How To Build A Backyard Greenhouse?

Building a backyard greenhouse sounds like a great idea. I could make it unique to my home and feel like I really had a part in putting it together, but I have no idea where to start. I decided to try to figure this out.

How To Build A Backyard Greenhouse? Building your backyard greenhouse involves more than just buying supplies and building the greenhouse. You also need to consider the following:

  • Permits
  • Location and orientation to the sun
  • Covering 
  • Flooring
  • Additional supplies to maintain an ideal temperature

It may sound overwhelming, but it’s not as bad as it sounds. If you read through this article, I’ll show you exactly what you need in order to build your perfect backyard greenhouse.

Check Permit Requirements

The first step before you really get going on your greenhouse is to figure out if you need a permit from your city before starting work. It would really stink to be halfway through building your greenhouse and have the city put a stop to your dream.

A local code enforcement official determines whether you need a permit or not. Set up a meeting with your local official and ask about the following:

  • Maps
  • Plans
  • Calculations

Sometimes the city wants a full set of professionally done drawings and other times, they may take a simple hand sketch.

You also need to find out what other signatures you need to get a permit. Sometimes, you’ll need other city officials such as zoning officials to give you the go ahead as well. 

If you’re running any water or electricity out to the greenhouse, the city may require a licensed professional do the work. You’ll probably have to put the professional’s information on your permit.

Any local, greenhouse hobby groups in your area can also be good resources for finding out the specific details of what you might need. 

Once you know any permit requirements, you’re ready to get planning.

Find the Best Location for Your Greenhouse

Before you plan the design for your greenhouse, you need to figure out the ideal location. Here are some things to consider when it comes to the best location.

  • Level ground
  • Clear of trees
  • Orientation to the sun
  • Accessibility

Level ground: Level ground with good soil is important for the location of your greenhouse. You can get by with mediocre soil if you plan to use pots or raised beds.

Clear of trees: Tall trees around your greenhouse block the amount of sunlight that reaches your plants. The only trees that might work around the greenhouse are deciduous trees that lose their leaves every fall.

Bird droppings, pollen, and leaves can also fall on the greenhouse and block sunlight.

Orientation to the sun: The direction you orient your greenhouse depends on when you plan to use it. If you’ll use it all year, orient it east to west. If you’ll just use it during spring and summer, north to sound is better so both sides get the same amount of light. 

Accessibility: You should have easy access to water and electricity for convenience. The closer your greenhouse is to the house also makes it easier to cart in fresh fruits and vegetables. 

After you’ve picked the ideal location, you can move on to finding or designing the perfect plan for your greenhouse.

Find a Plan for Your Greenhouse

Now, comes the fun part…unless you lack creativity like me, then it might be more work. You can choose to design your greenhouse on your own; draw out your ideas, add in the details and come up with your blueprint. If you’re like me, though, you can hop online and start looking for plans. 

There are three general types of greenhouses. Here’s a look at the basics of each type.

Lean-toDetachedRidge and Furrow
Built against the side of another structureShares wallTough, wind resistantStand independentlyMany typesMore freedom with sizeMultiple greenhouses connected at the top by a common gutterInternal wall removed between greenhouses 

Ridge and furrow greenhouses are generally used more often commercially because of their size. In this post, we’ll take a closer look at lean-to and detached greenhouses so you can pick the right plans.

Lean-to: A lean-to greenhouse is sometimes called a half-greenhouse. Its ridge line (half the roof) is attached to the side of your house or garage. Usually, a doorway leads from there into the greenhouse. 

The proximity of the lean-to to your house make access to electricity and water super easy. The cost of a lean-to is lower and it’s easier to maintain. The main downside is that you’re limited on size and the shared wall may block some sunlight.

Detached: Since a detached greenhouse doesn’t share any space, you have quite a bit more freedom when it comes to its size. Detached greenhouses also get plenty of sunlight as long as you pick a good spot. Because detached greenhouses are larger, they do require more of an investment since you have to provide electricity, ventilation, irrigation, and heating.

Once you decide on whether you want a lean-to or detached greenhouse, you need to consider whether you want a cool, warm or hot greenhouse. I know, like me, you probably had no idea that greenhouses were also broken down by their temperature. Here’s a look at the specifics for each type.

Temp doesn’t dip below 40°FPropagate seeds and cuttings for early plantingInexpensive due to no heatingTypes of plants restricted because cooler temperaturesTemp stays around 50°FGrow perennials through winterSome heating equipment neededTemp stays around 60-65°FHeating and lighting equipment may be neededGood for growing exotic or tropical plants

The design and equipment you use for your greenhouse depends on the type you want to build and the temperature you want to maintain.

