Sometimes we see roofs that have two layers of shingles. Not completely a huge deal other than tearing off two layers of shingles will raise a new roof price, but having four or maybe even more layers is just plain crazy. Some building codes do not allow more than one layer of shingles and some allow up to two, contact your local building code office for requirements in your area. When you put extra protection for the underlayment like doing 30# felt instead of 15#, there is really no need for another layer. There are many reasons why it is not a good idea to keep adding layers.
- Extra labor cost to remove more than one layer of shingles. Especially if the building is a two story.
- Too much weight for the roof. Some contractors may say it is ok to put another layer on the roof can handle it, but they may not always be right. Most residential roofs cannot handle too much weight so having more than two at most, can start to damage the structure of the roof and the home. (The fact there seems to be there is that they want to save on labor by not tearing off.)
- Laying new shingles onto of old ones will cause problems later on because when the old ones underneath start to curl or deteriorate, and wind and rain become involved where do you think the water is going to go? Yep, you got it, right under the shingles that are curled or lifted up, which leads to leaks.
- It may not be allowed for your area and insurance companies will not pay for the labor to tear of extra layer or replace both layers. Once the top layer needs to be replaced, all layers must be torn off, but if there are two layers, this does not mean the insurance will pay to have two layers put back on.
- When there is a repair due to a leak, it is going to be harder for the contractor to locate where the leak is coming from.then because of the number of layers repairing will not be cheap either.
- And for the next reason, it just doesn’t look good. The more layers can make the roof look lumpy and funny.
There are some that do not care what building codes there are and do not follow them and sadly sometimes it is the same for a building owner as it is a contractor. Always make sure to do your research and if suggested by a contractor to just roof over top of what you have, make sure to contact another professional roofing contractor to get a second opinion. In most cases with the new advances of shingles and other roofing system products, there really is no need to have a second layer.