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Thread: Cabin Foundation beam question

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    Member AKtrpr's Avatar
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    Default Cabin Foundation beam question

    I'm building a 16x24 cabin, and my question is I can have my beams special cut to 24' length or can I sandwich 2x8s staggered lengths side by side to make the 24' beam? Which would be my best option?

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    Member 4merguide's Avatar
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    Quote Originally Posted by AKtrpr View Post
    I'm building a 16x24 cabin, and my question is I can have my beams special cut to 24' length or can I sandwich 2x8s staggered lengths side by side to make the 24' beam? Which would be my best option?
    The solid beam would be the best if you could find some good ones. But.....there is an actual engineered 16 penny nailing pattern to use to make sandwiched 2xs structurally sound. Sorry I don't know it off hand but I'm sure you could look it up somewhere...
    Sheep hunting...... the pain goes away, but the stupidity remains...!!!

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    Member DRIFTER_016's Avatar
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    You could also get timberstrand or paralam beams in pretty much any size you want and they would be the best of all choices for strength and trueness.

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    Do you plan to have any kind of a deck on either end. If so you might want to figure that as part of your total length.That way it is all part of one framing and not added on .

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    Member AKtrpr's Avatar
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    I was actually going to put a deck on one side instead of the ends, with the door on the 24' side versus the 16' side. Logistically I have no way to transport a super long beam, my truck is a crew cab with a 6' bed

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    Quote Originally Posted by 4merguide View Post
    But.....there is an actual engineered 16 penny nailing pattern to use to make sandwiched 2xs structurally sound. Sorry I don't know it off hand but I'm sure you could look it up somewhere...
    I'm sort of skeptical of this statement. There are nailing patterns for splices, but the splice is generally supposed to be directly above a support member such as a column. For simple spans (beam supported on both ends with no support in the middle) there's no building code or home inspection program that allows splices. For multi-span beams (supported by columns in the middle) splices are allowed directly above the column or at the quarter points surrounding a column. So, a 20 foot beam with a column at ten feet could be spliced at ten feet, 12 1/2 feet and 7 1/2 feet.

    Throw enough wood and enough nails at it and I'm sure it can work. But be wary of just looking up a nailing and but splice pattern and thinking that it's applicable to simple spans. It's probably not meant for that application.

    Having said all that, If I were to build up a spliced beam for a simple span, I'd avoid splicing at the mid-point, I'd make it 5-ply instead of 3-ply, and I'd use copious amounts of wood glue along with all of the clamps that I could beg borrow or steal. I suspect that I'd find the resulting beam satisfactory.

    But, I'd go to a lot of effort to carry un-spliced beams to my building site before I did all that. I'm pretty sure I could figure out a way to transport 16-foot beams in a truck with a 6-foot bed. Not sure if a reputable lumber yard would let me load the beams, but Home Depot would.

    This might be why my truck looks like it went through a war.

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    Quote Originally Posted by HikerDan View Post
    I'm sort of skeptical of this statement. There are nailing patterns for splices, but the splice is generally supposed to be directly above a support member such as a column. For simple spans (beam supported on both ends with no support in the middle) there's no building code or home inspection program that allows splices. For multi-span beams (supported by columns in the middle) splices are allowed directly above the column or at the quarter points surrounding a column. So, a 20 foot beam with a column at ten feet could be spliced at ten feet, 12 1/2 feet and 7 1/2 feet.

    Throw enough wood and enough nails at it and I'm sure it can work. But be wary of just looking up a nailing and but splice pattern and thinking that it's applicable to simple spans. It's probably not meant for that application.

    Having said all that, If I were to build up a spliced beam for a simple span, I'd avoid splicing at the mid-point, I'd make it 5-ply instead of 3-ply, and I'd use copious amounts of wood glue along with all of the clamps that I could beg borrow or steal. I suspect that I'd find the resulting beam satisfactory.

    But, I'd go to a lot of effort to carry un-spliced beams to my building site before I did all that. I'm pretty sure I could figure out a way to transport 16-foot beams in a truck with a 6-foot bed. Not sure if a reputable lumber yard would let me load the beams, but Home Depot would.

    This might be why my truck looks like it went through a war.
    Good post. A nailing pattern could certainly be engineered (assuming relatively small loads on the beam) but I would caution against the use of any internet nailing pattern.

    If you're going to splice it avoid the location of maximum moment (mid-span on a simple span uniformly loaded beam).

  8. #8

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    Is the 24 ft going to be a eve side or the gable end? What general area is this cabin being built? If your door is on the eve side you will have to contend with snow dumping in the door way.

