Build a low-slope roof drainage map

Start with the building records

Collect roof plans, prior proposals, repair photos, drain service records, and any documents identifying the roof system. Mark interior leak points on a floor plan and note when they appear. From the ground or other safe locations, photograph visible scuppers, downspouts, overflow outlets, and roof edges. Do not climb onto the roof. The initial map is a handoff tool, not a drainage diagnosis. A qualified contractor must verify actual slope, low areas, outlets, membrane condition, and safe access.

Connect collection areas to outlets

During professional inspection, the roof sketch should identify drains, scuppers, gutters, overflow provisions, walls, curbs, crickets or saddles, seams, and notable low areas. Debris lines and surface discoloration can provide clues but need context. Record whether outlets are clear and whether strainers, flashings, or transitions are damaged. Water that remains after rain may increase exposure, yet the presence of ponding alone does not locate an opening. Keep observations separate from confirmed defects.

Use the map to define corrective work

A repair proposal should show which drainage or membrane conditions it addresses and which remain outside its limits. Cleaning an outlet, repairing its flashing, adding tapered materials, changing slope, or rebuilding a low area are different scopes. Structural and overflow questions may require additional design or permitting review. Request before-and-after photos keyed to the map and record products used at each location. Future inspections can then compare the same points instead of starting from an unlabeled set of close-up photos.

• Label primary and overflow outlets separately
• Record debris sources and maintenance responsibility
• Do not promise drainage changes before field verification

Connect maintenance to observation

Assign responsibility for keeping approved outlets and drainage areas free of routine debris using qualified personnel and property procedures. Record service dates and photograph conditions from safe, authorized access. If water repeatedly collects in the same area, preserve the observation for professional review instead of treating repeated clearing as a complete correction. Changes to equipment, pipe supports, walk pads, or rooftop storage can also change flow or block paths. Update the map whenever roof work occurs so future bids reflect the current layout rather than the original plan alone. Add interior observations to the same dated entry when drainage concerns coincide with a leak. This keeps surface conditions and indoor symptoms connected without claiming one automatically caused the other.