Request a Free Long Roofing Quote ▾

What Causes a Sagging Roof?

Published on Tuesday December 1, 2020
Sagging roof

A brand new roof should be completely level, with flat, straight surfaces that allow debris and water to run off with ease. The roof shouldn’t sag, bend, or catch any debris on its surface. Unfortunately, roofs can’t maintain this level of pristine quality for long. As your roof ages, there are a few factors that can contribute to a sagging roof.

So, what causes a roof to sag?

We’re going to answer that question, as well as a few others — like how much roof sag is acceptable and how to repair a sagging roof — so that you can remain informed as a homeowner and stay in control of your home maintenance projects. Always keep in mind that the best course of action for your specific roof repair or replacement may be unique. It’s always best to consult a professional to identify the exact issue at hand and learn the best steps to correct that issue as quickly as possible. Reach out to Long Roofing with any questions. 

How Much Roof Sag is Acceptable?

We all want a perfectly smooth roof, but is a little bit of sag a problem? You’ve maybe even searched for different ways to jack up a sagging roof online in the hopes of prolonging the issue. Before you take the route of ignoring the issue, remember that usually leads to pricier repairs down the road.

A small amount of roof sag isn’t necessarily a cause for alarm — meaning, you’re likely not on the verge of an emergency like a roof collapse. However, you should never ignore a structural issue. When you neglect to fix a sagging roof quickly, you can put the rest of your home’s structure at risk of worsening — which will lead to more expensive roof repairs.

So, how much roof sag is acceptable? None. You may not be facing an emergency and the sag may be repairable by adding some simple supports, but never ignore the issue. Preserve your roof and save yourself on maintenance costs by getting a sagging roof repaired as quickly as possible.

What Causes a Roof to Sag? 4 Possible Causes

1. Water Damage

Your roof is continually exposed to wind, rain, and snow. Over time, these elements can cause a great deal of water damage to your roof, especially if your roof is poorly maintained or was improperly installed. Since roofs deal with a lot of runoff throughout the year, you must pay attention to how rain and snowmelt drain off your roof. Imperfections in your roof surface, poorly designed gutters, and damaged shingles can all lead to water damage and eventually to a sagging roof. 

Taking good care of your roof can help prevent this problem, but keep in mind that any type of damage to the surface of your roof opens the way for water to get in and weaken the overall structure of your roof. It only takes a small amount of time for trapped moisture to create an environment for mold and mildew growth, easily developing into a sagging roof and even a roof collapse. If this is the case, consult a professional for a roofing inspection and a sagging roof repair.

2. Excess Weight

If you live in an area that gets snow or ice in the colder months, keep in mind that this can add a lot of weight to your roof. While your roof should be designed to withstand a certain amount of weight, too much weight can lead to a sagging roof, a roof collapse, and other serious structural damage to your home.

If you’re noticing your roof is sagging under snow, or if you’re expecting a larger amount of snow than usual, you should find a way to safely remove as much excess snow as you can from your roof to help reduce the load. Be careful with snow rakes so as not to break any frozen shingles, and always know you can hire a licensed roofing contractor if you need help with snow or ice removal.

3. Bad Materials or Poor Installation

If your roof has been constructed using bad, warped materials or by an unskilled roofer, it’s possible to face issues of a sagging roof much sooner than expected. If the roof joints or rafters are poorly installed and constructed, your roof can end up sagging later on in its life due to the weight the roof itself pushes down.

4. Age

Even if your roof was installed by the most skilled of roofers using the best materials on the market, it will not last forever. Even the highest quality of materials and installation jobs will decay in time. Roofs can last between 15 and 70 years depending on the materials used, the design of the roof, and the surrounding climate, so if you look at your roof just to notice, “My roof is sagging,” then check how old your roof is. If it’s over 30 years old, getting a roof replacement rather than a sagging roof repair may be the most efficient way to resolve the issue.

How to Repair a Sagging Roof

You first need to identify the extent of the damage so you know if a repair or replacement is more appropriate. While there are different ways to jack up a sagging roof, you want to be sure the job is done right to keep you, your family, and your home safe. It’s always recommended that you consult a professional to handle the inspection process for your sagging roof so you don’t hurt yourself, damage your roof more, or misdiagnose a serious roofing issue. 

Here are the steps to better identify the extent of the damage to your roof:

  • Conduct an external examination of the roof and determine from where inside your attic you’ll be able to best view the sag.
  • Go up into the attic with a flashlight to inspect the rafters nearest where the roof is sagging. Also be sure to inspect any of the metal or plywood gusset plates.
  • Check for signs of damage, including rot or mold, cracking, breaking, etc.

Document any damages to help determine the extent of the damage. Some problems behind a sagging roof can be resolved by jacking up loose rafters, adding struts and supports, and replacing shingles, but some problems will require help from a professional roofer. Don’t attempt to fix your sagging roof yourself if you aren’t a skilled professional. Call an experienced expert to get a proper inspection and hear their repair costs.

Replace Your Sagging Roof Today

If you’re looking for high-quality roof replacement, the experts at Long Roofing can get the job done. Find your closest Long Roofing location or request a quote online today.

Interested in Long Home Products?
See our special offers now.


*Excludes labor. Subject to credit approval.

**Excludes labor. Subject to credit approval.

One-day installs contingent upon municipal rules and regulations.

By submitting a form, I authorize Long Home Products to contact me with information abouts its products and services via mail, email, phone and/or text at the contact information provided, even if I am on the national do not call list. Long Home Products may use automated telephone technology to initiate calls to its customers. Calls and in person estimates may be recorded for quality and training purposes.