One of the most expensive things that a homeowner will have to do in their lifetime is pay to have a new roof put on their house. The cost can vary depending on whether or not the old roof is removed. Local building codes should be the first concern when making the decision to put new shingles down over old.
Some areas only allow you to put new shingles on top of old ones a fixed number of times before the old roof has to be torn off for the new roof to be put on. This is because if the roof becomes too heavy, it can damage the structure of the home. Each layer of shingles adds quite a bit of weight to the roof.
There are a few other things to think about when putting new shingles over old ones any time your home needs a roof repair:
Are the old shingles curled?
If the old shingles are curled up around the edges, the new shingles will not be able to lay down the way they are supposed to. Sometimes this is even visible from the ground and it makes the roof look unappealing. The old, curled shingles can even have an effect on the flow of water off the roof that will eventually create leaks when it rains.
Is your roof leaking?
One of the advantages of tearing off an old roof before putting on a new one is that the decking can be checked for leaks and rotting spots. New flashing can be installed if the old flashing is faltering and any other issues can be corrected before they cause further damage to the home. You may already have the beginning of a leak or other serious problem in the decking and not even know it.
Are you willing to put another roof on sooner?
Having a new roof installed over the old one simply will not last as long as having the old roof torn off and the new one installed directly onto the decking. You will have to do it again sooner because the new shingles will wear faster.
Are you selling your house anytime soon?
If you are going to be putting your house on the market, you will want to consider removing the old roof. Houses with multiple layers of shingles are not as attractive to buyers because they see an expensive project in their future. It may even have an effect on the selling price of your home.
