Sunday, December 30, 2007

Planning Early For The Roof

The house will have open ceilings, with a large ridge girder supporting the entire roof structure for the main part of the house. Of course this means that the walls that support each end of the ridge girder will have to be strong enough to support that weight.

At one end of the house the ridge girder is supported by an outside wall, which is concrete, so support isn't an issue. However, at the other end of the girder, the support will have to come from interior walls only, which are not made of concrete. In order for those interior walls to carry that weight, we need to go right down to the basement pad footings with a big column.

To build the column - which also supports one end of the main floor beam - I've started with two 2x10s with a 3/4" plywood spacer between them. That gives me a column that's 3 - 3/4" wide; the same width as the main floor beam. Then I added two more 2x10s to the outside of the column. (This gives me the equivalent of an 8x10 column that - according to lumber specs - will support 40,000 pounds.) This second pair of 2x10s extend up beside the main floor beam as well. This makes a nice saddle for the beam to sit in, and also gives me the large bearing area I need to continue with similar columns on the main and second floors. On the main and second floors, the columns will be part of the walls, so they won't be visible as stand-alone columns.

When I'm all done, the weight of one end of the ridge girder will basically be supported by one "virtual" column that goes all the way down to the pad footings in the basement.

On one side of the main floor beam I've also padded out the width of the beam with double layers of 3/4" plywood; so that I could attach the side-by-side joist hangers for the double joists required to support the wall above.

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