4×4 Vs 6×6 Deck Posts: Which is the Best Option for Your Deck?

Imagine yourself on your back deck on a lovely summer day, sipping a refreshing beverage and taking in the sunshine.

You love your deck – it’s your go-to spot for relaxation and entertaining. But lately, you’ve noticed that the deck posts seem shaky. You start to worry – is your beloved deck safe?

You are not alone if you find yourself in a similar scenario. Choosing the right deck post size is one of the most important decisions you’ll make when building or upgrading a deck.

But how do you know which size is right for your deck?

6×6 deck posts have a significant load-bearing advantage over 4×4 posts. For a 3-foot post, 6×6 can support up to 20,834 lbs, 16% better than 4×4’s 17,426 lbs. Taller posts show a bigger difference, with 6×6 handling up to 64-78% more load capacity. Choose 6×6 for higher load requirements.

In this blog post, we’ll closely examine 4×4 vs 6×6 deck posts and help you understand the key differences between them.

Comparison Factors Between 4×4 And 6×6 Deck Posts

Whether you’re a DIY enthusiast or a homeowner planning to hire a professional contractor, this section will provide you with everything you need to know about choosing the best deck post size for your project.

Factors4×4 Deck Post6×6 Deck Post
Size3.5″ x 3.5″5.5″ x 5.5″
Load-Bearing Capacity17,426 lbs (3ft)6,468 lbs (8ft)2,339 lbs (14ft)20,834 lbs (3ft)18,032 lbs (8ft)10,550 lbs (14ft)
StrengthAdequate for small to medium-sized decksRecommended for larger or heavy load decks
StabilityMay be less stable compared to 6×6 postsOffers greater stability compared to 4×4 posts
Building CodesMay meet local building code requirements for smaller decksMay be required by local building codes for larger decks
MaterialCan be made of wood or composite materialCan be made of wood or composite material
Environmental FactorsMay be suitable for areas with moderate weather conditionsCan withstand harsher environmental factors, such as heavy snow or high winds
Estimated Cost (USD)$5-$15 per post$30-$45 per post


The size of deck posts is a critical factor to consider when building a deck. The 4×4 post is like a compact car, while the 6×6 post is like a full-size SUV. Both get the job done, but one has more room to stretch out.

4×4 deck posts measure 3.5″ x 3.5″, while 6×6 deck posts measure 5.5″ x 5.5″.

This size difference can significantly impact the deck’s load-bearing capacity, strength, and stability.

If you’re building a small to medium-sized deck, 4×4 posts may be adequate, but for larger or heavy-load decks, it’s recommended to use 6×6 posts for their increased size and strength.

Load-Bearing Capacity

When it comes to load-bearing capacity, the 6×6 deck post has a clear advantage over the 4×4.

For a 3-foot post, the 6×6 can support up to 20,834 lbs, which is 16% better than the 4×4’s capacity of 17,426 lbs.

However, the difference becomes more significant for taller posts. An 8-foot 4×4 post can support up to 6,468 lbs, while an 8-foot 6×6 post can handle up to 18,032 lbs – a whopping 64% more load capacity.

Similarly, a 14-foot 4×4 post can support up to 2,339 lbs, while a 14-foot 6×6 post can handle up to 10,550 lbs – a staggering 78% increase in load capacity.

Therefore, if you’re building a taller deck or a structure that requires higher load-bearing capacity, the 6×6 deck post is the better choice.


The 4×4 post is like a runner who can handle a 5K, while the 6×6 post is like a marathoner who can go the distance.

The strength of a deck post depends on its load-bearing capacity and size.

A 4×4 post is adequate for small to medium-sized decks, while a 6×6 post is recommended for larger or heavy-load decks.

Your deck will be safe and structurally sound if you choose the right size.


The stability of a deck post refers to its ability to resist lateral movement and sway.

The 4×4 post is like a tightrope walker, while the 6×6 post is like a wider balance beam. Both can stay upright, but one has more room for error.

A 6×6 post offers greater stability than a 4×4 post, which may need to be more stable. This factor is significant in areas with high wind loads or seismic activity.

Building Codes

Building codes dictate the minimum standards that must be met to ensure a deck is structurally sound and safe.

