When faced with the perceived cost or inconvenience of replacing a roof, some homeowners may consider “re-covering,” or adding a new layer of shingles as an alternative. While re-covering may save some money, mess, and the hassle of removing old shingles, there are considerations that you must weigh. For instance, building codes in your area will limit the total number of acceptable layers of shingles on your roof. Additionally, you will need to consider the type of roof you have and its structural soundness when deciding whether to re-roof or add to your existing roof.
How Many Layers Is “Too Many?”
There are a variety of factors that determine how many layers of shingles a homeowner can have on a roof, including:
- Local building codes: Checking building codes in your area is an important first step. Depending on climate and weather, some areas may only allow one layer. Also, building codes are subject to change frequently, so it’s important that you know what current local codes allow.
- Roofing materials: In the Portland area, as of 2018, the current code allows up to three layers if the current layer is in good condition. However, this depends upon the roof materials. For example, cedar or tile roofs are only allowed one layer.
- Structural soundness: The soundness of the building you’re re-roofing is another consideration. Adding a second or third layer of shingles adds significant weight to the structure. If the current roof is in poor shape, re-covering may not be a sound choice.
Other Factors to Consider
If local building codes allow for an additional layer of shingles, you’re adding composition shingles over composition shingles, and your structure is sound, there are other considerations to examine before moving ahead with re-roofing:
- No mixed mediums: Not only can you not add a second layer to cedar or tile roofs, you cannot put composition shingles over them as a second layer. Neither cedar nor tile are flat enough to put composition shingles on them and damage or defects to existing shingles will transfer through to the new layer.
- Voided warranty: You want your roof to last for several years, but if there’s an issue, you want to be able to recoup loss and pay for repairs using your warranty. Unfortunately, most manufacture warranties are either voided or significantly reduced for re-covering composition shingles with new shingles.
- Soft spots: Roof replacement requires an inspection to determine if there are soft spots on the wood sheathing which can indicate a need for repairs. Because a re-cover does not involve a tear off, soft spots may go undiscovered and unaddressed, leaving your home vulnerable to damage from wind, rain, ice dams and more.
- Flashing replacement: Flashing prevents water from penetrating your roof and should be replaced if you’re adding additional layers.
While re-covering may seem like a less expensive fix, it may only serve as a temporary band-aid, covering over potentially serious defects and damaging your roof even more. If you are considering re-covering, you should research all options available to you and consider the long-term impact versus the short-term savings.