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xinull
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# Posted: 17 Apr 2021 06:11pm
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Is cedar good enough to be used instead of Pressure Treated wood for girders/skids?
with the price of wood, i'm trying to find alternatives to having to purchase Pressure Treated wood from the big box stores. I can't find any lumber yards treating their wood in the area. But I could get my hands on milled cedar for a good price, better than what PT is costing these days.
just checking if that's an option or not. My guess is that you guys might say that cedar is too soft
in case the size of the skids makes a difference, skids will be made of 4 plies of 2x8
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gcrank1
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# Posted: 17 Apr 2021 08:32pm
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My '83-'84 build had local (SC WI) white oak beams.
As of last Sept (2020) when I last saw it they looked every bit as good as when I built it. They were not ground contact, they were on cement block 'piers', tallest about 18" above grade.
I did have good overhangs on all sides of the roof.
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ICC
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# Posted: 17 Apr 2021 09:15pm - Edited by: ICC
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DaveBell, Janka hardness value? That 1900 value for a pine is, I believe, incorrect if you are comparing woods using standard US pounds-force (lbf). The 1900 value appears to be correct in the Newton scale. That is apples & oranges though.
In my tables I see alaska and yellow cedar at 580, red oak at 1290 and most common pines range 400 to 650 with white western pine at 420. Southern yellow pine is the most commonly used wood for pressure treating. Its Janka is 690 lbf in my chart. A little harder than most cedars.
SYP is preferred for PT because it absorbs snd retains the treatment chemicals better than other species. Some species require insizing. I like buying local but there are fewer small tteatment plants these days and I am not sure I would trust them all.
The cedars have a lower modulus of elasticity than pines. They would not span as far between supports. However if the cedar was all heartwood, no sapwood, they would be rot resistant. But any sapwood will rot out easily.
Being that these girders will be under everything, I would try to save money someplace else. Buy PT that is ground contact rated, not the lighter treated stuff suitable only for above ground. Use the cedar for decking, siding, windows or doors.
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Brettny
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# Posted: 18 Apr 2021 06:17am - Edited by: Brettny
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Locust would be another good choice. Although this is a structural component of your foundation and shouldn't touch he ground and shouldn't need to be PT.
If your going to make skids out of it just cut to parallel cuts in a log.
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Aklogcabin
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# Posted: 18 Apr 2021 08:52am
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I believe you're cedar would made great skids. It's one of the most rot resistant woods there is. Yes sapwood will rot but that is only a small portion of the outer area. And usually removed. Any reason you don't want to have a larger beam cut likke a 6x8 instead of 4 each 2x8s?
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mj1angier
Member
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# Posted: 18 Apr 2021 09:58am
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We use the standing dead Eastern Cedar for skids, post, fence post... all the soft wood is gone and easier to size of project.
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xinull
Member
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# Posted: 18 Apr 2021 11:49am
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Quoting: Aklogcabin Any reason you don't want to have a larger beam cut likke a 6x8 instead of 4 each 2x8s?
not what-so-ever. Initially my plans were to buy PT wood, and they would have been 2x dimensional lumber. If i'm going to be milling them, i could go straight to 6x8 instead.
Quoting: ICC The cedars have a lower modulus of elasticity than pines. They would not span as far between supports. However if the cedar was all heartwood, no sapwood, they would be rot resistant. But any sapwood will rot out easily. Being that these girders will be under everything, I would try to save money someplace else. Buy PT that is ground contact rated, not the lighter treated stuff suitable only for above ground. Use the cedar for decking, siding, windows or doors.
exactly the kind of info i was expecting. My beams would probably only span about 5' 4" between each cinder block piers.
I'm not looking to save money at the expense of the structure.
Thanks for all the good advice
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