Introduction
A greenhouse is a structure made primarily of glass or other transparent material that allows sunlight in to create a controlled environment suitable for growing plants. Greenhouses come in all shapes and sizes, from small DIY kits to large commercial operations. Building your own greenhouse can provide many benefits:
- Extend your growing season. Greenhouses allow you to start seedlings earlier in spring and grow plants later into fall compared to an outdoor garden. The protected environment shields plants from frost and cold temperatures.
- Grow heat-loving plants. The warmer greenhouse temperatures allow you to grow plants that need more heat like tomatoes, peppers, and herbs.
- Control growing conditions. Factors like temperature, humidity, ventilation, irrigation, and fertilization can be regulated in a greenhouse to optimize plant health and growth.
- Protect plants from pests. Keeping plants isolated in a greenhouse prevents damage from deer, rabbits, insects, diseases, and other garden pests.
Building a greenhouse requires some basic tools like a saw, drill, shovel, and tape measure. The main materials are the greenhouse frame (typically wood or PVC pipe) and the glazing or covering material (glass, plastic sheeting, polycarbonate panels, etc.). Basic construction skills like measuring, cutting, leveling, and assembling the frame are needed. Critical steps include preparing the site, building the foundation, installing glazing, setting up ventilation and temperature control systems, and arranging utilities like electricity and water.
This guide will walk through the key steps involved in building a greenhouse from start to finish. With proper planning and preparation, you can have your own greenhouse up and growing in no time! The process includes choosing a location, determining the size, selecting a design, obtaining permits, preparing the site, building the foundation and frame, installing glazing and ventilation, and finishing touches. Let's explore each step in more detail.
Choose a Location
When selecting where to build your greenhouse, there are several factors to consider:
- Sunlight - Greenhouses require a lot of direct sunlight, ideally 6-8 hours per day. Choose a south-facing location that receives sunlight throughout the day and isn't shaded by trees or buildings.
- Utilities - Think about how you'll provide electricity, water, and gas (if needed) to the greenhouse. Having utility hookups nearby will make setup easier.
- Drainage - Good drainage is crucial so water doesn't pool around the foundation. Select a site on high ground that naturally slopes to divert water away.
- Access - Pick a spot that's convenient to access from your home or garden. You'll want to be able to easily tend to plants in the greenhouse.
- Local Regulations - Check with your local zoning office regarding any restrictions, permits, or codes for building a greenhouse on your property. Many neighborhoods have rules about outbuildings.
- Security - It's smart to build your greenhouse in a place that you can keep an eye on from your home. Also consider proximity to fences or installing security features.
Take your time surveying potential sites on your property to select the right greenhouse location. This crucial first step will ensure your greenhouse has the sunlight, drainage, and convenience needed to thrive.
Determine the Size
When determining the size of your greenhouse, there are several factors to consider:
- Space available: Measure the amount of space you have in your yard or on your property for a greenhouse. Consider existing structures, trees, and utilities that may impact placement. Optimal sun exposure is also key.
- Plants to be grown: The types of plants you want to grow will impact the size. For starter plants, smaller benches suffice. For mature plants, allow for taller growing heights. Fruiting plants like tomatoes need more space than leafy greens.
- Budget: Greenhouse costs correlate closely with size. Compare material and construction estimates for different dimensions to find the most affordable option. Generally 12x8 is a practical small size, 12x16 medium, and over 16x20 for larger.
- Energy efficiency: Larger spaces are harder to keep heated and cooled. Glazing material, insulation, and ventilation systems also impact efficiency. Factor in your climate and supplemental temperature control needed.
- Permanent vs temporary: A permanent greenhouse can maximize the footprint and height. A temporary hoop house will require enough height inside for you and plants.
- Planned usage: Will your greenhouse be just for starting seeds and small plants? Or do you want space for growing beds, potting benches, storage shelves? How much head room and work space is needed?
Consider your specific needs in these areas as you determine the optimal balance of space, affordability and functionality for your greenhouse project. An experienced greenhouse supplier can also provide guidance on size options.
Select a Design
When selecting a design for your greenhouse, you have a few main options to consider:
Freestanding
A freestanding greenhouse is completely detached from your home or other structures. This allows you to build the greenhouse to any size or specifications you'd like. Freestanding greenhouses work well if you have enough outdoor space and want a large growing area. They allow light to enter from all sides and offer maximum flexibility with the design. Consider placement carefully to utilize passive solar heating.
