the plastic fastening. I wrapped the plastic around the side of the frame, and trimmed to have excess. That will give an overlapping edge and should help with the weather proofing. You can also see the roofing felt nails I used to reinforce the staples at possible stress points. The extra surface are will help hold the plastic down in the wind. Seems to be working since all the plastic survived a cold-front passage last week that had hours of 40-mph wind gusts.
This is the full outside cover, minus the door. You can see how the plastic is overlapped on the ends. Also, the plastic is actually lapped under the door frame. I was able to stretch the plastic myself on a very calm morning. If there had been any wind I would have require help! I haven't measured the loss of light but you can tell that the "clear" plastic still blocks a fair amount of light.
More detail on the framing and the hardware. The space between the edges of the framing will be key for insulation. When I tried a cattle-panel greenhouse, the single layer of plastic provided NO insulation. As a result it was VERY difficult to keep above freezing when it got cold here.
This is the fully-covered frame with the door installed. The 4' x 6' door as specified in the kit was difficult to square and fit the opening. I added metal corner braces and a cross-beam, but two smaller 2-foot wide doors would still probably be easier to fit and use. If I have too much trouble I will rebuild the door later. You can't see it, but the door is held closed with a pivot hasp. It can be locked, but doesn't have to have a lock to keep the door closed.
The vents are standard aluminum 12" x 18" gable vents. They were about $10 each locally. I will be adding an attic-exhaust fan with thermostat to the other end. If the airflow isn't adequate with these vents I will add another pair directly above these.
This is the detail of the vent installation from inside. The vent wall has yet to have the second layer of interior insulation. You can see the bubble wrap on the side wall and the inside of the door. I will make a roll-up flap of bubble wrap for inside the vent that can be closed if we are expecting REALLY cold temperatures.
This is a broader view of the inside layer of plastic. It is 48"-wide bubble wrap, bought online. (The roll is 175', so I still have plenty of wrap available.) I started at the top, center, rafter and brought the plastic down each side, fastening it as I went. The roll is just wide enough to have an inch or so for stapling at the sides as well as a couple of inches overlap in the middle. I stretched and fastened with staples on every wood surface. I used some clear plastic wrapping tape on the overlapping edges. Don't know if it will hold in the long run.
All the interior and exterior stapling used an entire box of 1000 staples! I was using 3/8" staples in a heavy-duty gun. Both the staples and the gun worked well.
Still waiting for the 14" exhaust fan and automatic louvers to arrive. Bought them from Amazon, too, since the local stores didn't have the small, lightweight fan that I wanted. Also, online pricing was much better...save about $40 for similar products. I will put the fan overhead on the end opposite the door. I have a section of plywood with a circle cutout that I will mount to the frame.
The powered ventilation is a must. It is in sunny and in the mid-sixties here today. The temperature is the closed greenhouse was up to 110-degrees! With the door open and a light breeze outside, the temperature in the middle of the greenhouse is still 90 degrees.
Added two more vents today and completed the installation of the exhaust fan. Some issues with the fan and louver. The framing for the shed kit isn't really right for the gable fan...If I did it again I would change the framing on the end so a fan would fit. Forgot to get a picture, though. I'll add one asap.
Confirmed that the 1500 watt heater will keep the greenhouse warm at temps in the mid thirties. Don't know what it will do if it gets REALLY cold.