All About Lumber: Moisture Content & Structural Performance

You already know how to select lumber for your project, but did you know its moisture content can play a significant role in your final choice? 

 

Yes, that’s right. Since lumber is a structural material, its moisture content can actually determine how well it will hold up once installed – especially when you factor in Ontario’s climate. Prone to extreme cold and freeze-thaw swings, the weather here can impact how wooden structures and frameworks behave over time. 

 

That’s why having sound knowledge of lumber’s moisture content is not optional, but a quality control requirement for contractors and builders.

 

Experts from Fonthill Lumber Inc., one of the most trusted lumber yards in the Niagara region, are here to share everything you need to know about wood and moisture. 

 

 

Why Does The Moisture Content Of Lumber Matter?

 

To understand why the moisture content of lumber matters, you need to know what “dry lumber” means. 

 

By definition, “dry lumber” is supposed to contain less than 19% moisture. SPF KD-19 is a perfect example of this type of lumber and is widely found across most Ontario lumber yards. 

 

Now you might be wondering – why 19%? Well, the choice of numbers is not random. This figure serves as the threshold that determines the dimensional stability of wood. That means dry lumber is less likely to shrink, cup, twist, or bow after it has been installed. You do not have to worry about it moving or shifting position, either as a consequence of high moisture content. 

 

In short, if the moisture content of lumber is too high, you can expect structural alignment issues. On the other hand, if it is too low, the wood is bound to be brittle and prone to cracking. The key is to strike the sweet spot with dry lumber. 

 

 

How Lumber Movement Affects Loads & Connections?

 

When the moisture content of lumber is high, it tends to shift and swell. This does not just affect its appearance but also its performance. Movement can alter your structure’s load paths over bearings, sheathing alignment, and truss set positioning. It also has a direct impact on fastener withdrawal resistance and increases the risk of drywall cracks. With excess moisture, lumber does not stay where it’s supposed to. 

 

 

How Ontario Weather Impacts Lumber Performance?

 

Now let’s talk about the weather. Ontario is no stranger to seasonal humidity swings. In fact, it rains, summers, and freeze-thaw cycles can be quite brutal, thus affecting the longevity of lumber structures. Moreover, installation practices such as framing with heaters on during the winter season or having covered vs partially covered framing schedules can influence how much moisture lumber absorbs. For example, installing lumber frameworks in the spring or fall season is recommended due to the stable weather and low humidity at this time of the year. 

 

 

How To Control Moisture Onsite

 

You cannot control the weather, but you can control your lumber’s moisture exposure. Here’s how:

 

• Store your lumber off the ground to prevent upward moisture wicking
• Use appropriate blocking methods to maintain airflow 
• Avoid creating dead zones that trap humidity and increase the wood’s moisture content
• Use tarps to cover logs onsite, but keep enough room to ensure ventilation 
• Schedule installation immediately after delivery to preserve the lumber’s stability 
• Partner with the right lumber yard to get premium materials

Proper moisture management can ensure the longevity of the structures you build, thus securing your position among key clientele as a trustworthy contractor.

 

 

Final Thought: Partner With The Right Lumber Yard For Moisture-Free Builds

 

Lumber that arrives in a twisted, swollen, or inconsistent state can ruin the structural integrity of your project. However, working with a reliable yard that puts the best moisture management practices to use ensures you get material you can work with. 

 

This is where we come in. Fonthill Lumber Inc. supplies high-quality kiln-dried lumber that is perfect for Ontario’s climate. Contact us to get materials that are well-suited to the site conditions you're building in. 

 

 

FAQs

 

Does kiln-dried lumber always contain less than 19% moisture?

 

Not always. But if it is rated KD-19, you can trust it to contain less than 19%  moisture when it comes out of the kiln. 

 

Is it possible for framing lumber to soak in moisture post-delivery?

 

Yes, if you do not store it correctly. If it comes in contact with wet ground or is stored under sealed tarps with zero ventilation, its moisture content can increase onsite. 

 

Does moisture content affect the fastener’s holding strength? 

 

Yes, it does. Lumber that’s too wet offers a significantly weaker hold, while extremely dry lumber is likely to crack when fastened with nails or screws.