Why Is My Roof Sagging? A Homeowner's Guide

July 29, 2021

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If you’re a homeowner asking, why is my roof sagging, it’s best if you find out the answer to that question quickly, as a severely damaged roof might risk cracking or even outright collapsing! Roof damage only gets worse over time, so that your eventual roofing service repair costs are even more expensive the longer you ignore that damage.

Excess weight typically leads to a sagging weight. Added shingle or tile layers, snow, ice, and other debris can mean too much weight on a roof and the risk of sagging. Damaged decking and structural materials can also lead to sagging, while algae growth and poor roof installation might mean a wavy or uneven roof surface.

As with many other home maintenance issues you might face over the years, you don’t want to put off fixing a sagging roof, as said. Knowing a bit more information about what causes sagging and how this issue is addressed can help you find the right contractor and ensure your home’s roof is always in good condition. Check out some added details about sagging or wavy roofs and then discuss your home’s roof with a contractor as needed.

Why Is My Roof Sagging?

measuring a sagging roof

The best method for determining why your roof is sagging is to call a roofing contractor near you and schedule an inspection! He or she can get onto the roof itself and also check the home’s attic or upper stories for structural damage, and quickly spot reasons for sagging, buckling, and other issues.

Note a few common reasons for roofs to sag, buckle, or wave so you know what you might be facing by way of needed repairs:

  • Excessive weight can cause a roof to sag, as said. This weight is often the result of added roof layers or heavy snow and ice. Note that roof decking and other materials are only made to hold so much weight; once that limit is exceeded, the roof will begin to buckle or sag.
  • Framing issues can also cause sagging. Over time, a home’s framing will tend to weaken so that the roof might begin to sag along those weak spots.
  • Poor-quality materials and construction can also lead to framing and structural issues over time, which can then risk a sagging roof. For example, missing internal bracing or undersized rafters for the roof’s size both allow a roof to sag in various spots.
  • Thin or poor-quality roof decking or sheathing might also begin to sag, as it cannot hold up the weight of the roof as it should.
  • Water damage along the home’s framing can also weaken rafters and joists or cause cracks along the decking, leading to sagging and unevenness.
  • A weak foundation will also allow a home to settle and then sink along one side or another. As it does, it can pull on a roof’s surface, leading to cracks, buckling, and then sagging.
  • As shingles age, they might dry out and become brittle, pulling up around themselves and buckling. This can create a wavy or uneven appearance along the roof.
  • Moss and algae growing between shingles can push up on those tiles, creating a wavy or uneven surface that can make the roof appear to be sagging in various spots.

Is a Sagging Roof a Problem?

A roof should never sag, as a home’s framing should carry the weight of the roof materials and added weight from snow and ice. A roof should also lie flat and even to allow water to run off its surface; a sagging, wavy, or otherwise uneven roof can absorb standing water and suffer even more severe damage.

contractor working on a sagging roof

While a roof might not actually collapse from excessive weight or weak framing, this can happen in extreme cases and especially the longer you ignore that damage. Roof collapse is also more likely if you continue to put weight on the roof, such as by allowing snow and ice to pile onto the home or by walking across the roof’s surface.

Because damage only gets worse the longer you ignore a sagging roof, it’s best to schedule an inspection at the first sign of unevenness or other issues. Making timely repairs ensures the roof stays in good condition and avoids otherwise unnecessary damage and repair costs.

Foundation Issues & Roof Problems

A homeowner might not associate a weak or damaged foundation with roof problems, but it’s not unusual to spot roof damage once a foundation weakens. A home’s foundation is meant to keep it level and even; once the foundation weakens, the home’s weight isn’t dispersed evenly across its span but will put added pressure on that weak area. This added weight allows the home to sink slightly along that side.

As a home sinks along one side or another, it pulls on surfaces and building materials including the roof. Roof rafters and joists, decking or sheathing, and other materials can then split or crack. Not only does this damage risk letting water or moisture into the home’s interior but it can also mean torn shingles or tiles, damaged flashing, and a sagging or uneven roof surface.

foundation issues lead to roofing problems

A damaged foundation can also risk other damage inside and outside the home, including cracked walls and ceilings, buckled floors or floor tiles pulling away from the subflooring, doors and windows that stick and don’t lock properly, framing damage, and mold growth. To avoid all this costly damage and ensure every surface of the home including its roof are in good repair, address foundation problems at the first sign of damage! Ensure you schedule a roof inspection as well, so you don’t overlook cracks and other damage.

Why Does My New Roof Look Wavy?

A wavy new roof doesn’t always signal poor-quality installation or materials. Note that shingles are somewhat soft and flexible and might bend or flex during the installation process and especially as they heat up under the sun. Once those shingles cool down and settle into place, the roof should lose its wavy appearance.

