How to Build a Greenhouse: Complete Greenhouse Building Guide

Greenhouses are a great way of addressing gardening needs all year round, especially in colder climates or environments that may not have the correct soil needs for your plants. They can also act as an alternative to spending so much money at the grocery store for herbs and other produce needs. If this sounds like what you are looking for, then you may be wondering how to build a greenhouse to care for your plants.

To build a greenhouse, you will need to do the following:

• Decide on the dimensions
• Select a greenhouse structure
• Choose the proper door and entryway
• Find a covering
• Create the floor
• Gather building materials
• Build the structure
• Consider add-ons

The idea of building your greenhouse may bring excitement for many and dread for a few! It can seem daunting, especially if you are not well equipped with constructional needs. For those that are ready to get their hands dirty (literally), read on to find out how to build a greenhouse step-by-step.

How to Build a Greenhouse: A Step-by-Step Guide

There are quite a few themes that overlap when it comes to questioning the best method for building a greenhouse. These overlaps are formed in the main steps listed above. However, there is plenty of information that needs to be understood before you start building your greenhouse.

This information includes knowing what dimensions you need, the structural archetype of the greenhouse, and all the other elements required to complete the build.

For ease of understanding the information, each of the following sections is designed to go into detail of what you should know based on the subject material.

Decide on the Dimensions

One of the first factors you should determine before picking up a hammer is the dimension of the greenhouse you want to build.

Consider the following questions:

• How large or small do you want your greenhouse to be?
• How much space do you have in your yard?
• How big are your plants or crops going to be at full maturity?

These are all questions you should keep in mind when you are planning the perimeter and height of your future greenhouse.

Generally, smaller greenhouses that are 6 feet by 8 feet will provide plenty of space for beginners and casual gardeners. If you are looking to plant a more expansive garden or you have years of prior experience in gardening and building, 12 feet by 12 feet or more should give you plenty of space for the necessary equipment and plants.

Permits You May Need

If you are going to build a greenhouse, remember that you may have to apply for a zoning and building permit, especially if you are going to be building on a larger scale. Unfortunately, as of now, there is no standard when it comes to which greenhouses need which types of permits.

The safest route is to start by meeting your local zone department to discuss your plans. They will be able to help determine how far from your property line the greenhouse would have to be.

From there, they may advise you to meet with the county building department to apply for a building permit. This will be especially true if you are building a detached greenhouse. Be sure to plan for two weeks of processing time to receive your building permit.

If you live in a community that has a Homeowners Association (HOA) committee, there may be even more restrictions on the building plans such as materials, height, shape, and even color.

Although each community with an HOA committee will have its specific limitations, the article “Homeowners’ Associations – What is an HOA?” addresses the main areas of concern as:

• Terminology – Be sure to check your lease or HOA agreement for the actual terminology used for what structures are not allowed.
  • “Additional structures” encompasses sheds, greenhouses, and any other building projects within your property line.
• Size – If your HOA does allow “additional structures” (or greenhouses specifically), they will have the maximum dimensions already established.
  • It is recommended to remain two feet under the maximum dimensions! It will reduce the risk of a citation.
• Color – Treat the outside of the greenhouse with the same rules established for your actual home.
  • If your HOA has defined specific colors or materials for exteriors, adhere to them as much as possible for your greenhouse.
• Be Ready to Appeal – If there is confusion on the actual rules defined by the HOA (known as “CC&R”), schedule a meeting with an HOA representative to discuss your greenhouse building plan before you start building.
  • If you are within your rights, you can appeal the final decision of the HOA that is limiting your greenhouse.

Here’s a helpful video that explains some important tips on size and location of your greenhouse.

Select a Greenhouse Structure

Contrary to popular belief, there is not just one type of greenhouse. Instead, there are many customizable options to consider when you need to build your greenhouse. These options are to ensure that the structure you make is equipped to handle the specific needs of the plant life within.

According to Texas A&M AgriLife Extension, there are three main types of greenhouse structures. Each type of construction is designed to highlight and address the needs that individual greenhouse owners may have, such as the space available and types of plants they are planning to grow.

Overall, there are three main types of greenhouse structures:

• Lean-to
• Detached
• Ridge and furrow (also known as gutter connected)

Lean-to Greenhouse

Lean-to greenhouses are structured in a way that one of the main supporting walls is an already established wall. Therefore, when you build a lean-to greenhouse, you will most likely utilize a wall of your house.

