Many home owners and roofing contractors often try to save a few dollars by roofing over existing shingles. This may or may not be a good option for the home you are working on. There are several considerations that you need to be aware of.
In many situations your warrantee will be null and voided if you add a second or third layer to your roof. If you already have a layered roof, adding yet another layer is not advised because of the additional weight on your home’s structure. Often times even roofing over a single layer of shingles can damage your roof’s structure over time.
There are also building codes in many areas that prohibit roofing over existing shingles, so check your local codes before you even consider it. Another draw back is that it can lessen the value of your home because some home buyers are aware of the possible structure damage that can occur.
Surely there are situations that do warrant for roofing over your roof’s existing shingles. For example, your home may not be expected to last another 20 years or you may have a well supported roof that can handle the weight.
Whatever your reason for wanting to layer your roofing, we will cover some necessary tips in this article to help you with your project if our opening paragraph has not already made you change your mind.
When is Layering your Roof a Realistic Option?
Of course there are situations that warrant a layered roof. In the next sections of our article we will discuss several situations where layered roofing is a realistic option and we will give you some tips to help you make the proper choices along the way.
If you home is 1-25 years old, you may want to think twice before layering your roof because you home has a long life ahead of it and you should only consider layering a roof once. If you do decide to layer a roof, it is best to do it later in your homes life, not within the first 30 years or so.
If your home is over 30 years old or you think that a layered roof will likely be the last fix for that roof, then go ahead and layer it because the new roof will most likely outlast the home anyway. Just take some precautions such as some of the ones mentioned throughout this article.
The first obvious thing we should mention is the use of metal roofing over asphalt roofs. If you want to do it, roofing over existing shingles is probably safest for the structure when you use metal roofing. Metal roofing only weighs about one pound per square foot, whereas asphalt shingles can weigh up to four pounds per square foot.
Clearly metal roofing does not weigh down an old structure nearly as much as shingles, making it a safer choice when structural integrity is a concern.
Underlying Leaks and Damage
Just because you are putting on a new layer of roofing, doesn’t mean that you can ignore any existing leaks or damages to the old roofing layer. You need to repair any leaks, rotten lumber, broken rafters or any other damages before applying another layer of roofing.
Pay particular attention to signs of stress on the roof’s structure. If you notice any sagging or buckling trusses, you may want to reconsider adding more weight to that roof or at least fix the structure so that it is sturdy before proceeding.
Adding an additional layer on top of the old shingles will prevent the shingles from damaging a new metal roof with corrosion, buckling, etc. Felt paper or tar paper is considered the industry standard underlayment to use between layers, but there are several options including many synthetic underlayments and E-foil. E-foil is a foil faced layer that reflects and insulates when used between shingles and a new metal roof.
So if you consider what is in this article, your home is most likely a prime candidate for a layered roof if it is an older home, you intend to use metal roofing, the roof has a strong structure and you use the proper underlayment material.
Building over an existing roof is not the best way to do the job, but in many cases it is good enough. It will save money on the installation because it costs less to not have to tear out the old roof.
Be sure that if you do this, that this is likely to be the last roofing job your house needs because it can get expensive if you have to redo a roof that has already been layered. It costs more in the long run if you have to redo the roof again in the future. That is why it is important to do the job right so that it will last the rest of your home’s lifetime.