Here’s a look at some do it yourself plans on Amazon.

8 X 10 Walk-in, Ventilated Wood Frame 

8 X 10 Timber Frame Post and Beam Greenhouse 

How to Build Your Own Greenhouse: Designs and Plans to Meet Your Growing Needs 

Buy the Building Supplies

Once you’ve decided on your plans, it’s time to think about the materials you want to use and go out and buy your supplies.

Frame: When it comes to the frame of your greenhouse, the most popular choices are aluminum, steel, and wood. 

Here’s a look at what you can expect if you choose an aluminum frame.

  • Low maintenance
  • Lightweight
  • Rustproof
  • Affordable 
  • Easy to work with
  • Not a good insulator
  • May not be sturdy enough for areas with high wind

If you’re thinking about a steel frame, here’s what you can consider.

  • Durable
  • Strong
  • Affordable
  • Difficult to work with

You’ll see these pros and cons with a wood frame greenhouse.

  • Aesthetically pleasing
  • Easy to work with
  • Good insulator
  • Natural material, so it can develop mildew or disease
  • Cost depends on which type of wood you choose
  • Bulkier, so may block some sunlight

Covering: Just like the frame, there are a number of options you can choose from for the covering for your greenhouse. The greenhouse covering is also called glazing. 

The most important factor to consider for the covering is that it allows as much sunlight as possible to get through. 

Glass: This is the typical choice for greenhouses because it allows the most light to get through, around 90-percent. Glass holds in heat very well, which is helpful in the winter but maybe not so much in the summer. 

Glass is very durable, but it’s also heavy so you need a strong frame to hold it up. Glass involves very little maintenance and is pleasing to look at.

Polycarbonate: This is a heavy-duty type of plastic. Polycarbonate is strong, allows plenty of sunlight to get through and is fairly flexible, making it easy to manipulate on your greenhouse.

Polycarbonate lasts for about 15 years and comes in single, double or triple-walled sheets.

Plastic film: Plastic film is weaker than polycarbonate, but still a good option for smaller, lightweight greenhouses. It’s very flexible, lightweight and affordable. Although they’re lightweight, plastic is pretty durable when it comes to wind, snow or hail. 

It allows the same amount of light to get through as glass, but you’ll most likely have to replace it every four years or so.

Fiberglass: Fiberglass is much lighter than glass, but still lets the same level of sunlight into your greenhouse. It diffuses the light differently than glass so it’s less likely you’ll harm your plants with too much sun. 

Fiberglass can have condensation problems and, if cheap, can yellow quickly. Cheaper fiberglass also has to be replaced more often. 

Take a look at your plans to determine how many materials to purchase for your frame and covering. 

When it comes to the frame and covering of your greenhouse, think about your budget, your ability to maintain it and how you want it to look. 

Prepare the Foundation for Your Greenhouse

Before you can start building, you need to prepare the foundation for your greenhouse. No sense in building on a weak foundation and having your greenhouse crumble to the ground later.

There are generally two types of foundations gardeners choose from, wood or concrete.

Wood is a simple, inexpensive choice for a foundation that gets the job done. Concrete is more expensive and will take a bit more time to lay, but is a good choice for holding up larger, heavier greenhouses. 

Take a look at the following steps to lay a wood foundation.

  1. Clear the area you plan to lay your foundation of any rocks, sticks, plants, etc.
  2. Determine the area of your greenhouse (length by width). Usually, plans tell you this information.
  3. Choose a naturally resistant wood. This type of wood helps prevent decay. Cedar, redwood or cypress are good choices. 
  4. Use 4 by 6-foot pieces of wood to set up a level site equal to the area of your greenhouse frame plus an inch on each side. Check the boards with a level to make sure they’re level. 
  5. Secure the pieces of wood at each corner with lag screws. The screw should be at least 3 inches longer than the board it is screwed through. 
  6. Scoot a weed barrier under the wood you just screwed together and cut any excess fabric off at the edges. The ground cover lets water drain but prevents weeds. Here’s an affordable one from Amazon. Check price on Amazon 
  7. Check the foundation to make sure it’s square. Measure from one corner across the frame to the opposite corner and then repeat with the other corners. The measurements should be the same. If not, adjust your base. 
  8. Anchor your foundation to the ground. You can do this by driving rebar into the ground and attaching the foundation or with an anchor set like this one on Amazon. Anchor set on Amazon 
  9. Add a base to your greenhouse floor. Gravel or sand are good choices because they allow water to drain. 
  10. Use 2-inch galvanized lag screws and washers to attach the greenhouse to the foundation once it’s built.

