Whether you want to build a greenhouse yourself or want to buy one, learning what materials are used to make a greenhouse is a must.
In particular, deciding which greenhouse frame material to use should be on the top of your priorities if you want to build it yourself.
The framework of the greenhouse is an important part of its structure as it provides strength to the whole construction and serves as a source of insulation.
What materials are used to make a greenhouse?
Choosing the appropriate material for a frame depends on the glazing you want to use, the type of greenhouse structure and the area you live in.
To make the greenhouse framework, you can use wood, aluminum, galvanized steel, PVC plastic and even resin. For the panels you can use glass, polycarbonate or polyethylene film. What cover to choose depends on your frame material.
Whenever I am hunting for a good frame I rely on several factors:
- Durability
- Insulation
- Affordability
- Ease of setting up
- Strength
- Appearance
So in this post, I am going to take a closer look at the available frame options and discuss them based on the criteria mentioned above.
1. Wooden Frame Greenhouse
Wooden frame in combination with glass glazing has been the most popular greenhouse option for many years.
It has earned its title to be a traditional greenhouse framework because of the nice appearance and ease of setting up. Also, wood frames have a massive advantage in providing insulation.
When you start researching wooden frames you will probably come across the term pressure-treated wood. What does it mean? I asked myself the same question…
What kind of wood is used for greenhouses?
Pressure-treated wood
Pressure-treatment is a procedure where chemical preservatives are applied into the wood. It prevents the wood from the insects like termites and fungal infections.
However, there is a debate between the gardeners whether it is acceptable to use a pressure-treated wood frame because of the toxicity. Chemical preservatives can leach into the plants.
For example, if you are growing food the chemicals can leach in the soil, alter its pH and eventually get into the food crops.
What is a best wood for greenhouse?
Another way to prevent wood is to use a priming paint based on the organic oils which protects it from moisture and decay.
I would recommend investing into a rot-resistant timber and well-thought drainage system. The very resistant woods are black locust and Osage-orange with over 15 years of life (indeed very rare and usually expensive).
Resistant and cost-effective types of woods are cypress, red cedar, redwood and white oak with an average of 7 to 15 years of life.
However, some of the resistant species are not relatively strong, so pay attention to the plastic options discussed below.
2. Aluminum Frame Greenhouse
In comparison to wooden frames, aluminum doesn’t rot, doesn’t rust like steel or doesn’t degrade from sunlight as in case with PVC.
It is quite light which makes it easy to handle and set up. The costs of the aluminum frames are really close to the prices of the wooden frames.
Overall, the aluminum frame is very durable, maintenance free and can be molded and painted to suit any design.
In terms of the strength of the aluminum construction I have some concerns if you don’t have a steady base of the greenhouse.
Aluminum greenhouse kits
From my experience I can tell that people getting an aluminum kit say that it comes with everything apart from the base.
The frame sets up directly into the soil leading to the bending of the frame and even swaying with the wind.
Another disadvantage of the aluminum is that it is not an insulator and does let the heat out.
Moreover, this might lead to condensation which is a major drawback if you planning on growing in winter.
Aluminum frame of different colors
Also, in the aluminum frame you can easily drill the holes needed whilst fastening glass or polycarbonate covers. If you started looking for aluminum frames you probably saw a green and silver option.
What is the difference? Well, as it was discussed already aluminum doesn’t rust, but it does oxidize in other words it does corrode. You might be a little bit confused here.
Term ‘rust’ is used only to iron and steel materials. With aluminum the corrosion is in dull gray or powdery white color which is not easily noticeable as with steel or iron.
Therefore, some of the manufacturers choose to powder coat aluminum frames in a green color.
Why do you powder coat aluminum?
Powder coating is a process in which aluminum is baked in the oven and the paint is chemically bonded to the surface. It makes the material more durable, resistant to UV degradation and corrosion.
With the variety of colors available for the powder coating your greenhouse will match any design you want and be a stand out feature of your outdoor interior!
So, if you are after an aluminum frame I would recommend going for the power coated option as it is worth the money in a long term.
3. PVC Frame Greenhouse
Okay, maybe some people don’t know what PVC is. Well, I had no idea a few years back! So, PVC or polyvinyl chloride also called polyvinyl or just vinyl is a plastic polymer.
It is the cheapest option compared to the previous ones and definitely is the easiest to mold. Building a greenhouse with PVC material is super easy, convenient, extremely quick and so cheap!
It doesn’t look as impressive as wooden or aluminum frames but it does carry the same functionality.
However, I need to point out that PVC is better for smaller types of greenhouses or DIY projects. Taking into consideration the durability, in comparison with other materials PVC is definitely on the last place.
The UV lights will eventually degrade it. Also, in the environment with predominant winds, rains and snows it is most likely to break.
You can increase the durability of PVC by assembling the frame with lots of steel supports. Don’t forget that one of the massive advantages of the PVC pipe is that it is not affected by moisture.
And the last type of material commonly used for a frame in the greenhouse is galvanized steel…
4. Galvanized Steel Frame
First, what is galvanized steel? Galvanizing is a process where a protective layer of zinc is applied to steel to avoid rusting.
Hot-dip galvanization is preferred for the material which is going to be used in a humid, hot, soil-based environment.
So, this increases the durability of the steel frame which is indeed very strong, but can be quite heavy in comparison to wood or aluminum.
Also, in contrast to aluminum which can be changed into a shape, this is not possible with steel. Moreover, it requires some sort of the glazing system to secure the glazing sheets.
Galvanizing steel is a low maintenance material as it doesn’t need staining or sealing.
The costs of steel frames are generally less expensive than aluminum or wood. However, it requires a little bit more care like periodic resurfacing.
Which glazing to use with a galvanized steel frame?
If you decided to use galvanized steel the best glazing option for it is a polyethylene film. Paint the frame into a white color to reflect an extra light inside the greenhouse.
The white painted frame is also cooler which in contact with plastic film prevents it from wearing of.
Similar to aluminum galvanizing steel is not an insulator and does conduct the cold air inside the greenhouse resulting in condensation.
Therefore, if you are planning to use a steel frame consider using heating systems and take proper care of the ventilation.
Please let me know in the comments which framing options are your favorite.
Happy growing 🙂
