When considering the options for the type of roofing materials that should be applied to your home, there is one major determining factor, aside from aesthetics, that plays a major role in determining your options and that is the pitch or slop of your roof. Pitch is often referred to in a manner that looks something like 4/12 or 10/12. What these numbers represent are rise and run. The first number is how many inches of rise there are for every 12 inches of run, the second number. The lower the first number, the lower the pitch of the roof. The higher the first number, the steeper the roof is. The real line in the sand with pitch comes at 4/12 and below. Anything above this can receive most roofing products or applications without problem. However, once the roof touches below a 4/12 pitch extra measures need to be taken to protect the home.
Shingling and other residential roofing materials made for pitches at or above a 4/12 are made to shed water and not hold it. Shingles are made to collect the water and get it off the roof and into your gutters to shuttle it away from the home and protect the foundation. When shingling is used on slopes lower than a 4/12 the shingling loses the ability to shed water and begins holding it. Water is persistent! When it is held on shingling it will find seams and vulnerabilities that the water will take advantage of to find access to your home. I see this regularly when visiting homes where customers had additions put on the back of the home or a porch roof was added and the contractor wanted to match the shingling that was already there. Maybe the contractor did not know what the manufacturers recommendation for lower sloped roofs consists of or what the current codes for roofing in Tennessee are, but whatever the reason, in the end you are stuck with a roof that leaks and the frustration and anxiety that goes with water coming in your home.
Here is a brief guide to how low sloped residential roofs should be handled based on manufacturers recommendations and local building code.
Pitches from 2/12 – 3/12 (this includes up to 3.9999/12)
Ice and Water Shield should be applied to the substrate, or decking, on the entire area and then shingling can be installed. It is common for contractors to skip the Ice and Water Shield because of the cost, but just having synthetic underlayment does not protect the home when this lower pitch is present.
Pitches from .5/12 – 2/12 (1.99999/12 really)
Residential rolled roofing products which come in multiple layer applications that include a membrane the is applied to the surface first and then one or two additional layers bonded to that with the final layer being granulated similar to shingling.
These roofing systems require products typically utilized in the commercial space such as TPO, PVC, or EPDM.
Having the right product in the right spot can ensure the longevity of your roofing system and also prevent the stress and frustrations of water in your home. Do your research and consult with a qualified roofing expert to get the low sloped portions of your home dialed in.