This home I am inspecting is 150 years old and the main beams are 10 to 12 inch diameter logs that are a bit punky arround the bottom half of the log. I can punkture the log with a sharp edge to the depth of 1/2 to 3/4 of an inch deep. The top of the log and ends appear solid. The moister content of the logs is running arround 15 percent and there is no apparent sag. My question is when would one consider that the logs need replaceing?
You found yourself one hell of an old home there. I run into these log (tree) built homes several times a year.
The picture you posted shows floor support logs that are of no concern whatsoever. Logs do not have to be replaced by age. They simply need replacing if they rot or are infested with WBI’s. Your probe will also penetrate these soft logs, but if there are no obvious issues. This structure is in fine condition.
I agree with Dave, I also see these several times a year. Unless the logs or sills are showing serious deterioration (1/2" for a 10" log over 150 years isn’t very serious) then leave them alone, they will be there for many years to come.
You can still report the fact that you found in your inspection. If they still own the house 150 years from now it may have become significant.
As for your responsibilities as a home inspector, what is the required dimensional lumber to support that floor? Are these trees not far superior to the capacity of dimensional lumber, even with some deterioration?
It’s all just common sense. Structural evaluation is not the inspectors job. We do not need to determine capacity. We are there to look for and identify deficiencies to these components which makes them obviously “broken”.
The first house I inspected was a 200 year old house I bought in 1980. It had the same main floor joist system- 9-10" logs adzed flat on one side. These had rotted to as much as 1.5 inches deep but still were able to support normal house loads…but were a bit springy when big house parties with lots of “happy” young folks started dancing.
The source of moisture for the rot at the bottom/outer edge of the logs is summer condensation from (1) damp basement/concrete/soil with no moisture barrier and (2) infiltration of hot/warm moist summer air into the cool basement space. Although it hasn’t been extreme, the rot process should be stopped and the logs will last for years and years.
BTW, this house led me into the HI field. I started asking local carpenters about replacing rotten sills, repairing/replacing the bowed (from frost) stone foundation, repairing plaster walls, etc but got everything from black to white answers. So I started studying more building science, framing, building, etc. About a year later while into my renovation was asked by a friend to inspect an old farm house he was considering buying…and so it began slowly 1-2-3 a year (I also ran an energy retrofit/ventilation/roofing/siding/window operation with 3 trucks and up to 12 employees at the time).
I purchased the limited/incorporated inspection company I presently own from an engineer and engineering tech in late 1984. I had been hired by them in special cases a couple of times and their new company was not growing as fast as they had hoped… they essentially dumped it on me with all the letterhead/copyrites/name protected for a song.
David and Scott got it. Nothing needs to be replaced until it’s no longer able to do its job. As long as these logs stay dry there’s a good chance they’ll last for much, much longer.
The way floor logs like these typically fail is that sooner or later, often as the result of a change of exterior grade, plumbing leaks, re-routing of a dryer vent or some other factor which routes moisture to the crawlspace, the moisture levels in the logs rise to the point at which decay fungi become active and the logs rot.
These are the ways that the rate of rot will possibly increase in modern times.
The house that I bought was very close to original (it still has about 80%+ original pine clapboard siding) except for wiring, plumbing and asphalt/asbestos-cement shingles for the last 50 years of its life to 1980. It had been unoccupied for a couple of years prior to my possesion and I did not live in it for another 2 years as we renovated.
In the first summer of renovation, I went into the basement in July to find water on the joists in droplets with some dripping to the damp dirt floor below. Put down 6 mil poly on the dirt floor and the condensation/dripping stopped.
Thank you all for the information which I will use accordingly. Seeing I am doing more and more inspections out in the country I do expect to come across a lot more old home and have started to research all that I can find on log and homes older than 100 years.