Is It Normal for 6×6 Posts to Crack? Considerations and Reasons

The question of whether it’s normal for 6×6 posts to crack is common. Homeowners and builders involved in construction are usually interested in knowing whether it’s normal for wood posts to crack. And the answer is yes. It’s normal for 6×6 posts to crack.

Usually, the wood posts shrink and crack as they dry until they reach an equilibrium with the surroundings. When the wood reaches an equilibrium both in moisture content and temperature, the cracks begin disappearing. Therefore, for the timber to reach an equilibrium with its surrounding environment, it’s likely to crack and it’s normal and inevitable.

In this post, we are going to discuss in detail the common reasons 6×6 posts crack, and the things you should consider as a homeowner or a builder.

Types of Cracks in Wood

Wood posts crack during the drying period as the wood shrinks from the surface inwards. Usually, wood shrinks approximately twice as much radially(along the growth rings) as it shrinks across the rings. This uneven shrinkage causes the cracking of wood. Notably, since the wood is highly affected by the changes in temperature and humidity, it is normal for the wood to shrink and crack depending on the surrounding weather conditions.

Importantly, there are various types of cracks categorized based on size, location, and growth. Some of the common types of cracks include checks, splits, surface cracks, and end cracks. The cracks can be categorized mainly into two major types, shallow or minor surface cracks, and deep cracks.

The minor surface cracks are normal, homeowners and anyone dealing with wood should be able to differentiate between normal and deep cracks. Mainly, the small normal cracks do not affect the structural soundness of the wood posts.

On the other hand, deep cracks weaken the wood’s ability to bear the load. Therefore, you should be concerned when you see deep cracks in your wood posts and take the appropriate action.

Why Do Wood Post Crack?

Wood posts crack due to different drying rates of the wood between the external and internal parts of the wood. Usually, the wood drying process begins from the outer layers inwards. During the process, the fast-drying-out layers shrink. To relieve the pressure from the internal wood section which is not shrinking fast, the dry outer layers begin to crack. Therefore, the cracks help enhance the structural integrity of the post because they help in releasing tension and pressure built up when the wood shrinks.

Notably, during the hot days, the wood dries faster especially the wood posts in outdoor spaces largely crack when exposed to extreme weather conditions. Importantly, you will notice the wood cracks mostly in the summer as the wood dries fast.

Although cracks are good and cracking is normal, you should be concerned when you notice large cracks. Mostly, the deep cracks affect the structural integrity of the posts hence you should be concerned when you see them.

While the normal cracks are due to differences in drying and shrinking rate, the deep cracks are caused by other aspects such as;

  • Wood failing due to rot.
  • Insect damage.
  • Excess loading.

Usually, the cracks caused by any of the above causes appear different from the normal cracks. For instance, while normal wood cracks appear perpendicularly to the rings, these other cracks entail breakage of the wood fibers. Also, the wood post will likely appear sagging.

Factors that Cause the Wood Posts to Crack

To fully understand cracking of posts is normal and you shouldn’t be worried, you should understand the factors that influence the wood’s likelihood to crack.

Also, when you understand the reasons your wooden posts are cracking, you are able to take good care of your posts. The following are some of the common reasons 6×6 posts crack.

  1. Fluctuations in moisture content. Changes in moisture content due to changes in weather conditions make the wood shrink and crack as it dries gradually from outside inwards. Mainly, wood is sensitive to moisture content level fluctuations.
  2. Temperature fluctuations. Changes in temperature can cause the wood to expand and contract leading to cracking over time.
  3. Exposure to weather elements. Direct exposure to elements such as sun and rain will affect the moisture levels balance in the wood; hence causing cracking when the wood begins to lose moisture. For instance, exposure to rain can cause the wood to absorb moisture leading to expansion. On the other hand, during dry conditions, the wood loses moisture causing it to shrink and crack.
  4. Installation process. If the wood posts are not properly installed, then they may experience stress on one side than the other leading to cracking. Notably, this kind of cracking can cause structural failure.

