The maintenance line from Skip's class
In class, I remember Skip saying; "The way we build, a log home
could last 200 - 500 years, and here's why...."
My first thought wasn't; "Big deal. I won't live that long", but I had
immediately graphed two charts in my pre-meningitis mind. One was
a thirty year chart and the other a 300 year chart.
Both charts had the life span (new homes about thirty years now,
and the house I'm currently in is living (dying) proof of that) run left
to right. The condition of the home was vertical. New, was upper left,
and, "bulldoze" was lower right. The line drawn on the chart was the "maintenance line".
In other words, A short life span will have a steeper line and all things
being the same (they aren't) a higher maintenance cost in labor and
materials. The total cost of the structure (cost to build or purchase,
plus maintenance costs) is then divided by the life span in years.
The obvious summary from the charts was "Wow, I can have a lot of
extra money for myself, family, friends, those in need, and I can't begin
to afford a cheap 2x6 and OSB built house."
In short, a house designed to have a short lifespan will be made of
materials meant to last a short time. Go beyond the projected useful
life and the maintenance costs will skyrocket. The charts made sense
to me and this certainly has been true with my present house. Many
times I 've said, "This house is alive and it's fighting me!! I fix one thing
and two more things break!!! The house is 41 years old, and I've been
fighting it for 15 years.
Does this make sense to anyone else, or are my charts just the product
of an overly active imagination?
-Rick
maintenence and durability
Rick,
Airplanes are designed to last 20 years of average service with 5% of components needing repair/replacement during that time (with 95% confidence). There are lots of older planes out there but the maintenence schedule goes up. say you are trying to run a 40 yr old 747, you are going to need to do A LOT more maintenence just to keep it in the air. We call this "metal fatigue" but it happens to all structures. Usually metal fatigue is plotted (nearly linear) on log-log paper. That is the logarithm of load (stress) on the y and logarithm of cycles (time) on the x. Metal tends to have a slope of 2: that is, if you increase the stress by 20%, you generally half the life.
therefore, if you shift the plot to the right by a factor of 10 (300/30), you can expect the allowable stress to also increase by 10 fold.
That is the general "what happens if" that I usually get. However, you ask a distinctly different question.
You ask about the scatter of that fatigue data. It turns out that the scatter is described very accurately by a "Weibull" distribution. The accuracy is not compromised much if you approximate this with the symmetric "normal" or "gaussian" distribution.
Remember that we have a tail area of roughly 5% at 20 years. That means that at 20 years, we expect that 5% of components will fail. we can draw an analog to a home. with a bell shaped curve, and general metals, 95% will fail in 4 lives.
that means that in 1 life, 5% fail, but in 4, 95% fail (this is why we test to 4 lives!). If you look at a cumulative distribution graph, you can see that the maximum slope (rate of increase) in the failure rate occurs at 2 lives (half the 95% life).
Long story short, I don't know what the 95% life for a new home is, but I susppect it is roughly 15 years, which means that at 30 years, you are well on the upslope of the failure curve by the time you get to 30 years. If your 95% life is 150 years, your have a much shallower curve, that is, you have to fix stuff much less frequently. I'll give you a better answer at the member's meeting, and will likely post something soon.
Anyway, the problem with this way of thinking is: we are basically changing the exterior method. the shower, toilets, eshaust fans, etc (the things that generally break) will (often) be used by members. If you use these, you will be doomed to fix/replace them as often as in a stickframe house. In short, the systems are my issue, not the structure.
-Peter
LOW maintenance, LONG life
I'm with you Rick. I'm less concerned with internal systems, and more so with the envelope. Roofs, siding, and windows are the real killers when it comes time to deal with them. Granted, if a kitchen or bath needs a full retro, it's going to hurt, but mainly those are done generally to bring things aesthetically up to date, not because they failed.
LOW maintenance, LONG life is my goal. When I took the class, I really went only half excited, as I suspected there would be significant maintenance required. After all, all I've ever known was kit log homes and the maintenance that went with them. In any case, I took the class because it promised a way to get your home much more affordably. What a thrill it was to find the bonus of extremely low maintenance using the LHBA method. It truly was a case of getting far more than I expected from the class.
I want my place to be the last place I HAVE to build, (unless I WANT to build another) and once built, be done with it. There's no siding, so I need not worry about that. Great care will go into my chinking and the logs will not be stained nor sealed. I hoping the borate treatments are more or less a necessity of fresh logs, and the need will subside with seasoning/aging. The roof will almost certainly be metal if at all within reach of my budget. I'd LOVE to have slate since it is the real maintenance free roof, but the likelihood of that happening is slim. (but not impossible!) Yes, a metal roof will occasionally need paint. I wish there was a permanent coating that could eliminate that maintenance, but so be it. I can't believe people use 25 yr asphalt shingles (which go at about 15-20 yrs) Then when they do reroof, they shingle over the old ones in an attempt to "save money" but instead reduce the lifespan of the new roof even more. (maybe to 10-15 yrs) In 25-35 years, they're having the third roof go on? (and have to pay to remove twice the amount of shingles on the third go!) Windows are what they are. It all depends on what you spend on them. I would like wood windows, but I don't want the painting and glazing maintenance. I'll probably use a high quality vinyl in a pleasing color. (GAWD, anything but white!!!!) The LHBA method does provide longer life to windows, by better protecting them from weather, just as it does the logs. You may also note in my model pics, that I don't plan on an extravagant number or size of windows. It keeps my costs down, both initially and for heating/cooling, but also, I'm an outdoorsy type that doesn't need to feel like I'm outside while inside, staring through a wall of glass. If I want to experience nature, I'll go outside! I'm still hashing out what I want to do for smaller things like plumbing fixtures. I can tell you it won't be cheapy cartridge faucets/valves. Dang, those things just stink to no end. Anything that's fitted with O-rings or rubber seats is off my list. Quality brass seat faucets and valves are worth the extra expense, both with labor savings and not having to replace it two (or three?) time over.
I wonder about the structures of spec homes built with OSB. It's been about 20 years? now since it really took off using wood-chips and glue to make sheathing, flooring, joists, columns, and girders. I wonder how long that stuff will stay together before one's home literally starts to come apart at the seams.
The maintenance line from Skip's class
1/4 round - Excellent idea.
I do spray with borate every other year.
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