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jayinwww
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# Posted: 31 Oct 2015 23:17
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Impossible to find 4x6x16 or 20 or 4x4x16 or 20 feet?
I want to build a cabin on a steady skid but the longest 4x4 or 4x6 I can find are 12 feet long. How can you build a steady skid with such short pieces?
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Wilbour
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# Posted: 31 Oct 2015 23:28
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I got two 6x6x16 last year at Homers.
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Don_P
Member
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# Posted: 31 Oct 2015 23:37 - Edited by: Don_P
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You wanted a stable timber, here's your sign. 12' is pushing beyond all a 4x4 or 4x6 are good for
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Steve_S
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# Posted: 1 Nov 2015 09:35
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You can do what I did to make skids as my bldg. inspector suggested: Take 2 6x6x12, cut a 1-1/2' Lap Cut into each, apply plenty of PL Premium Construction Adhesive (it's made by LePage & used commonly around here) and join them together with Hot Galvanised 1/2 Bolts & big washers then apply liberal amounts of End Cut preservative over the lap joint. Point to NOTE which he suggested & I concur, put the Lap Joint on top of the concrete cottage blocks. I was using 16"x16"x6" precast cottage blocks under the skids to keep them off the hard packed surface.
We changed our plans and went with a frost protected heated slab but when I decided to separate the 6x6's to reuse for other things... Well, I took the bolts out and had to use the chain saw to cut them... The glue wouldn't give at all !
Hope it helps
Steve
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Tyler Danann
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# Posted: 6 Nov 2015 20:18 - Edited by: Tyler Danann
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I had to DIY my own using an Alaskan Sawmill at a friends property. I made 3x5s, 4x5s and 5x5s that were about 8' 6" long.
The nearest city had only 4x4s and 2xwhatever. This was for rafters though not romper-stomper sills etc.
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KinAlberta
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# Posted: 9 Nov 2015 01:32 - Edited by: KinAlberta
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A couple weeks ago I bought 4x6x16 pt beams at a country hardware store, so they are available. I just put them under a small shed but the lumber guy flipped open a chart saying that they were equivalent to 3 laminated 2x6x16s and cheaper too.
I was going to call to see if they had 24's that I could use on another building. I can't see why they can't be available. Telephone poles are longer than that aren't they?
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Borrego
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# Posted: 9 Nov 2015 10:27
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They're all over the place around here, but as Don P said that is way over their useful span...I suppose you could want a single piece of wood for the look?
http://www.homedepot.com/p/Unbranded-4-in-x-6-in-x-20-ft-Premium-2-Better-Douglas-Fir -Lumber-185477/202094258
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Don_P
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# Posted: 9 Nov 2015 18:28 - Edited by: Don_P
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Quoting: KinAlberta A couple weeks ago I bought 4x6x16 pt beams at a country hardware store, so they are available. I just put them under a small shed but the lumber guy flipped open a chart saying that they were equivalent to 3 laminated 2x6x16s and cheaper too.
No, he was misunderstanding something.
A 4x6 has a section modulus, the number used to describe the geometric strength of a shape, of 17.65"^3
a triple 2x6 is 22.69"^3. The triple is already significantly stronger by shape (thickness) A triple built up member is also allowed a 15% strength increase due to the distribution of defects when you make up the beam of several thinner plies.
If you really want to see a jump, increase depth, a single 2x10 has a section modulus of 21.39"^3... whenever you can, "Deeper is Cheaper".
You can obtain lumber in just about any length. Many suppliers do not stock 4x over 12' long to keep folks, and their reputation, out of trouble. 4x lumber is generally boxed heart juvenile wood, unstable and weak to begin with. Mailbox posts.
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rockies
Member
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# Posted: 10 Nov 2015 19:59
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Hmm, Don_P, I forgot to bring my math book  Is this going to be on the test
I was watching an episode of "This Old House" and they had to put in a very long, strong beam to hold up a second floor and a roof and the used a "flitch beam", which is a steel plate sandwiched between two wood beams and held together by bolts.
