The pitch sounds good. Forget the hassle of tearing off your old roof. You do not need a dumpster. You can save a lot of money and put the shiny new roof right over the old shingles.
Sometimes, going with the easy option is the good choice. But other times, it is a quick fix that you might feel bad about after five years. Here are some things that the contractor may not tell you at first.
Yes, It's Usually Allowed. No, It's Not Always a Good Idea
Most building rules let you put one new roof layer over an old one, as long as the old roof is still in good shape. If you're checking prices on westernslopemetals.co, remember that just because you can do it does not always mean it is a good idea. If your old shingles are flat, dry, and nailed down tight to a strong base, putting a new metal roof on top can work well. But if the old shingles are twisting, feel soft, or hide water damage, you are just covering up a problem under a roof that should last many years.
The Code Limits You Need to Know
Under the International Residential Code, adding a new roof layer is not allowed if the roof is soaked with water or worn out, or if there are already two or more layers on it. This 2018 IRC re-roof guide from East Point, Georgia explains the rules in clear words. Your local building department might have its own rules, so be sure to ask them before you get panels.
Bottom line: if you already have two layers of shingles on, you cannot skip the tear-off.
Five Things That Get Overlooked
1. Rotten decking stays hidden. When the crew takes off all the old material, the team can see each bit of plywood. But if they put new material over the old one, you do not see what is below. A weak area that you do not find today is still there and weak.
2. Weight adds up. Metal is light, but your trusses also carry the old shingles. If you have an older home or a long span, it is good to have someone look at the structure quickly.
3. Shingles are not flat. If you put a metal roof straight on top of shingles, you get bumps, and the panels do not sit even. A lot of workers put furring strips (purlins) or a slip sheet on first. This gives a flat and open surface.
4. Moisture can get trapped. If there is not enough underlayment and air movement, water can build up between the layers. This can cause rust on the bottom and mold to grow in the deck.
5. Flashing still has to be redone. Chimneys, skylights, vents, and walls all need new flashing made for this type. This spot is where low-cost jobs start to leak.
When an Overlay Makes Sense
Go for it if:
• You have one layer of shingles, and they are in good shape
• The deck is firm in all the places. There is no sagging at all.
• There is no past of leaks or water in the attic
• Your installer will make sure that purlins or a good underlayment and ventilation be part of the plan.
There are some real benefits. You have to do less work. Almost nothing goes to a landfill. It gets put in place pretty fast. You also get one more layer for keeping heat in and blocking sound.
When to Tear It Off
Skip the overlay if:
• There are already two layers on the roof
• You see parts that sag, feel soft, or have water spots in the attic
• The shingles go up in curls or are not there in some parts
• You live in a place where it snows a lot and the building is old
For a quick and honest look at the two, this comparing metal roofs and shingles talks about what you get with each in ten key points.
The Bottom Line
An overlay can help you keep more of your money and also avoid trouble. But it works best when the old roof should still be kept. Make sure you have someone check the deck. Look up your local code for roofs. Plan out how to give the roof good air flow and also put in new flashing. If you are not sure, the team at westernslopemetals.co can help you choose panels and parts for an overlay or a whole new roof.
FAQ
Can you put a metal roof over two layers of shingles?
Yes, you can put a metal roof over two layers of shingles. You just need to be sure that the roof is in good shape. Check that there is not any major damage or leaks. A metal roof is light, so it does not add too much weight for your house. This can save you time and money because you do not have to take off the old shingles before you start the job. But, always check your local building codes before you begin. Some places do not let you put a metal roof over more than one layer of shingles.
No, most rules say you can only have one layer on your roof. After that, you have to take it all off before putting a new one on.
Does a metal overlay void the warranty?
It depends on who made the product. Some panel warranties say you must use certain types of underlayment or purlins. Make sure you read the fine print.
Is an overlay noisier in the rain?
Most of the time, no. The old shingles can help cut down the sound a little bit.
