Deck Post-to-Beam Connection: Quick Answer

A conventional deck beam should transfer its gravity load into the post through direct bearing or another specifically designed structural connection.

For prescriptive residential wood decks, the two connection concepts homeowners are most likely to encounter are:

1. Beam bearing on top of the post with an approved post cap or post-to-beam connector.
2. Beam bearing in an applicable notched-post connection.

Both approaches can create a continuous load path when they are correctly sized and detailed.

What you generally should not do is place beam plies against the sides of an otherwise unnotched post and assume a few through-bolts or structural screws automatically create an equivalent prescriptive gravity-load connection.

A connector is not a substitute for understanding the load path. The approved detail must transfer the required vertical load and resist horizontal displacement at the support.

How a Deck Beam Transfers Load Into a Post

Understanding the load path makes post-to-beam connections much easier to evaluate.

On a typical deck, gravity loads move approximately like this:

The post-to-beam connection is the transition between two major structural members in that chain.

The beam collects loads from multiple joists. The post concentrates those loads and transfers them downward to the footing.

That is why the beam-post interface matters so much: a connection can contain large bolts and substantial hardware yet still be poorly configured if the intended load path is wrong.

Bearing First, Connection Second

There are two separate jobs happening where a conventional deck beam meets a post.

1. Transfer the Gravity Load

The connection needs a defined way to transfer the downward beam reaction into the post.

In a conventional bearing connection, the beam physically rests on the post or on the bearing shoulder created by an applicable notch.

2. Keep the Beam Properly Connected to the Support

Bearing alone does not finish the connection. The beam also needs the required restraint against horizontal displacement and other movement addressed by the connection design.

That may come from:

• a manufactured post cap,
• a notched-post fastening detail,
• specified bolts,
• connector nails or screws, or
• another approved connection system.

A good post-to-beam detail has a clear answer to both questions.

How Much Bearing Does a Deck Beam Need?

The IRC deck provisions require beam ends to have at least 1½ inches of bearing on wood or metal and at least 3 inches on concrete or masonry for the entire beam width, unless another approved means of support is used.

Where a multiple-span built-up beam bears on an intermediate post, each ply must have full bearing on the post in accordance with the applicable IRC beam-to-post figure.

That second point becomes especially important with built-up beams.

A three-ply beam cannot be treated as properly supported simply because one or two plies happen to land over the post while another ply hangs beyond the bearing surface.

Method 1: Beam on Top of Post With a Post Cap

One of the cleanest ways to create a post-to-beam connection is to place the beam directly over the post and use an approved connector designed for the actual post and beam configuration.

In this arrangement:

• the beam bears over the post,
• the post transfers the gravity load downward, and
• the connector maintains the required beam-to-post relationship and provides its published connection capacity.

This approach is especially useful when the beam is too wide for a practical prescriptive notch.

Post Caps Are Not Universal

A metal connector that happens to fit over a post is not automatically the correct connector.

Post caps are manufactured for particular combinations of:

• post size,
• beam width,
• solid or built-up beams,
• connection geometry,
• required capacity,
• fastener type, and
• corrosion exposure.

Simpson Strong-Tie, for example, manufactures several different families of post caps rather than one universal “deck post cap.”

Method 2: Notched Deck Post-to-Beam Connection

A notched-post connection creates a bearing shoulder in the post so the beam can sit directly on the remaining wood.

Conceptually, the connection works like this:

• the horizontal notch shoulder supports the beam vertically,
• the remaining portion of the post helps maintain the beam’s position, and
• the prescribed fasteners complete the connection.

This is fundamentally different from hanging a beam beside an unnotched post because the beam has a direct wood bearing surface beneath it.

Notching Rules Need Care

The IRC includes a prescriptive notched post-to-beam figure, while AWC DCA 6 uses its own narrower prescriptive path: DCA 6 specifies 6×6-or-larger posts and permits its shown notch for a two-ply 2x beam, while three-ply beams use an approved post cap. These sources should not be blended into one universal notch rule.

However, notching rules are not identical across every prescriptive deck guide, design standard, and local code adoption.

That means the correct rule is not:

“A notched 6×6 is always acceptable.”

Instead, confirm that the adopted code or approved deck detail permits the specific notch, post size, beam configuration, and fastening method before cutting the post.

