If you have a shingle roof now and are considering upgrading to a metal roof, you might think the easiest thing to do is just to put the metal roof overtop your old shingles.
For some installers, this is standard operating procedure.
Others recommend tearing off the old roof and installing a the new metal roofing without extra layers underneath.
So, what’s the answer? Can a metal roof go over shingles?
Can I Install My Metal Roof Over Old Shingles?
The short answer is…maybe.
The type of metal roof you choose, the type and condition of your asphalt shingles, and even your local building codes impact whether or not you can install your new metal roof over the old shingles.
Here’s how you can determine whether or not it’s a good idea to tear off the old shingles before you start installing your new metal roof.
1: Check Building Code
In a majority of localities, building code dictates that no more than 2 layers of roofing materials can be used before you’re required to do a complete tear-off.
If that’s the case where you live and your current roofing already has 2 layers, you’ll need to remove the shingle roofing before you install the metal.
2: Check Current Roof Condition
While some wear and a little bit of damage is probably going to be present when you’re upgrading your roof, you should be conscious of the condition of your roof under your existing shingles.
Things like water damage, punctures, and other more serious problems might make for an unsuitable base for your metal roof.
It would be a real shame to go through all of that work installing a metal roof, only to have it leak in 2 years.
3: Decide Metal Roof Type
The best kind of metal roof to install over asphalt shingles is a metal shingle system.
Standing seam metal roofs shouldn’t be installed over asphalt shingles because the natural expansion and contraction from temperature will cause friction and wear over time. This wears your roof out faster, which kind of defeats the purpose of installing a metal roof.
If you do plan to install metal shingles over your asphalt shingles, be sure to build a correct foundation and vent properly so that the metal can expand and contract as it’s designed to do.