Old growth fir or engineered lumber for floor joists? I keep seeing guys rip out solid 2x10s for I-joists.

I was on a reno in Portland last week and the contractor insisted on pulling out perfectly good 1950s Douglas fir joists to put in engineered I-joists. He said it's for consistent span ratings but those old fir boards have been holding up for 70 years without a sag. Which side are you on, keep the old growth or swap it for the new stuff?

3 comments

3 Comments

parkerp8015d ago

Has anyone actually looked at the real cost difference after you factor in labor for sistering those old joists if you ever need to open up a wall for plumbing? I bet the engineered stuff comes out way cheaper in the long run when you account for that.

uma_johnson15d ago

Keep the old growth every time. Those 1950s Douglas fir 2x10s are way denser than anything you can buy today, they don't rot easy, and they'll outlast the house. Engineered I-joists are fine for new builds where you need consistent spans, but swapping sound old growth is just wasteful and often a contractor trying to pad the bill. I've seen 100 year old fir joists in Victorian houses that are still dead straight, no sag, no bounce.

park.abby15d ago

50 years in that wood actually means it was milled back in the 1970s, not the 1950s. Those old growth trees were already gone by then, so you're mostly looking at second growth with tighter rings but still way better than what Home Depot sells today. I mean, you're not wrong that the older stuff is denser and more rot resistant, but just a heads up on the timeline. That 1970s fir is still solid, don't get me wrong, just not quite the same as the virgin timber they pulled in the 40s and 50s.