Notched Post vs Post Cap

Both methods can create a good connection when properly designed and installed. The better choice depends on the framing geometry and the requirements that apply to the project.

For many straightforward deck configurations, the decision comes down to whether the beam geometry fits an applicable notched-post detail or is better served by a correctly sized manufactured connector.

Why Bolting a Deck Beam to the Side of a Post Is a Problem

One of the most recognizable older deck details places a beam ply against each side of a post and runs bolts through the entire assembly.

It can look substantial:

BEAM PLY — POST — BEAM PLY

But appearance is not the same as load path.

If the beam plies do not bear on the post, the gravity reaction has to transfer through the side connection rather than through a direct bearing surface beneath the beam.

That puts the connection into a very different structural condition.

AWC explains that, beginning with the 2015 IRC, wood deck beams carrying gravity loads must have full bearing at supporting posts; the older straddled-post detail relying on through-bolts for gravity-load transfer is no longer the ordinary prescriptive IRC path.

Can You Sandwich a Deck Beam Around a Post?

Do not treat the traditional “sandwich beam” — beam plies attached to opposite sides of an unnotched post — as equivalent to the conventional prescriptive bearing details used for modern residential decks.

That does not mean every possible side-mounted beam configuration is structurally impossible.

Proprietary evaluated connectors or an engineered connection can create load paths that differ from the ordinary prescriptive bearing details.

The important distinction is:

Engineered side connection ≠ beam plies casually bolted to the sides of a post.

If a project requires a side-mounted beam for architectural or geometric reasons, use a connection specifically designed and approved for that configuration.

Double vs Triple Deck Beam Connections

Beam width can determine which post-to-beam details are practical.

Remember that nominal lumber dimensions are not actual dimensions.

A triple 2x beam is therefore wider than an actual 4×4 post.

This illustrates why beam size, post size, and connection type need to be planned together rather than independently.

Use the Deck Beam Size Chart and Deck Post Size Chart before choosing the final post-to-beam connector.

Can You Notch a 4×4 Deck Post?

Do not assume that a 4×4 can simply be notched to receive whatever beam your deck requires.

Removing material from a small post leaves substantially less wood in the remaining section, and many common prescriptive deck details involving notched beam supports are based around larger posts and specific beam configurations.

The correct question is not:

“Can I physically cut this notch into a 4×4?”

It is:

“Does the applicable deck design permit this post size and this exact notched connection?”

Start with the Deck Post Size Chart rather than sizing the post around a preferred notch.

How 6×6 Posts Affect Connection Geometry

A 6×6 provides approximately 5½ inches of actual width, which creates considerably more connection flexibility than a 4×4.

Depending on the approved design, that additional material can make it easier to:

• support wider built-up beams,
• use applicable notched-post details,
• match common post-cap configurations, and
• maintain more wood around connection fasteners.

That does not mean every deck automatically requires a 6×6. Post size still depends on the applicable structural requirements, including height and loading.

But the post-to-beam connection is one more reason to consider connection geometry when selecting the post rather than looking only at axial capacity.

Deck Beam Splices at Posts

Built-up deck beams often need to be assembled from lumber shorter than the total beam line. When that happens, splice location matters.

In the prescriptive beam arrangements covered here, beam splices occur at support locations rather than being placed arbitrarily between posts.

That allows the beam pieces to transfer their reactions into the support instead of asking an unsupported field splice to behave like a continuous beam.

See the Deck Beam Splice Guide, Deck Post Spacing Chart, and Deck Beam Span Chart when laying out the beam line.

End Posts vs Interior Beam Posts

An interior post on a multi-span beam can support beam segments extending in both directions, while an end post typically supports the beam near the end of the beam line.

That difference affects:

• beam splice layout,
• connector selection,
• beam cantilever possibilities, and
• the geometry of the post-to-beam connection.

At intermediate supports, make sure the required beam plies have proper support. Do not allow a built-up beam splice or ply arrangement to leave part of the beam without the bearing required by the applicable detail.

Can a Deck Beam Cantilever Beyond the Post?

Yes, where the applicable beam design permits a cantilever.

A beam extending beyond an end post is not the same thing as a beam lacking proper bearing.

