Does Pressure Treated Wood Shrink?

Wood will always react to temperature changes. And more specifically, untreated wood shrinks to the smallest possible size in cold seasons. It also grows to its largest dimensions during warm periods. However, is this true for treated wood? Does pressure treated wood shrink? Let’s get the answers.

Yes, pressure treated wood shrinks slightly across its width as it dries. Moreover, treated boards usually warp and twist if you leave them out in the sun for too long. Thus, expect some changes on treated wood as time goes by. 

But, fortunately, the treated wood does not contract or change as much as untreated lumber. So, you have an advantage when using it. This article provides more insight on how treated wood shrinks and how to handle such scenarios. Keep reading for more information regarding the subject.

How Much Does Pressure Treated Wood Shrink When it Dries?

Pressure treated wood shrinks about a quarter inch after drying. Hence, it is advised to fasten planks as tight as you can. Also, a natural gap will always appear gradually. Thus, tightening the planks will ensure that the resulting space is not that huge.

Thankfully, the natural gap in planks is useful as it lets debris and dirt fall away and enhances drainage.

How Much Will Pressure Treated Deck Boards Shrink?

Pressure treated deck boards shrink a quarter inch after curing. In addition, you can expect a natural gap to appear on the boards over time. Hence, it would be best to factor in these changes during installation to keep the boards intact.

Besides that, you can account for the shrinkage on overhangs. For example, the board may contract to flush after curing if you leave a quarter inch overhand. But the gap may end up being short if you want to create a flush edge.

In addition, it would be best to install boards during drier months. Humid months make the process a bit more complicated as they can reverse your work. Also, you will have to factor in wood expansion during the rest of the humid period and the resulting shrinkage in the warmer months.

Please note that the majority of the wood shrinkage appears in the board’s width. The wood is hygroscopic, and thus you expect changes to happen across the grain’s face. In addition, the length shrinkage, if any, is usually minimal. Imagine having to cut your board’s length to accommodate a five to nine percent shrinkage rate. What a nightmare!

How Long Does it Take For Pressure Treated Lumber to Shrink?

The duration varies with the humid and temperature conditions. But, generally, pressure treated lumber shrinks faster in less humid and low-temperature seasons. Also, it develops cracks, called ‘checks’ on the surface if it remains outdoors for about six to twelve months.

How Do You Dry Pressure Treated Wood Fast?

You can dry pressure treated wood by drying it out with a homemade kiln. Also, the wood will dry if you stack it in a dry area. However, you’ll have to wait for around two to three days.

On top of that, unseasoned wood that has not undergone kiln drying takes long to dry. We are not referring to hours, days, or weeks. It is more like months. But, fortunately, you can combine the strategies and use air drying for seasoned wood.

Let us go through the techniques in detail to see what you need to do.

  • Kiln-drying Method

Most half-decent wood yards provide already kiln-dried lumber. However, it is not strange to get unseasoned wood. So, you can choose to build the kiln or purchase one. But, it would be best to construct a DIY kiln as it is cheap and easy to make.

The kiln strategy involves drying lumber in a space where you can control relative humidity, air circulation, and temperature. Here, you reduce the moisture content to a target point while avoiding drying defects.

In addition, you are more likely to find dehumidification and conventional kilns as they are common in woodworking. On the other hand, solar and vacuum kilns are rare as they are suitable for special conditions and applications.

Below are some of the kilns you will find in the market.

  • Conventional Kilns. These kilns use steam inflow through pipes that radiate and increase heat in the atmosphere. Then, water content converts into vapor and evaporates from the kiln with hot air. 
  • Dehumidification Kilns. They are among the most common equipment you will find in the lumber products industry. Unlike conventional kilns, dehumidification kilns optimize continuous heat recycling in the kiln rather than discharging it. Also, the water in the coils condenses, and you can drain it in liquid form instead of ventilating it outside the kiln.
  • Vacuum Kilns. These tools are around three to four times more expensive than either the dehumidification and conventional kilns. They also deliver a limited drying capacity, and thus, are not a common preference. However, they offer a very high drying speed.

Besides that, it would help to learn about kiln schedules. They determine the relative humidity and temperature levels you need in the kiln to dry specific lumber. Also, it would be best to ensure that you dry the wood satisfactorily without causing severe or objectionable drying effects.

Even so, remember to avoid over-drying the wood during kiln drying. Unless, of course, you want to get cracked splinter-prone lumber.

  • Air-Drying Method or Wood Stacking

This technique is easy and highly effective when you do it right. Also, pressure treated wood may take longer to be completely dry, but the method does not disappoint. Eventually, you will get perfect and ready to use wood for your work.

In addition, the strategy is less expensive than the kiln method, especially if you do not own a kiln. Therefore, you only need your wood and some safe space to store it. The process also delivers higher quality and easy to work on wood than kiln drying.

Does Pressure Treated Wood Expand When Wet?