Local building codes may require the use of a 6×6 post for larger decks to ensure that the structure can support the weight and stress placed on it.


The 4×4 post is like a classic car, while the 6×6 post is like a modern luxury vehicle. Both can get you where you need to go, but one has more bells and whistles.

Both deck posts are made of wood or composite material.

Due to their sturdiness, resistance to decay, and minimal maintenance requirements, composite materials are growing in popularity.

Environmental Factors

Environmental factors such as climate and weather conditions can impact the structural integrity of a deck post.

The 4×4 post is like a sun hat, while the 6×6 post is like a winter coat.

A 6×6 post is better suited for areas with harsher environmental factors, such as heavy snow or high winds, while a 4×4 post may be suitable for areas with moderate weather conditions.

Estimated Cost

The 4×4 post is like a bargain store, while the 6×6 post is like a high-end boutique. You get what you pay for, but sometimes the more expensive option is worth it for the added benefits.

A 4×4 post typically costs between $5 and $15 per post, while a 6×6 post costs between $30 and $45 per post.

It’s important to consider the cost in relation to the size and weight capacity needed for your deck to ensure it is structurally sound and safe.

When Should You Go For 4×4 Deck Post?

When it comes to building a deck, choosing the right size of the deck post is an important decision that can impact the overall strength and stability of the structure.

In some cases, a 4×4 deck post may be the best choice. Here are some situations when a homeowner may want to opt for a 4×4 deck post:

Small to Medium-Sized Decks

A 4×4 deck post can be a suitable choice for small to medium-sized decks that don’t have a heavy load-bearing requirement.

For decks that are less than 10 feet in height, 4×4 posts can offer adequate strength and stability.

They can handle up to 17,000 lbs of weight, which is sufficient for most smaller decks.

Tight Budget

4×4 posts are generally less expensive compared to 6×6 posts.

Homeowners may opt for 4×4 posts to keep costs down if budget is a concern.

The size of the deck, the materials used, and the design’s complexity will all impact the project’s entire cost, so it’s crucial to keep that in mind.

Local Building Codes

In some cases, local building codes may allow using 4×4 posts for smaller decks.

Homeowners should always consult with their local building department to ensure compliance with any applicable codes or regulations.

Building codes may dictate the size and spacing of deck posts based on factors such as the height and size of the deck, the weight it will bear, and the deck’s location.


Sometimes, homeowners may prefer the look of a smaller deck post.

4×4 posts can offer a more streamlined and traditional look compared to larger posts, which can have a more imposing and bulky appearance.

This is a personal preference and can vary based on the design and style of the deck.

It’s important to note that while 4×4 posts can be a suitable choice in certain situations, they may not be appropriate for larger or heavier decks.

When Should You Go For 6×6 Deck Post?

A 6×6 deck post is the best choice in situations where there are high load-bearing requirements or other factors that demand a stronger support structure.

Here are some of the key reasons why a homeowner might choose to go for a 6×6 deck post:

Larger Decks

For larger decks or multiple levels, a 6×6 deck post can offer greater stability and strength compared to a 4×4 post.

The larger size of the post allows it to bear more weight and resist greater forces, which is important for ensuring the safety and longevity of the deck.

High Load-Bearing Requirements

If a deck has a heavy load-bearing requirement, such as when it is supporting a hot tub or other heavy equipment, a 6×6 post may be necessary to provide the necessary support.

A 6×6 post can typically support up to 20,000 lbs, which is significantly more than a 4×4 post can handle.

This makes it a more suitable choice for decks that require greater strength and stability.

Taller Decks

For decks taller than 10 feet, a 6×6 post may be necessary to provide adequate support and ensure the structure’s safety.

Taller decks are subjected to greater forces from wind and other environmental factors, so it’s important to use a post size that can withstand these stresses.

A 6×6 post can offer the necessary strength and stability to keep a tall deck safe and secure.

Harsh Environmental Factors

If a deck is located in an area with harsh environmental factors, such as heavy snow or high winds, a 6×6 post may be necessary to provide the necessary support and ensure the structure’s safety.

A larger post size can better withstand these forces and prevent the deck from being damaged or collapsing under stress.

