I Hate Flat Roofs!

“I hate flat roofs!  They ought to outlaw them!”  I recently heard these words from a roofer who has experienced what many business owners, home owners and even roofing companies have experienced with a flat roof or a low slope roof.  In my own neighborhood, I recently met a frustrated neighbor who spent a significant amount of money building a pitched roof over his flat roof after two companies failed to fix his problem.  So why are flat roofs or low slope roofs more leak prone?   

A flat roof should be designed to vacate the water from the surface just like a sloped roof does.  However, due to the design of a flat roof there are more challenges in getting the water off the roof.  Standing water often reveals weaknesses that would not be found if the water quickly ran off like a sloped roof.

There are six basic reasons flat roofs or low slope roofs are more leak prone.

1. Age.  A flat roof is more problem prone as it ages. Settling of the structure or bowing of wood joists that would only affect the cosmetics on a sloped roof can cause a flat roof to hold water in those low lying areas.  Insulation can compress with age creating places for water to stand.  Leaving water standing on a roof for an extended period of time will lead to premature deterioration of the roof surface or worse.  One small puncture hole can allow water to get under the surface and soak into the insulation destroying it, or worse, it can cause rot or rust of the decking surface.  I have removed roofs where there was literally water standing on the decking surface underneath the roofing insulation; the decking was rusted through like an old car.  As a roof ages, the surface is affected by the elements.  TPO, Hypalon, and PVC can become brittle with age; modified bitumen experiences granular loss and cracking; a built up roof surface cracks and separates when left exposed to sun; metal roofs begin to leak at the seams as the sealant deteriorates.

2. Improper repairs. It can be difficult to find someone competent to do roof repairs, so they are often repaired by a well-intended maintenance man or a repair man.  A common repair is a 5 gallon bucket of tar or the old gray fibrous sealer that is brushed on over the surface where it is leaking below. This repair only complicates the problem by causing water damming and water ponding.  I have seen this issue on metal roofs, modified bitumen roofs, built-up roofs, and single ply roofs.  I have seen silicone caulking put on TPO and EDPM seams, and, instead of fixing the problem, the issue continues to grow causing additional problems.  With these types of repairs, though, the reality is that where the repair was done may not be the place where water entered the roof.  For instance, a flat roof can have a small puncture hole allowing water to enter and run undetected.  The water can then follow a joist or beam and drop down in a totally different location than the actual leak.  This is just one of the problems with diagnosing a leak on a flat roof and why many roofing companies steer away from flat roof repairs.

3. Clogged gutters. A clogged gutter can cause a backup of water on the edges and allow water to creep back under the edge or onto the roof surface until it is covered in water. A church I did this past year had clogged gutters and had six inches of water standing on the roof surface revealing every weak spot on the roof.  Water can be incredibly heavy, and when that weight is added to the weight of the roof, it can put a tremendous force on the walls of the structure.  I was also called out to a residential flat roof and found the roofers had covered over the drains to the gutters, and the weight was literally pushing the walls outward!

4. Foot traffic.  A flat roof can easily be damaged by someone walking on the surface. A built-up roof covered in gravel can have a piece of gravel puncture the tar soaked paper.  This will allow water to begin to slowly seep in between the layers causing damage that will not be discovered for a long length of time.  A TPO roof is even more vulnerable to foot traffic, as it is a thin layer of single ply (40 – 60 mil.) that is easily punctured.  This allows water to quickly spread into the insulation potentially causing mold issues. In fact, a TPO warranty can be voided by damage caused by foot traffic.  A modified bitumen roof should not be walked on when it is hot, because the surface will be severely compromised and the warranty voided.  Unfortunately on commercial buildings, the air conditioning units are usually on the roof, and when there are issues with the units it is the hottest time of the year!  For example, I was recently on a 6 year old modified bitumen roof on a very large gym center that had a lot of a/c issues.  There was extreme damage to the surface, and it is now leaking.  They indeed had hail damage, but it was masked by the excessive foot traffic damage, thus inhibiting their ability to get their insurance company to replace the roof.