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    Member AKtrpr's Avatar
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    Cabin being built in Nenana, 24' is the eve side but was going to account for the snow by having a covered porch...

    i guess I could hang the 24' beams over the roof of the dodge and the other end hang over the tailgate and strap the piss outta them beams

    if someone who decided they needed my trailer and snogo more than I did (stolen out of my driveway ) I'd have it

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    Member ChugiakTinkerer's Avatar
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    The following comment is probably overkill for most cabins, but if you'll be spending money building it you want to start with a good foundation. I suggest you figure out what code says is appropriate and make your decisions based on that.

    A built-up beam made of 2x is actually in the International Residential Code for light construction. It also covers nailing patterns too. There is a web site that hosts HTML versions of the IRC, but when I checked it tonight but I get redirected. It looks like older versions of the IRC are available from the International Code Consortium at http://premiumaccess.iccsafe.org/collections/I-Codes and click on the 2012 tab.

    Table 502.5(1) gives minimum girder (beam) dimensions for various building width, floor loads, and support spans. URL is http://premiumaccess.iccsafe.org/doc...de/362/6075390 and the girder stuff in section 502.5 starts about a quarter down the page.

    It's a pretty daunting table to figure out, but you start by looking at your snow load. I'm in a 70 lb per square foot area so I use the rightmost portion of the table. I'm planning only 16' wide so will use the 20' and decide if I need to stick with that or can go with a lighter beam. Now scroll down to find the description of your cabin design. A basic cabin with one floor, no loft, and only two beams supporting it would have girders supporting roof, ceiling and one clear span floor. If there will be a third beam supporting the floor (my cabin plan) then you would look at roof, ceiling, and one center-bearing floor. From there it's up to you which way you want to go. In the example above with a clear span floor, you can use two 2x8 to build up a beam, but the unsupported span can be no greater than 4'-6". Assuming 6x6 posts you would need to have them on a 5' center. Adding a third 2x8 you can move up to an unsupported span of 5'-11".

    If your post spacing is already determined, you then look at which combinations can meet the strength requirements for the beam. Again with the 20' cabin in 70 psf snow area and with just roof, ceiling, and clear span floor, for a 24' long building using 4 equally spaced 6x6 posts the unsupported span is 7'-4". You can achieve that with three 2x12 nailed together, or four 2x10 nailed together. If you have five posts under each beam, that helps things a lot. Then your unsupported span is a tad under 5'-5" and you can achieve that with two 2x10 or three 2x8.

    The nailing requirements for a built-up beam aren't much. Here's what's in Table 602.3(1) ( http://premiumaccess.iccsafe.org/doc...de/362/6080198 ): 10d nails at 32" OC at top and bottm, staggered, and two nails at end and splices. It's probably somewhere in the code, but you must have your splices supported by a post.

    The IRC requirements are prescriptions for permanent dwellings and have a lot of built-in assumptions on how much actual load the building will be supporting. If you are building a recreational cabin that will be sparsely furnished you can probably step down from the minimum requirements. if you're looking for something that will safely hold your family and belongings, you'll probably want to stick as close to code as you can.

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    Member cdubbin's Avatar
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    Quote Originally Posted by ChugiakTinkerer View Post

    The IRC requirements are prescriptions for permanent dwellings and have a lot of built-in assumptions on how much actual load the building will be supporting. If you are building a recreational cabin that will be sparsely furnished you can probably step down from the minimum requirements. if you're looking for something that will safely hold your family and belongings, you'll probably want to stick as close to code as you can.
    Amen to that; code also requires continuous perimeter footings....you throw that out, you mights well throw the rest of it out too, because you started off on the wrong foot.....
    " Gas boats are bad enough, autos are an invention of the devil, and airplanes are worse." ~Allen Hasselborg

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    Member ChugiakTinkerer's Avatar
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    Here's a better link for the IRC, 2015 version: http://codes.iccsafe.org/app/book/to...TML/index.html

    If you're thinking about insuring this cabin or selling it at some later time, you may want to consider whether code compliance is worth whatever additional costs might be required. My brother built a place in Palmer years ago and couldn't get a bank to finance completion until he made some foundation repairs to get it up to code. Being in Nenana you have no requirement to build to code, but if there will ever be a buyer, insurer, or lender they will most likely want to see as few variances from code as practical.

    As for hauling lumber, I'd make a poor-boy rack and secure it to the truck bed so that you can haul 12' or 16' lumber up on top.

  13. #13
    Member AKtrpr's Avatar
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    Thanks to all for their input

    no one but me presently
    cabin is being built out of pocket
    year round use
    dint plan on a **** ton of furniture besides a bed kitchen table, recliner, dresser, refrigerator, stove and wood stove

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    Member logman 49's Avatar
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    If you have a siding rear window on your crew cab you can easily haul 16 foot lumber, put up the tailgate, slide the wood though the window.

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