If you want to replace your asphalt shingles with a new metal roof, you might be thinking about putting the metal panels over the old shingles. Since metal is lightweight roofing, it's possible to place them over your old roofing, but you need to make sure that's the best choice for your residential roof replacement.

The roofing contractor will inspect your old roof first and determine if it's a good idea to put metal panels over old shingles or if the old roof should come off first. Here are two reasons it might be necessary to tear off the asphalt shingles first.

1. You Can Make Sure The Deck Is In Good Shape

One of the main reasons it's good to tear off an old roof rather than cover it up is so the roofer can actually look at the deck and make sure it is in good shape. If your shingles were leaking, the deck might be rotted in places, and you don't want to cover up the deck damage with metal panels.

Instead, when the old shingles are torn off and the roofer sees there is water damage to the roof, the water damage can be repaired before the metal roof is put on, which helps the roof have a longer life.

2. You Can Tell If The Deck Is Uneven Or Wavy

Another reason to tear the asphalt shingles off down to the old deck is so the roofer can check if the deck is still smooth and level. If your roof is old, the deck is old too, and it may have settled in places. It's difficult to notice a wavy deck when asphalt shingles are in place, but once they're off, the roofer can spot uneven areas.

The problem with an uneven deck is that the wavy appearance will transfer through the metal roofing panels. This can cause your roof to look unattractive. If the roofer knows the deck is uneven, they can compensate by putting down insulation board that covers the old deck and makes the surface smooth and level. This eliminates problems with waviness so your metal roof gets off to an attractive start.

Once the roof replacement contractor has checked your roof for these potential problems, they can advise you on whether it's a good idea to put metal over old shingles or not. If the deck is dry and in good shape, the roofer can cover the shingles with insulation board or underlayment and then place the metal panels right on top of the old roofing, and that might save a little money on your residential roof replacement.

For more information, reach out to a company such as Sombreros Roofing.