On This Page:
- What Size Greenhouse Are You Planning?
- Material Options
- Framing
- Excavation
- HVAC, Lighting & Permits
- Greenhouse Kits & Frames
- DIY Considerations
- Conclusion
Greenhouses make great additions to any home. They provide a structure for growing plants that will protect them from the climate of wherever you live, even allowing for plant growth that may not be native to your area. They can extend your growing season and, for the green-thumb, provide a relaxing escape. Gardeners and horticulturists often spend more time in their greenhouses than they do in their residential houses!
Greenhouses help provide ideal growing conditions for edibles and flowers. Many who enter local competitions use them to make sure they produce the biggest and the best examples. With near-complete control over light and humidity, greenhouse work is a science as much as it is a hobby.
The cost to build might be hard to predict due to dimensions, materials, excavation, lighting, and permits among other considerations. All factors considered, the average cost to build a greenhouse is around $13,893 if professional labor is used. Your average price can drop to about $3,500.00 if you know how to build it yourself, and even lower if you buy a basic kit.
To help figure out what your cost should be, read on…
What Size Greenhouse Are You Planning?
Consider the size. Obviously, a larger greenhouse will require more material, which will increase the cost. But what size do you need?
For the serious gardener or horticulturist, a 10x10 greenhouse is the minimum size. For the casual “greenie”, 6x6 is usually fine. If you aren’t sure, opt for a larger space. You will fill it up easily, and it’s difficult to add-on to an existing smaller structure.
Basic Beginner
About $240
A basic beginner’s greenhouse is fairly inexpensive. A 6’x8’ hoop-house (an arced greenhouse) package has everything you need to build it yourself and get started. This, however, is a very basic design more for moderate climates. It doesn’t have any plumbing or electronics, being essentially a polyethylene-covered Quonset hut.
Experienced Growers
About $3,500 to $7,000
For the more dedicated grower, a 12’x12’ greenhouse might be more suitable. For this type, there are many extra costs involved including grading the foundation, laying the floor, and running plumbing and electrical systems. They’re usually best installed by a professional and might require permits. The siding is usually polycarbonate or glass with a vented roof for temperature/humidity control.
For the Serious Grower
About $13,000 to $25,000
The average cost for a greenhouse structure (except for kits) is about $25.00 per square foot. These large greenhouses are 500 to 1,000 square feet. They usually have all of the amenities a plant could hope for. HVAC systems maintain temperature and humidity for some, while computers and sensors automatically open or close roof vents and windows. Automatic watering systems and feeders provide nutrition, and grow lights help provide optimal conditions. Flooring is often poured concrete with drainage systems. These greenhouses should be professionally installed.
Material Options
The materials used will have the biggest impact on your cost. Frames are usually made of wood or steel. Siding runs the gamut from polyethylene to tempered glass. Each material has its pros and cons.
Glass
Double strength (minimum recommended) about $2.50 sq ft
Glass is the preferred siding for greenhouses. Not only is it beautiful, it also gives your structure a look of permanency.
Pros
- Visually attractive
- Excellent heat conductivity
- Doesn’t need replacing unless broken
Cons
- Doesn’t diffuse light, which can burn plants
- Heavy, requires a strong frame
Maintenance involves cleaning the same way you would the windows on your home, but also inspect periodically for cracks, chips, and breaks, especially after a storm.
Polyethylene
About $0.12 per square foot
Polyethylene is a plastic film used as siding on many greenhouses. Its flexibility makes it popular for hoop-houses.
Pros
- Very inexpensive
- Can fit any shape
Cons
- Must be replaced every couple of years.
Maintenance requirements include routine hosing off and inspecting for tears. Tears can be repaired easily with patches of the same material and packing tape, with patches applied to both sides of the tear. If it’s getting yellow and brittle, it must be replaced.
Fiberglass
About $72.00 per 6x8 panel
Fiberglass is light but rigid while allowing a degree of flexibility, making it a fairly popular choice. It often comes with a 10-year warranty against yellowing or structural failure.
Pros
- Light and sturdy
- Provides excellent light diffusion
Cons
- Expensive
- Can crack in high winds
Maintenance requirements include routine hosing off and inspecting for cracks and breaks, especially after storms. Fiberglass patch kits cost less than $20.00.
Polycarbonate
About $55.00 per 8x4 sheet
Polycarbonate is a good alternative to glass. Light and rigid, it’s almost as transparent as glass, but the double-wall construction insulates against burning.
