Apply Horizontal Liquid-Applied Membranes QA Checklist

Definition: Apply horizontal liquid-applied membranes with this field-ready checklist for contractors and inspectors, ensuring roller/squeegee application, DFT verification, curing control, pinhole detection, adhesion testing, and complete documentation.

Focus on roller, squeegee, and brush application—spray systems excluded
Verify DFT, curing, pinholes, and adhesion with measurable evidence
Prevent leaks, blisters, and debonding through controlled procedures
Interactive, commentable, export features with QR code for authentication

Start Interactive
Checklist

Apply horizontal liquid-applied membranes confidently with a job-ready, non-spray workflow that prioritizes thickness control, cure verification, pinhole detection, and adhesion. This checklist aligns with common liquid waterproofing practices and roller-applied or squeegee-applied coating methods to deliver uniform, durable protection on slabs, podiums, balconies, and wet areas. It excludes spray systems to reduce overspray risk and improve consistency on horizontal substrates. You will confirm environmental conditions, mix and apply materials correctly, measure wet and dry film thickness (WFT/DFT), monitor curing, perform holiday testing, and verify bond strength—capturing photos, readings, and sign-offs as you go. Following these steps helps avoid common failures such as under-thickness, entrapped moisture, cratering, and poor adhesion, all of which can lead to leaks, blistering, and premature repairs. Use this interactive checklist on any project where project specifications and authority requirements govern acceptance. Start now: tick items, add comments, attach evidence, and export to PDF/Excel from a QR-secured link.

Achieve reliable, uniform membranes by controlling substrate moisture, ambient conditions, and application rate. Measure WFT during placement and confirm DFT after cure to match specified thickness, minimizing underbuild, pinholes, and future leakage risks on horizontal works.
Reduce rework and delays through early detection of incompatibilities and defects. Test patches, reinforcement at details, and real-time curing checks prevent fish-eyes, cratering, or dust contamination that often compromise bond and long-term waterproofing performance.
Interactive online checklist with tick, comment, and export features secured by QR code.
Demonstrate compliance with project specifications and authority requirements using time-stamped photos, environmental logs, WFT/DFT records, holiday testing outputs, and adhesion results, giving traceable evidence for sign-off, warranties, and facility handover.

Pre-Application Conditions

1. Confirm substrate is sound, clean, and sloped to drains (≥1:80 or per specs); remove laitance, oil, curing compounds; document with wide-angle and close-up photos.
2. Measure substrate moisture with a carbide (CM) meter or equivalent; acceptance ≤5% or per approved project specifications; record readings, method, grid locations, and photos.
3. Record ambient/substrate temperature and relative humidity; ensure substrate is ≥3 °C above dew point; acceptance: no condensation risk; log thermometer, hygrometer, and dew-point calculations.
4. Verify surface profile/texture matches project specifications; acceptance: uniform profile without loose fines; capture scaled photos (ruler/coin) across representative areas.
5. Mask terminations, drains, and joints; install temporary protection and plug drains; acceptance: edges defined, no pathways for runs; photo evidence before priming.

Materials and Mixing

6. Check product type, batch numbers, and shelf life; acceptance: within expiry and approved submittals; record lot numbers, delivery dockets, and COAs.
7. Condition materials to 18–25 °C; verify with IR thermometer; acceptance: within range for stated pot life; log container temperatures and ambient conditions.
8. Mix components using a low-speed drill and paddle (≈300–500 rpm); scrape sides/bottom; acceptance: streak-free, uniform mix; record start/finish times and pot life start.
9. Apply a 1 m² test patch on representative substrate; acceptance: no fisheyes, no bleed, good wet-out; document photos and note working time.

