Shingle Nail Pattern
- Varying manufacturer requirements for nail patterns.
- Nail Warranties.
- Overdriving or underdriving nails.
- High and low nails.
- Nails to Close to Shingle Unions.
- Nails and valleys.
- Nailing for high or low slope roofs.
Varying Manufacturer Requirements for Nail Patterns:
The scary reality is that untimely and premature roof failure occurs because of Improper shingle nailing. This issues often lead to leaks, mold, rott and a lot of other potential issues. This is why it is critical that nails be properly placed and driven.
Each manufacturer typically has different requirements for their nailing protocol. GAF for example states that they do not want contractors to fasten shingles directly onto insulated deck or insulation unless the contractor has authorization in writing from GAF.
IKO even goes as far as to describe in great detail exactly what the characteristics are of a proper roofing nail all around: “A roofing nail should have a minimum nominal shank diameter of 12 gauge, 2,67 mm, and a minimum head diameter of 9,5 mm. Roofing nail should have a barbed shank until the head which eliminates nail pops, blow offs and roof leaks. A large nail head and heavier shank gauge provide greater holding power. All nails must be corrosion resistant; for example galvanized by various processes, aluminium, copper or stainless steel.”
The IKO Dynasty line and the Owens Corning Duration Line both require only four instead of six nails per shingle. It is generally accepted that the less nails one can manage to put in a shingle the less chance it has of leaking, because each nail spot has a potential for leaking if not nailed in correctly. Visit our page on “Exposed Nail Heads” for more information on some possible nailing related issues.
In the case of the Dynasty and Duration lines both shingle types come canvas reinforced. Meaning less nails are needed to obtain the same amount of wind resistance as the average 6 nail system. Making these a smart choice for wind durability and leak resistance.
Common issues with improper shingle nailing
Proper nailing of a roof is not just to assure the avoidance of issues like mold or rot. Another major factor is whether or not the manufacturer warranty will be valid. Manufacturers can be particular about their requirements if a contractor is putting a warranty on the roof. “GAF studies indicate that more than two-thirds of the problems people experience with their new roofs are due to the contractor’s workmanship — not the roofing materials. This is an important distinction to keep in mind when deciding on warranty coverage.”
Some roofing companies will encourage a customer not to worry about these issues because their roofing company offers workmanship coverage. GAF points out the following: “Obviously, that coverage is only good for as long as the contractor remains in business. Since roofing is a “high-turnover” business, the majority of roofing contractors are out of business within five years— making their warranty worthless and leaving you with nowhere to turn in the event that you have a workmanship problem.” This is yet another reason why it is so critical to make sure your installer follows the manufacturer’s protocol, to help assure the job is done right the first time.
Overdriving and Under Driving Nails:
Starting at the left to right:
Correct nail, under driven nail, over driven nail, angled nail.
One of the most critical aspects of proper nail use to making sure the nail goes into the shingle correctly. Common misnailing issues include over driving a nail, under driving or driving a nail in at an angle. All of these issues can lead to detrimental circumstances for the roof. Improper nailing can result in the area around the nail not sealing correctly, allowing water in. Once water gets in the roof, the roof becomes susceptible to rot and mold anywhere the water goes. Additionally, the shingles themselves can blow off if the nails are not securing the shingles correctly to the roof. The result of these issues can often be costly repairs that will not be covered by insurance, because insurance will view the damages as being caused by improper installation.
Above: Proper Nailing Technique according to IKO Website
1. An underdriven nail is much like a nail pop, leaving an incomplete seal around the hole which without a seal allows water in.
2. Overdriven nails don’t allow for the nail top to protect the opening.
3. Angled nails have the same issue, a proper seal does not form when the nail is angled and the head cannot provide adequate protection. In the last two cases the proper procedure is to cover the nail with cement to seal it off completely and put a new nail in next to it.
IKO states: “Many roofers use pneumatic nail guns to nail down the shingles. When the pressure is set too high, the nails simply get driven into the shingles too far. When the nails are overdriven, the heads of the nails punch right through the mat of the shingle. This voids the shingle manufacturer’s warranty and greatly increases the potential for shingles to come loose and be blown off, possibly in full shingle sheets.”
High and Low Nails:
Nails too Close to Shingle Unions:
Nails that are misplaced too close to the unions can leak. A union is the point where two shingles meet up side by side and there is supposed to be 6” of space from the last nail to the edge of the union. Union leaks are where the water goes between the unions, hitting the nails and allowing leaks into the house.
For further information on improperly driven nails please see the below roof bulletins: https://www.gaf.ca/Warranties_Technical_Documents/Steep_Slope_Technical_Advisory_Bulletins/English_Bulletins/Improperly_Driven_Nails_Steep_Slope_Technical_Point_TAB_R_2011_117.pdf
Nails & Valleys:
Valleys are where two roof points meet. That means water will flow off the other areas of the roof and into the valleys causing an excess of water in these areas. That is why it is critical that special provisions be taken to assure leaks do not occur in these areas. Please see our Ice and Water Shield Page for more information on these preventative measures. Critical components to designing the valleys often includes how nails are used in these areas. The main rule with a valley is to keep nails 6 inches away on each side of the valley. This provides a total 12 inch areas around the valley that is free of nails so that water flow does not go over the nail heads and turn into possible leaks. It is worth noting there are multiple ways to shingle a valley to ensure proper coverage. But all methods go back to keeping nails out of the actual valleys itself. See video below for examples of possible valley shingle methods:
Nailing for High and Low Slope Roofs:
The first thing to know when shingling a uniquely pitched roof is that shingles cannot be used on a roof with a low slope under 2/12. These roofs being mostly flat require EPDM or TPO roll out roofing instead. Nails for these roofs must seal tightly against the roofing material to help assure that any pooling water does not penetrate underneath and into the decking of the roof. The less nails used on low pitch roof the better, this helps to limit any possibility of leaks caused by excess water on the low pitch.
On the other side of the scale a roof that is 12/12 or steeper should be rated for those heights. A Lot of weight goes on those nails since the roofs are nearly straight up and down like a mansord, and it becomes critical that the nail not only hold the shingle in place, but that it can also hold the full weight of the shingle up.