building on piers

Discussion in 'Homesteading Questions' started by pcdreams, May 31, 2005.

  1. pcdreams

    pcdreams Well-Known Member

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    We're looking at building a house (16x24) on piers and (since I'm new to building) I've got a few questions that the pictures @ http://www.jshow.com/y2k/listings.html don't seem to explain (or I'm simply to ignorant to understand).

    I'm assuming the 16x24 are the outside dimensions (because I can tell there is overhang of the floor joist on the load bearing sides. My question is how far these piers need to be set in. From the pic it looks like maybe 1-2 feet on each side.

    I'm also assuming the non loadbearing sides would NOT overhang the beams (front and back).

    I've also noticed that in some of the photos there is bracing that appears to run from the beam to the floor joist at each pier. I'm assuming this is for stabilization?

    If anyone has any good sites that explain such I'd be very happy to have a link :)
     
  2. Cyngbaeld

    Cyngbaeld In Remembrance Supporter

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    I don't know of any sites that explain this in detail. But your library should have some good books on it. Mine are packed or I would look it up for you. Look for books on pole construction and framing books. Any book in print can usually be got on an interlibrary loan, so if you find an interesting looking book on Amazon or someplace your library can order it. Then chose the ones that seem most helpful and buy those. They have lots of charts and other helpful references that you will want to have on hand while building.
     

  3. Cosmic

    Cosmic Well-Known Member

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    The overhang part is what as known as cantilevered. The combination of pier placement, number of piers and main carrying beam is primarily determined by the size and strength of those main beams. As shown in this step. (In theory you could have only four piers, if the footings are big enough and the main beam span is still in spec.)

    http://www.jshow.com/y2k/listings/9.html

    The use of the cantilever design in this application allows for a smaller span that the floor joists have to bridge, hence the comment that the floor system is better / stronger for the same floor joist size. The critical item is the main carrying beams attached to the piers. Want those to be very beefy. Usually can cantilever out one joist bay width without any sweat using the same size floor joists. Also the number of piers is also determined by the footing design and the size of those beams. It would appear, they choose to do it this way because it gives a neater look and the piers / support beams are tucked back out of the way and gives good easy clearance all around the cabin.

    Yes, the front / back do not overhang the main carrying beam.

    I don't see the bracing you are talking about but it is normal to put a X-bracing between floor joists. This in essence turns them into box shaped structures. Sometimes it is done but cutting wood pieces but they also use prefabbed metal braces designed for the purpose. That bracing in some pictures is just temporary to hold walls plumb and true during the construction until the roof is put on, again a normal practice.
     
  4. pcdreams

    pcdreams Well-Known Member

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  5. painterswife

    painterswife Sock puppet reinstated Supporter

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    We have a 16 x 24 building on piers. It was actually moved on to the piers. It was built somewhere else. I am not at home but I belieive it is on 8 cement filed sonotubes. Our sonotubes are close to the edge some down the middle(I think).

    The sono's are two to three feet in the ground(frost depth).
    There is winter picture of it here.

    http://www.natureartists.com/artists/artist_studio.asp?ArtistID=1084a

    Jill
     
  6. pcdreams

    pcdreams Well-Known Member

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    painterswife:

    The link doesn't work.

    What you are refering to is what we planned to do (sonotubes).

    unfortunatly we will have to go around 4 feet to get below frost line (in VT not here) :)

    If I can get this figured We plan to start this summer. :)


    I know that say 2x4 are actually +/- 1.5x3.5. Is the same true of the length? Say you have a 2x4x8. would it be a true 8 feet or would it be less?

    I'm also looking for away to save lumber cost by buying 8 foot pieces for the beams(doubled of course, most likely 2-2x8) but I'm not sure how I'd go about joining them. I think the pier spacing would be a bit less than 8' on center?

    Fraid I'm stuck with buying 16' for the floor jost though :)
     
  7. painterswife

    painterswife Sock puppet reinstated Supporter

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    I can't get the link to work. If you pm me your email I can try to send some pictures this evening.

    The sonotubes work great. We actually just set the building down on them. The building has not moved. Now that I think about it I do not believe there are tubes down the middle. I will check later.

    Jill
     
  8. VALENT

    VALENT Well-Known Member

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    lengths will be exact or sometimes a little bit more(8feet means 8 feet or maybe 8 feet 1 inch,sometimes). And when I built my lumber the costs were per board foot and longer lengths were no more expensive than the equal length of smaller pieces. Also, a 16 foot piece will be structurally better than two 8 footers joined in the center.
     