While 6×6 posts may be more expensive than 4×4 posts, the investment is well worth it for the peace of mind and safety that comes with a more robust and stable support structure.

How To Turn A 4×4 Post Into A 6×6 – A Comprehensive Guide

If you’ve already built a deck using 4×4 posts and you now want to upgrade to 6×6 posts, you may be wondering if it’s possible to convert them.

The good news is it is possible to turn a 4×4 post into a 6×6 post, and it’s easier than you may think.

In this guide, I will walk you through the steps on how to turn a 4×4 post into a 6×6.

Section 1: Removing the Existing Post

  • Begin by removing the existing 4×4 post from your deck.
  • Cut through any screws or nails, keeping the post in place using a reciprocating saw.
  • Next, gently use a pry bar to pry the post loose from the deck frame.
  • Be careful not to damage the surrounding boards or railing during this process.

Tools required

  • Reciprocating saw
  • Pry bar

Section 2: Preparing the New Post

  • Purchase a new 6×6 post that is long enough to reach from the ground to the height of your deck.
  • Cut the new post to the appropriate length, which should be the same as the height of the existing 4×4 post plus the additional height of the new 6×6 post.
  • For example, if your existing 4×4 post is 4 feet tall and you want to add a 2-foot extension to make it a 6×6 post, your new post should be 6 feet tall.
  • Sand the edges of the post to smooth out any rough spots.

Tools required

  • Circular saw
  • Sandpaper

Section 3: Installing the New Post

  • Place the new 6×6 post into the existing post hole.
  • Make sure the post is level and plumb using a level and plumb line.
  • The new post should be centered in the hole and should have at least 2 inches of clearance from the sides of the hole.
  • Secure the post in place with post brackets or by nailing the post to the deck frame.
  • If using post brackets, attach them to the post and then secure them to the deck frame using wood screws.
  • If nailing the post to the deck frame, use 16d nails to ensure they are driven at an angle.

Tools required

  • Level
  • Plumb line
  • Post brackets or nails
  • Wood screws
  • 16d nails

Section 4: Finishing the Post

  • Add decorative trim to the post using a miter saw to cut the trim to size and to finish nails to attach it to the post.
  • The trim should be cut to fit the length and width of the post and should be at least 1 inch thick to match the thickness of the post.

Tools required

  • Miter saw
  • Finishing nails
  • Stain or paint

By following these steps, you can successfully turn a 4×4 post into a 6×6 post and upgrade the strength and stability of your deck.

However, it’s important to note that if you’re not comfortable with any part of this process, it’s always best to hire a professional to ensure the safety and integrity of your deck.

Bottom Line

As you contemplate the ideal deck post size for your project, it is crucial to weigh the pros and cons of each option carefully.

While 4×4 and 6×6 deck posts have their unique features and strengths, it ultimately comes down to your specific needs and preferences.

If you are building a smaller or medium-sized deck and want to save on costs, a 4×4 deck post may be suitable, meeting building codes and providing adequate support.

However, for larger or heavier load decks or those in areas with harsh environmental factors, a 6×6 post may offer greater stability and load-bearing capacity, although at a higher cost.

Regardless of your choice, always ensure that your deck meets the necessary building codes, and if in doubt, consult with a professional to ensure a safe and secure installation.

So, go ahead and make your choice, and enjoy your beautiful and functional deck for years to come.


How far can a 4×4 post span for a deck?

When it comes to the spacing of 4×4 and 6×6 deck posts, there are specific guidelines to follow.

For a sturdy railing, deck frame, or fence, you’ll want to keep your 4×4 posts no more than 6 feet apart, while 6×6 posts can be spaced up to 8 feet apart.

So, whether you’re a seasoned DIYer or a first-time builder, don’t skimp on the post spacing – your deck will thank you for it in the long run!

How long does a 6×6 post last?

A 6×6 PT (pressure-treated) post has the potential to last for many years, especially when embedded in concrete and protected from ground contact.

If installed correctly, it may last anywhere from 5 to 10 years in soil alone but can have a longer lifespan with the right maintenance and precautions.

Creating a slope around the post for water runoff and preventing ground contact can help extend its longevity.