How to fix a sagging flat shed roof

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If your roof appears to be dipping or sagging, this could highlight a problem with its structural integrity. However, in some cases, it could also be minor and require a simple fix. But when it comes to any potential problems with the roof, it’s best to have a professional roofer look at it to ensure it’s safe. It can be dangerous if you’re not experienced, untrained, or comfortable with heights. If you’re wondering how to fix a sagging, flat roof, here’s how the process goes.

Determine the Cause

First and foremost, identifying the source of the problem that’s causing sunken areas on the roof is important. In some cases, it could be caused by moisture damage, weakened sheathing, rotting joints or sagging insulation. Flat roofs are typically more susceptible to water damage due to their design. If water pools on the roof with nowhere to go, it can eventually weaken the structure and lead to rot and potential low dips. A complete teardown and roof replacement would be ideal, depending on how severe the water damage is. However, lets try and mitigate a teardown situation by learning how to fix a sagging flat roof through a variety of different methods.

Here are the most common culprits that cause roofs to sag:

Water damage
Weakened Sheathing
Insulation that sags
Age of the roof
The excess weight caused by snow and ice
Improper design and construction
Poor quality roofing materials
Sunk or shifted foundation

Materials that Can Raise Sunken Areas

When sunken areas develop, and it’s not due to structural issues, they can be raised using a range of materials, depending on your roof-specific design. Here are the materials that can be used:

Sheet Fillers

When learning to fix a sagging flat roof, it’s vital to know about the materials the home is made from, and their age. Many older homes with older roofs were constructed using pieces of asphalt felt paper, which were combined with tar to create flat roof designs back in the day. With felt roofs, sunken areas can be filled using this same method, requiring a few extra layers of felt and tar to prop up those low dips. There are a few different options today, but it’s best to stick with something that’s on par with your existing roof material. Asphalt-infused, tar-saturated or polyester felt are the main options to choose from today. Whichever is used, always adhere to the manufacturer’s instructions carefully. Then place gravel, cap sheet, or asphalt over the top of the felt once it’s applied. For more modern, flat roofs that use rubber, you can prop up sagging areas by using the same rubber material and then just cut it based on where it needs to be placed. It’ll need to be bonded with bitumen after applying the rubber. This is a great example of how to fix a sagging flat roof.

Liquid Patching Materials

Alternatively, you could use a liquid filler such as roof patch putty to fix a sagging flat roof. A general epoxy concrete filler, followed by mastic sealant, can also work. For gravel roofs, make sure to brush away the gravel so you can apply the material directly on the roof.

Asphalt Fills

Asphalt fills can be applied, along with a liquid asphalt roof coating. This is suitable for roofs made from asphalt, metal or concrete. This will provide a waterproof coating to protect the structure from future moisture damage. An excellent approach to fixing a sagging flat roof.

The Bottom Line

The reality is there can be a range of reasons why the roof is warped. And any roof structure can be susceptible to damage since it’s constantly exposed to the weather elements, especially older, flat roofs, which are usually at a higher risk. If a noticeable sag develops on your roof, don’t risk injuring yourself. Instead, hire a licensed roofer who knows how to identify the source of the problem and perform repairs that will ensure it’s safe and protected. Please let us know if you need any more details about how to fix a sagging flat roof.

Contact our team at Roofmaster for all of your roofing needs in Ottawa!

A sagging roof is not only an eyesore, but it could also be dangerous for you and your family. Since roofs are designed to be straight, a curved or sagging roof means that its structural integrity is insufficient, and it may be a warning sign that your roof is headed for collapse.

But don’t worry! Before you start panicking, remember that you can have your sagging roof fixed without breaking the bank, whether you want to do it yourself or hire a professional to do it for you. If you’re not experienced in roofing, we wouldn’t recommend doing this project yourself without the proper preparation and assistance. That’s where our team comes in at Legacy Service. We install and replace roofs for residential and commercial customers throughout Pennsylvania, New Jersey, and Delaware. You can get in touch with us by giving us a call at 215-798-9790.

But if you are experienced in roofing and would like to take care of it yourself, let this article be your guide. We cover the causes of a sagging roof, determining the extent of the damage, and how you can fix it. Here’s how to fix a sagging roof (as well as anything else you might need to know):

What Causes a Sagging Roof?

Even if you’ve done everything you can over the years to ensure your roof remains in perfect condition, age can creep up on it and cause it to droop. In other cases, maybe your roof isn’t even that old, but it’s been hit by tons of big storms over the past year. Understanding why your roof is sagging is essential to being able to repair it. Here are some of the main causes of your roof sagging problems:

There’s too much weight on it – When was the last time you had the structural integrity of your roof checked? Problems with the structure may cause your roof to droop. Since roofs are designed to handle a maximum weight load, anything more than that can create sagging. When you have undersized rafters or inadequate storm bracing, snow or ice resting on your roof may cause it to sag.

Water damage – Although roofs are designed for optimal water drainage, flooding or heavy rainstorms over time can cause damage to the structure of the roof. If you have a flawed gutter system or damaged shingles that impede the flow of water, moisture can get into the support structure and cause it to deteriorate.

