Quick Answer: How Far Apart Should Deck Posts Be?

For structural posts supporting a deck beam, the maximum post spacing is controlled primarily by the allowable span of the beam between those posts.

For example, if your selected beam is permitted to span 7 feet 4 inches under your actual framing conditions, the posts supporting that beam cannot simply be moved to 8 or 10 feet apart because those dimensions are more convenient.

Likewise, a larger beam may allow substantially wider post spacing.

This means statements such as “deck posts should always be 8 feet apart” are incomplete.

Eight feet is a common layout dimension on residential decks, but it is not a universal structural rule.

Structural Deck Posts vs. Railing Posts

This guide covers structural support posts beneath deck beams.

It does not cover guard or railing post spacing.

If you are looking for guard-post requirements, see our Deck Railing Post Spacing Guide.

Deck Post Spacing Chart

The most useful way to understand deck post spacing is to look at how the allowable distance changes when the beam or joist span changes.

The table below provides a Southern Pine planning example under common residential loading assumptions.

It is designed to demonstrate the structural relationship between joist span, beam size, and post spacing. Your locally adopted code, species, grade, loading, and framing configuration may produce different allowable values.

For the complete beam-sizing explanation, see our Deck Beam Span Chart.

The Most Important Rule: Post Spacing Is Beam Span

For a conventional straight beam supported by posts, the distance between adjacent posts establishes the beam span.

That means you cannot determine structural post spacing independently from the beam.

This is the key relationship behind deck post layout.

A larger beam may allow fewer posts. A smaller beam may require more posts.

But every time you change the post layout, you also change the load delivered to the posts and footings below.

Understanding the Deck Load Path

A conventional deck transfers gravity loads through a predictable structural path:

The post does not determine the load by itself.

It receives the reaction created by the beam above it and transfers that force into the footing.

This is why post spacing, beam sizing, and footing sizing need to be considered together.

What Determines Deck Post Spacing?

Why Joist Span Changes Post Spacing

Joists collect load from the deck surface and transfer it into their supports.

When joists become longer, the exterior beam generally receives load from a larger area of deck.

That increased beam load can reduce how far the beam is permitted to span between posts.

This is why a double 2×10 does not have one universal post-spacing limit.

Related: Deck Joist Span Chart and Deck Joist Spacing Guide.

What Is Tributary Area?

Tributary area is the portion of the deck surface whose load is carried by a particular structural member.

For posts, think of each post as supporting a section of the beam, while that section of beam supports part of the joist system above it.

An interior post usually receives load from beam spans on both sides.

An end post generally receives load from only one adjacent span, plus any beam cantilever beyond the post.

This is why removing a post may require both a larger beam and a larger footing.

Why 8-Foot Deck Post Spacing Is So Common

Eight feet appears frequently in residential deck layouts because it is a convenient dimension and many common beam configurations can fall somewhere near that range under suitable loading conditions.

But 8 feet is not a code rule.

Depending on the framing system:

• a smaller beam may need posts substantially closer than 8 feet
• a larger beam may be permitted to span farther than 8 feet
• long joists may make an 8-foot span too large
• short joists may allow considerably more than 8 feet
• higher design loads may reduce allowable spacing

Can Deck Posts Be 10 Feet Apart?

Yes, some residential deck beam configurations can support approximately 10 feet between posts.

But 10-foot spacing is not automatically acceptable simply because the beam uses 2×10 or 2×12 lumber.

For example, under the Southern Pine planning table above, a double 2×10 supporting a 12-foot joist span is limited to substantially less than 10 feet, while a triple 2×12 under the same joist-span condition can exceed 10 feet.

The beam configuration determines whether 10-foot post spacing works.

Can Deck Posts Be 12 Feet Apart?

Sometimes — but this is where generic post-spacing advice becomes especially dangerous.

A sufficiently large beam carrying a relatively small tributary load may be able to span 12 feet or more.

The same beam carrying much longer joists may not.

If the prescriptive table does not permit the required span, the solution may be:

• add another post
• increase beam size
• change the framing layout
• reduce the joist span
• use an engineered beam or engineered design

How to Determine Deck Post Spacing Step by Step

1. Determine the deck dimensions.
2. Choose the joist direction.
3. Determine the applicable design load.
4. Select joist size, species, and spacing.
5. Determine the actual joist span.
6. Account for any joist cantilever.
7. Select a candidate beam size and species.
8. Look up the maximum allowable beam span.
9. Lay out posts so every beam span remains within that limit.
10. Check any beam cantilevers.
11. Calculate the load at each post.
12. Size the posts and footings for those reactions.
13. Verify the complete layout against your locally adopted code.