Yes, pressure treated wood tends to expand when wet. Also, you will find the wood to be somewhat wet when new. Thus, the need to ensure that it dries out before you begin the wood project.

On top of that, ensure that you leave the recommended gaps in boards and planks. This practice leaves room for expansion and contraction. Therefore, the lumber will not crack when the temperature and humidity levels change.

Should You Let Pressure Treated Wood Dry Before Using?

It would help to let pressure treated wood dry before using it. The chemicals that treat the wood leave moisture behind. Thus, the lumber needs a few weeks or months to dry. Also, the drying times vary based on climate and weather conditions. So, you can choose a fairly warm season to work on your wood projects.

On top of that, you will have an advantage if you possess a kiln. The tool helps to dry the lumber faster. Hence, you can get on with various building projects a few days after the wood arrives.

Also, the woodblock can dry in normal environmental conditions. But it will take up to months for it to be ready for use. Also, most builders work on a timeline and need the wood to be ready as soon as possible. Thus, be ready to spend some money to kiln dry the wood.

In addition, it is possible to get wood stores and yards that offer dry pressure treated wood. They will also prove costly in the future, but you will reduce the waiting time and work involved in drying wood.

Still, you can use wet pressure treated wood if you do not have an option. The wood is still fit for use as the primary stage of wood protection is complete. However, the caveat is that the wood contains so much water. Hence, it will be challenging to lift it from one place to another.

How Long Does it Take For Pressure Treated Wood to Dry?

Pressure-treated wood will take about 72 hours to dry enough for you to begin staining or painting. However, ordinary treated wood from a home center needs two to three days to dry properly.

Always remember that wet wood is not appropriate for paint and stain coats. Therefore, it is prudent to wait for the lumber to dry, regardless of the duration.

What Happens If You Paint Pressure Treated Wood Too Soon?

The paint will not adhere tightly to the wood’s surface if you paint on wet pressure-treated lumber. Hence, the wood will not get proper coverage. Also, the paint coat will not adhere to the surface and will lead to peeling. So, you will have to repaint it sometime in the future, which is more work on your plate.

This aspect applies to staining applications too. The stain will soon come off if you use wet wood. Thus, please wait for the lumber to dry well, then pick up your staining supplies.

Is It Better to Stain or Paint Pressure Treated Wood?

Although sometimes people consider painting and staining to be the same process, they are different. Hence, it is essential to factor in their varying benefits before determining the best strategy.

Painting is a good option to protect pressure treated wood from elements. It protects the surface from UV light and moisture. But it is not the best strategy as constant expansion and shrinkage cause the paint finish to peel over time. Hence, you will not have a beautiful piece to look at anymore with exposure to harsh conditions.

On the other hand, staining guarantees a more secure footing. It also adheres more tightly to the surface for a longer duration. In addition, a stained surface is not as slippery as a painted one. Thus, give a more quality finish.

Remember that pressure treated wood has chemicals that protect it from elements. However, excess exposure causes chipping and peeling. So, it would help if you had a long-lasting solution. And fortunately, staining offers just that with its superior durability and slippage qualities.

Additional benefits of staining include:

  • Rot Prevention

Rot and decay remain one of the biggest dangers you’ll face, especially if the wood stays outdoors. Moisture seeps into the lumber’s structure and causes it to rot. Therefore, it would be best to stain and seal the surface.

On top of that, rot makes the surface less appealing, which ruins the overall aesthetic. Also, the rot can get severe and compromise the wood’s structural integrity. Ultimately, the lumber runs the risk of collapsing.

  • Protection From the Sun

Excess sunlight exposure is also a threat to wood’s beauty. The UV rays from the natural body cause discoloration and fading of the wood’s surface. In addition, you’ll find that the wood will have an uneven appearance depending on which parts have exposure.

  • Preserve the Wood’s Natural Beauty

Wood is preferred for decorations and interior work because of its natural beauty. This element explains best why staining the surface is better than painting it. Paints, especially opaque ones, cover the wood’s texture and grain, whereas stains expose the wood grain.

In addition, we have semi-transparent stains that expose the lumber’s natural aesthetics. Thus, they guarantee superior protection to the patterns and natural look on the surface.

What a way to showcase the wood’s glory!

How Do You Know When Pressure-Treated Wood is Dry?

You can use the sprinkle test to check if the wood is dry enough for painting or staining. It involves you sprinkling some water on the wood’s surface. Then, check whether the lumber soaks up or absorbs it.

Dry pressure-treated wood absorbs the water in ten minutes or less. On the other hand, it would be best to give the lumber additional drying time to cure if you still see water beads.

Please note that the lumber may appear or feel dry on the surface. Water pooling or beading on the surface shows that the wood’s interior is still wet. 

How Long Does It Take For Pressure Treated Wood to Turn Gray?

Pressure-treated wood takes three to six months before staining or painting to turn gray. This condition usually happens because of the ultraviolet rays from the sun. The rays degrade the cellulose fibers and the wood’s surface. Thus, the more the wood stays in sunlight exposure, the more discolored it appears.

