How to make a proper frame material option for your greenhouse

In most cases, some greenhouses are sold in kit form that won’t give you any options for the framing materials, but if you are building a custom greenhouse, you have the option of choosing the material you use for the frame structure. Here are things to consider with the four most common options for greenhouse framing: wood, aluminum, galvanized steel, and PVC plastic pipe.

1. Wood
Wood generally has good insulation value and is fairly easy to fabricate and assemble into a frame for a small greenhouse in your backyard. But greenhouses are wet, damp spaces and most wood will eventually warp and rot under the ongoing presence of moisture found in a greenhouse. If you do use wood, opt for a species with known resistance to moisture and rot, such as cedar or redwood. Or, use chemically treated wood designed for outdoor use. Whatever wood you use, applying a sealer every few years will extend its life.

2. Aluminum
Aluminum is a very low-maintenance material, because it doesn’t rust or break down from exposure to the elements in use. But aluminum is not very strong and when used for a greenhouse frame, the support members must either be made from heavy gauge pieces or doubled up for strength. Aluminum does, however, provide a good rigid form for glass panels in glass greenhouses sometimes. Aluminum can be painted or anodized in any color you choose.

3. Galvanized Steel
Galvanized steel provides durability at a low cost. Because steel is very strong, your greenhouse will require fewer framing members, which means that fewer shadows will be cast into the greenhouse. However, most steel frames are designed to be used with polyethylene film rather than solid glass or polycarbonate panels. Greenhouses with galvanized steel frames and polyethylene film covering are popular with commercial growers, but they are not particularly attractive in a residential setting. And a big negative for galvanized steel is that the galvanizing will eventually wear and the steel will rust.

4. PVC Plastic Pipe
PVC plastic pipes are low cost, lightweight (portable), and very easy to assemble in plastic greenhouses today. A frame made from a plastic pipe is not as rigid as metal or wood, but the industry is addressing that designs that incorporate metal supports along with the PVC framing. PVC also has the advantage of allowing less heat loss than metal framing. Greenhouses with PVC frames almost always use polyethylene film for walls. Plastic pipe does not work very well for a large greenhouse. Most hobby greenhouses sold in kits now come with PVC frames.