Application (Roller/Squeegee)

10. Prime substrate by roller at specified rate (g/m²); measure WFT with comb at start/middle/end; acceptance: continuous film, WFT within spec ±10%; record readings.
11. Broadcast kiln-dried sand to refusal if required; acceptance: uniform coverage; remove loose after cure; document with close-up photos and quantity per m².
12. Apply base coat by squeegee, then back-roll crosswise; measure WFT every 10 m²; acceptance: target WFT per specs ±10%; log location-tagged readings and photos.
13. Reinforce cracks, joints, and penetrations with fabric embedded in wet base coat; acceptance: full wet-out, 50 mm minimum laps; photo evidence at each detail.
14. Apply second coat after tack-free; cross-rolling to avoid pinholes; acceptance: cumulative DFT meets spec; verify via WFT targets and later DFT checks; record batch usage.

Thickness Verification (WFT/DFT)

15. Calculate expected DFT from measured WFT and solids by volume; acceptance: projected DFT ≥ specified minimum; attach calculation snapshot with inputs.
16. Measure DFT after cure using appropriate gauge (magnetic/ultrasonic); take ≥5 readings per 10 m²; acceptance: average within spec, no point <−10%; record gauge ID.
17. Mark thin areas; apply additional coat by roller; remeasure DFT after cure; acceptance: meets specified minimum; capture before/after photos and final readings.
18. Reconcile material usage versus covered area (L/m²); acceptance: variance ≤10% from theoretical; upload consumption log and area take-offs.

Curing and Protection

19. Record tack-free, recoat, and walk-on times at measured conditions; acceptance: within product data expectations; time-stamp observations and photos of status labels.
20. Protect fresh membrane from dust, traffic, rain, and standing water; acceptance: no indentation or contamination; install barriers/signage; photo evidence daily.
21. Perform tack test and solvent rub (if applicable); acceptance: no pigment transfer, surface firm; log results and any hold points.

Pinhole and Holiday Testing

22. Inspect in raking light and with magnifier; acceptance: no pinholes, craters, or fish-eyes; mark defects on plan and photos.
23. Conduct low-voltage wet sponge holiday test on conductive substrates after cure; acceptance: zero indications; record instrument, settings, sweep paths, and readings.
24. Repair all defects with compatible material; feather edges; allow to cure; retest; acceptance: zero holidays after repair; upload repair logs and photos.

Adhesion Verification

25. Perform pull-off adhesion testing with dollies; ≥3 tests per 100 m²; acceptance: bond strength ≥ value per specs; record MPa, failure mode, and locations.
26. Check edge adhesion using a putty-knife lift test at perimeters; acceptance: no debond beyond 5 mm; photo evidence and notes.
27. Confirm terminations at drains and upstands are sealed or mechanically secured per details; acceptance: continuous bond and seal; close-up photos of each termination.

Documentation and Sign-Off

28. Upload environmental logs, WFT/DFT records, holiday and adhesion test reports, and batch data; acceptance: complete set on file; QC initials and date.
29. Obtain digital approvals from contractor and inspector; acceptance: e-signatures with timestamps; attach distribution list for stakeholders.
30. Export final report as PDF/Excel with embedded QR for authenticity; acceptance: archived to project folder; verify accessible link.

Control the substrate and environment before any coating touches the slab

Successful horizontal liquid-applied membranes start with a substrate that is sound, dry, and properly profiled. Remove contaminants and confirm slopes toward drains to avoid ponding that overloads young films. Moisture is a silent failure driver: verify content using a reliable method and ensure the surface temperature sits safely above the dew point to prevent condensation. Exclude spray systems to eliminate overspray and improve control; roller, brush, and squeegee methods provide predictable film build on horizontal areas. Mask and protect terminations, and plan traffic routes to keep wet areas clean. Establish a small test patch to confirm compatibility with primers and treatments before full production. These controls reduce fish-eyes, cratering, and early debonding, while giving you usable data to schedule coats and handovers. Capture wide-angle and close-up photos, and record all instrument IDs so your evidence is audit-ready and defensible at sign-off.

