If you notice sagging that you believe is caused by roof lapping, you may have to redo the entire thing, or at least replace the offending panels.

There are all sorts of problems that can befall a roof over the course of its lifetime. Most of them aren’t a big deal.

Lose a few shingles after a heavy wind, and you can just replace them with a couple of hours of work. Even a leak doesn’t necessarily equal a serious problem. It just means you’ll have to spend a little time locating the source of the dripping so that you can seal it with any one of a number of methods.

If you notice your roof is sagging, however, this can indicate a much more serious problem. Indeed, it could mean that your roof has reached the end of its useful life and must be replaced quickly before a catastrophic failure. A sagging roof can mean a lot of smaller problems have accumulated without being caught in time, which can lead to great expense for the owner of the house or other building.

Although it’s a serious problem, a sagging roof isn’t always a lost cause. In some cases, it’s possible to repair without incurring too much expense. You’ll need to understand when it is and isn’t possible to make repairs. Below, we’ve tried to make sagging roof repair a little easier with these six facts:

1. You Have to Know the Cause

Before you can even think about making any sort of repairs, you’ll need to know why, exactly, your roof is sagging. There are a number of causes that can ultimately lead to a roof sagging.

It may be as simple as weight resting on the roof. While roofs are sturdy and built to withstand a great deal of weight, this strength only lasts up to a point. If there’s too much snow, ice, or plant matter sitting on the roof, it can begin to sag. This is a simple fix since all you need to do is clear the added weight off the roof, but it can also damage the roof in other ways or indicate a larger problem.

Water damage and aging materials are the other main causes of a sagging roof. Over time, water can cause the materials making your roof to warp and weaken, leading to sagging.

Even without leaks being the culprit, the materials can weaken due to age. While roofs are built to last for decades, they don’t last forever and will eventually need to be replaced; otherwise, a collapse can occur.

2. And How Bad It Is

If your roof is sagging due to damage or age, it’s likely that the problem has already become severe. It’s a good idea to regularly inspect your roof before there are any obvious signs of damage. Catch the problem ahead of time, and you’ll greatly extend the life of your roof.

Occasionally, head into your attic with a flashlight and look for any warped or discolored wood. This could be a sign of water dripping through the roof, where it could be warping the support beams. Eventually, this could lead to the roof sagging and, ultimately, collapsing.

If the roof is already sagging, take a look around for the cause. You might notice the rafters themselves sagging. If that’s the case, replacing them is the only way to repair your roof.

You may also notice moisture has gotten past the roof itself, ultimately leading to various parts of the roof failing. The insulation may have become damp and this led to sagging. If that’s the case, you’ll have to fix the leak as well as replace the damaged insulation.

3. It Might Be the Roof Lapping Too

If you have a metal roof, the part where the roof overlaps is known as lapping. The lapping on your roof must be installed properly because if it’s not, any sort of weight will pull the panels apart.

The weight of rain, snow, and leaves can all begin to pry the joints of your roof apart, ultimately leading to sagging that will be difficult to repair. Properly installing the lapping on your roof is key: always ensure that you allow at least 3 1/2 inches of overlap, and place a bit of sealant between each panel.

If you notice sagging that you believe is caused by roof lapping, you may have to redo the entire thing, or at least replace the offending panels.

4. It’s Not Always Necessary to Remove the Entire Roof

If the problem is caused by one element of the roof failing but has yet to spread to the other parts of the roof, you may not need to remove or replace the entire roof.

 This, of course, is ideal because replacing a few parts—even large parts such as the rafters—is much easier than entirely overhauling, and effectively replacing, the whole roof.If you determine that the rafters are the cause, you may simply be able to reinforce them without replacing them entirely.

5. But, Sometimes, You Will Have to Replace Everything

Sagging roof repair isn’t necessarily a huge job, but if the damage has spread, it may leave you with no other option than replacing every part of the roof.

Usually, you will do this layer by layer. You might, for example, replace the rafters first to ensure the roof has the necessary strength before moving on to replace the joists, flashing, insulation, and ultimately, the shingles.

In some cases, you can simply put new shingles over the old ones in another layer. However, most building codes will not allow you to have more than two layers of shingles.

Once again, it’s easiest to do this piecemeal before the problem becomes catastrophic. What we mean is, regularly inspect your roof, both inside and out, and replace parts as they become weak. This is infinitely preferable to having to replace every single part of the roof in one enormous job.

6. You Need a Great Contractor

Of course, it’s not always possible to easily make repairs by yourself. This is especially true if you have to repair or replace an entire roof.

We’ve mentioned that a roof should be inspected regularly, but that’s not always possible. For example, if it’s a house you have purchased recently rather than one you have lived in for years.

It’s a good idea to have a great contractor to perform occasional inspections and regular repairs for you. The same contractor can perform larger jobs, such as sagging roof repair or roof replacement, should the need arise.

Search for a reliable, experienced, and well-regarded roofer in your area; for example, Interstate Roofing if you live in the Portland area.


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If the problem is caused by one element of the roof failing but has yet to spread to the other parts of the roof, you may not need to remove or replace the entire roof.



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