Roof shingles and tiles are also installed over what is called underlayment, or a felt-like material that provides added insulation and a solid base for the roof’s upper layers. If the roof’s underlayment was damp when installed, it might create a wavy appearance. As with shingles, this underlayment should go flat once it dries out.

checking on a wavy roof

In some cases, poor-quality installation can create a wavy, uneven appearance. Shingles and tiles should be aligned properly and lie flat against the roof and one another. If your roof doesn’t start to lose the wavy appearance a few weeks after installation, you might have another contractor inspect it for poor-quality workmanship.

Fixing a Sagging Roof

A homeowner should never address a sagging roof on their own, in order to ensure quality repairs that last. A qualified roofer will also ensure their own safety when on a ladder or the roof! However, you might note some work involved in fixing a sagging roof, so you better understand how your contractor might address this damage and the roof repair costs you might face.

  • Damaged decking usually needs replacing. A roofer might remove shingles or tiles over the decking and install new plywood, fill in any cracks that have developed and correct other water damage, and then replace the underlayment and shingles or tiles.
  • Gusset plates connect roof rafters and joists. If these are damaged, they will usually need replacing so they can provide full support at those critical connections.
  • Damaged framing will need bracing, or shims pounded underneath the roof materials to keep them in place.
  • Improperly installed shingles or tiles will usually need removal and reinstallation. In many cases, the shingles themselves are salvageable but will need a better alignment or connecting to the roof decking, so that the roof stays flat and even.
  • If algae or moss is growing along shingles and tiles, the roof will need a thorough power washing. A roofing contractor can then replace damaged shingles or tiles or reinstall pieces that have shifted or come loose due to this growth.

Is a Sagging Roof Covered By Insurance?

roof damages covered by insurance hail damage

Homeowners insurance doesn’t cover repairs needed due to age or everyday wear and tear, and typically won’t cover damage caused by a property owner’s neglect. For example, if you allow snow and ice to pile up on the roof during wintertime, an insurance carrier might argue that the roof needs repairs due to neglect and that they don’t need to reimburse you for repair costs.

However, an insurance policy will usually cover damage caused by falling tree branches, fire, storms, and the like. If your home’s roof is sagging due to a branch having fallen on it or because a house fire weakened the rafters and joists, you might then be reimbursed for damages.

Can You Jack Up a Sagging Roof?

A homeowner might add shims along a roof’s rafters and joists to provide support for a sagging roof, but note that this is just a temporary solution! Damaged framing, roof decking, and other materials need replacing so that the roof doesn’t continue to crack and risk collapsing.

stopping a roof from collapse

Note, too, that a sagging roof might mean cracks have formed along its surface; these cracks need patching and repairing, to prevent water damage and mold growth in the home. A cracked roof is also weak and risks sagging or collapsing even with shims and other temporary supports.

Probability for Roof Collapse

It’s often difficult to evaluate a roof’s overall condition from the street, and especially for homeowners with little to no experience in checking a roof’s condition. In some cases, a roof suffering severe structural damage might look somewhat stable and even, while a very wavy roof might only need washing to remove algae and then some minor repairs along its surface.

To ensure you don’t risk a roof collapse, schedule an inspection at the first sign of damage, discoloration, or unevenness. It’s also good to schedule regular inspections every 2 to 3 years, so your roof repair contractor can note developing damage. You can then have the roof repaired as needed, and keep that damage from getting more extensive and costly over time.

Knowing If Your Roof Is Damaged

hiring a professional for a sagging roof

A quick visual inspection might reveal damaged shingles and tiles, torn flashing, or roofing layers pulling away from the decking below. However, a homeowner should never rely on their own inspection to indicate it’s time for roof repairs! Check out a few indicators that you should call a roof inspector near you and have your home’s roof inspected for potential damage:

  • As shingles degrade, they lose granules and pull away from the decking. You might then notice those granules, nails, and other bits and pieces in the home’s gutters or around the lawn near the home.
  • Water stains along interior ceilings can indicate roof leaks and needed repairs.
  • Schedule a roofing inspection if you notice missing shingles or tiles. A few missing pieces can be repaired easily enough, but this can also indicate damaged decking or underlayment and the need for reroofing.
  • Worn shingles and tiles can start to look dull and dingy. If you’ve had the roof washed recently but it still looks rather dull, you might schedule an inspection for needed reroofing.
  • Since a home’s roof is a major part of its overall insulation, spiked utility costs can mean that the roof is suffering leaks, cracks, and other damage. Those cracks let out your heating and cooling while letting in outside heat, cold, and humidity.
  • Roofing materials, like other materials around the home, will simply break down with age. The more exposure to harsh sunlight and extreme weather conditions, the earlier those materials will break down and degrade! If your home’s roof is reaching the end of its expected lifespan, it’s time to schedule an inspection for needed repair or reroofing.

Professional Roofing San Diego is happy to provide you with this information about why a roof is sagging, and hopefully you found it helpful! If you need roof repairs in San Diego or know it’s time for a new roof altogether, give us a call. We offer full-scale inspections and expert repair services, at prices you can afford. To find out more, give us a call today!

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