Flat Roof Problems
This page deals with what flat roofs are and gives examples of various types of problems they can experience. The Flat Roof Repair and Coating Page explains the patching and coating process in detail. The page your on now and the Flat Roof Repair and Coating page together tell you what the roofs are, how they work, what their problems are and how they are repaired and coated.
I personally own a house with a flat cool coated roof, and my office building in my back yard also has a flat roof on it. So not only do I work on them I also live with them. According to some people this is a great thing and others think its terrible. More on that later.
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 with 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 normal 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. The heat then shortened the life of the roofing materials.
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 (the heat not the excitement) personally. So the figures I use above are not based on theory but my actual experience. A shingle roof easily reaches 150 degrees under hot the summer sun. An old style silver roof would frequently hit 140 degrees whereas a cool-coated white roof would be more like 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 can almost always 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. 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, but you are probably not viewing this page because your roof is in great shape but because you have a problem. Shown below various problems associated with flat roofs.
The common problems are shown below and categorized here:
Sores. The most common flat cool coated roof problem. This happens with age. Heat from the sun causes the roof to expand during the day, and at night as the roof cools it shrinks. This is called a heat cycle. Over the years not only is the roof experiencing hundreds of heat cycles, the coating is also slowly drying out and getting brittle. So basically the coating is always moving and its getting dry and more brittle. Eventually it cracks and splits.
Scupper Leaks. The most common problem we get called for. Sores are more common than scupper leaks, but don’t typically let a lot of water into the house in a short period of time. A leaky scupper is like having a crack on your bath tub drain, and the water is leaking onto your bathroom floor. It gets your attention. Two reasons why scupper leaks are such a big deal. First they are usually the lowest point on your roof so they have the maximum amount of water passing over them. Second, they are built with at least 4 different kinds of material and each material expands and contracts at a different speed as it goes through the daily heat cycle from the sun. All these different materials moving at different speeds cause them to crack sooner than the rest of the roof. Link to Scupper Page where there is 15 or so more pictures of scupper issues.
Split Seams. Another common problem I see several times a week are split seams. Sores are when the material drys out and cracks in random areas. Splits along the seams occur for the same reasons as sores, which are drying of the coating combined with physical movement. The difference being there is typically ALOT more movement at the edge of the material (seams) and the movement is in the same spot every day. A thick coating well applied will typically develop splits at the seams before it starts to get sores. The remedy for this is to put fiber tape and patch compound on it prior to re-coating.
Ponding. 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.
Wrinkles. Wrinkles are not as common as sores, split seams and ponds but I do see them about once a month. My belief is wrinkles are caused by not enough tar (glue) being used when the tar paper or sheeting was put on top of the plywood roof as the house was built. The tar paper is not supposed to sit on the plywood roof decking , its supposed to be glued to the decking. When not enough tar is used, the paper has some wiggle room. For lack of a better way of explaining this, the loose area now accepts any growth in the paper. I may not know the exact reasons for what causes it, but there are several basic options once wrinkles have happened. In most cases from a cost benefit point of view ripping off the roof and getting a new one installed is overkill. There are several other options. The first, if the wrinkles are not cracking down the center is to leave them alone. If the underlying paper or fabric is thick and in good shape the wrinkles can be there for years without causing issues. This is assuming no one is stepping on them as this will cause them to crack. The second choice is to put fiber tape or polyester fabric on the wrinkles along with patch compound and coating. Lastly the wrinkles can be cut out and new fabric or papers patches can then be put on them along with cool coating. I used to believe the best method was to cut them out and fabric over them. Years of experience have caused me to change my mind. Cutting them out and patching is more work than it sounds like, i.e. more expensive than necessary. I now believe the most cost effective way for homeowners to deal with them is to run a piece of fiber tape down the ridgeline (highest spot) of the wrinkle and to coat over it with cool coat. I could write quite a bit more about wrinkles but its easiest to say its basically a manufacturing defect which you’re dealing with after the fact so there are no great answers.
Blistering. 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 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. There is a large page on this site with lots of information regarding parapet patching, repairs and coating. Click Here for Parapet Page.
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.
Skylights. 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. As a side note. Notice the homeowner applied OLD gray silicon caulk around the edge of the plastic domed lens. From a professional point of view this is a no-no as the water is supposed to weep around the edge of the metal frame and drip out the bottom.
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.