It is constructed almost like a screened-in back porch or patio. These types of greenhouses are the most common structure and are best for hobbyists. They generally don’t take long to build and can be completed within a day!

Pros of building a lean-to greenhouse:

• Simple design plans
• Doesn’t take too long to build
• Beginner-friendly
• Easy access to the greenhouse

Cons of building a lean-to greenhouse:

• Limited space
• Not able to be moved
• Won’t withstand harsher climates
• Insects may invade your home more often
• No control over sun direction

Here’s a video of someone building a lean-to greenhouse to show you what you would be getting yourself into.

Detached Greenhouse

Detached greenhouses, or “freestanding greenhouses,” are built to be able to stand on their own, separate from your home. These types of greenhouses can range from being arches coming straight up out of the ground to looking like miniature glass houses in your backyard.

Detached greenhouses are the best structure for agriculture and crop growing needs. This is because they can stand on their own and not depend on outside factors to create a growing environment.

Pros of building a detached greenhouse:

• Control over how large or small space is
• Warmer environment from sunlight
• Better conditions for crops
• More control over sun direction

Cons of building a detached greenhouse:

• Less growing room because of dome-like walls
  • Lower efficiency
  • Lower production
• Not connected to one another
• Distance from home or garden
• Snow is a hazard

Ridge and Furrow Greenhouse

A ridge and furrow greenhouse, also known as “gutter connected,” are structured to be used with other ridge and furrow greenhouses. These greenhouses all connect to a similar eave (edges of the roof that overhang to allow water to drip off the roof) and usually do not have the wall underneath the connecting gutter present.

This helps open up space and allows for more direct sunlight. A ridge and furrow greenhouse is best for uses with all plants but budding flowers especially.

Pros of building a ridge and furrow greenhouse:

• Increased space and sunlight
• More efficiency
• More productivity
• Capable of meeting a wide range of plant needs
• More cost-effective

Cons of building a ridge and furrow greenhouse:

• Higher risk of water damage
• Not beginner-friendly to build
• Shadows from gutter
  • Blocked sunlight
• Generally takes up lots of space

Once you have chosen the type of structure you would like to build, it’s time to move onto the next decision making factor: doors and entryways.

Choose the Proper Door and Entryway

Choosing the proper door and entryway for your greenhouse will ultimately depend on your environment and what you would like to keep in (or out) of your structure.

Some tips for deciding on a door or entryway include:

• If you’re looking to grow heat-sensitive crops or herbs in a colder climate, then you will need a more heavily structured door to keep any drafts from entering in.
• If you live in a more tropical environment that has higher humidity levels all year round, then you may benefit from not having any door.
• If you do decide to build a lean-to greenhouse, you will need to invest in an entryway that can be closed. Otherwise, you risk inviting bugs into your home or having the humidity created by the greenhouse rot your inner walls away slowly.
• If you choose to build a ridge and furrow greenhouse, there will not be any doors. Instead, the entryway will be the missing wall. It is advised to invest in fencing around your gutter connected to the greenhouse to keep animals out of your crops and prevent them from spraying your plants.

Although these tips name specific structures of greenhouses, doors and entryways are universal across the board! If you prefer to have a heavily structured door for a warmer climate, that’s fine. It is your decision on how you would like your door to look.

Pro-Tip: Do not use wooden doors. Wood is a porous material, so it allows the moisture from humidity to pass through it.

Because of this, untreated wooden doors will rot faster than any other material. Even treated wood is advised against since some of the chemicals used to treat it can be harmful to plants.

Find a Covering

One of the most critical aspects of building a greenhouse is the covering and the material you use. The goal is for the roof and walls of the greenhouse to be able to allow the most sunlight in without sacrificing durability or structure.

Without a doubt, glass is the best material to use as a covering. However, it can be challenging to work with as well as support. It can also cause issues if you live in a cold climate that gets multiple inches of snow weekly.

There are many great alternatives to using glass as a cover for your greenhouse.

Fiberglass

One alternative cover material for greenhouses is fiberglass. Some of the pros and cons of using fiberglass are outlined below.

Pros of Using Fiberglass:

• Sturdy – Fiberglass will withstand regular gusts of wind.
• Availability – It is always commercially available at most hardware stores.
• Cost – For the most part, fiberglass is cheaper than any other alternative per square foot.