The beam still has a defined support at the post. It simply continues beyond that support for an allowed distance.

See the Deck Cantilever Guide for cantilever limits and layout considerations.

How to Choose a Deck Post Cap

Start with the actual framing — not with the hardware aisle.

Before choosing a post cap, identify:

1. the actual post dimensions,
2. the actual beam width,
3. whether the beam is solid or built-up,
4. the number of beam plies,
5. the connection geometry,
6. the required structural capacity, and
7. the corrosion exposure.

Then select a connector whose current manufacturer documentation matches those conditions.

Common Post-Cap Categories

Simpson Strong-Tie, for example, offers several post-cap families for different applications, including products within its BC, BCS, AC, LPC, PC/EPC, CC, and related connector families.

Those product names should not be interpreted as interchangeable choices.

For example, Simpson’s current BCS family includes a configuration for two 2x members on a 4x post and another for three 2x members on a 6x post. That is exactly why “6×6 post cap” is not a sufficient specification.

Some are intended for relatively light connections. Others are designed for specific built-up beams or substantially different loads and geometries.

Post-Cap Fasteners Matter Too

The connector and its fasteners work together as a tested structural system.

Do not install a post cap and then fill the holes with whichever deck screws, structural screws, or nails happen to be available.

Connector documentation specifies the permitted:

• fastener type,
• diameter,
• length,
• quantity, and
• fastener locations.

Substituting another fastener can change the capacity of the connection even when the substitute appears larger or stronger.

See Deck Screws vs Structural Screws for the full distinction between decking screws, structural wood screws, connector screws, nails, and bolts.

Recommended Layout & Structural Fastening Tools

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The exact post cap should be selected from the approved connection detail—not from a generic shopping recommendation. These verified BYS database picks are useful for laying out the connection and for appropriate structural wood-to-wood fastening where the specified detail permits them.

Pressure-Treated Posts, Notches & Field Treatment

Notching or cutting a pressure-treated post exposes wood that may not have the same preservative retention as the original treated exterior surface, depending on the lumber and treatment process.

Field-cut and notched surfaces should therefore be treated as required by the lumber or preservative manufacturer and applicable field-treatment standards.

AWPA M4 is commonly referenced for field treatment of preservative-treated wood.

The connection should also be detailed so water is not unnecessarily trapped against end grain, cuts, connectors, or horizontal surfaces.

Corrosion Protection at Post-to-Beam Connections

Post caps, bolts, screws, nails, and other hardware on an exterior deck need corrosion protection appropriate for the lumber treatment and exposure environment.

This is especially important because many deck posts and beams are preservative-treated lumber and the connection is exposed to exterior moisture.

Depending on the application, suitable hardware may include:

• hot-dip galvanized connectors and fasteners,
• manufacturer-approved exterior coatings, or
• stainless-steel hardware for more aggressive environments.

The connector and its fasteners should also be materially compatible rather than selected independently.

Does a Post Cap Replace Deck Bracing?

Not necessarily.

A post-to-beam connector addresses a specific structural connection. It should not automatically be assumed to provide all of the lateral stability required for the entire deck.

Depending on the adopted code/design path, deck height, attachment, post configuration, and lateral-load system, the deck may need additional measures such as:

• diagonal or knee bracing,
• lateral-load connections,
• moment-resisting or engineered connections, or
• another approved lateral-resistance system.

This is especially important on taller freestanding decks, where long posts can create substantial lateral-stability concerns.

Common Deck Post-to-Beam Connection Mistakes

1. Bolting Beam Plies to the Sides of an Unnotched Post

Do not assume bolts replace the direct bearing used by conventional prescriptive beam-post details.

2. Supporting Only Part of a Built-Up Beam

Make sure the beam plies have the support required by the applicable bearing detail.

3. Using the Wrong Post Cap

A connector that physically fits is not necessarily rated for the beam, post, load, or geometry.

4. Using Ordinary Deck Screws in Structural Connectors

Install post caps with the fasteners specified by the connector manufacturer.

5. Notching a Post Without Checking the Applicable Detail

Notching rules vary among prescriptive guides and design conditions. Confirm the detail before cutting.

