If you're wondering can you install a metal roof over asphalt shingles , the brief answer is generally a resounding yes, but there are usually a few items you really need to appear at before you start hauling sections up a ladder. It's one of those do-it-yourself topics where everyone seems to have a good opinion, but when you strip away the noise, it's mainly about local developing codes and the particular actual condition associated with your current roof. Doing a "lay-over" can save you a ton of time and cash, yet if you ignore the prep work, you may just be investing a leaky roof for an costly mistake.
Exactly why People Love the "Roof-Over" Idea
Let's be real: nobody likes the particular mess of a roof tear-off. If you've ever observed a crew strip old shingles, you know it appears like a literal war zone in the front yard. Right now there are nails almost everywhere, dusty shingle granules in the shrubbery, and that huge dumpster sitting upon your driveway regarding a week. By installing metal ideal over the old things, you skip that will entire chaotic stage.
Beyond the particular lack of mess, it's a budget-friendly move. Labor expenses for tearing away from and disposing associated with old shingles can add thousands to a quote. In addition, keeping those older shingles around the roof means they won't end up in a landfill, which usually is a good little win for the environment. You also get a bit of extra insulation. All those old shingles work as a thermal break and a bit of a sound dampener, which usually can help to keep the house a bit quieter when it rains.
Check Your Local Building Codes First
Before you obtain too excited, you have to play by the rules. Most building rules in the U. H. follow a "two-layer limit. " This particular means if you already have two layers of shingles on your house, you almost definitely cannot add a third layer associated with metal on top. You'd be pushing the weight limits of the home's structure, and when a heavy snow hits, you're requesting trouble.
It's always worth a quick call for your local building division. They'll tell you straight up if a lay-over will be allowed in your own specific area. Don't skip this part—if you ever try to sell your house as well as the inspector sees an unpermitted "third layer, " it's going to become a massive headache to fix.
The Condition of Your Current Roof Matters
You can't just hide a disaster and expect it to go away. If your own current asphalt roof is sagging, or if you understand for a reality the plywood decking underneath is rotting, you absolutely can not install metal over it. Metal is definitely light, but it's not magic. This needs a solid, flat, and durable base to screw into.
If you have gentle spots, that's a sign that this wooden beneath is affected. If you screw metal panels into rotten wood, the particular screws won't grab, and the initial big windstorm that comes through might just peel your new roof off like a tin can lid. Walk the particular roof (carefully! ) or hire somebody to do a quick inspection. When the structure is definitely sound, you're all set.
To Make use of Furring Strips or Not?
This particular is the huge debate in the roofing world. Whenever you're putting metal over shingles, you have two primary options:
- Direct-to-Deck: You put an underlayment over the shingles and screw the metal directly through the shingles into the wooden deck.
- Furring Strips (Battens): You nail down 1x4 wood strips (purling) horizontally across the roof, and after that attach the metal to those pieces.
I'm a big fan associated with furring strips. They will create a flat surface, which is great due to the fact old shingles in many cases are bumpy or curled. More importantly, they will create a small air gap between the old roof and the fresh one. This space helps with venting and prevents "oil canning, " which is that wavy, distorted look you sometimes see upon cheap metal rooftops. However, if you're on a tight budget and the shingles are relatively flat, direct-to-deck with a thick underlayment can work great.
Don't Skip the particular Underlayment
Actually if you're making the shingles upon, you need a barrier. Asphalt shingles are basically made of sand and oil. Over time, as the metal expands and contracts with the heat, it can rub against all those rough shingle granules. It's like sandpaper. Over a several years, that scrubbing can actually wear away the protecting coating around the underside of your metal panels, leading to premature rust.
A high-quality synthetic underlayment or a layer of breathable foil insulation functions as a barrier. It protects the particular metal and adds an extra layer of moisture protection. Don't let a contractor tell you it's unnecessary—it's a small cost for a lot of comfort.
Dealing with Condensation plus Airflow
1 of the greatest risks of "stacking" roofs is trapping moisture. If comfortable, moist air from your house gets up into the particular attic and strikes the underside of a cold metal roof, it turns straight into water. If that will water gets captured between the metal and the older shingles, it has nowhere to visit yet into your wooden rafters.
For this reason ventilation is non-negotiable. You need to make sure your own soffit vents plus ridge vents will work perfectly. If you use the furring strip method We mentioned earlier, it actually helps quite a bit along with this since it allows some airflow directly under the metal panels. Just create sure you aren't creating a "moisture sandwich" that's heading to rot your home from the best down.
Exactly what About the Weight?
I touched on this with the building codes, but let's talk quantities. A typical asphalt shingle roof weighs in at between 2 to 4 pounds for each square foot. Metal is incredibly light, usually weighing regarding 1 to one. 5 pounds per square foot.
Although metal is the "featherweight" of the roofer world, when you add it in order to an existing roof, you're still growing the total load on your trusses. Most contemporary homes are built to handle this with no breaking a sweat, but if you live in a very old house with hand-cut rafters that are usually spaced pretty far apart, it's well worth having a pro take a look. You don't desire to see your own ceiling joists start to bow after the first big snow.
When Need to You Definitely Rip Off the Old Roof?
As significantly as I such as the idea of saving cash, sometimes a tear-off is the only smart move. Listed below are the "red flags" where you need to stop and just pull the older shingles off:
- Leaking almost everywhere: If you have multiple active leaks, you need to view the decking to repair the main cause.
- Wavy roofline: This particular usually means that the framework is sagging or even the plywood is usually delaminating.
- Existing "two layers": As I mentioned, 3 is a masses and usually illegal.
- Bad flashing: If the outdated flashing around chimneys and valleys is definitely totally trashed, it's often easier to simply start fresh so you can close off those critical areas properly.
Final Thoughts
Therefore, can you install a metal roof over asphalt shingles ? Absolutely. It's a common practice that will, when done perfect, gives you a roof that can last 40 to 50 years. The main element is to be sincere concerning the condition associated with your current roof. Don't use the metal as a "band-aid" for structural troubles.
When your deck is usually solid, your air flow is on stage, and you make use of a good underlayment or furring pieces, you're going to end up with a fantastic-looking roof that will save you a great deal of money for the install. Just do your homework, check those regional codes, and make sure you aren't cutting the incorrect corners. A little extra prep today means you won't have to think about your roof once again for the following few decades.