terrible counter-flashing

Ten Common Residential Roofing Errors

By Brad Caldwell – Owner of Roof, Rinse & Run – May 4, 2014

Brad Caldwell, owner of Roof, Rinse & Run, recently had the privilege of attending a 2014 GAF Expo held in Franklin, TN (close to Nashville, TN). One class covered ten common residential roofing errors. We feel like it is important for the homeowner to understand what these errors are, and that Roof, Rinse & Run knows about and addresses these issues. Not only are they the most commonly encountered problems as seen by GAF, but the NRCA (National Roofing Contractors Association) also sees these as the ten most common residential roofing errors in their estimate.

Ten Common Residential Roofing Errors:

(1) Installing Shingles on Low-Slope Roofs.

When a roof’s pitch is 2:12 or lower, shingles simply can’t function right. Shingles aren’t a waterproof roof layer, they’re a water-shedding roof layer. As long as gravity can keep the water traveling down the roof, they work great; however, when you get to too shallow of a pitch, water is going to seep (or “wick”) up under them and cause leaks. In fact, Roof, Rinse & Run doesn’t like to install shingles on anything under a 4:12. So what do you do for low-slope applications? You have to use a “singly-ply” (i.e., TPO/PVC) membrane, or a special asphalt product (as roll roofing).

(2) Neglecting to Install Drip Edge.

While drip edge is only “required” on the eaves of a home, it is still recommended on the rakes as well, and Roof, Rinse & Run always requires its use at both places. Drip edge (the small metal trim-piece right below the edge of the shingles) serves a number of purposes:

  • Keep insects & squirrels out of the attic.
  • Prevent wind-driven rain from entering under the edge of the roof.
  • Provide a “drip point” for water to drip off of (which helps prevent fascia rot).
  • Keep shingles from “sagging” as they extend past the edge of the roof.

Drip edge needs to be fastened sufficiently (every 8″-10″), and shingles only need to overhang the drip edge by 1/4″ – 3/4″.

(3) Improper Starter Course.

Using “upside down” 3-tab shingles for the starter is a practice so ubiquitous that it hardly needs mentioning. However, the proper way to do starter is with the special starter material provided by manufacturers, with the tar line about 1″ from the edge of the roof. The proper starter material is about half as tall as a shingle.

(4) Leak Barrier Problems.

Will your roofer provide leak barriers in valleys and around skylights? It’s important!

(5) Improper Nailing.

Shingles are made of a fiberglass mat with asphalt applied to the bottom and top. When nails are driven at an angle, they “tear” the fiberglass mat and “compromise” the integrity of the shingle. Any such compromised shingles should be removed and disposed of (not reused). Additionally, over-driven nails (due to poorly-set compressor pressure) similarly tear the shingle’s mat and should be replaced. A good practice is to spend 3 minutes before a roof job to test the pressure of the compressor, and ensure that the nails will be driven correctly. Another common problem with nailing is “high nailing,” where a roofer places nails too high. The problem with this is that a dimensional shingle is a “two-ply” product with a thin area that is glued together. If the roofer fails to nail the shingle at this proper location, the bottom ply can come unglued and fall off the roof, leading to leaks. Also, roofers should avoid a “rainbow arch” where the two end nails are good, but the middle 2-4 get “out of hand” and end up too high. Similarly, roofers have to watch out for “shiners” (nails that are too low and can be seen from the ground [and which can leak]).

(6) Valley Problems.

While there are a number of methods of shingling a valley (California-Cut, Closed-Cut, Woven, Open-Valley), only the Closed-Cut method is recommended (whilst California-Cut is “allowed”) for dimensional shingles. The “Woven” style is acceptable only for 3-tab shingles (which are not industry best-practice to use, anyway). Of course roofers should never put nails in the valley area! One other concern in valleys is that the “corners” of the overlaying roof plane’s shingles should be “cut back” to prevent water working its way over and creating a leak.

(7) Bad Flashing Details.

Improper flashing accounts for a good deal of roof leaks. Step flashing should be insisted upon in every case of roof-wall details (with a “peel & stick” underlayment product going under the shingles/flashing, and up the wall), with appropriate counter-flashing for brick applications. One piece of step flashing should be used for each shingle course. The step flashing must be nailed to the roof deck, not the wall; whereas the counter-flashing is attached only to the wall (this allows for expansion/contraction of wall relative to roof).