How Many Deck Posts Do You Need?

Once you know the allowable beam span, estimating post count becomes much easier.

For a simple straight beam with posts at both ends and no beam cantilever:

Example: 16-Foot Beam

Suppose your approved beam configuration can span a maximum of 8 feet.

16 ÷ 8 = 2 spans

Two beam spans require three posts:

Post — 8 ft — Post — 8 ft — Post

Example: 20-Foot Beam

Suppose the same beam can span 8 feet.

20 ÷ 8 = 2.5

Round up to three spans.

Three spans require four posts.

The posts can then be distributed so none of the actual spans exceeds the allowable maximum.

See our How Many Footings Do I Need for a Deck? guide for the next step.

Example: Post Spacing for a 12×16 Deck

Consider a 12-foot-deep by 16-foot-wide attached deck.

Assume:

• joists run approximately 12 feet from the house toward the exterior beam
• the beam runs along the 16-foot width
• there is one exterior beam line
• there is no significant joist cantilever for this simplified example

Now compare several Southern Pine beam options using the applicable 12-foot joist-span condition:

This example demonstrates why deck size alone cannot tell you how many posts are required.

Changing the beam changes the possible post layout.

Post Spacing vs. Footing Spacing

On a conventional beam-and-post deck, each structural post typically bears on its own footing.

That means the footing layout generally follows the structural post layout.

But footing spacing and footing size are different decisions.

• Post/footing spacing: where the supports are located
• Footing size: how much bearing area each support requires
• Footing depth: how deep the foundation must extend based on frost, soil, and local requirements

Continue with our Deck Footing Size Chart and Deck Footing Spacing Guide.

Can You Use Fewer Deck Posts?

Often, yes — but reducing post count changes the structural system.

Removing a post usually creates a longer beam span.

That may require:

• a deeper beam
• an additional beam ply
• a stronger lumber species
• an engineered beam
• larger post reactions
• larger footings

This can still be a good design choice when fewer posts improve patio clearance, appearance, access, or construction around obstacles.

More Posts vs. Larger Beam: Which Is Better?

There is no universal best layout.

The goal is to find the most efficient combination of beam size, post count, footing size, cost, and usable space.

What Size Should Deck Posts Be?

Post size is a separate structural calculation from post spacing.

The appropriate post size depends on variables including:

• post height
• tributary area
• lumber species
• design load
• bracing and restraint
• applicable prescriptive limits

Do not select a post size solely because it is commonly used.

Beam-to-Post Connections Matter

A correctly spaced post still needs a proper load path from the beam into the post.

For conventional prescriptive wood framing, the beam needs actual bearing at the support rather than simply hanging from the side of the post on through-bolts.

Common approaches include:

• beam bearing on top of the post with an approved post cap or connector
• beam bearing in a properly detailed post notch where permitted
• another approved structural connection providing the required bearing and restraint

The beam also needs appropriate restraint against lateral displacement at its supports.

Post-to-Footing Connections Matter Too

The load path continues below the post.

A post-base connection can help locate and secure the post while keeping the wood appropriately separated from concrete where required by the selected connector and construction detail.

The connector must be appropriate for:

• the post size
• the foundation type
• the required loads
• the treated-lumber environment
• the specified fasteners and anchors

How Beam Cantilever Changes Post Layout

The outside posts do not always have to sit directly beneath the ends of the beam.

A beam can cantilever beyond its outside bearing locations when the framing satisfies the applicable requirements.

Current prescriptive deck provisions generally limit beam cantilever beyond a bearing location to one-fourth of the actual adjacent beam span.

Example

If the actual outer beam span between posts is 8 feet:

8 ft ÷ 4 = 2-ft maximum beam cantilever

See our Deck Cantilever Guide for joist and beam cantilever rules.

How Joist Cantilever Affects Post Spacing

Joist cantilever and beam cantilever are different.

When joists extend beyond a drop beam, the cantilevered deck area still contributes load to the beam.

As that joist cantilever increases, beam demand can increase.

