How to build a post & beam

Written by bob haring
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How to build a post & beam
(Comstock/Comstock/Getty Images)

Post and beam construction is a technique used to build barns, carports, sheds, garages, cabins and other buildings. It can even be used for houses, although most of those are built with conventional stud walls. With the post and beam method, you anchor posts to the ground, then put beams across them to support a roof. You may cover side walls or leave them open, depending on the use of the building. Post and beam construction is relatively easy and inexpensive.

Skill level:
Moderately Challenging

Things you need

  • Post hole digger or other excavator
  • Concrete mix or footings
  • Saw
  • Hammer and nails or screw gun and screws
  • Tape measure
  • Level

Show MoreHide


  1. 1

    Build a foundation. This can be almost any type -- it will depend to some extent on the size and purpose of your post and beam building. Start with level ground on your building site. You can dig a hole, sink posts into it and then set them in concrete. You can pour concrete footings with metal anchors to hold posts. You can pour a concrete slab embedded with anchors. You can build concrete walls, for a basement or underground storage, with post anchors on top. But it needs to be solid and capable of supporting the planned weight of your post and beam building. Check with local building agencies about regulations and permits.

  2. 2

    Install your posts. Most post and beam structures use 4-inch by 4-inch or 6-by-6 posts. You'll want one at each corner and perhaps some in between, depending on the size of your building. The post height is up to you -- most are 8 or 9 feet (if a sloped roof is used, the height will vary with the roof pitch). Put angle braces at the pole tops or build diagonal supports (of the same wood as the posts) to brace the posts and connect posts and beams. Use a level to make sure your posts are set straight and plumb and a tape measure to make sure they're the correct height.

  3. 3

    Place your beams on your posts and fasten them, using braces or angled supports (or both). Use strong bolts or big screws to fasten them. You can use roof trusses or cross beams for the top, depending on how you plan to finish and use your building (you can buy prefabricated trusses at lumber yards and building supply centres). For a conventional roof, you will need to install decking and roofing material. For a shed or barn, you may want to use boards, covered with roofing material and shingles.

  4. 4

    Cover the sides of your post and beam building. Usually this will involve nailing 1- by 8-inch or 1- by 12-inch boards between posts. Use big (8d) nails and put three in each plank at each post. Start at the back, then work along the sides to the front (this will vary with carports and open sheds). Use battens or trim boards to cover the end siding joints. If you are installing any doors or windows, you will have to cut and frame those openings.

  5. 5

    Finish the interior and flooring. For barns, sheds, carports and garages, you may choose to leave interiors unfinished. For cabins or houses, finish the interior with insulation and drywall. If you built a barn or shed, you may leave the floor unfinished, dirt. For carports, garages or cabins, you probably elected to place posts on a concrete slab, which can be a floor. In a cabin, you can cover the slab with wood, tile, carpet or other surfacing.

Tips and warnings

  • This construction is at least a two-man job; setting posts and raising beams can be heavy work.

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