How to build a Greenhouse
|Page Contents 1: Introduction, Description, Position 2: Sizes, Angles, What you will need3: Making the base||6: Erecting the side walls and roof 7: Making the end walls and doors8: Making the window, The cover
Appendix 60° and 30° Angle patterns
This is a revised and updated version of the ‘How to build a Greenhouse’ project. The old version can be seen at http://www.buildeazy.com/greenhouse_imp.html
In this version, the greenhouse frame is constructed mainly out of 2″x4″ (100mm x 50mm) which is a more common stock (in North America, anyway) than the 2″x3″ (75mm x 50mm) called for in the original version. We will talk more about lumber sizes a bit further down the page.
Other modifications include a wider door to allow for a wheelbarrow if need be, and a bit more inside height. See, we do listen to feedback.
To view some photos of greenhouses sent into us by people who have used the plans go to http://www.buildeazy.com/greenhouse5-10.html. Photos of other peoples handiwork are a good source of help and inspiration.
This greenhouse consists of a lumber frame suitable for a cover such as a clear UV-resistant polythene film. It is 8ft (2400mm) wide by 10ft (3000mm) and stands 8′ 6″ (2550mm) off the ground at the highest point.
There are two opening windows that span along the very top of the greenhouse and a door at either end (optional).
The greenhouse basically sits on the ground and is held in place by a few stakes around the bottom that are hammered into the ground and nailed to sides of the base. It could be fixed more permanently if required without too much ado, and would probably need to be, if positioned anywhere other than a sheltered area.
It is ideal for areas that have just enough winter frosts to be annoying.
Where to place the greenhouse.
Choose a place likely to get the winter sun. The greenhouse should not be placed in a potential boggy area without drainage.
If the site is a low lying area, then it might be necessary to put in a drain (open, tile or metal) to re-direct any water flow away from the greenhouse site.
Wood sizes and measurements
This projects is in both imperial (inches) and metric (mm).
All measurements are given in inches first followed by millimeters (mm) in brackets ().
The size of the framing lumber referred to in his project is the actual size, which is the size of the lumber after it has been dressed (smooth, planed, finished). When the lumber is dressed, the actual size is then less than the nominal size. For example: 2″x4″ (100mm x 50mm) when dressed may be 1 1/2″x 3 1/2″ (90mm x 45mm) actual size. The actual sizes can vary slightly from place to place.
Note: The imperial sizes are not an exact match to the equivalent metric sizes. A structure built using the imperial measurements (ft and in) will be approximately 1.6% larger than the same structure built using the metric (mm) measurements. The imperial measurements are more suited to North America. The metric measurements are more suited to Australasia.
About the angle cuts
There are two different angle cuts (off square) required for this project. One is 30 degrees off square, the other is 60 degrees off square.
To cut the 30 degree angle, simply set the blade on your miter saw to the required angle. The 60 degree angle will have to be cut with a circular saw, as miter saws will not do such a cut.
There is a 30 degree and a 60 degree angle pattern in appendix http://www.buildeazy.com/greenhouse5-9.html
You will need
Around 330ft (100 meters) of 1 1/2″x 3 1/2″ (90mm x 45mm) treated, or natural decay-resistant lumber for the frame. Some will need to br ripped down for parts of the windows and doors.
36ft (11 meters) of 4″ x 4′ (100mm x 100mm) treated for the base. (sawn lumber will do)
10ft (3 meters) 3/4″x 7 1/2″ (190mm x 19mm) treated board for the fascia.I sheet of 4ft x 8ft x 3/8″ (1200mm x 2400mm x 10mm) treated plywood for the gussets
350sq ft (30sq m) ultra-violet-resistant polythene for the covering
You will also need miscellaneous such as nails, galvanized plates, strapping, hinges, handles, latches etc.
Step 1. The greenhouse base
Use 4″x4″ treated, or natural decay-resistant, sawn lumber to make the base.
Make a rectangle 8ft” x 10ft” (2400mm x 3000mm) as shown in the drawing above. Fix the lumber together in the corners by using galvanized nails and nail plates.
Before you site (position) the base, make sure the ground where the base will rest is level and firm.
Use a level or a water level to check the grade, and dig accordingly to level the ground directly beneath where the lumber will be sitting.
Go to www.buildeazy.com/fp_waterlevel.html for an article on ‘how to make and use an inexpensive water level’.
Check that the two diagonal measurements are equal. If they are not, make any necessary adjustments. When the diagonals are equal, then the base is square.
Secure the base in place by driving stakes into the ground around the perimeter. Nail the stakes to the base and cut flush any stakes protruding higher than the base lumber.
Step 2. The side wall-frames
Construct all the framing out of 1 1/2″x 3 1/2″ (90mm x 45mm) treated, or natural decay-resistant lumber.