5. Weather Conditions. Wind and hail are a reality in many areas of the country.  This is why many insurance companies put a wind and hail clause in their insurance coverage. Hail can seriously damage a roof’s surface.  Modified bitumen can be easily damaged by hail on the surface.  Hail can break the backing on a TPO roof while the surface still looks fine.  EDPM is considered more hail resistant than TPO but is an expensive option.  Foam roofs are very vulnerable to hail and to birds who love to peck holes in the surface!  Silicone coatings have become popular, touting incredible sounding warranties of 50 years.  However, the warranties specifically list hail as something that is not covered (as well as any issues caused by the subsurface under the coating). The old built-up roof is still one of the most hail resistant flat roof systems out there if it is covered and protected by gravel.  Extreme wind can also have a catastrophic effect on a flat roof.  If wind can get under the cap metal or the termination point areas it can literally peel back the roof like a can opener. Extreme cold temperatures can make a PVC roof brittle and at risk for cracking if walked on.  A good rule of thumb is to consider the weather conditions of your area and what will take place on your roof before you choose a product.

6. Lack of Maintenance.  A roof is often the least maintained part of a building.  Siding gets a fresh coat of paint, windows receive new calking, concrete is sealed, but a roof is out of sight and out of mind!  The gravel is sometimes moved or removed on a built up roof thus exposing it to the weather and sun which causes cracking and blistering.  A puncture can easily occur on a TPO or EDPM roof from someone performing maintenance on the a/c units or any number of reasons people get on a roof.  The puncture occurs and goes unnoticed until extensive damage has occurred.  I was on a large modified bitumen roof recently where the plastic pipe support stands had cut through the roof causing multiple leaks.  A flat roof left unmaintained in most cases is a roof without a warranty and a roof in trouble.  Every flat roof should be scheduled for a six month inspection.  Gutters should be cleaned regularly, and seams should be checked to see if any are pulling apart from building movement or material shrinkage. Pipe flashings should be checked to insure the sealant is still holding, and metal flashings should be inspected to insure nothing has come loose.

What is the Best Flat Roof System?

There is a lot of debate about what is the best flat roof.  A built-up roof or hot tar roof, properly installed, is still one of the best flat roof systems.  Their downsides are weight, smell, fire risk, and finding a contractor who is skilled at properly installing a built-up roof.  Leaks are also very hard to find on these roof systems.  A modified Bitumen roof is often the cheapest option. There is the torch down style, a hot mop style, and the newer peel and stick design.  Peel and stick is by far the easiest to install, and works well in low traffic areas and small residential applications. EDPM is a rubber roof and has proven to be a good product alternative for the old built-up roof.  However, it is more expensive, and it still has seams that need to be inspected.  TPO in the last few years has become the favorite of many roofing companies, and it can be a good option when properly installed using the thicker more expensive options.  Companies who were never able to do built-up roofs (and were afraid of flat roofs) are finding it easy to install.  Seeing the trend and trying to capitalize on a profitable business, many manufacturers have jumped into the game.  The downsides of TPO, though, are the number of seams, the fact that it is easily punctured, and it is not necessarily foot traffic friendly.   Also, a warranty can be voided if regular maintenance is not performed.  If not installed properly, it is not uncommon to see wrinkles in the material because it was improperly stretched.  It is wise to exercise caution because of the number of roofing companies who are jumping into the game that are not properly trained.

At Proformance Roofing we install many different types of flat roofing systems depending on the application and the customer’s needs. We like to clearly present all options, and then leave it to the owner to make an educated decision concerning their facility.  At Proformance, we have another option that we like to present that is truly a revolutionary product for the flat roof industry.  This revolutionary product is called Tritoflex, and is manufactured by Triton Industries (www.tritonwp.com).  Tritoflex is a spray-on, liquid rubber membrane that dries immediately to the touch in any desired thickness.  Tritoflex is a true seamless roof system (even including vulnerable flashing areas).  It is impact resistant and hail resistant up to baseball-size hail.  Tritoflex is a water-based Green Roof System that you can literally plant a garden on without damaging it, and being water-based, has a Class A fire rating and is self-extinguishing.  Tritoflex has excellent adhesion properties giving it a wind rating of 1-990, the highest possible rating.  It stands up well to foot traffic, and its warranty is not affected by water ponding or foot traffic.  Tritoflex is also puncture resistant beyond any other product we install, and it expands and stretches without damage to an amazing 1600%!  In addition, it does not require a costly tear off of the old roof, replacement of expensive insulation, or removing all the a/c and roof equipment.  Cost is typically the same as a TPO roof, and the standard warranty is 10-15 years labor and material depending on the thickness of the membrane. The standard warranty can be extended up to 45 years with a Tritocryl or Tritotherm reflectant coating.  For a free demonstration of this amazing product, please give us a call.

Compare Flat Roof Material - Click Here


If you would like more information about any of the roofing systems call 405-283-2205.