A Guide to Turning Your Shed Into a Greenhouse

Every gardener has dreamed of owning a greenhouse in the off-season when the seed catalogs arrive and planning begins. If you are itching to work your green thumb year-round, the warm temperatures, humidity, higher carbon dioxide, and reduced insect levels in a greenhouse create the perfect ecosystem for starting seedling indoors.

Trapping heat from the winter sun provides a safe environment to start plants early (January/February) and extend their production long after the summer growing season (November/December). Or, start a winter garden and harvest your own fresh vegetables during the holidays and crock pot season.

As a matter of fact, whether you already own a shed or plan to purchase a new one, converting this simple structure into a greenhouse is a real possibility with a little bit of knowledge.

Step 1. Location and Structure

When converting a shed into a greenhouse, one of the most critical parts is location. Make sure the location receives enough winter light (at least 6 hours per day) or plan to add grow lights. The greenhouse should be situated away from other buildings and deciduous trees so light accesses the plants from all four sides of the shed (three sides if the shed is positioned against another outbuilding). South or east-facing greenhouses will receive the most sun year-round.

If you are converting an existing shed already situated on your property, it may need to be moved if the location requirements aren’t met. If you are now pricing sheds to convert to a greenhouse, check local ordinances during the planning phase. Outbuildings may require a building permit by the town or county. Next, select the best growing location on your property and begin preparing the foundation and floor.

The size of your greenhouse will be dependent on your budget and available space on your property. Many seasoned gardeners recommend the largest greenhouse you can afford that will fit in your garden. This is because it's almost impossible to expand or enlarge an existing greenhouse than starting with a larger one.

A smart greenhouse will provide enough headroom to stand while you work and allow for tall and hanging plants. The floor area should include space for heating and airflow systems. Mockup the footprint, where you will install the plant tables or shelves and enough room to move around the shed, bend over, and transport plants.

If your shed already has wood walls, you may remove the entire wall or only the wall from the height of your workbench up. A wood exterior below the plant shelves creates shade for plants that can't take high heat or direct sun in the warm season. 

If your shed already has a floor, you'll want to remove it. Place the structure on cement footers or on a foundation with the center floor removed. The foundation or floor should allow for water drainage, as your greenhouse will get wet from watering the plants and retain much more humidity than it did as a shed. Pea gravel is a popular choice for flooring as it naturally allows water to drain and is less likely to encourage weeds. Metal grating, gravel, pavers, or flagstone also make a good greenhouse floor.

Step 2. Let the Light In

A wood-framed structure is acceptable, however, you’ll need to let light inside to create the greenhouse effect. The roof and walls can be replaced with any clear or transparent material that is heavy enough to withstand harsh weather conditions, and light enough that the structure can bear its weight. Generally, there are three directions greenhouse gardeners go when selecting glazing for the roof and walls.

Glass

Both clear and patterned glass is acceptable. If you use old windows as the glazing for your greenhouse, any existing hinges can be used to open the roof during hot months, naturally cooling the greenhouse. Single pane glass is heavier than plastic, yet breaks easily. That said, glass must be attached to your greenhouse with brackets to keep it from breaking as it expands and contracts with seasonal temperatures.

Plastic Films

Plastic sheeting appropriate for greenhouses includes polyethylene, copolímeto ethylene, vinyl acetate, and polyvinyl chloride plastics. They are easy to lift, cut, and fit to the frame of your greenhouse. Plastic films reflect the intense summer heat, and the frame of your structure can be a bit more flexible with sheeting. However, plastic films only withstand weathering for 2-4 years. 

Rigid Plastics

Polymethyl methacrylate (acrylic, acrylic glass, plexiglass), polycarbonate, and polyester are stiff plastics that work well on greenhouses. These materials are manufactured in sheets and are easier to cut than glass, but more difficult to maneuver than flexible plastic films. However, polycarbonate is almost as transparent and strong as glass. If you choose double or triple-wall polycarbonate, it can have an R-value (ability to insulate) up to three times that of glass. 

All in all, your best option depends on cost and the amount of insulation your greenhouse needs. Any transparent material can be used as long as it lets the light in, allows the air to circulate, and withstands heavy snow and wind. 

So, whether you are purchasing a shed or converting an existing shed into a greenhouse, selecting the right location and how to let light in are the first two considerations. 

If you’re in search of a garden shed to convert into a greenhouse, browse our selection at Country Cabins today.

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