  9. pcdreams

    pcdreams Well-Known Member

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    I'm just wondering if its hard to locate 24 foot stuff. I can get 16 here but never see any long than that. I'm not sure if its the same in other parts of the country
     
  10. Cosmic

    Cosmic Well-Known Member

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    Most places you can get 24 footers but it is probably a special order. Most don't stock it, same with anything very heavy or even longer. Just ask most dealers if they can special order.

    In most places, you pay a premium the longer the lumber per foot. Example: a 16 footer costs more than two 8 footers. If you buy a 8 foot 2 x 4 it should be exactly 96 inches.

    Those pier systems look like over-kill to me. I have built sheds about that size and just used pressure treated 4 x 4's, something like 8 for a building that size and it all worked fine for all the years I was involved with them.
     
  11. Cabin Fever

    Cabin Fever Life NRA Member since 1976 Supporter

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    There is no reason that you should need any 24-foot long dimensional lumber for a 16 x 24 cabin. The 24 foot long beams can be made by splicing shorter lengths together into a two-board or three-board wide "laminated" beam.
     
  12. wy_white_wolf

    wy_white_wolf Just howling at the moon

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    If it is labeled as a "2x4x8' stud" it will be 92 5/8" long.
     
  13. pcdreams

    pcdreams Well-Known Member

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    this is what I was getting at. Wasn't able to explain it
     
  14. bearkiller

    bearkiller Well-Known Member

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    pcdreams,

    Building on piers is quick and easy so I've done a lot of it. The building code tells you everything you need to know, but I agree the code books can be difficult to interpret AND code requirements have become pretty over the top.

    For non-inspected structures here is how I proceed. Dig holes through the topsoil to undisturbed subsoil...whether this is 4 inches or 4 feet. Then I like to use old discarded tires as forms because they are "ready made", they slow concrete drying, are free, and they are easy to use. I've made up a metal form in the shape of a pier block and screw this down on the tire for a monolithic footing/pier. Top with pressure treated 6" X 6" with nails through to hold it in place. Spacing of piers at the ends is usually 1 foot overhang on girders with joints landing on a pier. Girders are usually set in 1 to 2 feet from the edge of the building, but sometimes (code dependant) they must be at the building edges.

    Spacing depends on the sizes of your girders/joists. For example, a 4 X 6 girder can accommodate piers on 6 foot spacing. A 4 X 8 requires 8 foot spacing. I usually simply let the girders run wild on the ends and trim them later. That way when you joist there is less hassle getting the frame exactly square. Simply nail joists and rim joists, then square the diagonals, and THEN nail joists to girders. Normally all this is done with a pneumatic nailer so it is quick and easy.

    If you want to cantilever code specifies a maximum cantilever of 25% of the length of the joists, but I generally try to stay 2 feet or less. Spacing between girders depends on dimensions of the joists. 2 X 6 joists require a maximum span of 9'6" on 16 inch centers.

    If you raise posts above the piers, yes you will need sway bracing running from girder to pier maybe one or two or even three piers away depending on the sizes. The sway bracing is required for stability. Any joints in girders or joists require a scab to span the joint...usually I span 2 feet beyond the joint minimum.

    All code remarks made here reflect specifics in the People's Republic of California so check your own location because every jurisdiction is different. But there is also safe and then there is code. My own choice is to build safe and screw the code since it is so strongly overkill.

    bearkiller
     
  15. papaw

    papaw Well-Known Member

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    This thread has lots of good info. Thanks for all the links. I'd like to see some more pictures of your cabin and other cabins.
     
  16. painterswife

    painterswife Sock puppet reinstated Supporter

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    I will try to post some later today.
    I emailed them to pcdreams. I also explained to him how it is structured.

    Both long sides of the the building are glu lam beams sitting on 4 poured sonotubes on each side. The floor system is TJI's hanging fom the beams with joist hangers. It is a very solid floor system. This cabin has been moved 4 or 5 times with no structual or cosmetic damage. It began it's life as a portable office.

    Jill
     
  17. Cabin Fever

    Cabin Fever Life NRA Member since 1976 Supporter

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    Well, as long as you asked, here is our 16 x 24 cabin built on piers:

    [​IMG]

    [​IMG]
     
  18. papaw

    papaw Well-Known Member

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    That's really nice ... thanks for posting the pics.
     
  19. pcdreams

    pcdreams Well-Known Member

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    can you remail me. I never recieved it. :)
     
  20. painterswife

    painterswife Sock puppet reinstated Supporter

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    I am sending them let me know if you get them.

    Jill