Best Use Cases for ADHERO VISTO

ADHERO VISTO is particularly well-suited for large-scale mass timber projects with extensive footprints, as these projects face increased exposure risks due to:

• Longer construction durations, leading to prolonged exposure before full enclosure.
• Greater surface area of mass timber exposed at any given time.
• Complex logistics, making prefabrication and just-in-time delivery more challenging.
• High precipitation zones, where drying opportunities are limited.

For large residential, commercial, or institutional buildings, ADHERO VISTO provides an ideal moisture barrier that allows trapped bound water to escape while preventing free water infiltration. This is crucial for ensuring mass timber remains structurally sound throughout construction.

Keep Wood Looking Good

Anyone who has worked on a mass timber project will tell you that a well-defined moisture management plan is essential to preserve the integrity and appearance of the wood elements. In short, a moisture management plan is a strategy developed by the project team to ensure that the mass timber remains dry throughout the construction phase. Consultants and other design specialists can play a role in defining this strategy, but ultimately the general contractors on the project are the ones responsible for implementing the plan and ensuring that it is performing as intended.

At its core, moisture management follows a simple principle: allow gravity to drive water down and out as quickly as possible. However, there are certain factors that can make this difficult:

• Unpredictable weather events
• Inconsistent construction timelines
• Murphy’s Law (whatever can go wrong, will go wrong)

CLT Structure of 122 Waverly Ave, New York City

Rendered Drawing of 837 Beatty St, Vancouver

From one of the first mass timber residential buildings in New York City to the adaptive reuse of a warehouse in British Columbia, we’ve had the opportunity to work with consultants to develop moisture management plans for Mass Timber projects across North America. If there is one lesson we’ve learned from these experiences so far,  it’s that there is no universal moisture management solution. Like so many things in building science - it depends. Luckily though, we have at least discovered what it depends on - and this is a great place to start.

What Does It Depend On?

When developing a moisture management plan with clients, we follow a framework very similar to what is outlined by Graham Finch from RDH:

1. Assess the Risks
2. Understand the Method
3. Determine a Solution

By breaking down the moisture management plan into these three phases, project teams can ensure they ask the right questions at the right time.

1. Assess the Risks

Key Considerations:

1. How experienced are the contractors with mass timber construction?
2. Where is the project located? (Sunny Arizona vs. Rainy Washington?)
3. What season will the mass timber be exposed?
4. How long will the structure remain exposed during construction?

While it is important to assess the risks to minimize precipitation exposure, some wetting is inevitable. Understanding the method of how Mass Timber buildings are constructed can help address water when it finds its way into the places it shouldn’t be.

2. Understand the Method

Mass Timber construction follows a stacked-floor sequencing as shown in the image below, meaning that the highest installed floor acts as a temporary roof until the structure is fully enclosed. The longer this phase lasts, the greater the risk of moisture damage.

Stacked Floor Sequencing of Mass Timber Buildings

Mass Timber panels are also commonly connected to each other using plywood splines. The spline connection is a particularly moisture sensitive area for many reasons:

• The notched profiles create a trough where water can easily become trapped.
• There is exposed endgrain on either side of the spline, which is the most moisture sensitive area of a mass timber panel.
• The plywood spline is a sponge, and can soak up a LOT of water.

Plywood Splines Connecting Two CLT Panels

Microscopic Image of Endgrain. These straw-like structures (tracheids) can carry water deeper into the Mass Timber Panel, making drying difficult

Key Considerations:

1. What is the Building Type? Commercial and Residential projects will have different sequencing and detailing.
2. What areas of the project will be particularly moisture sensitive?
3. Should moisture build up in a specific area, how difficult will it be to dry?

3. Determine a Solution

Before we get into solutions, let’s look at what moisture problems on Mass Timber projects look like:

Common Moisture Damage Issues

Staining

Movement

Mold

Checking

Decay

Catch it Quick

One of the first signs of moisture damage is staining of the mass timber. If staining is found in specific areas, it is important to take note of it and address the cause by figuring out where the moisture is accumulating. Resolving the stained areas will greatly reduce the risk of more severe damage such as checking and decay from occurring. Pay close attention to the panel edges and around penetrations for staining. [include photo of ADHERO VISTO with spout]

While staining is considered only minor moisture damage, it can lead to hours time spent remediating it and refinishing the wood. 

The Role of Bound Water vs. Free Water in Moisture Damage

The different moisture damage issues can be explained by how wood stores moisture. It is important to understand that mass timber always contains some amount of moisture. Even wood with up to 19% moisture content is considered dry enough to encapsulate per the building code. This is because in conditions where the wood moisture content is 19% and lower, all of the water is able to be taken up by the cellular structure of the wood. The water that is stored by the wood in this way is called bound water, which will cause small dimensional changes to the mass timber, but won’t cause moisture damage. 

However, when the moisture content tips past the 19% threshold and begins to reach the fibre saturation point (approximately 26% MC), the wood no longer has room to store moisture within its cellular structure. When this occurs, water is stored in the spaces between the wood cells and you get free water, which can cause moisture damage because it can lead to swelling and serve as a breeding ground for mold and fungi. 

Project teams will often conduct regular moisture readings on their mass timber panels to ensure that the moisture content isn’t increasing, and also to ensure that the mass timber doesn’t reach the fibre saturation point. [photo of moisture reading] If panels reach their fibre saturation point, it is important to ensure that it dries out as quickly as possible.

The Role of Prefabrication

Prefabrication can significantly reduce moisture exposure by assembling mass timber components off-site and enclosing the structure quickly. A great example of this method was used on the Brock Commons project at the University of British Columbia. This 18-story mass timber building used prefabricated wall panels to complete the facade system in just 67 days (Canadian Wood Council).

However, not all projects can access sufficient capital for extensive prefabrication, which leads to alternative strategies.

Just-in-Time Delivery

For some projects, just-in-time delivery—where mass timber arrives on-site only when needed—can significantly limit exposure to moisture. However, this requires careful logistics planning:

• Remote projects may struggle to find suitable storage locations.
• Urban projects face tight space constraints that make staging difficult

Mitigation Strategies

Some effective solutions include:

• Temporary Protection Measures – Tarping, roof sequencing, water diversion strategies.
• Vapor-Permeable WRBs – Like ADHERO VISTO, which allows panels to dry while still repelling water.
• Edge Sealing – Treating CLT panel edges to prevent moisture ingress.
• Dehumidification & Heat Drying – Accelerating drying when moisture exposure occurs.
• Simpson Strong Tie Plywood Splines [photo]

Conclusion

A well-thought-out moisture management plan is crucial for mass timber construction success. By assessing risks, understanding the construction method, and implementing appropriate solutions, project teams can significantly reduce moisture-related issues. ADHERO VISTO plays a key role in this approach by providing a vapor-permeable yet highly effective moisture barrier, ensuring that mass timber remains protected throughout the construction process.

Looking for expert advice on your mass timber project? Contact us today to discuss your moisture management strategy.