Flat Roof Problems - And Repairs
I have a "flat" cool coated roof on my house, and my business A A Brite 24/7 also repairs flat coated roofs professionally. This page is here to show homeowners and other contractors what the various flat roof problems are and how they can be repaired or minimized. First, the term "flat roof" is somewhat misleading. Many people think of "flat" as being the same thing as level.
A flat roof should ALWAYS have a little bit of slant so the water can drain off. Think of a flat pool table where the balls always roll to one end because the table is not level. The table is "flat" but will drain off the balls or water because it has a slight rise in it from the low end to the end which is a little bit higher. At first glance many flat roofs will appear to be level, but upon closer inspection you can see they are have a slight rise. I mention this to avoid the confusion I often see with regards to clients who don't know what to call their style of roof.
A pitched roof is typically considered to be shingle or tile. The easiest way to communicate your roof type is to call it one of the three: "Flat, Shingle or Tile". Before getting into the many different types of problems associated with flat roofs there are some things you need to know. The sheer number of types of problems presented on the following pages might give some the impression that flat roofs are not desirable. In the Southwest and arid climates they are extremely desirable for several reasons which are described in the story below.
I grew up in the Mid West and we had lots of snow and cold winters. Shingle roofs were the norm and every 15 years or so the roof had to be replaced. It was known and expected. When a bad storm or small tornado came through every few years it was common for people to have 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 20 years and Robert is living in Arizona and there are not many houses with shingle roofs. Why? Shingle roofs soak up a TREMENDOUS amount of heat and turn a tucson attic into something that can cook food in the summer time. This is not energy efficient and the people living here figured this out a long time ago. A reflective roof was the answer then and now. Back then the reflective coating was silver. The thinking was to have the roof act like a mirror and reflect away the heat. This was better than shingles, but not by much. The reflective coating reflected away some of the visible light but the UV light was still soaked up in the coating and the roof heated up significantly.
As technologies and knowledge grew, white cool coating came to the rescue. It reflected a lot more of the UV and when clean would stay within a few degrees of the air temperature. If it was 115 degrees outside then the clean white roof would be 115 degrees. Now people were excited! I've measured this personally, so the figures I'm using are not theoretical but my actual experience. A shingle roof could hit 150 degrees under the summer sun. An old silver roof (I never see any new ones so I can't comment on them) would easily hit 140 degrees. And a cool coated white roof would be 115 degrees. I can't tell you mathematically how many calories of difference there is between the shingle, silver and white cool coat. But I do know that on a 2,000 square foot house a reduction of roof temperature by 25 degrees for months at a time is going to translate into significant savings on air conditioner electric bill.
From a maintenance point of view there are many advantages to owning a cool coated roof. Finding a leak on a shingle or tile roof can be troublesome to say the least. Tile roof leak problems are typically dealt with on a larger scale. If the corner is leaking it's common for 40 square feet of tile to be removed to try and 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 don't match and the roof looks patched. For me the choice is easy: live in a house with a white cool coated flat roof. If there is an issue I'll be able to see where it is and how to fix it. Annual inspections are also easy and quick. More on this later since very few people look at their roof yearly - including me.
White cool coated roofs have huge advantages and after having worked on the three different types of roofs here in Tucson I decided to buy a home with a flat roof. The choice was intentional. Now the groundwork has been laid on the positive aspects of flat roofs. But you probably didn't get to this page out of a desire to read about the joys of a flat roof. You have a problem. A well built flat roof will always drain off all of the water. The difficulty is most flat roofs are not well built in certain respects and I've seen the same problems over and over. Thus getting the pictures for this page was relatively easy.
I've categorized the troubles experienced here in Tucson into the following categories:
| Sores The most common issue and they 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 the coating grows increasingly brittle with age until eventually it cracks or splits. |
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| Ponding The most difficult of all flat roof problems and it's 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, but if a little too much is used then a new pond forms behind it. Areas with ponding age faster than other parts of the roof. In general we are very conservitive when we treat areas with anti-ponding material since using a little too much compound will cause a new pond to form. |
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| Blistering Not nearly as common now as it used to be. If the roof was damp when the coating was put on this would likely happen. The newer formulations of coatings are not nearly as susceptible to this problem. If a roof has been fine for years and then blisters start appearing this means water is getting into the roof, and the blister is created by water vapor as it tries to escape. If blisters are grouped together then their is probably a leak near by. Over a period of years a blister will eventually break open. |
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| Flashing Lifting In other words terrible workmanship. This type of metal flashing has 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've seen. |
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| Emulsifier Issues Emulsifier is a roofing product that dries oil out of the top layer of tar so water based coatings can stick to it. Was the General Contractor or Roofer in a hurry when the house was built? Then there are emulsifier issues. Hopefully two weeks passed between putting the emulsifier on the tar, and 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. Irnoically if unemulsifiedtar 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 and the area can be patched or cool coated without first emulsifying it and waiting the two weeks for a cure out. |
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| Parapet Leakage Sometimes this is a natural part of the aging process and other times it's a build quality issue. Almost all of the homes in this subdivision have these large (and much larger) cracks. The photo to the right shows a construction defect, but it can be repaired. |
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| Leaking Flashing Aging and movement will cause leaks here. They can be easily sealed. |
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| Cracked Penetrations (vent pipes) There is no way to prevent vent pipes from cracking the roof coating. The roof gets bigger during the day from heating up in the sun, and the vent pipes don't want to move. Then a crack develops. Fiber tape and sealer over the crack will prevent leaking for another four to seven years. |
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| Cracked and Leaking Scuppers (drains) If the drain is lower than the roof like as it's supposed to be then they are easy to repair. If they are above the roof line and are preventing all of the water from draining then they are more difficult to deal with. But they can be sealed. |
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| Skylights Not exactly a glamorous picture but you get the idea. Renee is patching a leaking skylight. This was a patch only, not a full roof recoat There are a couple of places where skylights typically start to leak. If you know what to look for they are not usually too difficult to repair. |
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