1860s Farmhouse: Replacing floor joists and other framing members
Hello All! We just bought an 1860s farmhouse and deliberately selected a home inspector who previously worked as a structural engineer. He indicated that the basement requires extensive work to support the structure due to moisture, powder post beetles, and insufficient support over time. He recommended replacement of essentially all floor joists and supporting beams but suggested leaving the sill plate in place, as it is a true 6×6 timber and is in materially better shape than the internal structural members.
For reference, the home is a two story center hall with a rectangular layout–gabled with a brick chimney at each end. The load bearing walls run parallel to each other from front to back on either side of the center hall.
While this home poses many challenges (and likely other posts to this forum) my primary question is this–if the sill is true 6×6, does that constrain our ability to use more robust dimensional lumber when replacing the floor joists? Should we use dimensional 2×6 with extra beams catching the middle of the spans? Each side of the house (on either side of the center hall) is a 12.5 ft span, so a beam mid span would mean 6.25ft carried by 2×6 lumber spaced 12in on center.
I realize that the options are extensive depending on spacing, beam support, and the capacity to provide basement support, but the issue of the sill plate dimension is what most perplexes me at this phase. Thanks in advance for your input!
Replies
You’re going to have to spend some time with span tables to see how far your 2x6’s can span. The general rule is a 2x4 spans 4’, 2x6 spans 6’. This is an approximate estimate. Delve into the span table or hire an engineer if you can’t find what you’re looking for.
Three possible solutions:
- use lvl’s instead of dimensional
lumber
- sister the 2x6’s so each one is like a mini- header
- add mid span girders in the basement to half the span. This could possibly be the least expensive in terms of lumber use, but you have to pour footings.
Good luck, sounds like quite the project
Thank you for your thoughts--fortunately load tables have helped me know what we *can* do, but we are still mulling over what is best to do. I like the idea of 2x6 lvl joists, since they will allow for more usable basement space but will they result in too much deflection over the 12.5ft span?
I agree that a mid-span girder would be both affordable and reliable but the work of adding more footings and piers is definitely an added challenge.
Hi @Upstate_fixer — congratulations on your new (and beautifully historic) farmhouse! It's great that you brought in someone with structural engineering experience; moisture and pest-related damage in older homes can be deceptively extensive.
To your question: having a true 6x6 sill plate doesn’t necessarily constrain you from using more robust dimensional lumber—it just sets a reference elevation and a connection condition you’ll want to consider. You can absolutely use deeper joists like 2x8 or 2x10s if your span/load calculations support that better, but you'll need to manage the height difference at the connection point to the sill. Options might include notching joists, adding a ledger, or using joist hangers (with structural blocking).
A mid-span beam under a 12.5' span is a smart idea—especially if you're planning to go with 2x6s. That beam would essentially reduce your joist span to just over 6 feet, which 2x6s can handle comfortably at 12" OC, assuming standard residential live and dead loads. That said, upgrading to 2x8 or 2x10s could future-proof the floor and improve overall rigidity.
Moisture management will be key—especially under a historic home. You might consider integrating materials below grade or around the perimeter that resist long-term humidity exposure. In some of our own architectural projects at Arc Surfaces https://arcsurfaces.com/ , we’ve seen how strategic material selection—whether it's engineered surfaces or breathable finishes—can dramatically reduce future structural maintenance needs.
Looking forward to following your restoration journey. It sounds like you’re taking a thoughtful and well-informed approach!
Ledger is a good idea. Notched joist ends and a 2x2 angle iron bolted into the wall could work well too
arcsurfaces,
I see you didn’t forget to add your shameless link.