That can reduce the allowable span between posts for a given beam configuration.

This is why cantilevered deck layouts should be checked against the specific table conditions rather than a generic post-spacing rule.

How Snow Load Changes Post Spacing

Higher design loads place greater demand on the entire support system.

In higher-snow-load areas, a deck may require:

• shorter beam spans
• larger beams
• additional posts
• larger footings
• different joist sizing

Check the design criteria required by the local building department before using any prescriptive span chart.

How Soil Conditions Affect the Post Layout

The beam determines where structural reactions occur, but the soil ultimately has to support those reactions.

Lower allowable soil-bearing capacity generally requires more footing area for the same post load.

Therefore, increasing post spacing can create a chain reaction:

This is why post spacing should not be optimized only around reducing the number of holes you need to dig.

Common Deck Post Spacing Mistakes

1. Assuming Every Deck Uses 8-Foot Post Spacing

Eight feet is common, not universal.

2. Choosing Post Locations Before Sizing the Beam

The allowable beam span should establish the maximum spacing.

3. Ignoring Joist Span

Longer joists can substantially increase the beam load and reduce allowable post spacing.

4. Ignoring Joist Cantilever

Cantilevered deck area still contributes load to the supporting beam.

5. Using a Beam Table for the Wrong Species

Identically sized beams can have different allowable spans depending on species and grade.

6. Removing a Post Without Checking the Footings

Fewer posts can increase the load carried by each remaining footing.

7. Confusing Structural Posts With Railing Posts

They perform completely different structural jobs and follow different design requirements.

8. Side-Bolting a Beam Without Proper Bearing

A beam needs an approved load path into the post.

9. Designing Every Member at Its Absolute Maximum

Code span limits establish structural boundaries; shorter spans can also improve stiffness and simplify construction.

Signs an Existing Deck Support System Needs Attention

Possible warning signs include:

• visible beam sagging between posts
• leaning or twisted posts
• posts no longer centered on footings
• movement at beam-to-post connections
• settled or heaved footings
• significant deck bounce
• cracked, deteriorated, or damaged posts
• beam splices without proper bearing
• corroded or loose connectors

Use our Deck Inspection Checklist when evaluating an existing structure.

How Post Spacing Affects Deck Cost

Post spacing creates a structural and economic tradeoff.

For some decks, adding one inexpensive support post is cheaper than increasing the beam size across the entire deck.

For others, fewer posts are worth the additional beam cost because they preserve usable space below the deck.

Related: Deck Framing Cost Guide.

Recommended Tools & Hardware for Deck Post Layout

Once the structural post locations have been determined from the framing design, accurate field layout and the correct post/beam hardware become the next priorities.

These are the products from our current Backyard Standard Amazon database that best match this stage of a deck build.

Disclosure: As an Amazon Associate, The Backyard Standard may earn from qualifying purchases at no additional cost to you.

Bosch BLAZE Pro GLM165-40 Laser Measure

Best for: Measuring beam runs, checking post spacing, verifying deck dimensions, and laying out footing locations.

This is our primary layout recommendation for most homeowners. It is compact, accurate, and much faster than repeatedly stretching a tape across longer deck dimensions.

• Buy it if: You are laying out a new deck, comparing beam locations, or checking diagonals and overall dimensions.
• Skip it if: You only need a handful of short measurements and already have a dependable tape measure.

Check Bosch GLM165-40 on Amazon →

Simpson Strong-Tie ZMAX Adjustable Post Base

Best for: Approved post-to-concrete connections where the selected post base matches the post size, anchor, exposure, and structural detail.

A post base helps create a defined connection between the wood post and concrete footing. Simpson offers multiple models and sizes, so the exact connector needs to match the framing design rather than being selected by appearance alone.

• Buy it if: Your approved post detail calls for a compatible adjustable post base.
• Skip it if: Your post size, load, exposure, or foundation detail requires a different connector.

Check Simpson ZMAX Post Bases on Amazon →

Simpson Strong-Tie Post Cap

Best for: Properly designed beam-to-post connections.

Post caps are highly relevant to this article because post spacing only works structurally when the beam reaction can transfer safely into each support. Simpson Strong-Tie offers several post-cap families for different post and beam configurations.

• Buy it if: Your approved framing detail specifies a compatible post cap for the beam and post sizes.
• Skip it if: You are choosing hardware without matching the exact geometry and connection requirements.

