There is no single maximum deck-footing spacing that applies to every residential deck.

For a conventional deck where each post bears on its own footing:

That means you should not start by deciding:

• “I’ll put the footings every 6 feet.”
• “Deck footings are always 8 feet apart.”
• “A 16-foot deck only needs three footings.”

Instead:

1. Determine the beam’s allowable span for the actual framing condition.
2. Determine how many beam spans are required.
3. Distribute the posts so every actual beam span remains within that allowable limit.
4. Place the footings under those posts.
5. Size each footing for the reaction it receives and the applicable soil-bearing condition.

If you already know your allowable beam span, use the calculator below.

The chart below shows how beam capacity can translate into footing spacing under one specific framing condition.

These examples use:

• No. 2 Southern Pine
• 40 psf live load + 10 psf dead load
• 12-foot effective joist-span condition
• built-up dimensional-lumber beams
• a simplified 16-foot beam run for the layout example

Use the Deck Beam Span Chart to determine the allowable span for your actual beam condition.

This is one of the most important concepts in deck foundation layout.

Suppose the beam table allows your selected beam to span:

That does not mean you should start at one end of the beam and place footings every 7′-4″.

Instead, use the allowable span to determine the minimum number of beam spans required.

Example: 16-Foot Beam

Convert 7′-4″ to approximately 7.33 feet.

Then:

You cannot build 2.18 beam spans.

Round up to the next whole span:

For a simple beam with supports at both ends and no cantilever, three spans require:

If the supports are distributed evenly:

So a beam with a 7′-4″ maximum allowable span may actually end up with footings spaced only about 5′-4″ apart on a 16-foot run.

That is not wasted capacity. It is simply the result of dividing the beam into whole, practical spans.

Deck-footing layout makes more sense when you follow the load path from the deck surface to the ground.

1. Deck loads reach the joists. The joists carry the decking, people, furniture, snow where applicable, and other design loads.
2. The joists transfer load into the beam. The length of joist supported by that beam is one of the major inputs affecting beam demand.
3. The beam spans between posts. The applicable beam table or engineered design determines how far the selected beam may span under that condition.
4. The posts establish support locations. Actual beam spans must stay within the allowable limit.
5. The footings support those posts. In a conventional layout, a footing is placed under each post.
6. Each footing must then provide adequate bearing. The footing area must be adequate for the reaction at that support and the allowable soil-bearing pressure.

These three foundation questions are related, but they are not interchangeable.

This distinction prevents a common mistake:

Lower allowable soil-bearing pressure often means a larger required footing area for the same post reaction.

Changing the support spacing is a separate structural redesign because it also changes:

• beam spans
• post reactions
• footing reactions
• possibly beam size

After establishing the layout, continue to the Deck Footing Size Chart.

For many conventional residential decks, yes in practical layout terms: one post sits over one footing, so the center-to-center spacing of the posts corresponds to the center-to-center spacing of those footings.

But the terms describe different structural components.

• Post spacing describes the supports under the beam.
• Footing spacing describes the foundation locations below those posts.

Special foundation systems, engineered details, or unusual structural arrangements can change the relationship.

For the beam/post side of the calculation, use the Deck Post Spacing Chart.

Two decks with identical length and width can require very different foundation layouts.

One of the biggest reasons is whether the deck is attached to the house with a properly designed ledger or supported independently by beams and posts.

If your question is primarily how many foundation locations the complete deck needs, continue to How Many Footings Do I Need for a Deck?.

Consider the same simplified attached 12×16 deck used in our framing examples:

• 12-foot effective joist-span condition
• 16-foot exterior beam run
• No. 2 Southern Pine example
• 40 psf live load + 10 psf dead load
• no beam cantilever in this simplified comparison

Now change only the beam.

The simple calculator above assumes supports at both ends of the supported beam length.

Real decks can be different.

A beam may extend beyond an exterior post, creating a beam cantilever.

That means:

You need to distinguish among:

• overall beam length
• individual span between posts
• left beam cantilever
• right beam cantilever

Cantilevers can also affect support reactions and therefore the footing design.