Here’s a look at laying a concrete foundation.

  1. Build a form out of wood for the perimeter of your greenhouse, adding an inch to the length and the width.  For an attached greenhouse, the top of your wood should be a step or two below the floor of your house. The top should be several inches above the ground for a detached greenhouse. A depth of three inches is usually adequate.
  2. Add reinforcing wire or fiber to the form to increase the strength of the slab.
  3. Place a drain in the center of the form for drainage. 
  4. Add at least 4 inches of compact gravel or stone to allow for drainage.
  5. Place a moisture barrier on top of the gravel to keep the concrete slab dry.
  6. Pour the concrete and give it about 24 hours to set before you remove the form.
  7. Add 1 to 1 ½ inch thick insulation board around the outside of the foundation at a depth of 1 to 2 feet. This helps keep the floor warmer in cold weather.
  8. Use concrete anchor bolts to attach your greenhouse to the concrete slab once it’s built. Place them within 1 foot of each corner and then about 4 feet apart after that. 

Building Your Greenhouse

Any plan you buy will come with an instruction manual. It’s time to get that out and build. The directions vary from plan to plan, but here’s a look at some tools you can expect to use.

  • Tape measure
  • Miter saw
  • Screw gun
  • Power drill
  • Cleaning rags
  • Scissors

In addition to these tools, you’ll need your framing and covering supplies as well as nails, wood screws, bolts, and other mounting hardware.

Once you have all your tools in hand, unpack your kit if you’re taking the pre-bought kit route. Check all the pieces compared to the instructions. Although plans can vary, you’ll generally build in a similar order to this.

  1. Put together the base of your greenhouse and the corner uprights.
  2. Attach the roof frame.
  3. Install the wall uprights and roof rafters. Following this order keeps the greenhouse sturdy while you build.
  4. Put in the wall panels.
  5. Customize your greenhouse.

You can see what’s involved in building a greenhouse from scratch versus a kit in these videos.

Here’s a look at one built from scratch. Watch a greenhouse be built from scratch 

Here’s one built from a kit. Greenhouse built from a kit

Customize Your Greenhouse According to Your Needs

Customizing your greenhouse to personalize it just for you is the fun part if you ask me. Here are some things you can add to customize it.

  • Shelves
  • Benches
  • Hooks

Shelves: You can attach shelves to your greenhouse walls or lay them on top of the framing. Shelves help maximize the space in your greenhouse. You can store seeds, tools, and pots on the shelves for easy access. You can also use shelves for growing plants in pots. 

Another benefit of putting flower pots on shelves is they get more light, which encourages more growth as long as it’s not too hot. On the flip side, make sure the shelves aren’t creating shadows over other plants trying to grow on lower levels.

Make sure you choose shelves with holes for drainage; otherwise, your plants will sit in puddles of water. This is a sure way to encourage growth of the mold and fungus and attract bugs. 

Benches: You can use benches similarly to shelves. The main difference is that you attach shelves to something and benches can be moved around the greenhouse. 

It’s a good idea to set up one bench for potting. A bench with a smooth surface is important so clean up is easy. Having a dedicated potting bench means you’ll keep any potting mess contained to one area.

You’ll generally find benches in one of three materials. 

MetalLast for a long timeWon’t rot or decayLow maintenanceExpensive
WoodWon’t decay if you choose the right type (cedar, redwood, cypress)WarpsHigher maintenance
ConcreteDurableWon’t decayPermanent, can’t move around

It might help to envision areas you want to put shelves and benches and then draw out a design. On your design, label what each area will be for, i.e. holding plants, storing tools, watering cans. 

Hooks: You can use hooks to hang fans or plants in your greenhouse to open up more space on the ground. You can even find spiral hooks made specifically for plants that need something to grow up onto, like tomatoes and beans.

You can find plenty of hooks on Amazon, like this pack of 50. Check price on Amazon 

Adding Additional Equipment for Climate Control

Although the building of the frame and cover of your greenhouse may be complete at this point, it won’t function without a few other critical components.

Every greenhouse needs a ventilation system and, depending where you live, ways to cool and heat the greenhouse as needed.

Without a ventilation system, plants won’t thrive in your greenhouse. Most gardeners consider a ventilation system as one of the most important requirements for a greenhouse. It does three main things:

  • Provides fresh air
  • Cools the greenhouse
  • Controls humidity

You’ll choose one of two types of ventilation systems: natural or mechanical.

