Mass Timber
Mass Timber is a recent sustainability trend in US design. Of course, it is beautiful. It took a while for Mass Timber to reach the US, perhaps because the idea of constructing the primary load-bearing structure with solid or engineered wood was counter-intuitive to some. But decades of experience in Europe have confirmed mass timber advantages, which include:
- Lightweight (reduces foundation size)
- Sustainability (15 -20% less carbon dioxide emissions)
- Prefabrication ability reduces construction time by 25% vs concrete, and up to 90% less construction traffic, which gives a safety advantage.
- Other advantages frequently realized are good thermal properties, seismic resilience, wind resistance, and acoustic advantages.
The Softwood Lumber Board, an industry funded initiative www.thinkwood.com supports development of mass timber construction. The Softwood Lumber Board supports research in areas of concern, which include moisture and termites. These are of special concern in hot, humid, and termite intensive parts of the South. Several studies have been initiated.
Mjostarnet in Brumunddal, Norway – as of 2019, world’s tallest timber building (Wikipedia) |
Two papers have been published concerning termites by researchers from the US Forest Service Lab and Mississippi State University.
- Results from this study suggest CLT , left unprotected, is susceptible to attack by subterranean termites. In addition, mass timber products such as CLT, may be susceptible to water absorption. See link here.
- The results showed that unprotected CLT is susceptible to C. formosanus attack. (see below) See link here.
CLT blocks prior to exposure to C. formosanus
CLT blocks after to exposure to C. formosanus
These results will not surprise entomologists. Termites prefer the soft wood used in many CLT laminates. Moreover, when wood is damp, termites need not leave the structure to obtain moisture. Damp wood is the ideal condition for termite colony development.
Polyguard’s TERM Barrier System addresses both moisture problems and termite problems. TERM Barriers are the result of over 20 years of interdisciplinary work of entomology scientists working with building envelope material developers. Prior to 1999, there had been little contact between these two disciplines.
Waterproofing
Polyguard has produced waterproofing membranes – almost a billion ft2 of them – for over 50 years. In the 1990’s below-grade waterproofing went above-grade to serve as a complete building envelope system.
Viking Stadium
Polyguard waterproofing being installed at Viking Stadium.
Major league stadiums usually have millions of ft2 of waterproofing.
Waterproofing upgraded to be a termite barrier:
In the late 1990’s Polyguard met with Dr. Roger Gold and other Texas A&M entomology scientists, with the goal of upgrading Polyguard’s building envelope waterproofing to additionally act as a non-chemical termite barrier.
After a decade of testing with Texas A&M, cooperative efforts expanded to other universities in high termite pressure states, including UGA, LSU, UF, and the City of New Orleans Termite, Mosquito, and Rodent Laboratory.
“Termite Village” – 50 miniature homes in a wooded New Orleans area. These homes had 4” concrete slabs and a steel roof.
This unprotected control structure collapsed after 2 ½ years
The outcome of this work is the TERM Barrier System, incorporating three elements:
- Water|Termite laminated membrane barriers and sealants.
- Tiny stone particles which are graded in size to be too large for termites to move, and too small for termites to crawl between.
- Stainless steel mesh with openings less than 1/50th inch.
How Termites enter structures
Termites have thousands of entry points – some causes
- Design and Construction: Designed and built into structures are concrete joints, slab penetrations, and bath traps or mop sinks. Pest control professionals will tell you that these are common entry points.
- Post Construction: Time and nature (wind, temperature, and humidity changes) expand and contract building components. Soil settlement, as well as soil expansion and contraction, stresses and shifts building components, creating new entry points, and enlarging existing ones
TERM Barrier System:
TERM is designed to exclude termites from entry points shown above.
- TERM waterproofing properties stop moisture problems.
- TERM elastomeric properties will accommodate movement of building components wherever TERM is applied.
- TERM sealant is applied at tiny gaps such as plumbing penetrations.
- Exposed building perimeters are protected by TERM Particle Barrier.
