Historically Accurate Framing: Pressure Treated or Fir

By: Mark Clement , Contributing Writer
In: Old Houses, Old House Construction, Home Improvement Tips, House Styles

Question: My house is about 90 years old. It needs work. As I remodel I try to keep things as close to original as I can, i.e I try to match moldings, use the same flooring, and so on. My current project is the porch. The floor boards are coming loose and I know I have to re-frame portions of it because I can feel bounce when I walk in certain spots. OK, so on to the question: The original framing materials looks like it’s Douglas Fir. It has certainly stood the test of time. But sourcing it (I swear I’m going to ask the question soon) will be both time consuming and expensive as I have to special order it. Should I just use regular ‘Hem-Fir’ framing material so I’m close? What’s your take?

Answer: My first take is that I love this question. It’s mostly because I love it when people can feel the history in their houses and, furthermore, have respect for it because it has made it this far. I know that if I were to pry up a porch floor and find those old timbers under there and I’d want to save them and re-use them for something, like a woodworking project.

OK, here’s what I’d do, both to build a sound structure and revere the history of the house. But before I answer I have to set it up:

This is one of those situations where the carpenters who built the house used what they had because they had it, not because wood back then was magic, or they knew some lost Freemason secret to building things that last. Fir is pretty decent in semi-wet service (I’ll infer that the porch flooring–which I bet is painted–is fir as well.

Anyway, my answer (which is coming soon, I swear) falls into a category I have called “If old time carpenters had plywood and nail guns they would have used them.”

In this case, if they had pressure treated material they would have used it here, which is what I would do for this application. First, you’re right: sourcing fir may be a not-cheap-challenge. Second, fir won’t do much if a colony of termites decides to make camp under your porch. Third, treated will be fine in wet-service and in contact with your masonry foundation and porch posts (I’m making some assumptions about how your house is built.) Fourth, it’s widely available and easy to get as you already know. I wouldn’t go with regular SPF (spruce-pine-fir) or Hem-Fir framing in this application.

Also, upon opening up the floor of the porch I would be prepared to re-frame the whole thing. While that may seem more difficult, it may actually be easier–especially if something has settled. Piecing things together can be significantly harder than just starting over.

Now that I’m thinking about this, I love porches. I wish I could help you with this project.