Most roofers like to work with a clean slate when reroofing a house. That means they want to pull up all of the old roofing material, the old underlayment and sometimes even the old roof decking. While this the most common way to reroof a house, it is not always done. The homeowner or roofer may choose to install the new roof directly over the old one. Let’s look at why this is done including some possible benefits and disadvantages of roofing over the previous roof.

Why Reroof Over the Old Materials?

Many homeowners may feel like the old layer might provide an extra bit of protection or even waterproofing but this is not the prime reason why it should be done. One of the main reasons is saving money. Tearing off the old roofing material is a labor intensive task, this labor will be passed on to the homeowner. Reroofing over the old material will basically skip a step in the roofing process, leading to an overall smaller bill. While this seems like a quick way to save money there are several issues that come with it.

Situations Where Reroofing Over Old Roofing Material is Inappropriate

Per Code or Warranty

City, towns and jurisdictions may not allow for roofing over old materials per their own code. Building code depends on individual cities or jurisdictions. Installing over an old roofing material may also void the warranty depending on the material being installed.

A Difficult Job on its Own

We talked earlier about how reroofing can save a large step in the reroofing process but skipping this large step can create many other baby steps. You will need to talk with your contractor to find out if all the additional steps will outweigh the benefits of skipping the tear off.

Can’t Check Other Components

By not tearing off the previous materials, it’s difficult to get an accurate assessment of the entire roofing structure. Bad underlayment or even bad roof decking will be missed and could lead to other issues down the road.

There are several factors that determine whether it’s appropriate or not to reroof over old materials. Discuss this with your roofing consultant to find out if reroofing over old materials is right for your roof.