This is a common question, and in many cases, yes, a metal roof be installed right over the top of another existing roof material. In fact, thousands of metal roofs have been installed over composition shingles and/or wood shakes with no problems at all.
With that being said, however, there are a few considerations for determining whether a metal roof installation over your existing roof would be appropriate.
You can make an educated determination of your roof's condition with a visual inspection. Start by checking the planes of the roof from the ground. The structure is likely sound if the planes you can see from the ground appears to be straight and true.. If you can see visible "bellies" or depressions in the roof, take it as a warning sign and move on to investigating the structural components of the roof.
If you're able and you can do so safely, you should climb up on the roof to look for any soft spots or signs of weak, rotten, or compromised structural components. If you have any doubts about your roof's structural integrity, removal should be a priority.
If the roof appears to be straight and solid, with no evidence of persistent leaks inside the home, then it's probably a good candidate for an over-the-top installation.
Adding another layer of roof covering raises the depth of the total roof covering. This can be an issue if you have roof accessories like skylights, roof-to-wall flashings, dormers, roof-top HVAC equipment and other adjoining details. Consider in advance the extra height of the new roof assembly to avoid potential problems.
Something that is often overlooked is the length of the nails and screws. Your installer will need to be able to securely fasten the new roof to the existing rafters or deck, and he'll need that nails or screws long enough to penetrate both the existing layers and the wood deck to do so. Without them, the proper mechanical attachment of the new metal roof will be compromised. If an installer can't determine how such secure attachment can be accomplished for your new roof, the old one will probably need to removed first.
With the right conditions and an installer comfortable with the job, installing a metal metal roof over an existing roof is not only better from an environmental standpoint, it can also save money and time. And there's no sacrifice to your new roof's performance, either. If you're considering upgrading to a metal roof, we're happy to help. Contact Metal Roof Network today.