On a flat surface, make up the two side wall frames to the dimensions shown in the above drawing.
Make the diagonal measurements equal (in the same way as with the base in Step 1), and when the frame is square, cut and fix the bracing members in place. (See above drawing.)
Step 3. The roof frame sections
Make up five roof sections that span from side-wall to side-wall. Refer to the plans and instructions below.
Cut all roof frame pieces to the dimensions given above. Use 1 1/2″x 3 1/2″ (90mm x 45mm) treated, or natural decay-resistant lumber.
In all, cut 5 long rafters @ 73-3/8″ (1835mm), 5 short rafters @ 53-5/8″ (1340mm) and 5 rafter uprights @ 11 3/8″ (285mm) all with end angle cuts as shown in the plan drawing.
Also cut five triangular gussets (equilateral triangles) from a sheet of 3/8″ (10mm) treated plywood, with all three sides being 20″ (500mm) long.
On a flat piece of ground, make up the five roof sections to the pattern and dimensions as shown in above drawing. Ensure the two furthest points are 8ft” (2400mm) apart and then nail the triangular gussets in place with galvanized flathead nails spaced every 2″ (50mm) apart, one gusset to each roof section.
Step 4. Erect the side walls and roof sections
Stand the two side walls upright on the base boards and support them with temporarily props. Fix the bottom plate of the side walls to the base with galvanized nails.
Lift the 5 roof sections in place on top of the side walls. First position a roof section at each end of the side walls, and then position the other three evenly spaced in between. Fix the roof frames to the side wall top plate with galvanized nails.
Temporarily prop the two end roof sections plumb (vertical).
Fix the 1 1/2″x 3 1/2″ (90mm x 45mm) window support plate against the top of the rafter uprights. (See drawing 4c.)
Nail the 3/4″x7 1/2″ (190mmx19mm) fascia board to the top ends of the long rafters as shown in the drawing, making sure all the roof sections are vertical and parallel with each other. Tuck some galvanized metal window flashing under and behind the fascia board prior to nailing the bottom of the board.
Brace the roof on the side that has no windows with two metal straps running diagonally across the top plane. Nail the straps at the ends and wherever they cross a rafter.
Step 5. The end wall frames
This is pretty much measure, cut, and fix as you go. Before you start, ensure the side walls are plumb (vertical).
For all wall framing lumber, use 1 1/2″x 3 1/2″ (90mm x 45mm) treated, or natural decay-resistant lumber.
Cut the door studs to size and fix in place. They should be 36 3/4″ (920mm) apart to allow for the door.
Cut the door head to size and fix in place. It should be 72 3/4″ (1820mm) above the base to allow for the door
Cut the top plates to size and fix them in place.
Cut the bottom plates to size and fix them in place.
Measure, cut and fix the bracing members.
Step 6. The doors
Step 7. The windows
For the windows use 1 1/2″ x 1 1/2″ (45mm x 45mm) treated or natural decay-resistant lumber for the top and bottom horizontal rails and 1 1/2″ x 3 1/2″ (90mm x 45mm) for the side styles and middle mullions.
Angle cut the bottom of the window frame 30 degrees (the same pitch as the roof).
Make two windows as per dimensions above. Fix them in place with two butt hinges on each window screwed to the top rails of the windows and the window support plate.
Fit a window latch to each window.
Measure, cut and fix a row of blocking below the windows and in between the roof frames as shown on the above drawing.
Step 8. The greenhouse cover
Cover the greenhouse with a UV-resistant polythene (there are other options also).
Hold the covering in place by laying thin battens (strips of wood) over the polythene (ensuring the polythene is taut) and nailing the battens to the greenhouse studs, roof rafters or any other solid member. Cover the doors and windows also.
Most hardware merchants or garden suppliers only stock the standard plastic polythene that is not UV resistant but they should be able to advise you where to get the polythene required for the greenhouse covering.
One source that might be worth looking at for cover (USA) is Tyco Plastics http://www.tycoplastics.com/. There are also other options such as acrylic sheet.
A 30° angle pattern and a 60° angle pattern
User photos – Other peoples handiwork
Below are some greenhouse photos sent to us from people who have used these plans to build their greenhouse. To see comments by the people that sent in the pictures below, go to User Photos/Comments http://www.buildeazy.com/greenhouse5-1.html#comments
User Photos/Comments about this project
Thank you for the wonderful greenhouse plan! Since I live in the northern states, I stepped it up and insulated the base and used twin wall polycarbonate for the windows. This should extend my growing season for all but the two coldest months. I also extended the length to twelve feet, but left the width at 8 feet. I extended the rafter tails so I can add eaves to collect rain water. There is a double window on the end opposite the door for ventilation. I appreciate your site. Thank you so much. Amber Christenson Strandburg, SD