Substrate ≥3 °C above dew point at all times
Moisture acceptable per approved project specifications
Use roller, squeegee, brush only—no spray systems
Create and evaluate a 1 m² test patch
Protect drains, edges, and traffic paths

Build and verify film thickness with disciplined, measurable methods

Uniform thickness is essential for waterproofing performance. Target wet film thickness using a comb gauge during placement, checking at consistent intervals and marking locations on a plan. Reinforce high-risk details first to prevent stretching thin. Once cured, confirm dry film thickness with an appropriate gauge, taking multiple readings per area and reconciling with material usage to flag underbuild. Keep a clear tolerance strategy: average DFT within specification and no local reading below an agreed negative tolerance. If you detect thin spots, repair immediately with an additional coat and remeasure after cure. Photographs with a scale, logged readings, and batch-usage summaries create a chain of evidence that aligns crews and approvers. This disciplined approach avoids leaks, blistering from solvent entrapment, and premature aging linked to inadequate coverage.

Measure WFT at start, middle, and end of runs
Verify DFT after full cure before handover
Average within spec; no point below tolerance
Reconcile litres used versus area covered
Document gauge IDs and locations

Verify curing, eliminate pinholes, and prove adhesion before handover

Curing ties product chemistry to real weather. Track tack-free, recoat, and walk-on times at measured temperature and humidity. Protect membranes from dust, rain, and standing water to prevent surface defects. Inspect in raking light to spot craters and pinholes; where applicable, use a low-voltage wet sponge holiday detector on conductive substrates for objective confirmation. Repair all indications and retest. Adhesion must be proven, not assumed: use a pull-off tester to document bond strength and failure mode at representative locations. Combine these results with perimeter lift checks and close-ups of drains and terminations. The outcome is a membrane that is cured, continuous, and bonded—supported by time-stamped logs and photos that meet project specifications and authority requirements.

Record tack-free, recoat, and walk-on times
Use raking light and wet sponge testing
Repair defects, then retest for zero holidays
Document pull-off adhesion MPa and modes
Photograph critical terminations and drains

How to Use This Interactive Non‑Spray Membrane Checklist

Preparation: Gather tools (WFT comb, DFT gauge, pull-off tester, wet sponge holiday detector, IR thermometer, hygrometer), rollers/squeegees/brushes, mixing gear, PPE, and project specifications. Establish test areas, masking, and protection routes.
Project setup: Create a checklist session, define zones (grid or by m²), add drawings, and preload target WFT/DFT, cure times, and acceptance criteria per approved project specifications.
Using the Interactive Checklist: Start interactive mode; tick items as completed, add comments, attach photos and readings, and tag locations. Log instrument IDs and batch numbers. Flag nonconformances and assign actions.
Quality review: Verify all evidence is uploaded—environmental logs, WFT/DFT records, holiday and adhesion tests. Resolve open comments, close actions, and request digital approvals from stakeholders.
Sign-Off and Export: Capture digital signatures, then export the full record as PDF/Excel. Share QR-authenticated links with the client and archive to the project folder.

Call to Action

wael ali wael ali

Feb 21, 2026

100

FAQ

Question: What thickness should I target for a horizontal liquid-applied membrane?

Target thickness is project-specific. Use the specified dry film thickness, then back-calculate a wet film target from solids by volume. During application, measure WFT frequently and adjust spread rate. After cure, verify DFT with a suitable gauge. Average must meet specification and no local reading should fall below agreed tolerance.

Question: How do I check for pinholes without damaging the membrane?

Start with raking-light visual inspection to highlight craters and pinholes. Where suitable and on conductive substrates, perform low-voltage wet sponge holiday testing after full cure. Mark indications, repair with compatible material, allow to cure, and retest until achieving zero holidays. Always follow product guidance to avoid overtesting thin films.

Question: When can I apply the second coat or allow foot traffic?

Base your decision on observed curing at measured temperature and humidity, not time alone. Record tack-free and recoat times on-site. Apply the next coat within the stated recoat window for intercoat adhesion. Allow foot traffic only after walk-on cure is achieved, then protect the membrane from damage and contamination.

Question: How is adhesion verified on horizontal membranes?

Use a pull-off adhesion tester at representative locations to measure bond strength and identify failure mode. Supplement with perimeter lift checks at edges and details. Compare results to approved project specifications and authority requirements. Document MPa values, locations, and photos, and repair or investigate any low results before handover.