Someone posted a question in one of our popular blog posts, "Pros and Cons of Going Over Existing Roof Material." Essentially, she had received conflicting advice from several different roofers regarding her failing composition shingle roof, and she was trying to make a decision between tearing off the existing shingles and replacing them with new shingles or upgrading to metal and going over what's already on her roof. Here's our advice to her and to anyone else debating their options when it comes to re-roofing.
Among the many good reasons for choosing a metal roof is the fact that many types can be installed directly over existing roof coverings (like asphalt or wood shingles and shakes), saving the time, expense and landfill impact of removing and disposing of an old roof. While this isn't necessarily true about every metal roof, such as many standing seam profiles which often require a smooth, flat deck as a substrate, choosing from the many that are designed for this purpose is not that difficult. Here's how you know what options your roof presents:
Four Signs that Tear-Off is Best:
1. The existing roof is so rough and uneven that it will compromise the appearance of the new metal roof.
2. The existing structure is rotten or broken and needs to be repaired before the new roof can be installed.
3. There are too many layers of existing roofing, and local or national codes restrict installing any more.
4. There are too many layers of existing roofing that will prevent the nails or screws for a new metal roof from penetrating down into a structural component.
Four Signs that Metal Roof Install on Top is Best:
1. There are only one or two layers of existing roof, and new nails or screws can penetrate what's there to firmly anchor into the structural deck.
2. The deck beneath the existing roof isn't rotten or damaged.
3. The existing roof isn't terribly uneven or irregular.
4. There are no local building code restrictions preventing such a job.
Usually, metal shakes, tiles and shingles are best suited for installing over existing roofing, but there are panels like our Value Panel that are also designed for such applications. All of them can be installed successfully over an existing roof - and without compromising the performance or warranty of the metal roofing.
Have a question? Use our Ask the Expert form or give us a call today. And if you have a roofing project, we encourage you to research the many options a metal roof gives you. Check out our Resources page for useful downloads or get a free estimate.