Decide where you want to build your greenhouse. Choose a location that will provide your greenhouse with a lot of sunlight. Attaching your greenhouse to your house is the best choice if you have limited backyard space, and also makes for easy accessibility and convenient for connecting water and power.
Think about the climate in the area when choosing a design. If there is heavy snowfall, make sure to choose a slanted roof instead of a flat roof. An insulated greenhouse, as well as a heating and ventilation system, is also appropriate for the cold Alaskan climate.
Choose the materials you want to use. Use glass or fiberglass covering, rather than plastic, to allow for more humidity and warmth in your greenhouse. For the roof, you can use waterproof and lightweight aluminum or steel, or a weather-resistant wood.
To build the greenhouse base, use timber to layout a square or rectangle and secure the edges with galvanized nails and nail plates. A recommended dimension is eight feet by ten feet. Use a level to make sure all the sides are even, and a square is constructed when the diagonals are equal. Secure the base by hammering the perimeter with pegs.
Make the framing with timber, with the recommended dimensions ten feet by four and a half feet. Secure the side walls to the bottom frame using galvanized nails.
For the roof frame, cut five rafters at the recommended length of six feet, five rafters at four feet and five uprights with a length of one foot, all with angled-cut ends. Cut five triangular gussets from treated plywood, each side one and a half feet in length. Layout the roof frame on the ground and secure it with nails and nail plates, setting the short rafters against the long rafters and using the triangle gussets to cover the area where the rafters intersect. Lift the roof frame on top of the side frames and secure with nails and plates.
Use timber to build the end walls, using four and a half foot angled-cut timber to support the ends of the roof frame and a door with dimensions of six feet by two and a half feet. Hinges should be put on the door to allow it to open and close. Cover the greenhouse with UV-resistant plastic polythene and secure tightly by nailing the stretched plastic into the rafters.