Sources of Flat Roof Failures - Inspection Guidance

Procedure code:
Hspg Prepared For Nps - Sero
Thermal and Moisture Protection
Membrane Roofing
Last Modified:

This standard includes guidance on identifying sources of flat roof failures by looking at specific problem areas.

Inspect Exterior walls of building:

Look for:

  • Settlement cracks
  • Stained or displaced flashing or drainage facilities
  • Efflorescence on the wall - this may be a sign of leaks in the coping or parapet above.

Inspect interior walls of building:

Look for:

  • Damp or stained walls
  • Chipped or discolored paint

Inspect underside of roof deck:

Look for:

  • Wood deck: rotted or warped boards
  • Concrete or gypsum deck: cracks and stains; spots ofrust may also appear on a concrete deck from wet reinforcing rods in the concrete; a gypsum deck may spellas a result of leaking water.
  • Metal deck: rust spots

Inspect roof surface:

Look for:

  • A sprung board in a wood deck. Identified by sharp indentation of roof surface, often caused by a broken board.
  • A noticeable "give" in the roofing under weight.
  • Cracks in membrane.

Inspect drainage:

Make sure drains are flush with the roof and free of debris.

Look for:

  • Change in original slope of roof
  • Standing water
  • Blocked drains and/or gutter

Inspect copings:

Look for:

  • Cracks, gaps or damage to coping joints

Inspect flashings:

Look for:

  • Loose, torn or missing flashing
  • Improper bond between base flashing and edge of mat or between counterflashing and wall
  • Flashing that is not turned up enough potentially allowing water to back up, stand against the wall and leak down into the roof deck
  • Rust on flashing or lack of protective coating on corrosive metals
  • Inspect roof at least twice a year and inspect after any severe storms:

Look For:

  • Debris accumulation and vegetation growth
  • Deterioration of the surface and membrane
  • Deck deflections (sometimes from structural problems)
  • Ponding and tensile splitting of water weakened felts and/or membrane
  • Ice formation and resulting membrane damage
  • Positive drainage
  • Wear spots at curbs and penetrations
  • Ruptures, bare spots, splits, metal flange splits, deteriorated felts
  • Warping, cracks, splits, slivers, cupping and rot

Note priority of defect

  • (i.e. none, minor, major, complete failure.)

Note changes from last inspection.

  • i.e. none, minor, major,
  • Note what changes occurred
Last Reviewed: 2017-08-13