One Happy

Create Intentional Happiness


If you aren’t ready to spend thousands of dollars on a greenhouse, and are good at DIY, I think this greenhouse, with a few enhancements is a great choice. I’m here to tell you a city-girl-turned-country can DIY with this greenhouse.

It took me about a week to erect my HFGH, after building a concrete block foundation, but then, I’m just an ambitious girl with a lot to learn, and I had to read all instructions and tips on the internet from folks who had enhanced their GH. Someone with experience can probably do it faster.

After first thinking I would make a greenhouse out of old windows, I saw the 10×12 Harbor Freight Green House (HFGH) on sale and decided to go with it.  It sells for about $650, but with a discount coupon on the sale price you can get it for just over $400.  The size is a little bigger than I had planned, but at that price I couldn’t resist.   (The smaller, 6×8 HFGH retails for $299.)

For the technical folks, this HFGH has a double-extruded aluminum frame, 2 ply 4mm UV-coated polycarbonate panels, two sliding doors, and four roof vents. The inside height is 10’ at the peak if set directly on the ground. The inside dimensions are slightly less than 10×12.

If you research on the internet, you’ll find the 10×12 HFGH has a reputation among some for being lightweight and unstable in high winds, but this is only if built as the manual specifies, without reinforcements. Other reports showed this greenhouse withstanding winds up to 90 mph when anchored correctly.  Some reported the panels being blown out, but there is a way to fix that too. Most of the reviews I saw were from desert areas and places with hurricane speed winds. 

Here are the modifications I made to reinforce the greenhouse:

Foundation: The manual shows the metal base plate sitting on the ground, with dirt packed around it.  I didn’t think this would be enough anchor the GH against high winds.  I used concrete blocks, with anchor screws in the GH base, and self-drilling screws with washers to anchor the frame to the base.  Some people have used concrete pads, landscape timbers or railroad ties under the base plate.

Metallic tape on corrugated sides of panels: I sealed the ends of each panel with aluminum tape to help keep dirt, condensation, and bugs out of the channels. I used rolls of 1 ½” wide aluminum tape (not duct tape) and cut it in half. Don’t tape the door panels. They fit tightly in the frame and won’t fit if you tape them

I applied 3/16″ thick weather stripping to the frame at the panel sides and 1/2″ weather stripping at the top and bottom of each panel where the gap between the frame and panel is larger. Be sure to get ‘closed cell foam’ or ‘water proof’ weather stripping so the rain won’t leak in.

Along the peak of the green house I used ½” foam backer rod to seal the gap. I also used a clear, silicone caulk at the top four corners of the frame and the two ends of the peak. I also caulked around the outside of the four vent panels on the roof.

Panel reinforcement: I was afraid the glazing clips that hold the panels in the frames would not be enough to keep the panels from flexing or popping out in a strong wind.  I reinforced the panels by adding weatherstripping around the frame, then attaching panels to the frame with No. 8 – 1/2″, self-drilling screws with two neoprene washers to account for the space between the cross frame.

I used screws on the door panels so I had a few extra panel clips to use around the edges of the wall panels. You can order extra clips from Harbor Freight if you want more.

Base reinforcement: There are two small metal brackets on each side of the GH that hold the frame and base together. These didn’t seem adequate to me, so I added self-drilling screws to secure the frame to the base foundation plate.

Note: It is critical to build a square and level foundation in order for the panels to fit correctly in the aluminum frame. Check for squareness frequently as you assemble the frame. Trust me on this.

Frame reinforcement: To prevent the two side walls from pulling away from each other or the frame from warping in a strong wind, I added horizontal braces, made out of ½” conduit, that go from side to side at the top of the walls.

I also braced the front and back walls with ½” conduit bolted to the frame.

You can get a lot of ideas from the internet on how to finish the inside of your GH. A lot depends on how you plan to use it.

Here’s my current situation. I was able to re-purpose some bricks from the back yard to make a floor in the center of the GH. I then added stones around the edge for drainage. The white PVC pipe in the right corner is there to run the electrical cord from the solar panels (also planned). Another PVC pipe is in the left front corner for water supply (also planned). I’m still planning on adding a ventilation system – fan and vent. Never a dull moment. It’s just one Happy Place after another.

So, I hope this information is helpful to those of you who have been considering a green house. As time goes on, I’ll update you how the HFGH improvements are faring.

Here is a link to a really good blog to check out with a lot of detail on how one couple built their HFGH in August of 2007 in New Mexico. I believe some improvements have been made to the kit since then.

I’ll be glad to answer any questions you might have on the HFGH. Feel free to share this post with others who you think may be interested.

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