How to Size a Deck Beam
A beam is a solid structural member that is supported by posts and footings that accepts and transfers the load from joists. Once you know the distance between support posts and the length of the joists that will be supported you can determine the required size by checking our beam-sizing chart. The size of a beam is a function of the amount of weight it must support and the distance it must span.
A common beam is composed of the same size and type of lumber used for the joists by nailing 2 or 3 together side by side. Even if you are allowed to use a smaller beam, you should maintain the same depth of material as the joists to present a uniform appearance. Never position your post “sandwiched” between two boards as is sometimes seen as a beam construction technique. The relationship between directly applied and fastened boards is what bonds the strength of a multiply beam.
Occasionally a beam application may require spanning a long distance that exceeds the design limits for conventional beams. In these cases you may have to use an engineered beam to meet the required load capacities. Engineered beams are fairly expensive, so you might want to add another post to reduce the span if possible. Your local building supplier should be capable to use your plans to determine which size and type of beam will work. Steel I beams are the strongest form of beam available and can be used to carry extremely long spans 20 ft + but are very expensive, heavy and difficult to work with.
How to Decorate Deck Support Columns
Browse some examples of decorative deck support posts for tall decks.
Framing a Deck Parallel to a House
Learn about an alternative framing method that allows you to install your decking perpendicular to the house and makes the deck free standing.
How to Use Shared Load Deck Support Posts
Learn how to support an upper and lower deck using one support post and a larger footing by bolting the lower deck into the side of the post.
Decking Patterns
Installing your decking at a 45-degree angle is a popular style for decks. This can be done to reduce decking seams or just for appearance.
Best Time to Build a Deck
People often wonder when the best time to build a deck is. Learn why building a deck in winter or fall might be your best bet.
Picture Frame Decking
Install a picture frame or perimeter board to finish the edge of your deck with style.
More Helpful Resources
Explore Articles by Topic
Footings
Information related to installing frost footings for decks
Framing
Learn structural framing methods
Decking
Learn about wood and composite decking materials
Stairs
An in-depth look at the complex issue of how to build stairs
Railings
How to install guardrails and handrails to meet IRC code
Features
An overview on water drainage, benches, planters and lights
Design
The basics of deck design
Planning
Learn about permits and working with contractors
Porches & Patios
Build a covered deck to enjoy all seasons
Ledger
Proper attachment techniques
Care
Maintain your deck to maintain your investment
Materials
An overview on water drainage, benches, planters and lights
Why is Joist Protection so Important for Your Deck?
If you’ve ever seen a piece of wood left out in the weather for any period of time, you know what happens: decay. Whether through wet rot, insect damage, or mildew, the fibers begin to break down.
How to Create Strong Post-to-Beam Connections
Learn how to create a positive structural connection for your post to beam connections. Use lag bolts, through bolts with washers, support cleats and hardware connectors.
Pool Decks
Decks constructed around above-ground pools are no different than any other free-standing deck.
Building an Outdoor Space with James DeSantis
Composite decking can not be placed directly on concrete. But a substructure can solve for this. Explore this deck project with James DeSantis
Dos & Don'ts for Homeowners to Consider When Building a Deck
Your dream deck can take whatever shape you like. The trick is making it fit your budget and site conditions. While the deck doesn’t have to be built as a rectangle, there could be good reasons for doing just that.
Picture Frame Decking
Install a picture frame or perimeter board to finish the edge of your deck with style.
Explore Articles by Topic
Footings
Information related to installing frost footings for decks
Framing
Learn structural framing methods
Decking
Learn about wood and composite decking materials
Stairs
An in-depth look at the complex issue of how to build stairs
Railings
How to install guardrails and handrails to meet IRC code
Features
An overview on water drainage, benches, planters and lights
Design
The basics of deck design
Planning
Learn about permits and working with contractors
Porches & Patios
Build a covered deck to enjoy all seasons
Ledger
Proper attachment techniques
Care
Maintain your deck to maintain your investment
Materials
An overview on water drainage, benches, planters and lights