As mentioned above, homeowners are legally limited to two layers of shingles. Therefore, if you already have two layers, you will need a full tear. Also, if your roof is severely damaged, you may not be able to support the weight of a new roof and have to tear it off. At most, you can safely lay up to two layers of organic asphalt or fiberglass roofing shingles with an inclination of up to 18.5 degrees.
If there are more than two layers, too much weight is added to your roof. Some local building codes don't allow overlaps; in those municipalities, you can only have one layer of shingles. It's always a good idea to review the applicable codes before starting a repair or renovation project. Having multiple layers of shingles will make your roof warmer because heat is trapped between the layers, which could mean premature aging of the shingles.
But if you have a tight budget and the current roof has a layer of shingles, it is possible to make a new roof with nails if the situation is right. This is because a second layer of shingles will hide the potential source of a leak and prevent you from seeing underlying layers, such as plywood. These complexities also make the second layer more vulnerable, undermining the integrity of the entire roof. When you notice tile damage to your roof, you may begin to wonder if you will soon pay the bill for a full roof replacement.
Roof flashing is a metallic material that is placed anywhere that shingles hit something, such as a wall, chimney, or in open valleys. This is because the first layer of shingles, if not already covered with algae and mold, will fluff the water, while the second layer of shingles will seal the water and provide the darkness that algae and mold need to grow. Roofers who are expected to carry a package of shingles on standing ladders and roof ladders know that the weight is approximately sixty-five pounds. If you're considering adding a second layer of shingles to your roof, know that it's not the best option for every situation.
In most states, only two layers of asphalt shingles are allowed on a roof for fire safety reasons. Keep in mind that when it comes time to replace your roof, removing a double layer of shingles will cost more than removing a single layer. A complex roof is aesthetically very attractive, and it would be a waste to make a scale, since the second layer of shingles will not lie flat, will not look the same as the first layer, and will be more prone to bending, peeling and blowing, all of which will make your roof look less pleasant. Since the second layer makes removal difficult, you'll find that roofers have to work longer to prepare the surface for a new layer of shingles, leading to higher labor costs the second time around.
In fact, a scale would only take longer because there are literally more factors to consider, since you have to think about everything you thought about installing your first layer of shingles plus your first layer of shingles. Since a second set of shingles undermines the quality of your roof, it's not the way to go.