Plan Moisture Control Beneath the Metal

Profile the building and attic

Record conditioned space, attic form, existing ventilation, insulation work, interior moisture concerns and roof geometry.

Separate moisture sources

Leaks, condensation and indoor moisture movement can require different evidence. Avoid deciding the source remotely.

Define underlayment roles

Ask which products are proposed at fields, eaves, valleys and transitions and how substrate, slope and exposure affect selection.

Map ventilation paths

Document intakes, exhausts, obstructions and proposed changes. Ventilation strategy must be coordinated with the building assembly.

Detail transitions and penetrations

Ask for compatible details at edges, walls, curbs, vents and material changes rather than generic sealant statements.

Keep a product-data file

Record product, version, instructions, compatibility statements and review responsibility for each hidden layer.

Draw the control-layer section

Create a section from interior finish through roof covering and label the intended air, vapour, thermal, water-shedding and ventilation functions. Mark discontinuities at walls, valleys and penetrations so product names do not substitute for an assembly strategy.

• Distinguish existing from proposed
• Show conditioned-space boundaries
• Flag unknown layer continuity

Match underlayment to roof details

Require the specified field and eave products, substrate condition, slope limits, exposure time, fastening and transition instructions. Ask how valley, curb, wall and edge details maintain compatibility with the selected metal system and anticipated construction sequence.

• Keep current product data
• Record primer and temperature limits
• Approve substitutions in writing

Verify ventilation as a connected path

Document intake and exhaust locations, free-area basis, baffles, blocked cavities, additions and interactions with insulation or mechanical exhaust. A vent count alone is incomplete; ask for the project-specific rationale and closeout evidence for the finished route.

• Map every roof cavity
• Separate exhaust ducts from attic ventilation
• Photograph concealed changes

Reconcile the hidden-layer package

Create a roof-section schedule connecting interior moisture context, air and vapour control assumptions, insulation, ventilation cavity, deck, underlayment zones and metal covering. Cross-reference product instructions at eaves, valleys, walls, curbs and penetrations, including substrate preparation, exposure limits and compatible transitions. Document intake and exhaust paths by cavity and photograph work before concealment. Any product or geometry change should reopen the assembly review. This package helps coordinate responsibilities but cannot establish the cause of an existing moisture condition or guarantee condensation control in operation.

• Draw conditioned-space boundaries
• Show every ventilation cavity
• Record underlayment zone changes
• Photograph edge transitions
• Keep substitutions under written review