b'MOISTURE MANAGEMENTFACTORY-APPLIED VAPOUR-IMPERMEABLE ROOFING MEMBRANE APPLIED OVER ROOF CLT PANELS FOR A FACTORY-APPLIED VAPOUR-PERMEABLEHIGH-RISE MASS TIMBER PROJECT. PANEL JOINTS, WATERPROOFING MEMBRANE APPLIED TO TIMBERFIELD-APPLIED VAPOUR-IMPERMEABLE ROOFINGDRAG STRUTS AND PENETRATION DETAILS, SEALED PANELS FOR A LARGE, LOW-SLOPED ROOFMEMBRANE APPLIED OVER TIMBER PANELS ON AWITH ROOFING MEMBRANE STRIPS OR LIQUID STRUCTURE. LARGE AND COMPLICATED FLAT ROOF STRUCTURE. FLASHING MEMBRANES SHORTLY AFTER ERECTION.tolerance and the available budget. To bePassive measures typically include factoryshould also attempt to optimize construc-widely applicable and effective, industryor field-applied coatings or membranestion sequencing to enclose and protect guidance for mass timber moistureapplied to the wood. These measuresthe moisture-sensitive wood materials as management needs to include both passivehave varying levels of protection efficacyquickly as possible. This is often where and active measures that can be adapted in(e.g. water resistant/repellent to fullysolutions such as prefabrication of the practical ways to specific projects waterproof), durability and lifespan. Costbuilding walls/faade can be utilized to and schedules.often drives this approach; however, theincrease the speed of construction and While mass timber building elements maymore robust passive-applied protectionreduce the exposure time of mass timber be exposed to moisture at any point oncemembranes generally result in less activeelements while also requiring lessthey leave the controlled environment ofmoisture protection measures beingsite labour.the factory, including transport and storagerequired on site. Contrastingly, a low-levelA good construction-phase moisture on site, it is the on-site exposure to mois- passive protection or no protection neces- management plan will also include ture during and after the structure has beensitates more rigorous active managementcontingencies for stain cleaning and erected that is the most challenging of water and additional site labour.removal, sanding, repairs and refinishing to manage. Active water management measuresthe columns/beams and undersides of At this stage of construction, the five biginclude regular removal of water/snow/icefloor/roof panels. Many different propri-risks associated with unmanaged mois- with squeegees, shop vacuums, industrialetary wood cleaners and acids (commonly ture and entrapment within mass timberfloor scrubbers or other means, givenacetic acid/vinegar for organic stains and include: schedule delays to dry out wettedmost mass timber structures are flat andoxalic acid for iron stains) are commer-wood, wood staining and constructionwill not self-drain. Temporary drainscially available. Trial and error with damage, wood movement and swelling,and a drainage plan for the removal ofmultiple applications may be required. fungal growth and, lastly, wood decay. water from each floor of the building areEven with care, the finished cleaning may necessary to avoid wetting the floor levelsbe accidentally bleached out or imper-These risks can be addressed with a goodbelow. In addition, active measures shouldfectly blended with the untouched wood, construction-phase moisture managementinclude provisions for heaters, fans, dehu- causing aesthetic concerns for the owner plan that includes both passive and activemidifiers, moisture monitoring sensorsor architect. Cleaning and refinishing measures. The best plans are assembledand other equipment to identify and drywork, including the contingency cost collaboratively with input from both theout wetted wood. and schedule delays, can be significantly design and construction team well beforeTall, large or slower-moving mass timberreduced by committing to effective mois-construction begins (even as early as theprojects often experience attrition andture management at the start.design development phase), with keyturnover of labourers, which can leadFor more information on evaluating and managing information provided by the mass timberto gaps in the execution of the moisturemoisture risk in mass timber structures, see RDHs supplier, mass timber erector and certainmanagement plan and, in particular,guide, Moisture Risk Management Strategies for subtrades (e.g. roofing). active management of water on site. IfMass Timber Buildings V2.1An effective moisture management planleft unaddressed, it is not uncommon for includes, at a minimum, consideration forthese projects to experience prolonged transport and storage through to erectionwetting and a related need for schedule- 1 www.rdh.com/resource/moisture- on site and protection of the mass timberdelaying mechanical drying interventions.risk-management-strategies-for-elements for the remainder of construction. As such, the moisture management planmass-timber-buildings-v216 BCBEC ELEMENTSA BCBEC PUBLICATION'