Check Simpson Post Caps on Amazon →

Simpson Strong-Tie Titen HD Heavy-Duty Screw Anchor

Best for: Approved structural anchoring of post bases and other compatible hardware to concrete.

The Titen HD is a high-strength concrete screw anchor used in many structural applications, but diameter, embedment, edge distance, hole preparation, and substrate condition all matter.

• Buy it if: Your connector or approved design specifies the correct Titen HD size and embedment.
• Skip it if: You are unsure about the concrete condition, required anchor size, or connection detail.

Check Simpson Titen HD on Amazon →

Calculated Industries Construction Master Pro

Best for: Feet-inch fractions, construction math, layout dimensions, and repeated field calculations.

This is most useful for homeowners or builders doing multiple construction calculations throughout the project. It is less essential for someone who only needs a few measurements for one small deck.

• Buy it if: You regularly calculate feet-inch dimensions, rise/run, pitch, or framing measurements.
• Skip it if: You are comfortable using trusted online calculators for a one-time project.

Check Construction Master Pro on Amazon →

See our Deck Building Tools Guide for the complete deck-building tool list.

Deck Post Layout Decision Framework

Frequently Asked Questions

How far apart should deck posts be?

Structural deck posts should be spaced so the beam span between supports does not exceed the allowable span for the selected beam size, species, joist span, cantilever, and design load. There is no universal post-spacing number.

Is 8 feet the standard deck post spacing?

No. Eight feet is common in residential construction, but it is not a universal code requirement. Some beam configurations require closer spacing while others can span farther.

Can deck posts be 10 feet apart?

Yes, some properly sized beams can span 10 feet between posts under suitable loading conditions. Other common beam configurations cannot. Check the applicable beam-span table.

Can deck posts be 12 feet apart?

Some larger beam configurations can span approximately 12 feet or more when carrying relatively modest loads, but many common residential beams cannot. Twelve-foot post spacing should never be assumed without verifying the beam design.

What is the maximum distance between deck posts?

There is no single maximum distance for all decks. The maximum spacing is established by the allowable beam span for the actual framing and loading conditions.

How many posts do I need for a 16-foot deck?

It depends on the maximum span of the beam. If the beam can span 8 feet, a simple 16-foot beam with no cantilever could use two 8-foot spans supported by three posts. If the allowable beam span is shorter, additional posts are required.

How many posts do I need for a 20-foot beam?

If the approved beam configuration can span 8 feet, divide 20 by 8 and round up to three beam spans. A simple beam with three spans requires four posts, assuming no cantilevers or other layout complications.

Does a larger beam allow wider post spacing?

Generally, yes. A deeper beam or additional beam ply can increase allowable span, provided the beam configuration is permitted for the applicable load and species.

Does wider post spacing require larger footings?

It can. Wider spacing often increases the tributary load carried by each post, which can increase the required footing bearing area.

Do joist cantilevers affect post spacing?

Yes. A joist cantilever adds deck area beyond the beam and can increase the load carried by the beam, potentially reducing its allowable span between posts.

Can the beam extend past the outside posts?

Yes. Prescriptive deck framing can permit beam cantilever beyond a bearing location, generally limited to one-fourth of the actual adjacent beam span when the other requirements are satisfied.

Should a deck beam sit on top of the post?

The beam needs proper structural bearing at the post. Common prescriptive solutions include bearing on top of the post with an approved connector or a properly detailed notched-post connection where permitted.

Are 6×6 posts required for every deck?

No. Six-by-six posts are common, but allowable post size depends on height, load, species, and the applicable prescriptive requirements.

The Backyard Standard Final Answer

Deck post spacing should not begin with a generic rule such as 6 feet, 8 feet, or 10 feet.

Start with the structure above the posts.

Determine the joist span and cantilever, select the beam, and use the applicable span table to determine how far that beam can safely span between supports.

Then place the posts within that limit and size the posts and footings for the loads they receive.

Continue with our Deck Beam Span Chart, Deck Beam Size Chart, Deck Cantilever Guide, and Deck Footing Count Guide.

Sources & Technical References

Last reviewed: August 2026

• International Code Council — International Residential Code
• American Wood Council — Residential Deck Resources
• American Wood Council — DCA 6 Prescriptive Residential Wood Deck Construction Guide