Ask The Inspector - Flashings

Home Inspector with National Property Inspections

Question: What are flashings and why are they important to the design of my roof?

Answer: Flashings on the roof provide weather tight conditions at seams, intrusions and junctions on pitched roof designs. No matter what material is used for covering the roof, leaks will occur if flashing is not installed and maintained properly.

Some common checkpoints for roof flashings would be:

  • Around plumbing vents
  • Around chimneys
  • Where a lower roof, possibly on a garage, intersects with a wall
  • Valleys
  • Where a sloped roof intersects a flat roof
  • Around dormers
  • Around skylights
  • Eaves, rakes, hips and ridges

Flashings may or may not be easily visible. For instance, a "woven" roof valley, constructed of roll roofing under shingles may not be as obvious as the chimney flashings typically made of metal. The most weatherproof chimney flashings have two parts because the chimney foundation may be separate from the house and therefore able to move independently of the roof deck. To maintain a weather barrier, base flashings are installed on the roof deck, and cap flashing is secured to the masonry. Overlap between the two prevents water from penetrating to the attic. Chimneys on the down slope may also have cricket flashing on the uphill side to prevent water from pooling around the base of the chimney.

Determining the location and condition of roof flashings is one part of an NPI property inspection. For more information, call your local NPI professional for a quote today.


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Bennie Guy

I plan to install 4' x 8' STYROFOAM sheet insulation in my attic over the 4" instulation installed between the studs.  This is an attempt to help the cooling and heating of one upstaies room.  This material is flamable are there any code problems? 


Thank you

Nov 12, 2007 06:55 AM #1
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