Do not simply subtract a cantilever from the beam length and assume the result is automatically valid. Use the cantilever limits and span conditions applicable to the actual framing design.

See the Deck Cantilever Guide for the broader cantilever rules.

Soil-bearing capacity determines how much footing area is required to distribute a support reaction safely into the ground.

Under common prescriptive residential assumptions, 1,500 psf is often used where a higher allowable value has not been established.

But site conditions can require different treatment. Examples include:

• undocumented fill
• disturbed soil
• expansive soil
• poorly drained sites
• high groundwater
• steep slopes
• unusual frost conditions
• locally identified problematic soils

Weak Soil Does Not Automatically Mean Closer Footings

Suppose a post reaction stays the same but the allowable soil-bearing pressure decreases.

The most direct consequence is that the required footing bearing area increases.

Moving the footings closer together could also change the reactions—but now you have redesigned the beam support system as well.

More footings are not automatically better. Fewer footings are not automatically cheaper.

Changing support spacing shifts cost and structural demand between the foundation and framing systems.

The most economical design often comes from optimizing the beam and foundation together.

For foundation budgeting, see Deck Footing Cost.

Not by itself.

A 12×12, 12×16, or 16×20 deck does not have one universal footing spacing.

Deck dimensions matter because they influence the framing geometry, but the final support layout can change with:

• joist direction
• joist span
• attached vs freestanding construction
• number of beam lines
• beam size
• beam species and grade
• beam cantilevers
• design loading
• stairs
• concentrated loads

This is why a rule such as:

can be misleading without a framing plan.

For quantity planning after the support system is known, use How Many Footings Do I Need for a Deck?.

A standard beam-spacing layout may not capture every load on the deck.

Additional or specially designed supports may be needed for:

Stairs and Landings

Stair systems can create their own support and foundation requirements. Do not assume the main deck beam footings automatically account for the bottom of the stair or an intermediate landing.

See: Deck Stairs Guide.

Hot Tubs

A filled hot tub can create a concentrated load far beyond ordinary distributed deck loading. Its framing and foundation should not be handled by simply “adding one more footing” without evaluating the load path.

Outdoor Kitchens

Heavy masonry, countertops, appliances, and equipment can create concentrated loads that need to be accounted for in the framing and foundation design.

Roof or Pergola Loads

Posts supporting a roof or other overhead structure can transfer additional gravity, wind, uplift, or other loads into the deck and foundation system.

Multiple Deck Levels

Stacked or intersecting framing systems can create load paths that do not fit a simple single-beam footing chart.

The beam-span → post → footing workflow works well for understanding conventional residential deck layouts.

Project-specific design may be needed when the deck includes:

• hot tubs or major concentrated loads
• roof loads carried by the deck
• unusual wind or uplift conditions
• multiple levels
• large or unusual cantilevers
• steep slopes
• questionable or undocumented fill
• unusual soils
• foundation systems outside applicable prescriptive details
• loads or geometry outside locally adopted code tables

In those situations, the answer is not necessarily “use more footings.”

The beam, posts, connections, foundation, and soil may need to be evaluated as a complete structural system.

Once the structural support locations are known, the next challenge is transferring the design accurately to the site.

1. Establish the Deck Reference Line

For an attached deck, this may begin with the house and ledger geometry. For a freestanding deck, establish a reliable baseline from the approved plan.

2. Establish the Beam Centerline

Locate the beam relative to the house or deck edge according to the framing plan.

3. Square the Layout

Do not assume a house wall, fence, patio edge, or property feature is perfectly square. Verify the deck geometry before marking footing centers.

4. Mark the Actual Support Centers

Transfer the calculated post locations to the beam centerline.

For the earlier 16-foot / 7′-4″ example, the four simple support locations would be approximately:

• 0′-0″
• 5′-4″
• 10′-8″
• 16′-0″

That assumes a simple beam with end supports and no cantilever.

