Sturdiness of a Conventionally-Framed Floor Over the Lifespan of a House
I have recently been visiting many old and new homes that have stick-framed floors, and I’ve come to recognize that the floor frame of almost all of the older homes has retained its solid strength through the years. The ages of the older homes range from 90 – 100 years old. The floor-frame of the older homes was framed using rough-sawn 2 x 10s which span up to 14 feet with 1′ x 6′ plank sheathing nailed on a 45-degree angle to the joists. The newer homes, however, have very bouncy and squeaky floors that have lost most of their stability. Their age ranges from 10-20 years old. Unlike the older homes, the newer homes are framed with conventional 2x10s which also span 12 feet, but plywood sheathing on top. This really makes me wonder if it is at all worth framing floors with conventional solid-sawn lumber, considering the fact that most of it comes from 2nd-growth logs. Maybe the newer homes have squeaky and bouncy floors for a different reason, who knows? Otherwise, is it possible for a floor frame built with today’s lumber to gradually lose its strength as the home ages, assuming that it is built within its limits according to code?
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Newer homes should be using engineered lumber/ TJI joists and glued plywood subfloors which will result in a bounce free stronger flooring system than the older homes.
It's that in between period where pwople didnt size sufficinetly or didnt glue down the subfloor that you need to be worried about.
Every home is only as good as the craftsmen who installed it. I've seen plenty of 100 year old homes that were terribly constrcuted too!
The old homes you're looking at are the few that have survived to this point. Most of them went to the landfill 50 years ago. But, you're correct that a 2x 10 that actually measures 2" X 10 1/2" is stronger than one that measures 1 1/2" X 95/8." You can still buy those full-sized boards but TJI's would probably be cheaper.
I have an old house (80 years) for a vacation home, and a newer one as my primary residence. The older one does in fact have more solid floors. I think its the blocking they put in, plus the old-growth timber - but I'm pretty sure it's the blocking every 6 feet that provides rigidity. Those joists have no place to flex.