Inspect façade breather membrane installation & lap direction

The checklist

Pre-Installation Conditions

1. 1Confirm substrate is smooth, clean, and dry; timber moisture content ≤18% using a calibrated pin moisture meter. Photograph readings with location tag and note instrument serial number.
2. 2Check wind at working elevation ≤8 m/s with an anemometer; postpone membrane lapping above this threshold. Log time, elevation, and reading in the checklist.
3. 3Verify surface and air temperature 5–35 °C using an IR thermometer; record values to ensure primers/tapes meet minimum application temperatures per approved project specifications.
4. 4Confirm drainage cavity is clear and continuous, ≥20 mm depth measured with a ruler/feeler gauge at 5 m intervals; photograph representative measurements.

Materials and Identification

1. 5Inspect membrane roll labels for product name, Sd value, fire classification, and lot numbers; capture close-up photos of each label before installation.
2. 6Verify tapes, primers, sealants, and collars are manufacturer-approved for the membrane; check expiry dates and record batch/lot numbers in the log.
3. 7Reject and quarantine any roll with edge damage, punctures, or water ingress; photograph defects and record quantities for replacement.
4. 8Confirm certificates (e.g., CE/UKCA) and fire performance match approved project specifications and authority requirements; upload current datasheets to the checklist.

Membrane Orientation and Lap Direction

1. 9Install with printed/weather face outward and arrows (if present) pointing upward; photograph first panel showing face and arrows at start of elevation.
2. 10Set first vertical run plumb using a spirit level; align bottom edge to base flashing within ±3 mm. Photo evidence of level bubble and datum line.
3. 11Establish shingle sequencing bottom-to-top so each higher sheet overlaps the lower sheet; perform a quick hose/bottle spill test at one lap to confirm shedding direction and video record.
4. 12Ensure horizontal laps ≥100 mm (≥150 mm in high-exposure zones, or per approved project specifications); measure with a tape at every 3 m and photograph with scale.
5. 13Stagger vertical laps between adjacent runs; maintain vertical lap ≥150 mm and avoid placing laps over openings; capture photos at mid-height showing lap width.

Overlaps, Taping, and Fixings

1. 14Prime dusty or porous substrates where tape will bond, following manufacturer dwell time; photograph primer application and note ambient temperature/humidity.
2. 15Apply seam tape centered on laps; roll with a hand roller applying firm pressure (approx. 20–30 N). Perform a simple peel check ≥1 N/mm; note result and photo.
3. 16Eliminate fishmouths and wrinkles by re-rolling or cutting and patching; install patches extending ≥50 mm beyond defect edges; photo before/after repairs.
4. 17Place staples/screws with washers within support zones only; spacing ≤300 mm field and ≤150 mm at edges and corners. Photograph typical spacing with a ruler.
5. 18Temporarily secure upper sheets to prevent wind flip and reverse laps; remove temporary fixings or replace under battens/rails; record locations corrected.

Penetrations and Terminations

1. 19Turn membrane up at base and lap over starter/drip flashing; bond continuously with butyl/compatible tape; verify water sheds to exterior. Photo close-up of termination.
2. 20Form membrane upstands ≥150 mm above sills, parapets, and penetrations; confirm with tape measure in photos at each detail.
3. 21Seal services with prefabricated collars or double-tape method; ensure tight fit with no gaps or creases; photo 360° around penetration.
4. 22Reinforce internal/external corners with additional patches ≥200×200 mm; tape all edges continuously; photograph each corner after rolling.

Documentation and Sign-Off

1. 23Record inspected area (m²), elevation/gridlines, and drawing references; annotate location of photos on marked-up façade elevations and upload.
2. 24List product and tape batch/lot numbers used per elevation; capture delivery notes and attach to the checklist for traceability.
3. 25Note nonconformances and corrective actions taken; reference approved project specifications and authority requirements; obtain installer and supervisor digital signatures.
4. 26Complete final walkdown ensuring no reverse laps were introduced by later trades; export report as PDF/Excel with QR code for authentication and archive centrally.

Preview the printable checklist

Preview page one below. Open the image or download the PDF for all pages.

At a glance

• Ensure the breather membrane is installed with the correct weather face outward and all horizontal laps shingled so upper sheets overlap lower sheets, directing water into the façade’s drainage plane and away from structure and insulation.
• Measure and document critical tolerances: substrate moisture at or below 18%, clear cavities at or above 20 mm, horizontal laps at or above 100 mm (150 mm in high exposure), vertical laps at or above 150 mm, and fixing spacing within prescribed limits, supported by timestamped photos.
• Interactive online checklist with tick, comment, and export features secured by QR code.
• Reduce rework by verifying tapes, primers, collars, and terminations are manufacturer-approved, correctly applied within temperature limits, and pressure-rolled. Capture lot numbers, test simple peel adhesion, and confirm window heads, sills, corners, and penetrations are reinforced and sequenced to maintain continuous water-shedding paths.

