FLAT ROOFS OVERVIEW

What is Hindsight? It’s the ability or opportunity to understand and judge an event or experience after it has occurred. So…. because of our Thousands and Thousands of inspections, the application of Previous Hindsight coupled with Experience and Education during a Building and Home Inspection ultimately creates 20/20 observations with Foresight. The most important aspect of our practice is “Analytics”, or in other words, giving accurate observations to form accurate conclusions. These are the strengths that Benefit our clients.

 
Based on some of your questions, the following discussions cover information on flat roofs that I know you’ll find interesting. So let me share some information, such as;

 TYPES OF FLAT ROOFS

1- Quick overview of various types of flat roofs
2- Some flat roof characteristics to look for and “Examples”
3- Some information on Do’s and Don’ts of materials used for a flat roof application
 
There are various types of flat roof materials, but for the sake of keeping this article short let’s just cover some types of roofs you would most likely see in the field; such as
-EPDM ( Rubber Type Roofing )
-Rolled Roofing
-Built-Up Roofing / Modified Bitumen Roof

EPDM ROOFING

 
We often see EPDM (Ethylene Propylene Diene Monomer) Roofing on residential and commercial structures. This is a rubber type roof ( synthetic ) that typically does not require a ballast / protective coating to protect it from ultra-violet rays. This material can be rolled out in large sheets to reduce seams. This in itself will help reduce water entry points and possibly make it easier to identify leaks. The manufacturers state these types of roofs have a 20 year life span…for a flat roof that isn’t terrible.  However, lets discuss a few things such as water ponding, wrinkles, open seams, and fishmouths for now.
Wrinkles always tell me a story such as; was the material installed correctly. Open seams and fishmouths at the perimeters will sooner or later allow water to enter the interior or exterior finishes. Ponding of water on the roofs may tell us various facts to consider. For example; review the following photo(s) where the water was only ponding on one section of the roof. Note, the material was in acceptable condition even though some fish mouthing and mastic patches were noted in other areas of the roof.  Notice the picture of the roof in question; it was filled with water while adjacent roofs were dry: ( read more below)
 

Water ponding on upper flat roof but not adjacent lower roof(s)

After reviewing this roof and structure further, it was apparent the framing was sagging at the center of this roof allowing water to pond while adjacent roofs were draining properly.

“Note: the rule of thumb is that flat roofs should substantially dry out after 48 hours.”

As a result, this roof will need repairs to the substrate structure before a new roof material can be installed. There are other approaches to draining this flat roof such as a solar pump, which I classify as a temporary “fix”, however, I can not confirm its volume rating or effectiveness. If you would like to read more about it visit solarroofpumps.com

Here is another tip; Presuming it is an EPDM material, when you see patches on the roof and they appear to be tarred / mastic covered, that would be a no…no. Tar or Mastics do not adhere well to EPDM roofs. Please review the following photo:

The Mastic Here Already Started Cracking

Please note: There are other materials such (Polysobutylene-PIB) that appear to be EPDM material whereby patches will adhere well using Mastic/Tar

ROLLED ROOFING MEMBRANES

Rolled roofing is very common and does have a shorter lifespan than other types of materials and applications. The manufacturers’ may say it has a ten year plus or minus lifespan, but what’s more important to me is the condition when I review the material. For example; is it face nailed, are the seams open, does the material still have a granular surface, is there buckling or wrinkling, is it cracked….I think we all get the picture.  Since we’re talking about pictures, take a look at the following photos to get an idea of what I am talking about:

Buckled roofing can cause premature failure and top nailing will cause leaks.

Both roofs in this photo look great to me!

BUILT UP ROOFING MATERIALS

Now..here are some pictures of a local commercial building’s roof where I was conducting a Full Inspection and Phase 1 Review. If you look at the details in the picture, my first impression was that this roof needs to be replaced immediately. Some localized areas exhibits cracks, alligatoring, etc.

Smooth-surfaced asphalt built-up roofs, where the surface mopping is relatively thin, usually show alligatoring of the surface coating within 5 years. Alligatoring is always most severe where the asphalt coating is thickest. As logic dictates,  I usually find tar applications over membranes the thickest at roof penetrations to reinforce the water tightness. However,  If allowed to proceed, alligatoring will develop into cracking. Once the surface coating is cracked enough, water can penetrate the membrane and the roof materials could deteriorate rapidly. Consequently, maintenance is necessary to prevent further cracking and membrane deterioration.
 
Significant cracking was noted here
Exposed membrane noted here
Larger view of roofing materials in question

So..what was the overall conclusion ?? The advantage I have over others is that I’ve been Building and Inspecting for many years now and have more field, book knowledge and contractor resources than most. In this this case I have a family member who only installs commercial roofs, So, I made a few calls and sent a few pictures to confirm my inspection observations. My final conclusion was that this roof exhibits some alligatoring and cracks in localized areas but the remainder of the roof only exhibits visibly worn protective coatings and minor damage. Therefore, I suggested either a new roof, which would be very expensive, or to conduct maintenance procedures immediately. Based on the feedback I received from my research and resources all agreed with my analysis whereby maintenance on this roof would be significantly less costly and could extend the life of this roof for many years.

DO’S AND DON’TS OF FLAT ROOF MATERIAL APPLICATION

For now let’s discuss Don’ts on flat roofs!

Do Not Use three tab or architectural roof shingles on a flat roofs. Take a look below at some pictures I took and what the results were using the wrong roofing material on this flat roof.

Flat Roof Using Architectural Shingles

Leaks Resulting Inside Garage As A Result Of Applying Architectural Shingles On A Flat Roof

Remember, a flat roof covering needs to be water tight. Typical roof shingles are not made for flat roof applications. If you refer to my previous article on Ice Damming, whereby the water builds-up and goes under the roof shingles, you will see that the same theory applies here.