Beware the Flat Roof!

Nashville Home Inspections – Beware the Flat Roof

While many commercial buildings have flat roofs, there are not that many homes that have flat roofs.  And I say good!  It seems that the challenges of flat roofs are just too great for most contractors to overcome.  This article deals with how a flat roof can go bad, and the ripple effects when it does.  Look at the picture below.  What’s wrong?

HINT:  Flat roofs do not drain very well.  They may be cheaper to build on the front end, but in the long run they can be fragile and problematic.

  Flat Roof

Flat roofs are frequently made of built-up material such as asphalt based slurry over layered composite sheeting.  Usually, the last layer of material is a cover of rock, or aggregate.  See the photo below.

Flat Roof Ag

Answer:  Two fold.  Flat roofs are not suppose to be truly flat.  They should have a small amount of grade that slopes to the edges or to drain ports.  Also, flat roofs without the aggregate layer are in direct line for damages from the sun.  The purpose of the rock is to reflect the sun’s rays, especially UV rays.  Without this aggregate, the sun has a straight shot at the bituminous slurry and that can lead to drying and cracking.  See the photo below.  Between that and the build-up of tree debris, this is a disaster waiting to happen.

Dried Flat Roof

Eventually this will crack and allow water and whatever else is on the roof penetrate the building.  If there is a buildup of tree debris, like leaves, then that “whatever” can be a mold soup.  See the photo below.

Flat Roof with Debris

The photo below is of the area above with an opening kicked through.  Mold soup like no other!

Mold Soup

If this roof leaks, the results in the space below can be significant.  See the photo of the walls in the room below this roof.  Parts of the ceiling have fallen down and mold is growing on the walls.

Wall Mold

The pic above of what happens when the mold soup runs down inside the walls below.  Back up on the roof, if this soup is allowed to stand long enough, stuff starts to grow in it!

Roof Growth

So while it may be cheaper to build a flat roof on the front end, in the long run, flat roofs require greater care and attention to make sure they are working properly.

Thank you,

Richard Acree

Comments in this blog posting are the copyrighted intellectual property of Richard Acree, President, HABITEC Home and Building Inspections, LLC,  and are intended to educate and otherwise assist home owners, sellers and buyers, building owners, sellers and buyers, realtors, real estate investors, property managers, and lenders in the process of owning, buying or selling homes or commercial buildings.  HABITEC is a residential (home) and commercial building inspection company serving Middle Tennessee including Nashville, Brentwood, Franklin, Murfreesboro, Smyrna, Mt. Juliet, Hendersonville, Dickson, Belle Meade, Columbia, Spring Hill, Lebanon, Gallatin and more!  In addition to building inspections HABITEC offers Environmental Services for mold assessments, radon testing and water quality analysis.  Additional information about HABITEC can be found on our website at, or call 615-376-2753. 

Richard Acree is the author of  the HABITEC Home and Building Inspections blog at ActiveRain, WordPress, and Blogger, and Founder of the ActiveRain Group Tennessee Home and Building Inspectors.  All are welcome to join and comment on those blogs and group.   You can also follow HABITEC on Facebook and Richard on Linked.  Thank you!


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