Thursday, 4 October 2007

After many weeks of waiting, we finally got a workable concept for removing the second floor of the historic building. Friday we started to install the collar ties that will hold the roof together, then progressed to the scissors truss that will tie the roof and the building together. The first picture is what it looked like before Friday, the second picture is how it looks now. A couple of snags, but generally it went smoothly and quickly.

I tried to go all This Old House on the thing and get the trusses lined up perfectly. The roof sill of this building loses 3” from east to west on the north side, and 4 inches from east to west on the south side. The south side is higher than the north by about 4 inches. The southwest and northeast corners are nearly the same height. The northwest and southeast corners are nearly 7” different. There’s a great trick that you can use when working with a slope like this. Measure the distance between your high side and low side trusses, line them all up, secure them together, mark the total height gain on the high side truss, and run a line from the bottom low side truss to your mark on the high side truss. Cut that line to the depth of your sill, and you’ve leveled the roof sill truss by truss. Two problems with this roof in particular – the sill has hills and valleys along its run, and the total height loss was too much to accommodate for in the 2x8 lumber that we had to use. The old ceiling joists were also in the way, and couldn’t be taken down until we got the new trusses up. Total bitch. Anyhow, we got them all level where they meet the roof and the sill is all over the place. We will fur them out to be in one plane later. If you don’t get the furring perfect, then the ceiling ridge line will wander all over the place and look like hell.

The other issue we are having is with perched water. When water gets stuck below ground level and above the water table by an impermeable clay layer, it is called perched water. Basically, it’s a huge zit in the earth. A sinkhole. Because of the way the soils are striated and how high the water table is in Old Town, you get these. So despite our very elaborate and effective two depth, 9 head well system, we still have to resort to bucket pumps here and there.

After a couple of weeks of doing tie backs (which hold back the metal sheets around the perimeter of the hole) we are back to digging. It’s going well.

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