Lean-To
Lean-to greenhouses are built against an existing building, like a home, garage, or shed. One wall of the greenhouse uses the existing structure while the other walls are newly built. This style saves space and building materials. It also allows convenient access to the greenhouse from inside the home. The attached wall provides some insulation. However, light is limited to the front and sides.
Window Mount
Window mount greenhouses are installed directly into a window opening. This is the smallest and simplest option. The frame fits into the window like an air conditioning unit. Window mount greenhouses allow easy access and good light while taking up minimal space. However, the size is very limited, so only small plants or seed starting trays may be accommodated.
Consider the size of plants you want to grow, the amount of space available, your budget, and access needs when deciding on a freestanding, lean-to, or window mount greenhouse design.
Obtain Building Permits
Before starting construction on your greenhouse, it's important to check whether you need any permits or approvals from your local municipality. Building codes and zoning regulations can vary significantly depending on where you live, so do your homework to avoid any issues down the line.
Research your local county or city building department to learn about requirements for constructing an accessory building like a greenhouse. Some key questions to investigate:
- Is a building permit required for a greenhouse of your planned size and specifications? Many areas require permits for structures over 100-200 square feet.
- Are there setback or height limitations for accessory buildings in your zoning district? Most residential areas dictate how close and tall detached structures can be.
- Do you need approval from a homeowners association or historic commission? If you live in a development with an HOA, they may want to review plans.
- Are there any special stormwater management requirements? Some municipalities regulate impervious surfaces.
It's better to find out about any needed permits early on rather than be forced to makes changes later. Being transparent with your plans also builds goodwill with local officials in case any issues arise during construction.
If permits are required, submit your greenhouse plans and application materials as early as possible. The review process can take weeks or even months. It's recommended to get permits approved before purchasing any building supplies.
With the proper permits in place, you'll have the green light to start building your greenhouse with confidence it meets legal requirements. Taking the time for due diligence now makes the actual construction process go much smoother.
Prepare the Site
Before beginning construction, you'll need to prepare the site where you plan to build the greenhouse. Proper site preparation is crucial for ensuring your greenhouse has a solid foundation and good drainage.
The first step is to make sure the ground is as level as possible. Using a shovel, rake, and leveling tools, remove any humps or dips in the area. Get rid of large rocks, roots, grass, and weeds. Pack down the soil and use a tamper to compress it. You want roughly 2-3 inches of packed soil as your base.
Next, address drainage. Good drainage will prevent water from pooling around your greenhouse, which can lead to flooding, moisture damage, and foundation issues. Install drainage pipes or trenches around the perimeter to divert rain and excess water away from the greenhouse. Dig trenches at least 12 inches deep and fill with gravel, then place 4-6 inch drainage pipes on top leading to a lower elevation.
You may also consider raising the site by bringing in extra topsoil. This will lift the greenhouse above the surrounding terrain and improve drainage. Mound the soil 2-3 inches above ground level across the entire footprint. Slope the ground away from the greenhouse in all directions so water flows away.
Finally, cover the site with landscape fabric to suppress weeds and vegetation. The fabric will keep the area clean and stable as you construct the greenhouse foundation and framework on top. Secure the edges with stakes or stones.
Now your greenhouse site should have compact, level ground and proper drainage or elevation to prevent water issues. With the site prepared, you're ready to start building.
Build the Foundation
The foundation is a critical part of building a greenhouse for several reasons. First, it needs to be strong and stable enough to support the weight of the structure. Second, it must be level to ensure the walls and roof align properly. And third, it helps prevent frost heaves during winter which can shift and damage the building.
The best material for greenhouse foundations is concrete. Concrete offers strength, durability, and stability unmatched by other building materials. To build a concrete foundation, first excavate the soil to the desired depth, generally 12-18 inches deep. Then install perimeter forms made of wood or metal around the edges.
Next, install steel rebar grid inside the form cavity for reinforcement. The rebar grid should have 6 inch spacing. Then pour the concrete into the forms up to ground level and let cure completely, which usually takes 5-7 days.
A gravel base can also be used for the foundation. Lay down landscape fabric, then a 4-6 inch layer of compacted gravel. This allows for drainage under the greenhouse floor. Pavers or poured footings can be used under structural posts for extra support if needed.
Take time to build a proper foundation, as it's challenging to fix foundation issues once the greenhouse structure is completed. A well-constructed foundation maximizes stability and prevents many problems down the road.
