The Historic District

Hi all

I have had a 1 1/2 story plank on plank house at the Oregon coast for about 40 years.
As best we can estimate, it was built NLT than 1905. That guess is based on the chimney design; a local expert
thinks it was designed/built by a mason that died that year.

I've done most of the work on it but haven't modified the basic construction. Until now.

I want to add a window in one room. Since it's plank on plank with rough cut fir 1x12s offset and
nailed together, the walls are 2 inches thick. Plenty strong, but it sure confuses the building
department out there, as well as my architect brother.

He maintains it will need a independent 4 inch thick header in the opening.
I think by attaching a 2x to the top of the opening into the 2 inch thick solid wall, it will actually be stronger
than cutting a larger opening, installing a separate 4x and trying to attach that to the wall above the 4x.

We may have another option, as the exterior has 1 inch battens that support the dutch lap fir siding.

So... Anyone have experience adding a window to these old places?

Welcome to the District. I can not speak to your problem with any experience of that kind of construction. It sounds like your home was built with what’s called balloon construction. If I read your description correctly you want to cut a hole for your new window and depend on the lapped construction alone for strength. I personally don’t think that’s a great idea. Whether it’s a full box window or modern vinyl flange mount it still has to float, you need to take any structural loading around the window, this requires a header, King and jack studs and cripples ect.