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south end up
Tuesday, May 22 2012
This morning I attached the struts made from half-inch black iron pipe to the greenhouse's new northern wall so it would stay near-vertical during the next phase of roof jacking. These struts were terminated at either end with 45 degree fittings and flanges so they could form 45 degree braces. Still, I wasn't complete sure those struts would be able to fight the wall-toppling pull of the roof once it was detached at its south end, so I also installed a single two by four brace on the west side. Then, what the hell, I unhinged the roof's south end so that it was only hanging from hinges from the top of the new north wall. Nothing seemed to give once released, so I felt it was okay to begin jacking up the roof from its south side. I used the same technique as I'd used on the north side, but since the south side had started out 23 inches higher, I had to resort to support poles immediately, and I had to cut myself two additional sets of support poles along the way, the first set being 53 inches each and the second set being 76 inches each. Meanwhile the pyramid upon which the bottle jack sat grew to so tall and unstable that I had to carefully restack it several times. Finally I gave up on putting a jack on such a precarious foundation, so I rebuilt a lower pyramid and raised the roof the rest of the way by jacking a pole with an automotive scissor jack (I have three functional auto jacks unconnected to any car, and they all use different mechanisms). In the end I was able to raise the south end of the roof about 63 inches, or 3.5 inches further than the 59.5 inches I'd jacked the north side (remember, I'd first jacked the north side up nearly an inch so I could install a subfloor, and there is no subfloor over the south side).
By the time the roof was very nearly in position, day had given over to dusk, so I quickly installed a new girder to support whatever glass-heavy solution that will comprise the new south wall. Since the downstairs of the greenhouse encroaches into the upstairs a bit along the south side, there had already been a 23-inch-high wall along the south side, and I needed to cap this with a solid bit of structure, in this case a girder. This girder consisted of a two by nine attached to solid foundations at the greenhouse's east and west sides (though mostly unattached to the existing 23 inch wall running between them). Flat along the top of this two by nine, I attached a wide two-by-eleven plank, part of whose width cantilevered out over the rest of the greenhouse below. Eventually this plank will serve as something of a window bench (as well as part of the rough opening for the south-facing windows to come).
Fearing the night might bring thunderstorms (and a potential for wind), I hastily cut 58.5 inch four by fours to make posts for to support the south roof girder at its east and west ends. Using some metal decking hardware (similar to joist hangers), I managed to attach the poles with screws at both ends. Though the structure was still pretty badly out of square (and I was leaving the jack in place for additional support), it seemed likely to survive the winds of a reasonable thunderstorm.
Viewing the jacked-up roof from the east, you can see the black pipe diagonal supports.
Soon after I began jacking the south side of the roof, viewed from the south.
The east end is a noticeably higher than the west! You can see the concrete-block-and firewood pyramid in the middle.
I've transitioned to a lower pyramid and a scissor jack.
Now the end columns and girder are visible.
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