Construct the Frame
The frame is what gives the greenhouse its shape and structure. There are a few main options when it comes to choosing a frame material:
Wood
Wood, typically cedar or redwood, is a traditional and attractive choice for a greenhouse frame. Wood can last for decades if properly maintained. Use lumber that is at least 2x4 thickness for durability. A wood frame will need to be sealed and painted periodically to protect it from rot and pests. Wood offers a classic look, but requires the most ongoing maintenance of the framing options.
PVC
PVC pipe has become a popular DIY greenhouse framing option. The pipes connect together easily with fittings and require no special tools. PVC is naturally resistant to rot and insects. It holds up well in a greenhouse environment. PVC framing can be customized into a variety of shapes and sizes. It is also paintable if desired. PVC is affordable, low maintenance, and can last over a decade when UV protected.
Metal
Using a metal frame made of galvanized steel, aluminum, or iron is a durable choice that will hold up for decades. Metal framing requires fewer ongoing repairs than wood. It will not rot or be damaged by pests. Look for powder coated metal for maximum UV resistance and corrosion protection. Metal can be painted as well. Professional installation is recommended for complex metal greenhouse frames. Metal offers strength and longevity but is generally the most expensive framing option.
The frame material determines the greenhouse's longevity, appearance, and cost. Consider wood for a classic look, PVC for ease of DIY construction, or metal for unmatched structural durability when constructing the frame. Make sure to check on snow load requirements for your area before finalizing a frame choice.
Add Glazing
Glazing is an important part of any greenhouse as it lets in the sunlight needed for plants to grow. There are a few options when it comes to glazing material:
- Glass - Glass is a traditional glazing choice for greenhouses. It provides excellent durability and maintains heat well. Tempered glass is a good option as it is stronger and more impact resistant. Double pane glass can also help improve insulation. The downside is that glass is heavy and can be dangerous if broken.
- Plastic Sheeting - Plastic sheeting like polyethylene film is lightweight, easy to install, and inexpensive. It's available in a variety of thicknesses and can be replaced as needed. However, plastic can degrade over time, especially in direct sunlight. Look for UV-protected and infrared blocking plastic for longevity.
- Rigid Plastic Panels - Rigid plastic panels made of polycarbonate or acrylic are extremely durable and lightweight. They provide great insulation and diffused light transmission. Rigid plastic is usually more expensive than plastic sheeting but will last much longer. Look for UV-protected, triple-wall polycarbonate panels for greenhouses.
- Fiberglass - Fiberglass panels are lightweight, strong, and durable. They allow lots of light transmission. Fiberglass insulates moderately well but not as much as polycarbonate. The glazing can become brittle over time. Fiberglass is a good option for small hobby greenhouses.
When selecting glazing material, consider insulation value, light transmission, longevity, and budget. Properly installing the glazing according to manufacturer specifications will help ensure it withstands weather and lasts. High quality greenhouse glazing improves temperature regulation and light for plants.
Install Ventilation
Proper ventilation is critical for a greenhouse to function well. Greenhouses need good air circulation to regulate temperature, control humidity, replenish carbon dioxide, and prevent the buildup of ethylene gas from plants. There are two main types of ventilation systems used in greenhouses:
Passive ventilation relies on natural airflow through vent windows, roof vents, side vents, and roll-up walls. Passive ventilation is the simplest and most cost-effective option. Vents should be installed on both upper and lower parts of the greenhouse to allow warm air to escape through the tops and draw cooler air in through the bottoms. Automated vent openers can be added to open vents at set temperatures.
Active ventilation uses fans and vents controlled by a thermostat. Fans actively pull air through the greenhouse and exhaust it outside through vents. Roof ventilation systems work well for larger greenhouses over 1000 sq ft. Small greenhouses may only need circulating fans for airflow. Active systems provide the most climate control but also require electricity.
Make sure to install enough total ventilation to exchange the greenhouse air at least once per minute. The ventilation system should be able to handle the hottest summer days when cooling is critical. Proper ventilation will create the ideal growing environment for your greenhouse plants.
For more DIY tips and tricks, DIYwithHelp have got you covered…
If you need some professional guidance for your project, be sure to sign up for a free account with DIYwithHelp.com. Once you have an account, you can search our site (or fill out a project request form) and connect with expert tradespeople who are willing to lend their advice over scheduled video-calls.