6. Putting a Beam Splice Between Supports

Prescriptive built-up beam splices should occur at the prescribed support locations rather than arbitrarily in the beam span.

7. Forgetting to Treat Field Cuts

Address exposed pressure-treated wood according to the applicable field-treatment requirements.

8. Assuming the Post Cap Provides All Deck Bracing

The beam-post connector does not automatically solve whole-deck lateral stability.

9. Choosing Post Size After Choosing the Hardware

Size the structural members first. Then choose hardware that fits the actual design.

10. Ignoring Corrosion Compatibility

Connector material, fastener finish, preservative treatment, and environmental exposure all matter.

Deck Post-to-Beam Connection Checklist

Before considering the connection complete, verify:

• The beam size has been established.
• The post size has been established.
• The required beam plies have proper bearing.
• The connection provides the required load path into the post.
• The beam is restrained against required horizontal displacement.
• Any notch matches an applicable approved detail.
• The post cap matches the exact post and beam configuration.
• Connector fasteners match the manufacturer’s schedule.
• Beam splices occur at appropriate support locations.
• Field cuts in treated lumber have been addressed.
• Hardware is suitable for the exposure and preservative treatment.
• Any required deck bracing or lateral-load system has been addressed separately.

Deck Post-to-Beam Connection FAQ

Should a deck beam sit on top of the post?

Direct beam bearing over the post with an approved post-to-beam connector is one common prescriptive approach. An applicable notched-post detail can also provide direct bearing. Other configurations require a specifically approved or engineered connection.

Can I bolt a deck beam to the side of a post?

Do not assume that simply bolting beam plies to the side of an unnotched post is equivalent to a prescriptive bearing connection. Side-mounted configurations need an evaluated or engineered connection specifically designed to transfer the required loads.

Can I sandwich a deck post between two beams?

The traditional configuration where beam plies straddle an unnotched post and rely on through-bolts for gravity-load transfer should not be treated as equivalent to current prescriptive direct-bearing details.

Is a notched 6×6 deck post code compliant?

The IRC includes a notched post-to-beam detail, but allowable notching can vary among adopted codes, prescriptive deck guides, design standards, and connection conditions. Verify the exact detail that applies to your project before cutting the post.

Can you notch a 4×4 for a deck beam?

Do not assume a 4×4 can be notched simply because the beam physically fits. The post itself and the resulting connection must comply with the applicable deck design.

Is a post cap better than notching?

Not automatically. Both can provide good connections when used in an applicable design. Post caps are especially useful where beam width or connection geometry makes notching impractical, while an approved notched detail can provide simple direct bearing in suitable configurations.

How much bearing does a deck beam need on a post?

IRC deck provisions require beam ends to have at least 1½ inches of bearing on wood or metal and at least 3 inches on concrete or masonry for the full beam width, unless another approved support is used. At intermediate posts of multiple-span built-up beams, each ply must have full bearing on the post.

Can a triple beam sit on a 4×4 post?

A triple 2x beam is approximately 4½ inches wide while an actual 4×4 is approximately 3½ inches wide. That geometry alone shows why the complete post, beam, bearing, and connection design needs to be checked rather than assuming the members are compatible.

Can a deck beam splice between posts?

In the prescriptive built-up beam configurations covered here, beam splices are located at support locations. A splice away from the prescribed support requires a design specifically accounting for that condition.

Can a deck beam extend past the post?

Yes, where the beam design permits a cantilever. The beam still has a defined bearing point at the post; it simply continues beyond that support for an allowed distance.

What screws should I use for a deck post cap?

Use only the nails or connector screws specified for the exact post-cap model and connection. Do not substitute ordinary deck screws or unrelated structural screws simply because they fit the connector holes.

Sources & Technical References

Technical references reviewed: September 2026

• International Code Council — 2021 IRC Chapter 5, Deck Beams and Post-to-Beam Connections
• International Code Council — 2024 IRC Chapter 5
• American Wood Council — How Are Deck Beams or Girders Attached to Posts?
• American Wood Council — DCA 6 (2015 IRC-Based) Prescriptive Residential Wood Deck Construction Guide
• Simpson Strong-Tie — Deck Connection and Fastening Guide
• Simpson Strong-Tie — BCS Post Cap Installation Guide

The Backyard Standard Final Answer