Donnie Cates' 8'x8' Cedar Greenhouse

When a back injury sidelined Donnie Cates’ golf game, he bought a few plants and set them up beside a sunny window. That cheerful diversion for a golfer with too much time on his hands tuned into something bigger. As it turns out, Donnie really likes working with plants, and the sunny window was soon overcrowded. A greenhouse was the only way to get his new plant hobby out of first gear, and after researching greenhouses online, Donnie called us up with a few questions.

GREENHOUSE KIT. VS. HANDMADE GREENHOUSE

The biggest question was whether to buy a greenhouse kit, or choose a handmade greenhouse design. Since we assemble greenhouse kits, and also build cedar-framed greenhouses, we aren’t necessarily partial to either option. But when it comes to greenhouse kits, perhaps the main consideration is that they vary widely - in quality and price - and the lower priced greenhouse kits are infamous for collapsing during severe weather events - often resulting in a total loss of the owner’s investment, however much of a ‘bargain’ that may have been.

The well-worn adage “ you get what you pay for” seems to be especially true when it comes to greenhouse kits, and the higher priced kits do seem much stronger than their budget counterparts. 

But assembling greenhouse kits is time-consuming work, and often our fee to build a greenhouse base and assemble a kit isn’t much less than the cost of the kit itself. So, after considering this true cost comparison between the two options, and after weighing factors like the strength of the frame and quality of the glazing, very often a customer chooses a handmade, cedar-framed greenhouse design over a kit. And this proved to be the case with Donnie.

 

SITE SELECTION

The site we selected for Donnie’s  greenhouse is in a small nook on the right side of the house. We chose this location because it gets lots of sunlight during the cooler months of the year, but is shaded by an enormous oak tree during the summer. This combination of sun and shade is ideal for most hobby greenhouses, which seldom have cooling equipment, and during the summer, typically serve as more of a work space or storage shed for garden tools and equipment. Shading a greenhouse during the summer also helps extend the lifespan of the polycarbonate glazing. Donnie’s greenhouse location is really convenient, too - just a few steps from the back door, and right beside a most delightful backyard water feature.

 

CEDAR BASE

Like any well made structure, a greenhouse requires a strong, level foundation. We made Donnie’s greenhouse base with two courses of red cedar 4”x4” timbers, joined together with structural steel screws and waterproof wood adhesive. With a little digging, we soon leveled the base, and then filled in the floor with several inches depth of small glacier pebbles. 

Now, we prefer decorative gravel for greenhouse floors instead of concrete for two main reasons.

One is that a gravel floor can never become clogged and back up the way a drain in a concrete floor sometimes does.  Water drains evenly through the entire gravel floor, anywhere inside the greenhouse.

Another advantage is that a gravel greenhouse floor offers more traction and stability. With exposure to the perpetually wet environment of a greenhouse, concrete slab floors can get slimy and slippery over time.

Plus, decorative gravel varieties like pea gravel and glacier pebbles have a natural beauty that a concrete slab just doesn’t have.

CEDAR FRAME

A good greenhouse frame maximizes strength and minimizes any shade cast by the frame itself. To achieve this, the components must be substantial enough to be strong, but not so big that they cast excessive shade. And a greenhouse frame has to hold up in a constantly wet environment, too, which means the frame material is just as important as the design itself. 

Our first choice for our greenhouse frames is always rough sawn red cedar, which is strong and famously long-lasting in demanding outdoor applications, and in wet environments like a greenhouse. Hefty 2”x4” cedar rafters spaced 24” apart, and joined to a stout 2”x6” ridge pole, create an extremely strong roof that easily shrugs off heavy snow, wind, and ice loads, and still minimizes the shade cast by the frame. Two roof vent windows are neatly built into the rafters, and open and close automatically, based on the temperature inside the greenhouse.

 

POLYCARBONATE GLAZING

There’s so much to love about twin-wall polycarbonate greenhouse glazing, and it’s always our first choice for custom greenhouse designs. It’s lightweight, and easy to cut and work with. It can be screwed directly to a cedar greenhouse frame, making the structure more rigid and strong. It has much better insulation value than single-pane glass glazing, and it’s virtually shatterproof, and safer to work under than glass glazing. And 8mm twin-wall polycarbonate glazing comes in clear, and also a matte/opaque finish that diffuses sunlight, making it gentler for the plants inside. We chose matte polycarbonate glazing for Donnie’s greenhouse, but because the door faces that captivating water feature, Donnie requested that we use clear glazing on the front of the greenhouse. We were happy to accommodate that request, and now he can tend to his plants inside the greenhouse and still enjoy that amazing garden pond at the same time.