The wood will discolor at a faster rate if you expose it to high foot traffic. Also, spilled food particles and wet leaves will compromise the lumber’s original color.

Besides that, you will get a subtle gray hue after 30 minutes to an hour of wait time, especially during staining. Also, you can wait two or three hours for even grayer shades.

How Do You Make Pressure Treated Wood GREY?

First, get your mouth mask and safety goggles to protect yourself when using the orbital sander. The sander delivers a large amount of wood dust, which may irritate your respiratory system and eyes.

Next, set the tool to medium speed and touch the moving pad to the wood. Also, ensure that you brace the sander with two hands to move it slowly across the surface.

Get a shop rag and wipe off the wood dust to examine your progress. Continue until you remove any imperfections.

The other step is to tear up a steel wool pad and position the pieces in a mason jar. Pour some vinegar into the container and ensure to immerse all the steel wool bits fully. Then, seal the tin and let it sit for about 24 hours.

Fill a second mason jar with a ⅓ cup of boiling water and add a teabag. Then, allow the tea bag to steep until the mixture has a dark and rich brown hue.

Next, brush the tea over the sanded wood and give it time to dry. Ensure that you follow with a light vinegar solution coat and wait for roughly 30 minutes. You will observe that the lumber will appear grey and texture after curing.

Finally, lighten the shade of the grey hue with fine-grit sandpaper. 

How Long Will Pressure Treated Lumber Last With Ground Contact?

Pressure-treated wood’s life depends on the climate, the type of wood in question, its uses, and how well you maintain it. But, generally, it will last for around forty years if everything is ideal.

However, treated lumber with ground contact has a shorter life span. Hence, decks and flooring may only last ten years. In addition, you can opt for ground contact pressure treated lumber. It delivers twice the chemical retention and protection level compared to above the ground-treated wood.

Also, remember to use the ground contact wood when it has poor ventilation or is less than six inches from the ground.

Frequently Asked Questions

Here are some of the most questions frequently asked by the readers:

  • How Long Will it Take Pressure Treated Wood to Rot?

Many manufacturers guarantee a lifespan of about thirty to forty years. However, the length applies if you maintain and treat the wood properly. On the other hand, the lumber will last about nine to ten years if you expose it to wet-dry and freeze-thaw cycles without proper care and maintenance.

  • How do I Maintain Pressure Treated Wood?

Begin by cleaning the surface with a brightener or cleaner that has a mildewcide. This exercise is preventive for a new wood structure. Thus, the expected damage over time will be minute.

Next, apply a water-repellent on the wood’s surface and test by sprinkling a few drops on the wood. Apply the semi-transparent stain or water-repellent product if the wood absorbs the water immediately. On the other hand, it would be best to wait a few days if the surface does not readily soak in the water in two to three minutes.

Ensure that you adopt a maintenance routine that allows you to clean up the wood at least annually. Also, it is prudent to check the location of the wood in regards to foliage coverage, sun, and moisture exposure.

These factors will determine the clean-up frequency. However, please use a power washer if you choose to wait two or more years before cleaning.

NB: it would be best to avoid using varnish or a conventional multicoat paint system. Also, sanding is not recommended for pressure treated lumber. The particles from the wood are toxic and may cause health issues when inhaled.

  • How Do I Make Pressure Treated Lumber Last Longer?

You can make pressure treated wood last longer by using mildewcide cleaners at any signs of mildew growing on the surface. Also, applying a water-repellent sealer every year goes a long way to keep excess moisture away.

  • Does Concrete Rot Pressure Treated Lumber?

Yes. Concrete does not rot pressure treated wood. But wet conditions such as trapped water in concrete leads to wood rot. Moisture moves in the wood as a wick carries hot wax and makes it swell over time.

  • Why is My Pressure Treated Wood Warping?

Pressure treated wood swells when wet, and thus it shrinks after drying. All goes well if it dries uniformly and in the right way. However, the wood gets stressed when it dries unevenly. Thus, it warps, twists, or cracks.

Fortunately, you can keep the wood in good shape by adopting the most suitable drying technique.


Pressure treated lumber has been available for many years, but most people only know little about it like the benefits and basic functions. In addition, the wood repels mold, mildew, fungi, and termites. Thus, it remains healthy for a long duration. However, a lot are still asked about the treated wood like, does pressure treated wood shrink?

Pressure treated lumber shrinks as it dries. Freshly treated wood is usually wet because of the immersion in chemicals. Hence, it shrinks as it cures, and so it will not be news to observe some changes across the wood’s width.

Thankfully, this shrinkage does not affect your work negatively. All you need is to ensure that the wood dries well before applying a paint or stain coat. So, this attribute of pressure treated should not discourage you from using the lumber.

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Tyron Otieno

Tyron is an avid woodworker and writer. He founded this website to help other woodworkers, whether hobbyists or professionals by sharing his knowledge and experiencie after a decade of woodworking.

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