Mass timber has quickly become one of the most talked about movements in modern construction. Architects, developers, and building owners are drawn to its sustainability profile, design flexibility, speed of construction, and natural warmth. From cross-laminated timber buildings to glulam structures, mass timber is helping project teams rethink what commercial and institutional buildings can look like.
But as more teams embrace mass timber, one important question deserves more attention: How do you protect a wood-based structure from the ground up?
Mass timber may be transforming the way buildings are designed above grade, but long-term performance still starts at the foundation. Below the slab, project teams need to account for risks that are often out of sight but can have a major impact over time. Termites, moisture vapor, and other soil-side conditions should not be treated as afterthoughts, especially when the building includes a significant investment in structural wood.
For mass timber to perform as intended, below-slab protection needs to be part of the design conversation early.
Mass timber is often selected because it supports high-performance building goals. It can reduce embodied carbon, create warm interior environments, and allow for efficient construction. It also represents a meaningful investment in the overall structure.
That investment deserves a protection strategy that looks beyond what is visible.
Termites are one of the clearest examples. Although mass timber is engineered for strength and performance, it can still be vulnerable to subterranean termites. A 2018 USDA Forest Products Laboratory study found that the cross-laminated timber (CLT) tested was susceptible to Formosan subterranean termite attack, demonstrating that manufacturing wood into CLT does not inherently make it termite-resistant. Termite damage within the structure may be difficult to spot until it becomes a larger, and more costly, problem.
While an intact concrete slab can help block direct access, termites can find pathways through cracks, joints, penetrations, slab edges, and other openings. Addressing these vulnerable access points early in the foundation design can help prevent termites from reaching the structure.
Moisture vapor is another below-slab concern. Moisture moving from the ground into a building can affect flooring systems, indoor conditions, and the long-term performance of materials installed above the slab. In buildings where wood is a defining structural and architectural element, managing moisture from the ground up becomes even more important.
A strong foundation protection strategy can help project teams manage these risks before they become problems.
One of mass timber’s biggest advantages is its connection to sustainable building. It gives project teams a way to use renewable materials, reduce reliance on more carbon-intensive structural systems, and create buildings that feel more connected to natural materials.
But sustainable design is not only about material selection. It is also about durability.
A building that is designed to use better materials should also be designed to protect those materials over the long run. That means thinking carefully about the conditions surrounding the structure, including the conditions below the slab.
If a mass timber building is designed for long-term performance, the foundation assembly should support that goal. Termite protection, vapor control, and thoughtful below-slab detailing all contribute to the bigger picture of sustainable design.
In other words, protecting mass timber is part of making mass timber more sustainable.
Termite protection is often discussed later in the project, especially when teams are focused on structure, enclosure, code requirements, and construction sequencing. But for mass timber projects, termite management should be considered early enough to influence foundation details and specifications.
That does not mean every project has the same termite risk. Climate, geography, site conditions, building type, and local code requirements all play a role. But when structural wood is part of the design, the project team should have a clear plan for how termite risk will be managed.
Available approaches may include soil-applied treatments, preservative-treated timber, bait systems, physical barriers, or a combination of these methods. The right strategy depends not only on initial effectiveness, but also on continuity, service life, inspection access, maintenance requirements, and the consequence of delayed detection.
Common approaches may rely on chemical treatments. While chemical treatments can be part of some pest management strategies, they may not address other below-slab concerns. They also may not align with every project team’s sustainability goals or long-term maintenance expectations.
Physical termite barriers offer another path. Rather than relying solely on chemical treatments, a physical termite barrier is designed to help prevent termites from reaching vulnerable parts of the structure by creating a continuous layer of protection below the slab. For mass timber projects, this approach can be especially valuable because it integrates termite protection into the foundation assembly itself.
Below-slab moisture vapor is not always as visible as other construction concerns, but it can influence how a building performs over time. Vapor moving through the slab can contribute to flooring issues, indoor environmental concerns, and material performance challenges.
For high-performance buildings, vapor control should be treated as a core part of the foundation strategy.
This is especially true for mass timber projects, where the structure is often central to the building’s value and design identity. Project teams spend significant time coordinating timber procurement, connections, fire protection, acoustics, and exposed finishes. Below-slab moisture control deserves the same level of attention because it helps support the conditions that allow the rest of the building to perform.
A low-permeance vapor barrier below the slab can help manage moisture vapor before it reaches the occupied space. When combined with careful installation and detailing, it becomes an important part of the building’s overall moisture management strategy.
In modern construction, materials are often expected to do more than one thing. Project teams are looking for assemblies that support performance, efficiency, code compliance, and sustainability without adding unnecessary complexity.
That same thinking should apply below the slab.
For mass timber projects, the strongest below-slab strategies are not limited to one concern. They look at the foundation as a critical component and consider how physical termite protection, vapor control, durability, installation quality, and long-term building value work together.
