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.

1.   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.

2.   Inspect interior walls of building:  

    Look for:

    -    Damp or stained walls

    -    Chipped or discolored paint

3.   Inspect underside of roof deck:

    Look for:

    -    Wood deck:  rotted or warped boards

    -    Concrete or gypsum deck:  cracks and stains; spots of
         rust may also appear on a concrete deck from wet
         reinforcing rods in the concrete; a gypsum deck may spall
         as a result of leaking water.

    -    Metal deck:  rust spots

4.   Inspect roof surface:

    Look for:

    -    A sprung board in a wood deck.  Identified by sharp
         indentation of roof surface, often caused by a broken

    -    A noticeable "give" in the roofing under weight.

    -    Cracks in membrane.

5.   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 gutters

6.   Inspect copings:

    Look for:

    -    Cracks, gaps or damage to coping joints

7.   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

8.   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

9.   Note priority of defect (i.e. none, minor, major, complete

10.  Note changes from last inspection.

                             END OF SECTION

Last Reviewed 2014-11-25