Check that the specifications require a written moisture management plan, state who prepares and approves it, and set the moisture limits the design team wants before timber is covered by membranes, mats, or toppings. Then check that the drawings show how water drains off each level, how end grain and panel joints are protected, and when toppings go down.
What WoodWorks says the documents should cover
WoodWorks’ mass timber moisture management guidance notes that it is common for design specifications to require the contractor to develop a written plan and submit it for approval. The design team may specify what the plan must contain, and it sets the moisture thresholds for covering wood with membranes, mats, or toppings.
The same guidance gives reference values: moisture content is typically 12% to 14% at fabrication, can reach 15% to 20% on site under normal conditions, and can exceed 30% in areas exposed to wetting. It says materials with low vapor permeance need panels below 16% before installation. Use the values your design team sets for the project. Sources verified October 22, 2026. Permanent water protection continues in mass timber building enclosure details. Insurers ask about the same plan; see preparing a mass timber project for builder’s risk insurance.
Where water gets in
WoodWorks explains that end grain absorbs water more quickly than the panel surface, so panel edges and penetrations carry more risk. Splines and joints can hold water out of sight. Water should be diverted off the timber toward drains or off the floor edges. It recommends installing protection details immediately after each panel is placed, such as membrane flaps over panel edges and bridging details at column-to-floor transitions.
Toppings and acoustic mats can trap moisture. The guidance advises against installing a concrete topping before the mass timber assembly is shielded, and suggests a maximum moisture content, such as 16%, before an acoustic mat or topping is installed.
Ten checks for the drawings and specifications
- Plan required. The specifications require a written moisture management plan and say who prepares, submits, and approves it.
- Plan contents. The specifications list what the plan must cover, such as protection, monitoring, and what happens after significant wetting.
- Moisture limits. The documents state the moisture content the design team requires before timber is covered by membranes, mats, toppings, or finishes.
- Supplier input. The plan draws on the mass timber supplier. The WoodWorks BC checklist asks whether the plan was prepared with supplier input.
- Scope split. The documents divide moisture responsibilities between the installer, supplier, and general contractor. The checklist asks whether that scope is clearly defined.
- Drainage paths. Plans or the moisture plan show how water leaves each level during construction, including temporary drains and floor edges.
- End grain and joints. Details or the plan show protection at panel edges, splines, joints, and penetrations.
- Topping timing. The sequence does not place a concrete topping or acoustic mat over timber that is not yet shielded or not yet dry enough.
- Exposed exterior members. Exterior timber has a specified coating for moisture and UV protection, and touch-up requirements are stated.
- Monitoring. The plan says where and how moisture readings are taken, including at joints and splines where water can hide.
Record each question so it can be closed
For each gap, record the specification section or sheet, what is missing, and who must supply it. Moisture questions often sit between the design team and the contractor, so name the decision owner. The Mass Timber Construction Success Checklist from WoodWorks BC and Seagate Mass Timber (April 2025) lists the tender-phase moisture questions in one place, and the mass timber drawing coordination checklist covers the rest of the package.
Where Groundbook fits
Upload the architectural, structural, and MEP drawings with the relevant specification sections, and run a cross-discipline review. Groundbook flags potential disagreements, such as an opening shown on an MEP plan but missing from the structural panel layout, with links to each source sheet. Your team decides what each finding means for the fabrication package. Groundbook does not check structural capacity, fire ratings, or the fabricator’s model.