Mass Timber
Mass Timber is a major sustainability trend in US design. It took a while for Mass Timber to gain traction in the US. But decades of European experience 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.
A fast growing market
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, such as moisture and termites, particularly in hot and humid parts of the country where the destructive Formosan termite has become a threat. Two reports concerning termite and moisture vulnerability have been issued by researchers from the US Forest Service and Mississippi State University:
- https://www.fpl.fs.fed.us/documnts/pdf2018/fpl_2018_franca002.pdf
- https://www.fpl.fs.fed.us/documnts/pdf2018/fpl_2018_franca001.pdf
The conclusion of these tests, that CLT is vulnerable to both moisture and termites, is not surprising. In regions and climates with termite pressure, it is well known that construction which limits termite access to wood materials and detailing to keep the wood dry are both strategies to help create durable wood buildings.
Polyguard’s TERM Barriers offer a design solution to both moisture and termite problems. TERM Barriers resulted from over 21 years of interdisciplinary work; entomology scientists working with building envelope material developers.
Specific to CLT, termite resistance tests were performed at the University of Hawaii on both TERM Water|Termite Barrier and TERM Particle Barrier:
- Protection of CLT from Formosan termites using Polyguard TERM Water | Termite Membrane Barrier.
- Protection of CLT from Formosan termites using Polyguard TERM Particle Barrier.
These two reports indicate that TERM Barriers protect CLT from termites. Since TERM Membrane Barriers are based on Polyguard waterproofing materials which have been used worldwide since 1970, the TERM System blocks both moisture and termites.¬
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 include a non-chemical 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 incorporate a non-chemical termite barrier.
In the decades since testing and cooperative efforts expanded to other universities in high termite pressure areas, including University of Georgia, Louisiana State University, University of Florida, University of Hawaii, CSIRO (Australia’s National Research laboratory) and the City of New Orleans Termite, Mosquito, and Rodent Laboratory.
The outcome of this work is the TERM Barrier System, incorporating three elements:
1. Water|Termite laminated membrane barriers and sealants.
2. Tiny stone particles graded in sizes too large for termites to move, and too small for termites to crawl between.
3. Stainless steel mesh with apertures less than 1/50th
“Termite Village” – 50 miniature homes in a wooded New Orleans area.
These homes had 4” concrete slabs and a steel roof.
Termite entry points:
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 termite 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 gaps.
TERM Barrier System:
TERM is designed to exclude termites from entry points shown above.
- TERM waterproofing properties stop moisture problems.
- TERM elastomeric properties accommodate movement of building components wherever TERM is applied.
- TERM sealant is applied at tiny gaps such as around 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 decades. Polyguard has provided waterproofing membranes to commercial construction since 1970.
TERM’s upgraded waterproofing membranes also act as non-chemical termite barriers, using 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.
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 are blocked by the particle barrier. Unable to reach moisture, the colony was eliminated in 19 days.
Termite Screen Barrier:
You may never have 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 FL
TERM Underslab Barrier:
TERM Underslab Barrier is the most important component of the TERM Barrier System. If you are designing for construction in a hot and wet region, you should seriously consider TERM Underslab.
For vapor barrier specifiers, TERM Underslab is the only part of the TERM System which creates a noticeable increase in project cost. Two reasons for this investment are:
Waterproofing:
Most projects call for an underslab vapor barrier. Vapor barriers, by definition, stop vapor, but not water. Plus, the incredibly destructive processes used in concrete slab construction will almost certainly result in numerous punctures. Here is a link showing damage potential in slab construction. Link- Vapor Barriers Construction
Class 1 vapor Barriers, as defined by ASTM E1745 have a puncture resistance of 4.9 lb. TERM Underslab Barrier has 224 lb. of puncture resistance.
This illustration, created by the University of Florida, shows that Formosan subterranean termite can have multiple colonies containing several million insects Link to University of Florida Entomology.
A large percentage of foraging termites search underneath the concrete slab. Since termites can penetrate gaps larger than 1/50”, there are numerous entryways (slab joints, cracks, penetrations, etc.) into structures.
Termite Exclusion:
TERM Foundation Barrier:
TERM Foundation Barrier:
TERM Foundation Barrier will look familiar to those who know below grade foundation waterproofing. It is an upgrade of the widely used Polyguard 650 Waterproofing Membrane.
The difference in the TERM Barrier is in both more thickness, backing, and in TERM’s proven non-chemical termite barrier sealant.
In 2002, the TERM Foundation Barrier received a Southern Building Code evaluation (SBCCI Evaluation Report 2136), which preceded today’s ICC ESR 3632 report. Once the 3632-report issued, TERM Foundation barrier began to be installed on numerous ICF Foundations in the Southeast, where ICF below grade usage had been prohibited unless protected by a termite barrier. With this development, TERM Barriers began almost 20 years of use in construction
TERM Foundation Barrier – SC
TERM Foundation Barrier – Florida -2002
Other TERM Barrier applications:
TERM Sill Barrier – LA
TERM Flashing Barrier – AL
TERM Particle Barrier protecting exposed concrete perimeter – OK
TERM Termite Sealant at penetrations – OK
TERM All Pest Bath Trap – TX
TERM Particle Barrier, Micromesh, and Termite Sealant are all used in the TERM All Pest Bath Trap/Mop Sink Barrier (mockup)
Thank you for reviewing this Mass Timber overview. If you are interested, here is a link to some research background.