Monday, February 27, 2012

Framing Adjustments

After the inspector visited and told me I could do what I wanted as long as I didn't mess with any of the structural members, I got to work.  The existing framing is a weird mishmash.  The real structural elements are 2x4 roof rafters at 24" o.c. spacing.  The span is about 11', so that's definitely undersized by modern code, and there are no collar ties attached to it.  All of the spreading load is resisted by the exterior wall, which is held together by the second story floor joists.  Stuffed in between those rafters is an interior subframe at 16" o.c., intended to support the lath and plaster.  None of it bears on the walls or goes to the crown of the roof, and it's got what looks like collar ties, except that they're barely toenailed on and can't resist any tension at all.  The kneewall studs are tacked to this framing instead of the actual rafters, so they're also not helping with the roof loads.  There's a lot of wood in here, but most of it isn't really doing anything.

That said, the house turned 100 last year and the roof looks flatter and straighter than many much newer houses.  The old wood is mostly really nice old-growth Douglas Fir, and the 2x4's are bigger than modern materials.  It is nearly 2" thick, some of it with saw marks from the mill, and the growth rings are 1/16" or less.  I'm saving some scraps to use for drawer fronts and other furniture parts, because it's beautiful and you just can't get material like this any more.

I started by removing the extra wood that was there to support the lath and plaster.  Then I  beefed up the structure with additional framing in key spots, metal framing connectors and more nails.  The kneewall studs all got moved over under the structural rafters, and I'm installing new collar ties / ceiling joists, which will be properly face-nailed to the sides of the rafters.  I also put headers over the closet doors, so all of the rafters now have a secondary load path down to the floor.  Never mind that there's nothing under the floor joists there...

Finally, I'm framing the openings for a couple of new 2' x 4' skylights.  I'll have to wait for a sunny weekend to cut into the roof and install those.