(8) Lack of Crickets Behind Chimneys.

A “cricket” might sound like a funny term, but it’s an important detail. A “cricket” is a water-shedding gabled roof plane that is built behind a chimney to divert the water around it. Crickets may be built from a single piece of metal, but it’s also perfectly fine to build them with wood and shingles.

Chimney Cricket (Or, “Saddle”)

(9) Insufficient or Non-Existent Attic Ventilation.

Did you know that 9 out of 10 attics in the US are improperly or not at all ventilated? An unventilated attic will be 20°-45° hotter than a vented one! Studies have found that 58% of childhood asthma is correlated to a lack of proper attic ventilation (the hot attics provide a perfect place for heat and trapped moisture, which microbes love to grow on)! Speaking of moisture, the average family produces 4 gallons a day of water vapor, which can get trapped in unventilated attics and cook your roof decking. Besides the issue of providing a place for microbial growth, poorly ventilated attics increase your AC bills and can reduce the lifespan of your shingles by causing heat blisters (which resemble hail damage).

(10) 3-Tab or Dimensional Shingles Used for Hips and Ridges.

When it comes to your roof system, the hips and ridges are one of the most vulnerable spots, where wind speeds are highest. That’s why it’s important to use special shingles (like GAF’s TimberTex® Premium Ridge Cap Shingles) for those areas. Not only are the proper hip/ridge shingles better for resisting the wind (how often have you seen homes with hip/ridge shingles blown off? It’s almost certainly because 3-tab shingles were used instead of the proper product), due to their added thickness, they look better from the road.

Now that you’re aware of the ten most common residential roofing problems, are you going to make sure you hire someone that won’t make those mistakes?

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9 thoughts on “Ten Common Residential Roofing Errors”

  1. Hi there! I was on a mission recently to find the best content on the web about the most common roofing mistakes for an article of mine and I came upon this post which I found very useful so I included it in my top list. I hope my collection of roofing mistakes to be avoided helps other people and thank you for you contribution! Here’s the full list if you’re interested: http://dhodgesroofing.com/top-16-posts-common-roofing-mistakes-preventing/

  2. What are best practices for adding on a wider width, to a gable house at 90 degrees? Here is what I mean, right now our house runs east and west. It’s 25’4″ wide and about 50′ long. Would like to add on to the north, but if I go wider than 25′ then the ridge of the new addition will be higher than the old. What are the odds of this leaking? Say on a scale from a roof vent to a skylight. :-)

    1. You can add wider, as long as you lower the slope of the added on part. Now, if you have a 4:12 slope roof on the existing roof, then you don’t want to lower the slope on the addition. What you can also do is let the addition ridge be the same slope and if it’s wider, then let the ridge be higher. On the side of the new ridge where it kills into the old ridge, hip it off (let the existing back roof plane come up at via two hips to intersect the new, higher ridge). If done properly, it won’t leak.

  3. Hi I was wondering if you could give me some advise on my garage roof. about 60 years old Has cedar shingles. hip roof. not much sun on front and one side so covered in moss. but no leaks. I am re roofing the front to make cosmetic changes and put a metal roof on the carport thats attached to the garage front then the lean to roof is attached to the house. I am ready to put the underlay on but its been very wet here. I have sprayed bleach to kill the moss and algae removed the cedar shingles and the rotten planks of the old decking put new OSB sheathing but just wanted to know how dry the sheathing and roof should be before i secure the felt underlayment. the garage has an attic but no vent. I dont want to trap moisture under the felt since it doesnt get a lot of sun. it is still just above freezing. I have a small heat source in the garage, heats the attic slightly 2 or 3 sunny days would be prefect but it looks like its going to remain wet for the near future lol we have had a week of heavy snow again that is gone since yesterday and i prefer to get something on it before we get another snowfall or rain.

    I can put cedar shingles back on but would rather put asphalt. will one or the other help in damp soggy roofing conditions? would it be better to cover the area with a tarp until it drys out more or just get the felt down and shingles on asap

    1. Sorry for the LONG delay

      I would say go ahead and put the felt on if the OSB is reasonably dry. It can continue to dry out the underside into the attic (I assume you have some kind of attic ventilation such as soffit and ridge vents or else gable vents).

      I think shingles or cedar would be okay, although cedar is very expensive and shingles aren’t.

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