Cons of Using Fiberglass:

• Thread Damage – The main downfall of using fiberglass is the threads within. These threads are susceptible to damage from UV rays and will expand.
  • When the expansion begins, there will be less light that filters through your greenhouse.
• Difficult to Adhere – If you’ve never worked with fiberglass before, it can cause respiratory issues if not handled properly.
  • You will need gloves, goggles, and a face mask if you want to cut or adhere fiberglass.

Typically, fiberglass lasts for five years as a cover for greenhouses.

Polyethylene Film

Polyethylene (PE) film is an excellent option for a greenhouse covering material! One of the most popular methods for PE film is the double-sided version for twice the protection against UV rays.

Pros of Using Polyethylene Film:

• Availability – Because it is such a popular option, it is readily available in most home improvement stores.
• User-Friendly – PE film is the easiest to work with and support.
• Lightweight – The reason it is so user-friendly is that the lightweight material only needs a few staples or nails into the main framework of the greenhouse to stay in place.
• UV Protection – Ironically, too much UV light can be harmful to many plants that dry out quickly. PE film negates many of the UV rays in sunnier climates.

Cons of Using Polyethylene Film:

• Lightweight – Just as it is an advantage, the lightweight material can be a disadvantage, depending on your environment.
• Does Not Last Long – Especially if there is snow or ice, the PE film won’t last many winters or summers.

Typically, polyethylene film lasts for about two years before needing to be replaced.

Polycarbonate Film

Polycarbonate (PC) film can be an option for those who are serious about their greenhouse building. PC film combines the strength and durability of glass with the insulation of fiberglass.

Pros of Using Polycarbonate Film:

• Durable – This stuff is incredibly durable! It will easily withstand intense heat, inches of snow or ice, and won’t blow off with huge gusts of wind.
• UV Protection – It has a bit more UV protection than its PE film counterpart but without the risk of blocking too much.
• Insulation – As stated before, PC film will insulate your greenhouse. This will keep your plants at a constant temperature and protected from the cold.
• Life Expectancy – PC film is the longest-lasting alternative to glass.

Cons of Using Polycarbonate Film:

• Not Readily Available – For the most part, you will have to custom order your PC film as most retailers do not carry it.
• Expensive – It is on the pricier side, averaging $55 per 8×4 feet, but it is worth the cost for those living in a less than ideal location for their plant needs.

Typically, polycarbonate film lasts for fifteen years, depending on the environment.

Create the Floor

As tempting as it may be to leave the grass on your lawn as the floor for your greenhouse, this isn’t advised. Not only will your greenhouse be the perfect growing conditions for your plants, but it will also have the right environmental needs for weeds and possibly mold!

To prevent these from growing and any bugs from making your greenhouse their new home, it is highly recommended you do not use the ground as your floor.

Here is a list of possible options ranked from most to least effective:

1. Concrete – Concrete will be substantial enough for you to walk on without damaging any plants that may be growing.
   1. Pros: Sturdy, can be poured with a gentle slope to help direct the water away from the structure to the ground outside, will stop weeds.
   2. Cons: Large commitment even after the greenhouse is gone, extra labor, can dry unevenly, isn’t the most attractive.
2. Bricks and Stones – If concrete seems like too much of a commitment, the second-best option would be to use bricks and stones for the floor of the greenhouse.
   1. Pros: Drains well, increases the humidity levels inside the greenhouse, and can create a molding pattern.
   2. Cons: Difficult to work with, expensive (depending on which stones you purchase), won’t lay even.
3. Mulch or Weed Pad – Mulch or a weed pad (patch of faux grass that stops weeds from growing) can be a great alternative to concrete flooring.
   1. Pros: Inexpensive, easy to work with, can add to the look of the greenhouse.
   2. Cons: Needs to be replaced, can attract bugs, need shoes to walk inside the greenhouse.

Here’s a helpful video explaining greenhouse bases, and showing the construction of a 6X8 base using concrete and bricks.

Gather Materials

Now that you know the structure of the greenhouse and all the nuances needed for the planning, it is time to put together your list of required materials and head to the hardware store!

• Level – helps check to make sure the terrain is flat before building
• Building material (such as PVC piping, metal, etc.) – the greenhouse will need a bare-bone structure (also called a “skeleton”) to be encapsulated by the cover
• Cover – can be fiberglass, glass, polycarbonate, polyethylene, or any other material of your choosing
• PVC pipes – these will be used to create the arch and support system for the greenhouse cover
• Saw – needed to cut wood, PVC pipes, etc.
• Staple gun – if using lightweight material and a wooden structure, it is an excellent alternative to wood glue
• Clamps – the best ones to invest in for this project are any clamps that can be tension modified
• Flooring materials – if you are using concrete, mulch, bricks, or any other material, be sure to have 1.5x enough to cover the area of the floor

Build the Structure

The following guide was created for building a simple hoop based greenhouse. It focuses on a detached greenhouse, but the steps can be used for all types of greenhouses!

