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Thread: Beams

  1. #1
    Member akriverunner's Avatar
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    Default Beams

    what does everyone prefer to use for beams to set floor joists on? my pilings are utility poles right at 8 1/2' apart. i am thinking 4x12's but not sure yet, i know i am going to use some 4" steel angle to secure the beams i use to the pilings.

  2. #2
    Member akriverunner's Avatar
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    anybody?..........

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    Member alaskachuck's Avatar
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    4x12 should be plenty...Remember to crown them...You can never go wrong with and angle iron or steel to secure beams...walls or rafters on a cabin....Thing shift alot up here
    Grandkids, Making big tough guys hearts melt at first sight

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    Member AKDoug's Avatar
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    Utility poles at 8 1/2' apart doesn't tell the story well enough. How big of cabin? How many rows of posts? One story, two story? Roof design? All this goes into figuring a support beam. I'll be glad to help with enough info.
    Bunny Boots and Bearcats: Utility Sled Mayhem

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    Will start by saying you should absolutely overbuild your floor, you will never regret it.

    Regarding 4x12s, they are generally overpriced, they underperform, and they're hard to work with (heavy, awkward).

    I highly recommend building girders (beams) in place with 3 2x12s or 4 2x10s (or 3 2x10s in a single story). I greatly prefer 2x10s because they are generally tighter grain, and they don't cup as much. go to SBS they'll have doug fir wheras the box stores will have crappier lumber and it will cost more. Glulams are certainly nice but still unwieldy in terms of size, and EXPENSIVE. You can build girders quickly by yourself to almost any length, and by picking good baords they will be nearly bombproof.

    For example under my house are 28' girders, each made of 4 pairs of 2x10s, one 10' and one 18' (total 28') with the seams set-up to lie directly over the footers. Seams are staggered so the beam functions as one unit. You can face nail the girder together with 3 nails every 4 feet or so, and some subfloor glue in between doesn't hurt and probably helps. I certainly could have gotten away with only 3 2x10s wide but I hate deflection in a floor, and this house has none.

    at just over 8 foot spans a girder from 3 2x10s would be plenty for a single story, but once you put 4 together, you are confident that you can drive a tank across your ground floor (which of course is very practical, right?).


    After you tie your beams to your posts, make sure you tie your floor joists to your beams with diamond shaped hurricane ties.

    Answer doug's questions for more specific info.

  6. #6
    Member akriverunner's Avatar
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    20x36, 20x20 loft, 10x10 root cellar under one corner framed out of 2x8's that the beams will sit on that way i will get rid of 4 pilings. so i will have one row with 5 pilings and two rows of 3 pilings. 12/12 pitch over the front 16' of the 36' length then the loft will have a 4' pony wall and a 6/12 pitch. that should keep my peak right at about 18' from the floor the whole length of the cabin.

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    Member AKDoug's Avatar
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    I just got back from Anchorage and I'm going out with the wife tonight. I will sketch up your info and try to get some suggestions for Monday.
    Bunny Boots and Bearcats: Utility Sled Mayhem

  8. #8
    Member akriverunner's Avatar
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    cool thanks Doug

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    Member AKDoug's Avatar
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    Two scenarios. Beam sizing will be different if you run a ridge beam or if you use freespan trusses. Ridge beam will transfer 1/2 of the roof load down to the center row of posts. If you use freespan trusses the load is transferred to the outside rows of posts.

    I will figure it using the freespan truss way because that would be the most load on the outer posts. Figure 120#/sqft for the roof load of snow and 40#/sqft for each floor. You end up with a load of 2000#/lf on the outer beams. That exceeds a 4x12 by almost twice. If you put another post in you could use 6x12's for the beams if you kept the spacing right at 7'. It's very unlikely you will ever reach the design loads on the roof or either floor, but that is the suggested loads for residential floors and what I use for roofs in this area. It provides a very big F' up factor.

    I don't have reliable data to suggest buildup beams like andweav suggested. My gut reaction is that a build up beam of three 2x12's with 1/2 CDX between them, glued and nailed, would provide more than enough strength and be much easier to haul in. That would also be using 6 posts per row on the outside.
    Bunny Boots and Bearcats: Utility Sled Mayhem

  10. #10
    Member Music Man's Avatar
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    Better increase that 40#/sqft for the floor, beer weighs a lot. Or he can just drop the beer off for Wes and me at my place on his way.
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