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.
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.
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.
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.
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.
Excellent heat conductivity
Doesn’t need replacing unless broken
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.
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.
Can fit any shape
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.
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.
Light and sturdy
Provides excellent light diffusion
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.
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.
Transparent but insulating
Doesn’t require a heavy frame like glass does
UV additives protect it from deterioration
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.
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
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.
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.
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.