A below-slab barrier (like Pango Wrap Termite/Vapor Barrier) that helps manage both termite risk and moisture vapor can simplify decision-making and installation requirements for project teams. Instead of treating termite protection and vapor control as separate conversations, teams can think about how one integrated strategy supports the overall performance of the building.
This is especially helpful in projects with tight schedules, complex coordination, structural timber, or expensive flooring above the slab.
A below-slab material has to perform in more than a laboratory setting. It must survive the jobsite conditions to be effective.
Before the concrete is placed, vapor barriers and termite barriers may be exposed to foot traffic, equipment, rebar, utility penetrations, weather, and other construction conditions. If the material is not durable enough for the environment, the integrity of the installation can be compromised before the building is even occupied.
That is why puncture resistance, installation quality, and detailing matter. For project teams, selecting a durable below-slab material is one part of the equation. Making sure it is installed correctly is the other.
Mass timber projects often depend on careful sequencing and coordination. A below-slab protection strategy should support that process, not create unnecessary complications.
When evaluating below-slab protection for a mass timber building, project teams should ask several key questions:
What is the termite risk for this site and region?
Are there code requirements or owner expectations related to termite management?
How will moisture vapor be controlled below the slab?
Does the selected barrier support both termite protection and vapor control?
Is the material durable enough for real jobsite conditions?
How will seams, penetrations, edges, and transitions be detailed?
Does the solution align with the project’s sustainability goals?
These questions can help teams move from a reactive approach to a proactive one. Instead of addressing below-slab risks after the design is already set, project teams can make better decisions earlier in the process.
Mass timber is changing expectations for what buildings can be. But the success of these buildings depends on more than what people see above grade. It depends on the strategies and assemblies that support long-term performance.
The foundation is one of those critical elements.
By addressing termite protection and moisture vapor control early, project teams can better protect the structural wood, support sustainable design goals, and help preserve the value of the building over time.
For Stego, this is where below-slab thinking matters most. Pango Wrap is designed to serve as both a physical termite barrier and a below-slab vapor barrier, helping project teams coordinate termite control and moisture vapor protection at the foundation. For mass timber projects, that kind of protection can play an important role in building with confidence from the ground up.
Mass timber may be the future of sustainable building, but its long-term performance starts with the foundation.
Yes. Mass timber products such as cross-laminated timber (CLT) are made from wood and can be susceptible to subterranean termite attack. USDA research has demonstrated that CLT can be attacked by subterranean termites, meaning the size, lamination, and engineered nature of the material should not be assumed to make it termite-resistant.
Termite protection is especially important for mass timber because termite damage may occur within concealed areas of large structural wood assemblies. Research has found that exterior visual inspection may not accurately identify internal cross-laminated timber (CLT) damage, while the size and location of installed panels can make ongoing monitoring more difficult. Preventing termite access can therefore be an important part of a long-term durability strategy.
Subterranean termites can use discontinuities in the foundation and slab assembly to move from the soil into a building. Potential pathways include cracks, construction joints, utility penetrations, slab edges, blockouts, foundation transitions, and other concealed interfaces. The concern is generally not termites moving through intact concrete, but finding a pathway through or around it.
A concrete slab alone should not be treated as complete termite protection. Although termites do not consume concrete, slabs and foundations commonly include cracks, joints, penetrations, edges, and interfaces that may provide pathways into the structure.
No. Moisture management and termite protection address related but different risks. Good moisture control can help support wood durability, but dry construction should not be considered a termite-exclusion measure. Subterranean termites can transport moisture within shelter tubes and may access wood located behind other building assemblies.
A physical termite barrier is designed to help prevent termites from passing through vulnerable building interfaces rather than relying on toxicity or discovering an infestation after termites have entered. Physical barriers can be detailed around slabs, joints, penetrations, edges, and other transitions and inspected before they are concealed by construction.
No. A conventional below-slab vapor barrier should not automatically be considered a physical termite barrier. Termite-barrier performance should be supported by product-specific testing or evaluation, along with appropriate detailing, accessories, installation requirements, and treatment of seams, penetrations, and terminations.
Yes, when the product is specifically designed and documented to perform both functions. Coordinating below-slab vapor protection and physical termite exclusion can help project teams address seams, penetrations, slab edges, and foundation transitions as part of a coordinated approach.
Pango Wrap is designed to serve as both a below-slab vapor barrier and a physical termite barrier. For mass timber projects, it can help project teams coordinate vapor control and subterranean termite protection at the foundation, including critical seams and penetrations, as part of a broader durability and pest-management strategy.
Not necessarily. Physical barriers can provide a foundational line of defense by helping prevent termite access at the soil-to-building interface, while chemical treatments, baiting, inspections, or other measures may still be used to address other access points and/or an additional line of defense.