Natural ventilation: A natural ventilation system uses vents on the roof and sidewalls of your greenhouse. Since heat rises, the warm air in the greenhouse rises to the top and flows out the roof vents. As that air flows out, it creates a vacuum that pulls cooler air in the side vents.

Mechanical ventilation: Mechanical ventilation uses an exhaust fan to push out the hot air as it rises; cooler air comes in through special openings on the sides of the greenhouse.

The ventilation system brings in fresh air, which has the carbon dioxide plants need to grow. Plants use sunlight to break down carbon dioxide and water to make sugar, which they use as food. Without the air circulating from a ventilation system, plants won’t get the necessary carbon dioxide.

The system cools the greenhouse by exhausting warm air out of the greenhouse to lower the temperature. It controls humidity by replacing moist, warm air with cool air. High levels of humidity can cause mold and other fungus to grow.

Even with a ventilation system, you may still need additional methods to cool or warm your greenhouse. The ideal temperature for a greenhouse is between 80 and 85 degrees Fahrenheit. When it dips below or shoots below this range, you need to control it.

Signs that your plants are too hot include wilting plants, scorched or sunburned leaves, and dry young plants. This happens because plants “sweat” to keep cool. They lose moisture through pores in their leaves. When they have to use any excess water to try to cool down, they’ll start suffering. 

In addition to keeping an eye on the condition of your plants, it’s always a good idea to buy a thermometer for your greenhouse. This one on Amazon measures temperature and humidity.  ThermoPro thermometer on Amazon 

When your plants do need cooling down, here are some ways you can do it.

  • Shade cloth
  • Misters
  • Evaporative cooler
  • Portable air conditioning unit

Shade cloth: Shade cloth helps lessen the strength of the sunlight coming into your greenhouse. It comes in a variety of colors, materials, and densities. The density you’ll use depends on the requirements of your plants. 

Aluminet is one type of shade cloth that’s very effective since it reflects sunlight as well as provides shade. Here’s some from Amazon. Check price on Amazon 

Misters: Misters work to cool down a greenhouse by putting small water droplets into the air; when the droplets evaporate, the temperature comes down a few degrees. 

One like this on Amazon should do the job. Check price on Amazon 

Evaporative cooler: Evaporative coolers store water in a compartment. Air from outside the cooler passes through the compartment and is put back into the greenhouse as cooler air, lowering the temperature.

Here’s a look at one on Amazon. Check price on Amazon 

Portable air conditioning unit: A portable air conditioning unit should be a last resort if the other cooling options don’t wok. A portable AC unit is effective in cooling the greenhouse, but it costs quite a bit more to run. 

If you need to warm up the greenhouse, here are some ideas.

  • Water barrels
  • Compost
  • Covering plants
  • Electric heater

Water barrels: Water barrels are one of the most inexpensive options for warming your greenhouse. Take a big 55-gallon barrel and paint it black, which helps it absorb heat better, and fill it with water. Put it in the greenhouse. It absorbs the heat during the day and lets it off at night.

If a 55-gallon barrel isn’t doable, you can fill capped, one-gallon jugs three-quarters of the way full and place those around the greenhouse.

Compost: Compost isn’t just a good fertilizer; it’s a good heater, too. You can dig a trench down the middle of your greenhouse or a pit in the middle and fill it with compost. When the chemicals in compost breakdown, they put off heat. 

Covering plants: Covering your plants can help insulate them on extra cold nights. It’s important to remove the covering during the day, though, to make sure your plants get enough light and air. 

Horticultural fleece, sheets, tarps, and row covers are all materials you can use to cover your plants. Here’s a row cover on Amazon that would be good. Check price on Amazon 

Electric heater: You can run an electric heater in your greenhouse if you have access to electricity. A heater is a more expensive option but will do the job. 

An auto shut off, like this one on Amazon, is always a good idea. This one also has a fan, which helps distribute the air more evenly. Check price on Amazon 

This is a lot to think about, even for an avid gardener.

If after reviewing this entire article, building your own backyard greenhouse from scratch still sounds too overwhelming, there are plenty of premade greenhouses out there. You can buy one that you just snap together and it will work just the same. 

Eyerly Family

The Eyerly Family is a family of 8 that loves gardening. Over the past several years we have been applying what we learn about gardening to our own 16x16 raised back yard garden. Our garden is very prolific and we grow a wide variety of vegetables which we love to eat! Click here to learn more about the Eyerly Family.

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