How to Install Deck Girder, Cantilever or Drop Beams
A girder, cantilevered or drop beam is a structural member positioned below the joists to support the weight of the frame. Cantilevered beams are stronger than flush style beams because they rely on the strength properties of the wood rather than the individual mechanical and fastener connections.
Notching posts lends itself well to cantilevered beam construction, as does the practice of chamfering the corners of the deck. In order to install a cantilevered beam you must have enough clearance below the joists to install the beam. Allow for a minimum of 6” airspace between the ground and the bottom of the beam.
Always remember to install the beam crown side up so the weight of the deck will level itself. If you install a beam crown side down the deck is more likely to sag. On the negative side cantilevered beams can create a ledge underneath the joists that can become a home to birds and insects nests as well as block views and limit headroom.
The American Wood Council’s Wood Frame Construction Manual states that beams can generally cantilever up to 1/4 their span over a post. This design criterion is generally limited to beams supporting equivalent joist lengths in its span as in it’s cantilevered sections. For example, a double 2x12 beam spanning 12 feet can cantilever up to 3 feet over a post. While this maximum is allowed in conventional code-compliant design, it may not provide the comfort and stability on the deck surface desired by the occupant.
How to Decorate Deck Support Columns
Browse some examples of decorative deck support posts for tall decks.
Deck Joist Water Protection
Learn about a technique used by many pro builders for wrapping deck framing lumber with a waterproof barrier to prevent corrosion and rot.
How to Use Steel Metal Deck Support Posts and Columns
Steel deck posts with base plates can be used as an alternative to wood posts for supporting your deck.
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.
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.
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 Attach Deck Post Bases to Concrete Footers
Follow our step-by-step instructions on how to install a support post to a concrete deck footing using a post base connector and anchor.
Building a Round or Curved Deck
Learn how to build a curved deck using standard wood-framing materials. Composite decking material is more flexible for curved decks than wood.
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
Introduction to Decking
Spacing between deck boards provides several critical functions, such as drainage & drying. Learn how to space and stagger deck boards at Decks.com.
Best Hidden Fasteners for Decking
Hidden fasteners create a clean deck surface and can be used with composite, wood and other materials. Learn about hidden deck fasteners at Decks.com.
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