Flat Roof Problems and Repairs
From my personal experience of owning a house with a “flat” cool-coated roof, and owning a business, AA Brite 24/7, that repairs flat-coated roofs, I have experienced various problems than can occur with flat roofs. I have outlined the problems below and how they can be repaired or minimized.
First of all, the term “flat roof” is somewhat misleading. Many people think of “flat” as being the same thing as level.
What is a Flat Roof?
A flat roof should ALWAYS have a little bit of slant to allow for water-drain off. Think of a flat pool table where the balls always roll to one end because the table is not level. At first glance many flat roofs will appear to be level, but upon closer inspection it can be seen they are built with a slight rise for drainage. This is important to avoid the confusion I often see with regards to clients who don’t know what to call their style of roof. Understanding this is important to avoid the confusion clients often experience in trying to describe their style of roof.
What is a Pitched Roof?
A pitched roof is typically considered to be a shingle or tile roof. The easiest way to communicate what your roof type is to call it one of the three: “Flat, Shingle or Tile”. The types of problems presented below might give some the impression that flat roofs are not desirable. In the Southwest and other arid climates, flat roofs are extremely desirable for several reasons which are illustrated below.
Why would I want a Flat Roof?
I grew up in the Midwest. As such, I lived in an area that had lots of snow and cold winters. Shingle roofs were common and, due to the weather, the roofs needed to be replaced every 15 years or so. It was commonly known and expected. Every few years or so, the region would experience severe storms or even small tornadoes. It was common for people to replace a few missing or damaged shingles. In general, the roofs held up well and drained off the water like they were supposed to.
Fast forward twenty years. I, Robert Anderson, am now living in Arizona! There are not many houses with shingle roofs. Why? Shingle roofs soak up a TREMENDOUS amount of heat and turn a Tucson attic into an oven in the summer time. This is NOT energy efficient and people living in the southwest figured this out a long time ago.
A reflective roof coating was the answer THEN and NOW. Back then, the reflective coating was silver. The logic was to have the roof act like a mirror and reflect the heat. This was superior to shingles, however, not by much. The silver coating reflected some of the visible light but the UV light was still soaked up in the coating and the roof heated up significantly shortening the life of teh roofing matgerials.
As technology and knowledge grew, white-cool coating became the solution. This coating reflected a great deal more of the UV and, when clean, would stay within a few degrees of the air temperature. If it was 115 degrees outside, the clean white roof would be 115 degrees. NOW, people were excited! I have measured this personally. So, the figures I use above are not based on theory but my actual experience. A shingle roof could easily reach 150 degrees under hot the summer sun. An old style silver roofwould easily hit 140 degrees whereas a cool-coated white roof would be 115 degrees. When the roof on a 2,000 square foot house is reduced in temperature by 25 degrees for months at a time, there is going to be significant savings on the air conditioner electric bill.
From a maintenance point of view, there are many advantages to owning a cool-coated roof. First of all, finding a leak on a shingle or tile roof can be troublesome and time consuming. Tile roof leak problems are typically dealt with on a larger scale. If the corner is leaking, it is common for forty square feet of tile to be removed to identify the problem. Shingle roofs typically leak at the edges or where two roof sections come together and water drains in a “V” shaped section. When the shingles are replaced they typically do not match and the roof looks patched. The choice is easy. Live in a house with a white cool coated flat roof. If there is an issue, I will be able to see where it is and how to fix it. Annual inspections are also simple and quick. It is much more cost effective and easy to repair.
What is the advantage of White Cool Coated Roofs?
White cool coated roofs have significant advantages and, after having worked on the three different types of roofs here in Tucson, I personally chose to purchase a home with a flat roof. My choice was intentional. Now, we have reviewed the positive aspects of flat roofs. You are probably reviewing this page because you have a problem. A well-built flat roof will always cause the water to drain properly. The difficulty is that most flat roofs are not well built in certain respects. I have seen specific problems repeatedly.
The common problems are shown below and categorized here:
The most common issues happen with age. Heat from the sun causes the roof to expand during the day. Over the years this repeated movement causes the coating to crack and open up. Additionally, roof coating will grow increasingly brittle with age until eventually it cracks or splits.
The most difficult of all flat roof problems is ponding. Ponding is a result of a poor design or roof installation. The drain is supposed to be lower than the rest of the roof, not an inch higher. Unfortunately this is a fairly common problem in Tucson. Anti-ponding material (filler) can be used; however, if too much is used, a new pond forms behind it. Areas with ponding age faster than other parts of the roof. In general, we are very conservative when we treat areas with anti-ponding material since using a too much, even a little too much compound, will cause a new pond to form.
Blistering is not nearly as common as it used to be because of the advances in roof-coating materials. One cause is that the roof was damp when the coating applied. The newer formulations of coatings are not nearly as susceptible to this problem. If a roof has not shown any problems for years and then starts to blister, and that possible reason is that water is somehow getting into the roof. The blister is created by water vapor as it tries to evaporate. If blisters are grouped together in a specific area, then there is probably a leak nearby. A blister will eventually break open after a number of years of weathering.
- Flashing Lifting
Flashing Lifting is also caused by inferior workmanship. A metal flashing needs to have fiber tape put on it at the joint or it will always crack out. This particular photo is one of the worst examples of workmanship I have seen in recent years.
- Emulsifier Issues
Emulsifier is a roofing product that dries oil out of the top layer of tar so water based coatings will stick to it. Was the General Contractor or Roofer in a hurry when the house was built? If so, there are emulsifier issues. Ideally, the contractor or roofer will allow two weeks to pass before putting the emulsifier on the tar, and then the cool coating over it. Obviously, if no emulsifier was used on top of the new tar, the cool coat failed to stick to the roof. Ironically, if unemulsified tar underneath the cool coating is exposed to the sun and elements for a year or more, the oils in the tar will dry out naturally. The area can then be patched or cool coated without first emulsifying it and waiting the two weeks for a cure out. Poor construction practices are a major cause of roof coating failure.
- Parapet Leakage
Parapet leakage is sometimes a natural part of the aging process and other times it is a construction quality issue. Almost all of the homes in this particular subdivision have these large (and much larger) cracks. The photo to the right shows a construction defect; but, the good news is it can be repaired.
- Leaking Flashing
Aging and movement will cause leaks here over time. They can be easily sealed.
- Cracked Penetrations (vent pipes)
There is no way to prevent vent pipes from cracking the roof coating. The roof expands during the day from heating up in the sun, and the vent pipes do not move, causing a crack to develop in the sealant. Fiber tape and sealer over the crack will prevent leaking for approximately four to seven years.
- Cracked and Leaking Scuppers (drains)
Cracked and leaking scuppers are easy to repair if the drain is lower than the roof as it is required. Repairs are more difficult if the drain is above the roof line, which prevents all of the water from properly draining. Nonetheless, the drain can be sealed.
The skylight shown is not exactly a glamorous picture but you get the idea. Renee is patching a leaking skylight. This was a patch only and not a full roof re-coat. There are a couple of places where skylights typically start to leak. These problems are not usually difficult to repair for the trained eye.
If caught in time, flat roof repairs can be relatively inexpensive and do not always require a re-coat. We at AABrite 24/7 recommend that you have your flat roof inspected every four (4) years by a trained professional. We are always available to serve your flat roof repair and emergency repair needs. A little bit of preventative maintenance goes a long way.