The span of a beam is dependent on a few variables. The species of lumber, size of lumber and the load it carries. Fewer posts on upper level decks are typically more desirable to the occupants and this drives the use of larger framing materials for longer spans. Beam span maximums are based on a maximum anticipated live load. Building codes for residential decks only require 40 psf.

The longer the joist, the more area of deck the joist supports, and thus the beam supports. For pressure-preservative-treated southern pine no. When supporting joists that span 12 feet with no overhang beyond the beam, a double ply beam can span in feet a value equal to its depth in inches. A double 2x12 beam can span 12 feet; a 2 2x10 can span 10 feet and so on. The numbers in gray indicate the distance between the support posts. Numbers in blue are joist spans beam to beam or house to beam.

In the article, it is stated that a 12' joist span corresponds to the double beam span a length equal to the 2x width; however, this seems to match the 6' joist span column of the table. Can you clarify? Looks like half the allowable beam span is suggested in the chart. Please do clarify. Register Log in. By clicking GO! About Us. All rights reserved.

Terms of use.There are lots of people who like building their stuff which can range from swings to cupboards to deck and everything in between.

However, not everyone can master the art of decoding how much suitable weight wooden beams of varied sizes can hold horizontally, with or without any vertical support. Nowadays, most of the wooden lumbers are full of pervasive knots. Thus, people should check the wooden lumber carefully and buy only the wood that is free of knots. Builders make use of yellow pine during building constructions for holding up everything in the newly built houses, from the floors to porches, which in turn offer a minimum support of 35LBs per square foot.

Post and beam is a general term for building with heavy timbers.

**Strength and stiffness**

It is a building method that relies on heavy timbers rather than dimensional lumber. Post and beam and timber frame are two different methods of building but most people think of them as one and the same. Both are methods of building that create a frame that is self-sustaining and carries the weight of the house. The main difference in the two types of construction is the method of joining the parts.

As quoted here.Plan in advance by knowing the correct deck beam span to use. You should also know the size of the post you are considering to use. See the Deck Post Size Table to make that determination because it will affect the size of beam you choose.

The Deck Beam Span Table on this page makes it easy to determine how far apart your posts and therefore the span of the beam should be.

If you have seen the Deck Joist Span Tableyou already understand the relationship between joist span and joist spacing.

The closer you space joists, the longer you can span joists — up to a point. For determining beam spans distance a beam can span between supporting postsconsider the following concept. The more weight, or the longer the supported length of joist that a beam must carry, the shorter the span of the beam — for a particular size of beam. Determine the length of the joist actually supported by the beam. This distance is half the distance to the next beam in either direction. If a joist is attached from a ledger to a beam, then the distance is the midway point between the supported ends either a ledger or beam of the joist plus any cantilevered portion of the joist past the beam.

It makes sense if you think about it. If a joist spans between two beams or a beam and a ledger, each beam or ledger supports half of the joist. The length of joist span actually supported by a beam is what determines the force that bears upon that beam and therefore the distance that a given size of beam can span before another post is required to support that beam. Refer to the Deck Beam Span Table below to assist in determining the maximum span of a given beam between posts. Obviously, the larger the beam, the greater the distance it can span between posts.

A Redwood 4x6 beam should span no more than 6' between supporting posts. Why Sign Up? Read Archives. My wife is a stroke victim, and she wants this deck to be as easy as possible for her to walk out on. She would like it to be as high as possible, with. Replacing my southeast MI year-old deck, was hoping just to replace the surface boards but many of the posts were set too deep and rotted at ground. Read More. I am building a ground level deck max 24 of the ground.

It is L shaped and will have 2 long beams The beams will be 3-ply PT SP 2 2x12's. Concrete Volumes. Beam Spans.

Joist Spans.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. It only takes a minute to sign up.

There are lots of span calculators available online, which help you determine what size lumber to use in home or deck construction. For example. You could try to figure out what the live loads and dead loads for the bed are and go from there.

Shortcut - I might try to get by with 2x4's spaced 2' or less apart if they run side to side across a single mattress, but I'd want 2x6's if they run long ways, or for a full or larger. Here are two documents I've found helpful, giving specs for southern yellow pine, which is the wood typically used in treated lumber for its added strength compared to SPF pines.

Assuming a 6ft length of 4x4 that actually measures 3. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. How to calculate the maximum safe load on a horizontal wooden beam? Ask Question. Asked 4 years, 6 months ago. Active 2 years, 4 months ago.

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Viewed k times. Active Oldest Votes. Great resources! I am waiting to see if anyone also finds something for loads concentrated at a point.

