Starting the Build
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A greenhouse structure for a home
The first significant savings came when we found a cactus nursery that was in the process of going out of business. We purchased one of their buildings for a paltry $1000. Sweetening the pot, it came with a 200,000 BTU propane heater.
Anchoring the support pipes
We traded the propane heater that came with the greenhouse to a local rancher for use of his rock drill and hired hands to put the support pipes in for us. Free is not a four letter word....Well, it is, but not in the usual way.
Leveling the support pipes
Using a cheap laser level at dusk, we marked the corner poles with a magic marker. Stretching a chalk line between the corners along each side, we measured the distance to the top of each pole. In these buildings, since the roof panels are corrugated the wrong way, we have to adjust the height of the poles to create a 1" in 12' slope end to end to allow water to run off the end rather than to the sides. Once calculation was finished, we measured up from the marks on the high end poles to the highest point at which all the poles would bypass the chalk line on both sides of the building using the same measurements. At the low end corner poles an inch for every 12 feet of the building's length has to be subtracted to accomodate the runoff slope.
Beginning of the ends
Standing the 4x4's on end and using a long level to set plumb, we marked where the top and bottom of the hoop crossed the 4x4 and the hoop on each side of the 4x4. Attaching to the sole plate was accomplished as shown using anchor plates. Building a foundation for the soleplate is covered in the barn section.
Attaching to the hoops
We cut the 4x4 off at the top mark following the general angle of the line with a 10" circular saw. Then created the notch at the top of the 4x4 can by setting a regular circular saw to the depth of the diameter of hoops and made a bunch of slots at 1/4" intervals. Using a tap hammer and chisel, we knocked out the the thin pieces left behind. Standing the 4x4 back up using the marks made on the hoop before, we used a wood to metal self drilling screw to attach to the hoop.
Metal roof without a goof
Putting a metal roof on one of these structures can be tricky. After the siding is on the building, we measured up each side of the two hoops at each end to find the actual center spot at the top. We snapped a chalk line across the tops of all the hoops, then went over those chalk marks with a felt tip marker. We set the first panel centered on those marks. The round roof required us to start at the top, and work our way down each side, using leftover wood scraps pushed between the previous panel and the hoops to hold the edge up so we could slide the next panel under it.
More on goofless metal roofing
Since we were doing this ourselves, we bought 17' long roof panels. The hoops of the greenhouse structure are set at 4' on center spacing, so we could hang 6" past the hoop at each end achieving a 12" overlap with the panels end to end. If you have enough helpers, and low wind conditions, it would be possible to use single panels that are roughly a foot longer than the length of the building. Butyl rubber tacky tape is used in the corrugation where the panels connect side to side, and three beads of 50 yr silicone rubber caulk between the laps.
Tying the roof to the siding
I special ordered pieces to fit into the corrugation and attach to the siding. I had them bend the edge the opposite way, so it creates a lip for drip edge where I can place gutters up inside the space created.
Hit the (floor) deck
Using my trusty laser level again, I swung and marked a point on all the support poles to measure from. Keeping in mind that I had to have enough height to allow for the correct slope of the drain pipes, I marked above that height using the same measurement at all my laser level marks to determine where to attach the first joists with wood to metal self-drilling screws. It makes a difference if the drain pipe will run along the joists or across them. We used 4" dia sewer drain pipe and 2" grey water drain pipe.
Hit the (floor) deck some more
After attaching the board(s) across the open space between the walls, with stantions to it at every six feet or less. We were careful about placement so that the stantions wouldn't interfere with attaching the joists and hangers. I used 4x4's notched out to fit the board, so it wasn't relying on lag bolts to hold it up. We got lucky in that the ground was fairly level going across the building, and a pressure treated 4x4 laid on its side fit almost perfectly to support the board and joists attached to it, at the garage end. We just shimmed underneath where it wasn't tight, and ran some screws through the joists into it.
Blocking the joists
Once all the joists were attached, we fitted boards between the joists. This blocking significantly stiffens the floor and also keeps the floor from creaking. We attached the blocking in a staggered pattern to allow driving nails straight through the joists into it. They should be spaced at least every 8'. Closer is better, but you have to keep in mind that you're going to have to get your plumbing under there yet, so you may have to stick it into the crawl space before hand, unless you're allowing for an access door from outside the structure, or your crawlspace is deep enough to allow you to angle a 10' long piece of PVC down in there.