Gravel, if you do not have access to a small truck, can be an expensive business. It pays to have friends with old trucks; however, I do not and so, I purchased the gravel I needed to level my building site in 30 kg bags trucked from Laval, Quebec. So much for “Buy Locally.” Six bags of ¾” and 6 bags of ¼” at about $6.60 per bag were delivered with my purchased lumber order by my semi-local, rurally-located building supplier. I “trucked” 6 of the bags 30 highway minutes in my car, as I had underestimated the gravel need.
I had staked out a 9’ perimeter using some old slats from my storage shed. Those were quickly flattened as the gravel and then the patio stones became mobile. Not a great photo. Those patio stones have been on and off the piles of gravel more than a few time as I worked on the leveling of the site.
Using my “tools of ignorance,” I spread the gravel to level my building site, and topped it with 22” patio stones. I used an 8’ piece of straight lumber and my level to make the gravel level. Starting with the high corner, located at the front of the greenhouse, I laid down 4” of ¾ ” gravel and topped it with about 2” of ¼ “ gravel.
I borrowed a friend’s dolly which was a real help moving the 30 kg bags of gravel and the even heavier patio stones. I might have been able to use smaller patio stones; however, the 22” stones gave me a bit more “play-space” for the base of the greenhouse.
I then leveled the second front corner and proceeded to the back corners. I have to admit that it is not perfectly level; however, it isn’t out by much, according to the level. Hopefully these are not “famous last words!” We’ll see.
I used Wolmanized/pressure treated lumber for the base of the greenhouse. 2 – 4” x 4” skids and 9 – 2” x 6” pieces to form the base. You’ll likely need pliers, as I did, to remove staples prior to use.
Wear gloves and if you are cutting Wolmanized/pressure treated lumber, wear a mask! Regardless, be sure to wash your hands frequently and prior to handling other materials in your home. Pressure treated lumber extends the life of wood exposed to the elements and to insects and fungus. The upside is that the wood will last longer and therefore potentially less lumber is harvested. The chemicals used to preserve the wood have changed over time; however, you do not want to have the chemicals on your hands, in your lungs, or the leftover scraps in your fireplace. Check out this link for a quick overview of the hazards and benefits of pressure treated lumber: http://en.wikipedia.org/wiki/Wood_preservation – retrieved June 10, 2014.
Use a pencil, ruler, and straight-edge to mark where the joists are to attach to the front and back boards that will form the platform (floor and base) of the greenhouse. Joists are spaced 16″ apart as measured from the centre of the joist. To do this calculation, measure 1.5″ in from the end of the front and back boards. 1 1/2″ is the actual width of a 2″ piece of lumber. Draw the line. Then continue to mark 16″ measures. Each line represents the edge of the board. The “X” that you see represents where the lumber joist will actually sit. In the end, the “X” is covered by the lumber that you will nail or screw to the front and back boards. Place the joists with the crowns up. See here for information on identifying the crown: http://www.gardenstructure.com/crown
I used 3 – 3” Robertson screws for each joist spaced 16” on centre to form an 8’ x 8’ base. Start by screwing the top screw, followed by the bottom and then the middle screw. Work your way down the front board, connecting the joists. Then do the same to attach the joists to the back board.