Barn Barn 3 3 bronze badges. These documents are for uniformly loaded lumber in a repetitive installation. Your question referred to a simple central load. I use working stress, not ultimate strength. Usually shear governs for short spans, and bending governs on longer spans. I get about 1, lbs. Sign up or log in Sign up using Google.

Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog.Use the span tables below to determine allowable lengths of joists and rafters, based on size and standard design loads. You can also use the Wood Beam Calculator from the American Wood Council website to determine maximum rafter and joist lengths. The lengths and sizes of joists vary depending on the species and quality of the lumber used.

For example, you can span a 1 grade no knots southern yellow pine a greater distance than a 2 grade with knots southern yellow pine. The 1 grade material is more expensive than the 2 grade, but if you can use fewer or smaller 1 grade joists or rafters in your design, you may actually save money. Rafter spans can be extended slightly beyond what the rafter tables suggest, when there is a cantelever extending beyond the supporting wall.

Ceiling Joist Span Use this table to determine the maximum lengths of ceiling joists based on species of lumber, joist spacing, and joist size. Floor Joist Span Use this table to determine the maximum lengths of floor joists based on species of lumber, joist spacing, and joist size. Roof Rafter Span Use this table to determine the maximum lengths of roof rafters based on species and grade of lumber, spacing, dimensions, load, and slope.

Leave span tables and visit our home page. Span Tables. First Name optional. I am at least 16 years of age. I have read and accept the privacy policy. I understand that you will use my information to send me a newsletter.Directions: Enter values for span ftspacing, species, grade, live and dead load psfduration of load and wet service conditions, allowable deflection criteria e.

Updated design values for Southern Pine dimension lumber, effective June 1,are included with the NDS settings. Choose design criteria by entering "yes" or "no" in the appropriate cells.

Press "update" button. The two lightest sawn lumber sections for the 4 framing plan options shown below will be displayed. More detailed explanations and examples of wood beam design can be found in my text. Note that the allowable stress method is used; only rectangular sawn lumber sections are tested; beams are assumed to be simply-supported and may be laterally-braced either continuously or only at the supports and point loads if any.

Four plan types are included for each selection of beam span and spacing, as shown in the framing plans below:. Disclaimer: This calculator is not intended to be used for the design of actual structures, but only for schematic preliminary understanding of structural design principles. For the design of an actual structure, a competent professional should be consulted. First posted Sept. Framing plans and load diagrams: a uniformly-distributed load; b single concentrated load at midspan; c concentrated loads at third-points; and d concentrated loads at quarter-points.

Select structural No.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

It only takes a minute to sign up. I need to build a footbridge across a creek and, due to soft and low land around it, will need a long span crossing the creek.

## Understanding Loads on Beams

I found this tutorial by Ron Hazelton where he makes a bridge with a 12' span with two beams supporting it, with supports only at the ends. Each beam is made up of two 2x6 boards mated together with construction adhesive and bolts every 2'. This creates a single 4x6 beam. Is there a reason for doing this with two 2x6x12 pieces instead of a single 4x6x12 board?

Would it be as strong or stronger if I did the same with a 4x6x12? It has to do more with the quality of the the 2x6s vs the 4x6. A 4x6 x 12 board would have to be clear all the way through, with no cracks or knots. Most softwood logs won't produce this board, and if it cracks, it is likely to break more easily vs the 2x6. On the other hand, drilling a bunch of holes in a 2x6 does it no favors, though because the two boards are tied together, weak spots in one board are often compensated by its partner.

So, if you could find a really good 4x6, go with it, but otherwise use the 2x6. In most cases, the 4x6 will be more expensive due to its rarity. In colonial times, they would have gone with the 4x6, as they had lots of hardwood timber and each individual cut took a long time.

Boards that are laminated in some fashion get an overall durability increase not necessarily net strength increase because they no longer suffer from a single grain dimension through the thickness.

Primarily, in the case you describe a split or warp will not impact the whole board, only half of it. A properly laminated beam like VersaLam or Glulam does have a strength rating beyond a comparably sized dimensional board but it's partly due to the process they use to glue it without adding a lot of weight. In the case of your footbridge, I strongly suspect the process was chosen because it saved significant cost and was more manageable for a smaller construction team maybe even 1 man. Optimizing for overall strength on a footbridge is usually not done, they prefer them to be inexpensive and last a long time without costly maintenance.

In architecture we use laminated timber in order to reach long distances. It would be impossible otherwise. Here is just to reduce weak spots.

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