5. Verify the Entire Layout Before Excavation

Recheck:

• beam-line location
• overall dimensions
• squareness
• post centers
• footing centers
• required setbacks
• utilities
• approved plans

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Once the structural spacing is known, the most useful tools are the ones that help transfer those dimensions accurately into the yard.

Not Sure Your Footing Layout Fits the Beam, Soil or Load?

A straightforward residential deck can often follow applicable prescriptive framing provisions. But unusual soil, slopes, roofs, hot tubs, large cantilevers, multiple levels, or other concentrated loads can make the foundation layout much less straightforward.

If you’re comparing professional options, make sure each quote is based on the same:

• deck dimensions
• framing layout
• beam configuration
• foundation system
• footing depth
• footing size
• stairs
• railings
• special loads

Compare Local Deck Contractors →

Disclosure: The Backyard Standard may earn a commission if you submit a service request through this link, at no additional cost to you.

Using a Universal 6-, 8- or 10-Foot Rule

Footing spacing follows the structural support design. There is no single spacing that applies to every beam, joist span, species, grade, load, and deck configuration.

Treating Maximum Span as the Required Spacing

An allowable beam span is a maximum limit under the applicable condition. Actual supports can—and often should—be closer together when the beam run is divided into practical equal spans.

Using Total Beam Length as Beam Span

Beam span normally refers to the distance between supports. Overall beam length can also include cantilevers beyond exterior posts.

Assuming Deck Size Determines Footing Count

Two decks with the same footprint can have different joist directions, beam lines, ledger conditions, cantilevers, and special loads.

Changing Footing Spacing Without Rechecking the Beam

Moving posts changes beam spans and reactions. Support layout cannot be changed independently from the framing design.

Assuming Weak Soil Means Closer Spacing

Lower soil-bearing capacity often increases the required footing bearing area. Changing support spacing is a separate structural decision.

Ignoring Post Reactions After Reducing Footing Count

Fewer supports can increase the load delivered to the remaining posts. Those footings still need adequate bearing area.

Forgetting Stairs or Concentrated Loads

The main beam footings do not automatically account for every stair, landing, hot tub, roof, kitchen, or other load on the deck.

Excavating Before the Layout Is Verified

Confirm dimensions, squareness, beam lines, support centers, utilities, setbacks, and the approved plan before digging.

1. Determine the framing geometry.
   Establish joist direction, joist span, beam location, attached vs freestanding construction, and cantilevers.
2. Determine allowable beam span.
   Use the Deck Beam Span Chart.
3. Establish post/support spacing.
   Use the beam limit to divide each beam into allowable actual spans.
4. Establish footing locations.
   Place the foundation supports under the structural posts in the conventional layout.
5. Determine quantity.
   For the whole-deck foundation count, use How Many Footings Do I Need for a Deck?.
6. Size the footings.
   Use the Deck Footing Size Chart to check bearing requirements.
7. Determine concrete quantity.
   Use the Deck Footing Calculator.
8. Verify the complete structure.
   Check posts, connections, stairs, railings, ledger details, special loads, and locally applicable requirements.

Technical references reviewed: September 2026

• International Code Council — 2024 IRC Chapter 5
• International Code Council — 2021 IRC Chapter 5
• American Wood Council — Residential Deck Resources
• American Wood Council — DCA 6 Prescriptive Residential Wood Deck Construction Guide

There is no universal 6-foot, 8-foot, 10-foot, or 12-foot deck-footing spacing rule.

For a conventional residential post-and-beam deck:

Then remember the second rule:

If a 16-foot beam can span no more than 7′-4″, two 8-foot spans do not work. The beam needs at least three spans, which can be distributed at approximately 5′-4″ each in a simple equal-spacing layout.

Once those support locations are established, the job is not finished.

You still need to verify:

• footing bearing area
• soil-bearing conditions
• footing depth
• post size
• connections
• cantilevers
• stairs
• special loads
• local code and approved-plan requirements

If you do not yet know the allowable beam span, go to the Deck Beam Span Chart. If your support locations are already established, continue to the Deck Footing Size Chart.