How to choose the right type of structural frames to be used in your greenhouse

Generally speaking, structure frames used in a greenhouse takes second billing to the material used as siding, but an unsuitable frame material can mean an unsteady frame that will never really be square. It is very hard to complete a greenhouse successfully unless the initial frame is properly built, and if you do get it completed, you may later find that it has cracks and openings that are hard to seal against drafts and invasion from insects and small animals.

In the current market, some small 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. On the one hand, aluminum is a very low-maintenance material, for it doesn’t rust or break down from exposure to the elements. 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 or polycarbonate panels. Aluminum can be painted or anodized in any color you choose. On the other hand, galvanized steel pipe 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.

If you are planning to build a small plastic greenhouse in your backyard, PVC plastic pipes would be a better choice for you. PVC plastic pipes are generally low cost, lightweight (portable), and very easy to assemble. 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. These are usually smaller, hobby-type backyard greenhouses while plastic pipe does not work very well for a large greenhouse. Most hobby greenhouses sold in kits now come with PVC frames.