Perhaps if you got a metal shop to cut the steel for you and drill the bolt holes you could build the beam to any length and strength that you needed.
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Don_P
Member
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# Posted: 10 Nov 2015 21:18
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LVL's have replaced flitch beams in most applications. From there it generally then goes to an I beam (actually a W shape, a wide flange beam)... sorry rockies, you never know what tidbit will trip the light, so I like to pack it in. I've always just assumed that architects don't own math books
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KinAlberta
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# Posted: 12 Nov 2015 23:35 - Edited by: KinAlberta
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Quoting: Don_P # Posted: 9 Nov 2015 18:28 - Edited by: Don_P Reply Quote Quoting: KinAlberta A couple weeks ago I bought 4x6x16 pt beams at a country hardware store, so they are available. I just put them under a small shed but the lumber guy flipped open a chart saying that they were equivalent to 3 laminated 2x6x16s and cheaper too. No, he was misunderstanding something. A 4x6 has a section modulus, the number used to describe the geometric strength of a shape, of 17.65"^3 a triple 2x6 is 22.69"^3. The triple is already significantly stronger by shape (thickness) A triple built up member is also allowed a 15% strength increase due to the distribution of defects when you make up the beam of several thinner plies. If you really want to see a jump, increase depth, a single 2x10 has a section modulus of 21.39"^3... whenever you can, "Deeper is Cheaper". You can obtain lumber in just about any length. Many suppliers do not stock 4x over 12' long to keep folks, and their reputation, out of trouble. 4x lumber is generally boxed heart juvenile wood, unstable and weak to begin with. Mailbox posts.
Yeah. I didn't care about the explanation, as it didn't relate to my needs but I thought that what he was saying sounded off.
Thanks for the information though. I'll be needing to review it in the future.
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Don_P
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# Posted: 13 Nov 2015 09:01
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I'm not sure how he was using a source and missing that concept so badly, not good for a material supplier to misunderstand that, but that is a whole other rant.
Just to keep rambling, cause it's blowing 40 out there. Look at the end of some 4x and 6x material. Most often you'll see the heart in the center of the bottom, or nearly centered. In other words, boards were sawn off the outside of the log until this heart centered timber was left.
Think about how a young tree grows, this timber is that young tree. Branches frequently as the tree stretches, this is prior to the self pruning that begins as the diameter of the trunk later increases. The tree is small diameter at that age, stretching and supple, right down to the microfibrils that weave the cell walls. They are knitted on the bias to allow the young tree to bend more without breaking. As the tree matures, in pines around 25 years or so, the fibers line up along the axis of the tree and mechanical properties go up. That wood does not accept treatment as well as non heartwood. In general it makes better posts, compression members, than beams, bending members. When you get beyond 8' with a 4x dimension the length to depth ratio as a column begins to move too deep into the buckling zone, a geometric problem really, it's too slender for its' length as a post.
There are about six directions that conversation can go.
Then a 6x begins to look good. There is a shift in design strength values as wood goes from "dimensional lumber 2-4" thick" (our 4x's) to the next timber classification "Heavy Timber". Because it is harder to grade a thicker timber reliably, we can't see as much of the wood inside, the design values shift above 5" thick and become more conservative. You can take a heavy ding at that crossroads in bending. In compression it is a no brainer, upsize a post, the geometric shape controls.
For a beam then the more efficient way is to stay within dimensional lumber, go deeper first (that increases the section modulus and the moment of inertia the fastest (where's rockies, we haven't been there yet ), then add plies. At 2 plies you can increase the design strength by 10% and at 3 plies you can increase the strength 15% due to the effect of scattering knots.
And finally several more ways to get into the weeds .
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Rowjr
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# Posted: 14 Nov 2015 07:54
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Most lumber suppliers will have them delivered if they don't normally stock them
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