The prime reason for adding another layer of shingles to an existing layer is for convenience and cost reduction. The difference in price can be substantial, so naturally such an option to simply add a layer will be considered. There are a few benefits to this method such as increased insulation and protection from weather elements. Other than these two, it is just less beneficial to add another layer for these reasons.
- Weight – Probably one of the more significant concerns is material weight. Shingles are not light by any means, so the structure beneath the building top needs to be strong enough to hold up the amount of layers that are placed. A contractor should know this based on building codes. Saving money at the risk of collapse is not worth the effort and will cost more in the long run.
- Heat Build-Up – More insulating properties for a building can be helpful; however, layers of shingles can also cause heat build-up between them, which will cause premature aging. If that happens, another layer or a complete strip down will have to be done sooner than if a complete new roof had been put on initially, which ends up being no cost savings in the long run.
- Leak Tracking – It is hard enough to find the origin of a leak with one layer of roofing material. Multiple layers will only compound that issue and potentially create a problem when roofers try to find it. Chances are an all-new roof will be needed and in the long run, offer no real savings.
- Tear Off – The initial reason that most people opt to re-cover a building top rather than tear it off and start new is cost. Eventually, a tear off will need to be done and when it does, the cost will be much higher than an initial tear off would have been before multiple layers were added. Labor and disposal fees can be double in this situation and will probably cost more money in the long run.
- Property Value – For all of the above reasons, a layered roof will also negatively affect a property’s resale value since realtors and home inspectors know that a major repair will be coming very soon.
Although it may seem like putting new material over a failing roof can be an economical way to handle such a concern, it will likely cost more in the long run. While the cost of having a roof replaced can be daunting, it is a wiser economical decision to do a complete tear off along with re-shingling as it will save thousands of dollars overall. By doing a complete job, contractors can also closely examine the decking surface, check for evidence of undetected leaks and make a more efficient home all around.
When working with a reputable and knowledgeable contractor, the wise choice is to follow their suggestions if a complete tear off of the building top is the wisest choice to be made. In order to have the most durable roof and the least amount of expense over its lifetime, a single layer is just a better choice than a double layer for any roof!