Roofs don't last forever. However, you do not necessarily need to replace your roof every time it suffers a little damage, either. That's part of the beauty of shingles. You can often replace just the damaged ones and get a few more years out of the rest of the roof. But how do you tell the difference between a roof that just needs some repairs and one that has to be replaced? Here are a few factors to look at.
1. How much of the roof is damaged?
If there is just one or a few patches of shingles that are worn, peeling, or deteriorating, this suggests the roof can just be repaired. However, if there are a lot of scattered patches of damage, you may be better off just replacing the roof. Even if you were able to replace just the damaged shingles, having to work on so many different patches will be time consuming and costly. Replacing the roof may just be cheaper.
Make sure you look closely at the roof when assessing how much of it is damaged. Just because a few spots show obvious damage does not mean that other spots are not less-seriously damaged and therefore also near the end of their lifespan.
2. What caused the damage?
Consider why the roof is damaged. Was the damage caused by a solitary tree branch, or did humidity in the attic cause it to deteriorate? If the cause is something that could soon also affect the rest of the roof, then you might want to address that problem. Doing so sometimes requires having the roof replaced. Moist, leaky underlayment is an example of such an issue. If the underlayment is moist and leaky, all of your shingles will be damaged before long. You need to have the shingles removed to replace the underlayment, so you may as well do it all at once!
3. Is the roof sagging?
Stand on the ground in a place where you can lower your eyes and look straight across the roof. Make sure you do not see any evidence of the roof sagging. (You may need to get up on a ladder to do this if your roof is particularly tall or at a sharp angle.) If you see evidence of sagging, you need to have the roof replaced, regardless of the state of the shingles. Sagging indicates a problem with the wood that underlays the shingles. A sagging roof is in danger of collapsing, so take action quickly, too!
4. Where are the leaks coming from?
Just because there is only one puddle of water in your attic does not mean that only one part of your roof is leaking. Water drops tend to dribble down the rafters and then fall to the ground all in one place. But the water may indeed be coming from several leaky spots. Try tracing the moisture back to its origin or origins. If a lot of areas are leaking, this could be a sign you need to replace the entire roof. (But before you do so, make sure you don't just have a few exposed nail heads. You can fix these with a glob of roofing cement—you don't need to replace the whole roof.)
Generally, shingle roofs do not last longer than 30 years, unless they are made with very high-end, 50-year shingles. You can use this to guide you in your decision to repair or replace, too. Call a company like Craven Construction to evaluate whether you are not sure whether you should replace or repair your roof. They will provide an expert opinion and probably give you an estimate, too.