Prevention and remediation of decay in mass timber using non-pressure applied borates

Practical solutions are needed to protect mass timber products from decay, and to remediate decay in mass timber structures. The present work explored non-pressure applications of borate-based preservatives for their ability to prevent decay initiation and regrowth. A treatment with a surface applied borate glycol/DDAC formulation and borate rods with a total uptake of 4.2 kg/m3 B2O3 basis was associated with reduced incidence of decay by G. trabeum after 12 months and R. placenta after 9 months. Application of a borate glycol/DDAC remedial treatment with average coverage between 0.29 and 0.40 kg/m2 was associated with significantly reduced incidence of continued growth by G. trabeum, R. placenta and I. lacteus after 6 months. As part of an integrated protection or remediation plan, borate-based preservatives may help to further reduce the risk of decay initiation or re-growth. Further work is needed to define the limits of their performance in the built environment.