- Drainage and ventilation points are protected by combinations of sealants, particles, and wire mesh.
Water|Termite Barrier membrane:
Self-adhesive waterproofing membranes have been the dominant below-grade waterproofing product in commercial construction for many years. Polyguard has provided waterproofing membranes to commercial construction since 1970.
TERM’s upgraded waterproofing membranes also act as non-chemical termite barriers. They use a modified sealant, proven in numerous tests as a termite barrier. A high strength backing is laminated to an extra thick layer of TERM sealant to create the water|termite barrier membrane.
Two other non-chemical barriers:
TERM Water|Termite membranes are by far the largest components of the TERM Barrier system. However, structures require openings for drainage and ventilation, and exposed exterior concrete perimeters are vulnerable to termite access. TERM Particle Barrier and TERM Micromesh Barrier (below) can block most of these miscellaneous vulnerable entry points.
Termite Particle Barrier:
Here is the development history of particle barriers
a) Particle barriers were developed in 1956 by Dr. Walter Eberling at the University of California, Berkeley.
b) In the 1980’s, Dr. Tamashiro Minoru, of the University of Hawaii, developed methods to use particle barriers in construction.
c) In the decades since, the use of particle barriers in construction has spread around the Pacific Basin, particularly in Australia and Hawaii which are areas of extreme termite pressure.
d) Usage of particle barriers has not taken grip in the U.S. mainland. Without a mainland source, freight costs are prohibitive.
e) However, there is no shortage of particle barrier research at mainland universities (primarily UF, UGA, LSU, and Texas A&M).
And now TERM Barriers provide a mainland particle barrier source. Data sheet
The magnified termites in this video have emerged from a building to find moisture.
They were unable to move the TERM Particles, and never reached moisture, eliminating the colony.
VIDEO: Termite colony eliminated in 19 Days using Non-Chemical TERM® Particle Barrier
Termite Screen Barrier:
You may have never seen a screen with openings this small – less than 1/50” (0.018”) aperture. It takes openings this small to block invasive termites. No wonder termites can penetrate almost every seam, crack, and gap in a structure.
Termite screens made of marine grade stainless steel for corrosion resistance, were developed in Australia during the 1980’s. These screens have been used around the Pacific Rim, and to some degree in the U.S. mainland.
TERM Barrier applications
TERM Underslab Barrier:
TERM Underslab Barrier is the most important component of the TERM Barrier System. The dominant termite species in the US are subterranean termites, and as the University of Florida points out in this link (UF studies) http://entnemdept.ufl.edu/creatures/urban/termites/formosan_termite.htm there can be millions in a single colony, as well as multiple colonies, under and around a structure. (link titled UF studies)
As you watch the concrete slab construction process, you see incredible physical abuse. Here is a link to the slab construction abuse page of our website. There you can see why vapor barriers are highly likely to be punctured, and why we designed high abuse resistance into TERM Underslab
Property | Measure | Exceeds all other underslab barriers? |
Thickness | .095” | Yes |
Puncture Resistance | 224 lb. | Yes |
Sealant elongation | >1000% | Yes |
Self-healing of punctures | yes | Yes |
ICC AC 380 Physical Termite Barrier compliance | ESR 3632 (link) | Yes |
Resists pesticide penetration | Yes | Yes |
Link to TERM Underslab Data Sheet
TERM Underslab Barrier – Florida
TERM Underslab Barrier – Hawaii
Other TERM Barrier membrane applications:
TERM Foundation Barrier – SC
TERM Sill Barrier – LA
TERM Particle Barrier protecting exposed concrete perimeter – OK
TERM Flashing Barrier – AL
Other TERM Barrier applications:
TERM Particle Barrier, Micromesh, and Termite Sealant are all used in this combination, which is called TERM All Pest Bath Trap
Thank you for reading this Mass Timber overview. If you are interested, here are some other links:https://www.polyguardproducts.com/term/science-based/