Pole barns and similar post and beam buildings are the ideal construction method for low cost applications. This page includes the post layout for a 40′ x 60′ with steel sides and metal roofing.
Pole barn – Options to Consider
Wooden trusses are simply the best way to go for a pole barn of any size greater than 20 x 30. Steel trusses are give more headroom and are cheaper, but they are a hassle to set if you are not experienced with them. Roof rafters require more skill and a building this wide would need some sort of beam. In this case, the beam would be massive to keep a clear span. Metal roofing is far and away the method of choice for a polebarn. It is cheaper and lighter than composite shingles. See How to Install a Metal Roof for instructions on laying metal on any building. The building site needs to be as level as possible and free from vegetation. If your site needs attention, then this should be done before any construction is started. Sometimes it is best to hire an excavation contractor for this.
Laying out for the post depends entirely on the size and style of truss you will be using. Only the width differs; the layout for the post on the long side is always 10′ center (or other even number such as 8′ or 12′). This means that from the outside of the corner posts to the center of the next post is where 10′ needs to be. The other posts are 10′ center to center. The overall length of the building will be 3 inches longer than a 10′ center. For example, this 40′ x 60′ barn will be 40′ 3″ long from the outside of the girts.
- For stick framing, the layout for the width of the post really does not matter. It just needs to be parallel from one end to the other.
- For steel trusses, the layout needs to have the post right on 40′ from outside to outside. this will make the building 40′ 3″ wide from the outside of the top plate.
- For wooden trusses, the layout needs to have the post 3 inches less than 40′. This makes the layout 39′ 9″. The outside edge of the top plate will measure 40′ from outside to outside this way.
Post setting techniques are covered in detail in How to Build a Shed, and How to Build a Barn. We recommend 6 x 6 treated pine for the post on a 40′ x 60′ polebarn. Use 10′ center for the post layout unless there is a real good reason not to. To support the weight of the roof on a 40′ wide building with posts on 10′ center, use a double 2 x 12 capped with a 2 x 4 for the banding . Make sure the boards are fairly straight before you nail them together. The outside of the double needs to be 1 1/2″ from the post so that it will serve as the top girt. To accomplish this, take a 1 1/2″ notch out of the outside top corner of each post.
Set the Trusses
If you have elected to use wooden trusses, and the posts are in good shape with the bands and top plates nailed on good and straight, then you are ready to set the trusses. 40′ trusses are big to say the least. A boom truck makes short order of setting them into position. Even thought the cost for the truck is high, it makes such a difference in setting the trusses, you almost Have to have it.
Whether you use a boom truck or elect to set the trusses by hand (good luck), you will start the process the same. Bracing the first truss is the most important thing you will do. A failure here would be catastrophic! For roofs with ridges to high off the ground, use 2 guy lines to brace the truss. Ropes stretched from the top of the truss down to solid 2 x 4 stakes work very well. For shorter jobs, use 2 long 2 x 4′s nailed together (about 18′ long maximum) from the top of the truss down to a solid 2 x 4 stake on the outside.