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Title: Evaluation of a Soil Termiticide or Borate Non-Pressure Treatments for Protecting Douglas-Fir CLT in a Field Test: Two Years Results

Source: AWPA proceedings

Author(s)Mankowski, Mark , E. .; Shelton, Thomas; Kirker, Grant T.; Morrell, Jeffrey J.

Publication Year: 2020  View PDF »

Category: Conference Proceedings

Abstract: Mass timber, which includes cross laminated timber, is becoming increasingly popular as a material choice for mid-level and high-rise construction. Material durability, especially in extreme exterior exposures, is a key concern of developers that has to date not been fully resolved. Data on the effectiveness of currently labeled soil termiticides, as well as spray-on borates applied either post-construction or as a remedial treatment, needs to be generated for cross laminated timber (CLT) structures. Current design standards do allow for preservative treated and naturally durable wood but incorporating treatment options into CLT manufacturing is a considerable challenge that is being addressed, albeit slowly. Soil and perimeter termiticidal treatment is also a necessity for CLT construction, especially if installed in southeastern United States climates, as most species currently used in fabrication of CLT are not naturally termite resistant. In this study, 3-ply 12”x14”x4” Douglas-fir CLT pieces were installed in an above ground protected test at the Harrison Experimental Forest (HEF) (Saucier, Mississippi) in September 2017. Test samples were placed in sets of two on bricks approximately 3-4” above soil and covered with ventilated waterproof covers. A total of 20 test sets (40 total samples) of four different treatments were installed in this test. Soil below five sets of CLT samples was treated with a soil termiticide (fipronil). One sample per set in the other five sets was treated with a sprayon borate (23% DOT) preventative treatment. The remaining ten sets were left as controls with no treatment. Ten control sets were examined for termite attack one year after installation. Five of the attacked sets were treated with the same spray-on borate as a remedial treatment to evaluate its ability to arrest active termite attack. After one and two years, most untreated control replicates were attacked by combinations of decay fungi and termites. Samples treated with borates at test initiation and remedially after one year showed limited decay or termite attack. Remedially treated samples showed no increase in degradation. Soil termiticide treated plots showed no sign of termite attack, but four of the plots had heavy decay compared to non-soil termiticide treated plots.

Keywords: Cross Laminated Timber; E21; E26; ground proximity; soil termiticide; borate; field test; durability; decay; termite

Publication Review Process: Informally Refereed (Peer-Reviewed)

File size: 5,120 kb(s)

Date posted: 03/12/2021

This publication is also viewable on Treesearch:  view
RITS Product ID: 10124
Current FPL Scientists associated with this product (listed alphabetically)
Kirker, Grant
Research Forest Products Technologist
Mankowski, Mark
Research Entomologist
Shelton, Thomas Guy
Research Entomologist

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