How to use this interactive inspection checklist

1. Preparation: brief the crew, confirm access (scaffold/MEWP) is certified, and gather tools (tape measure, spirit level, anemometer, moisture meter, IR thermometer, hand roller, primer, tape, chalk line) and PPE.
2. Open the checklist on your device, select project, elevation, and gridlines, then start interactive mode to enable ticking, photo capture, and geotagging.
3. Work systematically left-to-right and bottom-to-top. For each item, enter readings, batch numbers, and attach photos with measuring scales visible; add comments for deviations.
4. Collaborate in real time: mention responsible parties, request clarifications, and track resolutions in comment threads without duplicating messages across apps.
5. Run pre-closeout review: filter incomplete items, assign actions, and recheck corrected details. Use the search to confirm all laps, tapes, and penetrations are documented.
6. Sign-Off: capture installer and supervisor digital signatures, then export the report as PDF/Excel. The export is authenticated via QR code for easy field verification.
7. Archive and distribute: file the signed report in the project CDE, share the QR link with stakeholders, and reference it in the façade handover package.

Why lap direction matters on façades

A breather membrane’s primary job is to shed wind-driven rain outward while allowing vapour to escape. Correct lap direction creates a shingle effect: each upper sheet overlaps the one below so water drains safely down the drainage plane, not behind flashings or insulation. Start bottom-to-top, align to base flashings, and maintain plumb sheets so laps remain uniform across elevations. Horizontal laps should be generous in exposed zones, and vertical laps should be staggered to avoid water pathways at joints. A quick water spill check at one representative lap can validate shedding without soaking the substrate. Field experience shows many leaks trace back to a single reversed lap hidden by cladding. Prevent this by photographing the first course and every change in sequencing. If gusts threaten to flip sheets, apply temporary fixings, then re-secure under battens or rails to preserve the shingle order before handover.

• Install bottom-to-top to maintain the shingle effect.
• Photograph first course to establish orientation baseline.
• Stagger vertical laps to break potential water paths.
• Use a small spill test to verify shedding direction.
• Secure sheets in wind to avoid reverse laps.

Overlap widths, tapes, and field adhesion cues

Consistent overlap widths and well-bonded tapes turn a membrane layer into a continuous barrier. Measure horizontal laps at several points and target at least 100 mm, increasing in high-exposure areas per approved project specifications. Vertical laps of 150 mm help resist wind blow-through; always tape verticals to close the seam. Prepare dusty surfaces with compatible primer and roll tapes firmly. A simple site peel indicates bond confidence: aim for about 1 N/mm without adhesive transfer failure. Temperature and moisture affect tack; keep substrate dry and work within recommended ranges. Correct fishmouths immediately—cut, lap, patch, and re-roll—to prevent water tracking. Space staples or screws appropriately and keep them within supports to avoid vulnerable perforations in the field of the sheet. Where fasteners are required near edges, increase tape coverage and rolling pressure as an additional safeguard.

• Measure laps frequently and photograph with a ruler.
• Tape vertical seams; roll all tapes under firm pressure.
• Conduct a quick peel check to confirm adhesion.
• Correct fishmouths with patches extending beyond defects.
• Keep fasteners within support zones at tight spacing.

Details at openings, corners, and terminations

Failures often start at transitions. At the base, turn the membrane over the starter or drip flashing, ensuring any water exits to the exterior. At window heads, sequence the head piece over jamb pieces and turn behind the head flashing so water cannot bypass. Form upstands of at least 150 mm at sills, parapets, and penetrations to provide a gravity-driven path. Use prefabricated collars or a robust double-tape method to seal services, avoiding wrinkles that create capillary routes. Reinforce internal and external corners with square patches and tape all edges; pressure-roll to lock the bond. Before cladding, verify no reverse laps were introduced by follow-on trades. Document each detail with close-up photos showing measuring scales, then mark locations on drawings for traceability and faster punchlist resolution during handover.

• Lap membrane over base flashings to drain outward.
• Head piece must over-jamb and behind head flashing.
• Upstands ≥150 mm at sills and penetrations.
• Use collars or double-tape for service seals.
• Reinforce corners and roll all edges.