How Do You Deal With Cracked Wood?

Usually, the most common wood cracks appear along the grain, are shallow, and do not extend to the center of the wood. Therefore, unless the cracks are deep and seem extreme, there is no worry. The only time you should have a concern about the structural soundness of cracked wood is when you see deep cracks appear near structural connectors such as bolts or nails.

However, even though the cracks do not cause structural problems, most homeowners still have concerns about cracks and the concerns may be valid depending on the location of the cracks.

Therefore, although the shallow cracks are safe, sometimes they may cause risks such as leaks and rot issues. Homeowners can deal with these wood cracking issues by;

  • Sealing the cracks.Usually, cracks in the upper radius of posts are a problem. If the cracks are upward facing, then you should seal them to prevent rot.
  • Rotate the wood posts. Rotate to the lower half to ensure the major cracks drain water instead of trapping it.

How Do You Stop Wood From Cracking?

Wood posts having cracks is normal and you shouldn’t worry about it. However, if you suspect that the cracks are affecting the strength and stability of the post, then you should take the appropriate measures to ensure the wood post does not fail.

  • Use of dried wood.If you get worried whenever you spot even small cracks on your wood, it’s important to use dried wood which has minimal chances of cracking. Notably, apart from using dried timber to avoid cracks, the dried wood is stronger and not prone to damage by insects and fungi.
  • Apply appropriate measures when using green wood.If you can not use dried, you can still opt for the available green wood and apply appropriate measures to prevent the wood from cracking. These measures include applying suitable end sealer at the end grain to slow down the drying of the posts. Also, you should ensure the wood is not exposed to direct and extreme weather conditions.

Cracking Preventive Measures

Although you may not prevent normal cracking 100%, you can still apply effective mechanisms to slow down the rate of cracking as well as minimize the risks of cracking.

Some of the ways to minimize the cracking rate and its effects include:

  1. Minimize exposure to rain. Usually, posts exposed to rain will absorb moisture and crack during the sunny season as the wood dries. Therefore, where possible, it’s important to shield the posts from rain.
  2. Minimize exposure to direct sunlight.The exposure to sunlight causes degradation of the wood making it more susceptible to cracking.
  3. Proper installation. Proper anchoring of the wood is important to ensure that it has a firm footing to reduce the likelihood of cracking. During the installation, you should use the appropriate equipment to ensure the posts are properly anchored.
  4. Pre-treatment. Usually, the wood posts are prone to damage from moisture, and insects. Therefore, to ensure the wood posts remain in good condition and are not prone to cracking, it’s important to treat them prior to installation. Proper pre-treatment ensures the posts are resistant to moisture absorption and decay, and cannot be damaged by pests.
  5. Regular maintenance.Maintenance entails implementing simple measures such as ensuring regular cleaning of the wood surfaces. You should ensure to thoroughly clean to remove accumulated dust, debris, and organic matter from the wood. Usually, the accumulated dirt holds moisture which can cause cracking when the wood begins to lose that moisture. Importantly, during the regular cleaning, you should ensure you use safe cleaning materials that do not cause the deterioration of the wood’s surface coating.
  6. Select high-quality wood. Usually, there are different wood species with each species having a varying degree of cracking rate. While some wood species are prone to cracking, others are highly resistant to cracking.


It’s normal for 6×6 posts to crack and you shouldn’t be worried about it. The normal shallow cracks that appear due to the differences in the drying rate between the external and internal parts of the wood are safe. You should expect and embrace them.

However, if you still have concerns about the rate at which your posts are cracking, you can still apply the appropriate preventive measures we have discussed in this post.

Lastly, not all cracks are the same and safe. If you see deep cracks that seem to affect the structural stability of the posts, you should take action to even replace the posts if the damage is so severe. Therefore, always be on the lookout to notice any abnormality in the cracks and address the problem.