Pros
- Transparent but insulating
- Doesn’t require a heavy frame like glass does
- UV additives protect it from deterioration
Cons
- Scratches easily
- Doesn’t cut easily for sizing
- Repairs are only temporary until you can replace the whole panel
Maintenance involves inspecting for cracks and replacing panels if necessary.
Framing
Wood
Cedar, about $1.00 per linear foot
Wood framing provides a natural look for a greenhouse, attractive while blending in with your landscape. Cedar is recommended for its outdoor durability.
Pros
- Beautiful and durable with regular maintenance
- Naturally insulating, won’t draw heat away from plants
- Easy to work with
Cons
- Can attract insects
- Treated wood should be shielded so that rainwater and other moisture doesn’t drip onto plants
Maintenance involves annual treating and sealing, the same as you would a deck.
Steel
About $2.50 per linear foot
Steel frames are stronger than wood, but are more expensive and harder to work with. A 20’ hoop-house steel frame costs around $560.00 and doesn’t include the covering or end walls.
Pros
- Stands up to adverse conditions very well
- Low maintenance
Cons
- Harder to work with than wood
- Draws heat away from plants.
Maintenance involves periodic inspections for rust and replacing rusted parts.
Excavation
While many greenhouse kits come with flooring, building your own will require you to level the ground at the very least. Some people leave a natural dirt floor, but this can become a muddy mess. Most people use some kind of flooring, often concrete, pavers, or gravel.
- Concrete – About $10.00 per square foot, should have texturing and drainage
- Pavers – About $8.00 to $11.00 per square foot on average
- Gravel – About $0.75 to $3.00 per square foot, but will require weed-block or constant weeding
HVAC, Lighting and Permits
Temperature and humidity controls for your plants is a must. A smaller greenhouse might do well with the gardener or horticulturist handling this manually, but larger greenhouses might fare better with HVAC and lighting systems.
Because these systems must be installed by licensed contractors, they can make up half to more than half of your project’s total cost. A large, $16,000.00 greenhouse could easily have over $8,000.00 in lighting and HVAC systems.
Grow lights cost from $30.00 to $130.00 each. HVAC systems cost from around $100.00 for a simple, portable heater useful in small areas to several thousand dollars for a full system.
Finally, building a greenhouse in your area might require a permit. It is considered an “outbuilding” or a “farm building” and may need to be permitted before construction starts. Check with your local code enforcement office. Failure to get a permit could result in fines.
Greenhouse Kits and Frames
Some greenhouses are available as kits. These usually consist of a frame, coverings, and sometimes a floor. Prefabricated frames are available at many “big box” hardware and home improvement stores, but even smaller stores may carry basic frames.
A very basic 6x8 steel tubing frame can be had for less than $200.00. On the high end, a 16x30 galvanized steel frame costs around $10,000.00.
Wooden styles are available as small herb-garden greenhouses that cost from $129.00 for a basic frame to around $5,000.00 for a model with areas for storage.
Kits usually don’t come with benches and other amenities. These will have to be bought or built separately, and the cost can vary widely depending on what type you get. In general, potting benches cost about $100.00 each.
DIY Considerations
If you know what you’re doing, you can build your own greenhouse. Many sites offer free plans; all you have to do is buy the materials. Here are some other considerations:
- Use salvaged materials. If you want to recycle and go green, re-using old material is a great way to go. You’ll have to clean the material and alter either it or your plan to make it fit, but the material is usually free.
- Learn about the climate where you live. In a cold area you’ll need insulating materials. In a hot area, you’ll need to provide for shade. Usually, you need a bit of both.
- Don’t forget air circulation, pest control, and temperature control.
- Be sure your greenhouse gets plenty of sunlight, but remember to have a shade cloth if needed.
- The type of covering you use will determine the strength of the frame needed. Polyethylene can use a lighter frame, but glass will need a stronger one.
- Remember to anchor your greenhouse firmly to the ground or the slab. High winds can cause a catastrophe.
- If you want “all the extras”, you can mitigate the cost by adding them slowly over time.
- Take advantage of “good bugs” to help protect and fertilize your plants.
- Include storage space in your design.
- Set aside the time to build it right. A small greenhouse might take a weekend or less, but larger ones can take several weeks.
- A simple 165 square foot hoop house can be built as cheaply as $50.00 to $130.00.
In Conclusion
For the hobbyist or serious grower, a greenhouse in a requirement. With careful planning, it can be attractive and affordable.
