5 Reasons We Don’t Recommend Re-Roofing Over An Existing Shingle Roof.
Having a new roof laid over the top of an old roof can be appealing to save on both time and money. However, we don’t recommend it and here are 5 reasons why:
1) Save a little now, added expense later - What it saves now, will be made up for later. Shingles work best when attached to the clean deck of a roof. Attaching them over an additional layer of shingles can interfere with the way the roofing system performs. The likelihood of wind uplift increases because they are not optimally secured. All of which can shorten the lifespan of your ‘new’ roof requiring yet another replacement sooner than you expected. Since the law states you can only have two layers of shingles, the cost of a new roof will cost more because both layers will have to be removed and require disposal.
2) Chasing Leaks - Having two layers of shingles can mask the origin of a leak. When a roof leaks it can be caused by many different factors, a wind storm can tear off shingles or flashing, attaching items like dish antenna or holiday décor improperly, or even a small branch can cause more damage than you realize if dragged off the roof, all easily identified causes. But when a leak occurs, frequently the cause is not sitting on your roof easily spotted. When there are two layers of shingles, the leak can begin in one place then track between the layers to another spot where it causes damage.
3) What Lies Beneath - When the shingles are torn off during the replacement of a roof, it allows the technicians to examine the substrate below, checking for any signs of concern. Rotten sheets can be replaced and improve the health of your structure. Without out this important step, problem areas could be missed and continue to plague your home.
4) The Weight - The weight of a roof shingle will vary from type to manufacturer. Deadload is the weight of the in place building components, including roof covering and waterproofing materials. The most effective waterproofing systems, at the lowest possible dead load impact to the structure are recommended.
5) The Warranty - The last reason we don’t recommend re-roofing over an existing shingle roof is the warranty. In most cases, a roofing company can not offer a workmanship warranty on this type of roof simply because they can’t predict what effect or problems will be inherited from the old roof to the new one. Some homeowners will be confused by this because the manufacturer warranty will cover the new material of a second roof, but what they don’t realize is according to industry leaders, 90% of leaks are caused by lack of maintenance, ice damage, wind damage or improper installation and easily dismissed by manufacturers when a second layer of shingles enters the equation.
Contractor’s Roof Service stands by the ideal of service and workmanship. We act as our clients’ advocate when it comes to their roof. We do what is in our clients'
best interests, and that means giving them all the information, so they can make the best roofing choices available to them. In this case that means going the extra step and tearing off that old, failing, shingle roof before adding the new one.