Common North Florida Roofing Problem - Shingles installed over low sloped roof
Many homeowners prefer the look of a shingle roof over other options like modified bitumen rolled roofing commonly referred to as Torch Down. Unfortunately, it’s common practice in North Florida for roofing contractors to install shingles on roofs with slopes that are too low for this type of roofing application. Furthermore, building inspectors in our area have historically let these borderline shingle roof installations slide. The result is a roof that leaks pre-maturely because of improper installation.
Shingles are designed for roof slopes that are greater than 2 inches of vertical rise over 12 inches of horizontal run, known as 2:12 slope. That’s because shingles are designed so that the slope allows water to shed off, eliminating the possibility of ponding water after a rain storm. Low sloped roofs are particularly susceptible to wind driven rain. Wind blowing up the roof slope causes water to actually flow backwards against the shingle. When this happens, water makes it’s way under the shingle and onto the secondary leak barrier.
If you have to depend on underlayment, asphalt cement, or Ice & Water Shield to block water after it gets past the primary roof covering (Shingles), you have the wrong roof system. Shingles get brittle with time, and at the reduced slope of a 2/12, a slight curl at the end of the shingle enables water to flow backwards under the leading edge. When you have a little wind blowing the water back up the slope of your roof, you don’t stand a chance at keeping the water out. Underlayment and Ice & Water Shield are a last resort, and should not be counted on for everyday protection.
Paul Fisette – Journal of Light Construction
The picture below shows how wind blows debris back up under the shingle, preventing it from sealing against the shingle below it. From the pictures, you can see that the nails are rusty. This is an indicator that water has made it under the shingle and has stayed there for a prolonged period of time. This is a common problem when shingles are applied on roof pitches of 2:12 or less.
So what can you do if your home has this problem?
There are a few options that can help you protect your home against leaks in this situation.
Option 1: Replace your existing shingle roof with a roof system designed for low sloped roofs.
The best thing you can do to protect your home is to have a roof designed for low slope applications. In North Florida, the most popular choice of roofing for low sloped roofs is Modified Bitumen Rolled Roofing. There are various configurations available. Three of the most common ones are:
Torch Down Modified Roofing – This is a rolled roofing product that is applied to your roof using the heat from a torch
Self Adhered (SA) Modified Roofing – This method utilizes rolled roofing products that have a built in adhesive that activates when a heavy roller is used stick the roofing product to your roof. This approach can be applied using a 2 or 3 layer system.
Cold Modified Rolled Roofing – This method involves the use of an adhesive that is applied to the base layer of your roof using a brush or trowel
Photo: Torch down Modified Rolled Roofing being applied to a North Florida Roof with low slope
Option 2: Restore your roof with a roof coating
If your roof has little or no sign of leaking and your wood decking is solid and dry, a roof coating might be a good option to help you prevent future leaks. There are many different types of roof coatings that can be applied on low sloped roofs to prevent roof leaks. In many cases, these roof coatings have a life expectancy of 15 years or more, so they may be a cost effective option.
One benefit of roof coatings is that they reduce the need for dumping large amounts of material into a landfill. Roof coatings offer a much more environmentally friendly approach to keeping your home dry than a total roof replacement
Roof coatings also reduce energy costs. In many cases, roof coatings are white so they reflect the sun, reducing the surface temperature of your roof by as much as 50 – 60 degrees Fahrenheit.
Under the right conditions, roof coatings have become a popular means of restoring a worn roof system, or a roof that was improperly installed.