Although this guide lacks specific measurements, this is done on purpose so that you can insert your own building needs into each step.

1. Flatten the ground: You will want to have a completely flat base to build on as any uneven ground could interrupt the water flow and cause rot or severe damage.
2. Build the floor frame: Start by creating a square outline that will border the flattened ground.
   • For lean-to structures: You will need to create the square outline off the back wall of your house. In other words, you will be creating a “U” border.
3. Create the hoops: Hoops are half-circles designed to support the covering material. These can be made with PVC piping (1/2” width minimum) that is folded over into an arch and runs from one sidewall to the opposing one.
4. Create the door frame: This can be as simple as putting two pieces of wood vertically next to one another with one horizontal piece connecting them.
   • For added support, create a T-support (looks like a small triangle that you place at the connecting corner of the floor and vertical support) and attach it to the door frame on both sides.
   • For Gutter Connected structures: Replace the door frame with another supporting wall as you won’t have a door.
5. Add support beams: These can be made by placing a large 2×4 across the top of the interior of the structure from the door to the end wall and by placing 2x4s from the floor to the top of the vertical door supports creating a 90-degree angle.
6. Create shelves: Although this step is optional, you can place 2×12 boards on the outside of the hoop arch connecting to the additional support beams in a rectangular fashion.
7. Make the floor: If you are adding a concrete, brick, mulch, or any other form of floor other than the dirt naturally below, now is the time to do that!
   • Remember: If you are using concrete, try to create a water flow that will take excess water away from the greenhouse.
8. Add the cover: Trying to keep the covering material as smooth as possible. Adhere the cover to the hoops with either glue or another adhesive material. The adhesive material you use will depend mainly on the cover material you have chosen.
9. Bring in your plants: Once the main structure is complete, all that is left is to start bringing in potted plants and decorating the greenhouse how you see fit!

And then you are done! There will be more steps involved depending on the size of the greenhouse you would like to build. However, these are the steps to create the main part of any greenhouse – large or small!

Here’s a helpful video of someone actually building a similar greenhouse to show you what the build would look like.

If you don’t feel comfortable building the actual structure yourself, consider a pre-built greenhouse kit like this Walk In Greenhouse Tunnel Tent from Amazon. You will still need to plan the location, flatten the ground, build the floor, and set up shelves the way you want them. But this can be quick way to avoid most of the building process.

If you still want a built structure, but are uncomfortable doing it yourself. I suggest using HomeAdvisor Outbuildings & Structures to find a local professional that can help you out.

Add-Ons

One final aspect of building a greenhouse you should consider is additional machinery that runs to the greenhouse, or “add-ons.” Add-ons can range from box fans in the windows to full plumbing capabilities.

Not every greenhouse will need add-ons. This is mostly personal preference.

Some greenhouses can function without a box fan because of their location in mild weather, while other greenhouses may need the addition of a humidifier if they are in an area that has drier air.

Each greenhouse build will have to address the needs of the nursery inside and cannot be summed up as a master list of add-ons necessary for every greenhouse.

However, there is a list of common conditions and possible add-ons that can accommodate these needs.

1. Dry air: If you live in a climate with dry air (such as Arizona, Nevada, or Maine), consider purchasing a humidifier for your greenhouse.
2. High humidity: If you live in a climate with high humidity (such as Florida, Mississippi, or Georgia), consider installing multiple windows or box fans into your greenhouse.
3. Late-night gardening: If your schedule keeps you from tending to your garden until wee hours into the night, consider adding battery operated lights such as fairy lights.
4. Heavy snow: If you live somewhere with lots of snow, consider adding a heater to your greenhouse to help keep your plants warm and melt the snow

In Conclusion

Greenhouses can be a fantastic way to spruce up your backyard and add value to your home both inside and out and allow you to enjoy fresh veggies! The real beauty of greenhouses is their simplistic design and full customization options to accommodate what your plants need.

The main factors to remember from this guide when building your greenhouse is: try not to use wood, you can never have enough support beams, size really does matter, and always accommodate for the extra humidity!

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