"An asphalt shingle roof should last between 20 and 30 years," says Claude McGavic, executive director of The National Association of Home Inspectors. "If you have a 40-year-old roof, there could be a problem—eeven if it looks good from the ground."

How much time you've got left: Five to 10 years, depending on your roof's condition. If you live in a development and your neighbors are all starting to replace their roofing, that could be a sign that you should do the same.

Shingles can curl in two ways: There's cupping, which happens when the edges of the shingles turn upward; and there's clawing, which is when the edges stay flat and the middle starts to come up. "Both are signs of weathering and indicate that problems — potentially leaks — are relatively close to fruition," says Mark Graham, vice president of the National Roofing Contractors Association.

How much time you've got left: "Depending on the extent of the curling, it could be anywhere from a year to five years before you need a new roof," says Graham.

From a functional standpoint, there should be no problem with just replacing a few shingles here and there. "What you do need to be prepared for is the fact that it's just about impossible to get a new shingle to match the color of an old one," says Graham. "Granule colors have changed pretty significantly over the years. Plus, the colors change slightly with weathering."

How much time you've got left: You can keep patching until a bigger issue presents itself, but if a roof starts to look like a checkerboard, people often opt to replace the whole thing.

Cracked shingles are typically a result of wind damage. If just a few shingles are cracked, you can certainly replace them. "If the cracking isn't isolated to one particular area and it's random throughout the roof, that's a telltale sign that you should start thinking about a new roof," says Graham.

How much time you've got left: You may need to replace the whole thing within three to five years.

If you just got a new asphalt shingle roof and you see a bunch of granules in the gutters, there's nothing to worry about: Those are just loose, extra ones. But if it's been 10 or 15 years, that's a sign of a bigger problem. "Granules help keep the sun off the asphalt," says McGavic. "Once the granules fall off and the shingles start to bake, the quality will deteriorate in a hurry."

How much time you've got left: If you don't have a new roof and you just started to notice the granules in the gutter, the shingles are probably halfway through their lifespan, McGavic estimates.

Okay, this is actually no reason to panic. "It's just a cosmetic issue," says McGavic. People may choose to replace the roof just because they don't like the aesthetic (and a lot of new shingles are algae-resistant). Whatever you do, don't take matters into your own hands by power washing or scraping away at the green stuff. "That's a good way to chip off all the granules, which again essentially renders your shingles useless."

How much time you've got left: As long as you can stand the look. Consider a wash that's one-part bleach and one-part water to remove algae or moss. Or look into zinc strips that can be installed at roof peaks and will eventually eliminate the problem. If you do decide to replace your roof, consider tiles that are algae-resistant, like GAF Timberline roofs, a Good Housekeeping Seal Holder.

You don't need us to tell you that this isn't a good sign, because it's not! If light can get in, so can rain, cold air, and snow. Check for light and also look for water stains. "If you find any, watch them over a few rainfalls and if they change shape or size, that means you've got an active leak," says McGavic.

How much time you've got left: It depends on the extent of the damage, so call a pro. Small leaks can be patched, but larger ones, structural damage, and the age factor might make it wise (and cost-efficient) to replace your roof sooner rather than later

This is when you should panic. "A sagging roof is typically an indication of a structural issue," explains Graham. There could be a problem with the decking in the attic or, worse, with the supports in the foundation. "You're not necessarily in imminent danger, but this is the kind of thing that's a lot easier to take care of when it's small and localized than when it has progressed."

How much time you've got left? Not much if you do nothing. If you see depression or a droop, call in an expert as soon as you can.

The professionals at DependaRoof can assess the condition of your roof and determine any early signs of roof failure. Contact us today for a free estimate. Don't wait until you notice a stain on your ceiling!