Other causes – Some other causes of a sagging roof include age, lower-quality materials, and a damaged or sinking foundation. If you need help determining the cause of your sagging roof, please feel free to contact our Legacy Service team to schedule a consultation.

Determine the Extent of the Damage

Once you figure out what’s causing the damage, it’s time to determine the extent. There are ways you can do this yourself, which we’re going to touch upon, but we usually recommend hiring a professional. Remember that you can always contact us at Legacy Service if you need help with your home’s exterior. However, here’s what you can do to try and figure out the damage yourself:

Go outside of the house and determine where the sag on the roof would be in your attic.
Using a flashlight, inspect the rafters and decking in your attic, especially in the areas where your roof is sagging. Then, inspect the metal or plywood gusset plates.
Look for any kind of damage (including rot, cracks, breaks, and more).

Fortunately, there are different ways to jack up a sagging roof. We’re going to cover them in the sections below.

Roofing Tools and Equipment List

So, you’ve already determined what the problem is and its extent. Now, it’s time to gather the necessary materials to fix your sagging roof. We’ve compiled a list of the items you’ll most likely need for the job. They include:

Flashlight
Bolts and washers
Chisel
Drill
Measuring tape
Nail gun and nails
Steel “L” channel
Plywood gusset
Plywood
Lumbar strapping
Styrofoam

Once you have everything you need, you’ll be able to get started on the project itself.

How to Fix Sagging Roof Trusses or Rafters

In many cases, you’ll need to fix sagging trusses or rafters to repair your roof. If that’s what you’re dealing with regarding your home, take these steps to ensure your rafter or truss gets fixed properly:

You’ll need a steel “L” channel to get your rafter or truss back into shape.
Drill four holes in each side of the L.
Remove any pieces of wood (broken scraps) that could get in your way using a chisel.
Starting at the end that’s the most difficult to access, mount the steel “L” channel onto the rafter or truss.
Fasten the end of the channel to the rafter or truss, using washers and bolts in the holes you drilled.
Move the broken piece into position when its end is in place.
Measure the gap that’s between the steel “L” channel and the rafter/truss. Then, select bolts that are 1.5 – 2 longer than the gap.
Insert the two bottom bolts and tighten them. Then, tighten the bolt that’s farthest from the break until the other bolt head is about 1/4″ from the channel.
Tighten the back bolt until it’s close against the steel “L” channel. After that, tighten the front bolt until the back one is about 1/4″ from the channel.
Keep tightening the front and back bolts until the rafter or truss is securely against the channel.
Insert bolts into the rest of the holes and tighten them.
Remember that you might want to add extra support to the area.

Fixing Roof Decking

If the roof decking is damaged, we recommend hiring a professional to get it fixed. However, you can create a temporary solution by following the steps below:

After measuring the damaged area between your roof trusses or rafters, cut a piece of 1/2″ plywood that will cover the area.
Glue a piece of 1″ rigid styrofoam to the plywood. (Driving nails into it might make it worse.)
Place the plywood and styrofoam (side up) against the damaged roof decking.
Push up on the plywood until the foam is touching the roof decking’s underside.
Keep the plywood in place using a piece of lumbar strapping until you can get a roofing expert to repair it.

Fixing a Gusset Plate

A gusset plate connects beams and girders to columns, and it can be fastened using bolts, rivets, welding, or a combination of the three. You can fix a gusset plate using these steps:

Remove the gusset plate that has pulled away from the wood.
It’s practically impossible to reinstall it, so replace it with a 1/2″ plywood gusset.
Use a nail gun to attach the gusset on both sides of the wood pieces.

When done properly, this should replace the original gusset plate’s strength.

What If I Can’t Repair My Own Roof?

If you can’t repair your own roof, don’t despair. Hiring a professional can actually be more time-efficient and cost-effective in the long run. At Legacy Service, we’re always willing and able to help out a customer in need. We’ll send out a consultant who will talk to you about a roof replacement.

Reasons you should hire a professional when it comes to repairing a bowing roof include:

It’s cost-effective – It may seem less expensive to just complete the project on your own, but unless you’re experienced in fixing sagging roofs, it might cost more in the long run. You’ll have to purchase your own tools and materials, and if everything isn’t done correctly, you might be paying for more damage down the line.
Quality materials – Professional roofers can determine the materials that would be best-suited for the type of job as well as the type of building.
You don’t have to do it yourself! Wouldn’t you rather relax on your day off from work rather than fix your roof? Whether you’d rather take it easy or work on something else that needs your attention, one thing you can check off your list is fixing your roof.

FAQ

Is a sagging roof dangerous?

A sagging roof is not only unsightly, but it can also be dangerous for your home. Roofs are designed to be straight, so sagging means that its structural integrity is no longer sufficient, and it may result in the collapse of your roof. It’s best to contact a roofing professional as soon as possible so that they can take care of it.

Can you fix a sagging roof?

A sagging roof is often due to broken trusses or rafters, and the extent of the damage will determine whether the roof can be repaired or will need to be fully replaced. Sometimes, it will just need to be repaired and reinforced, and other times, it will require a full replacement. Get in touch with an experienced roofing professional to see what they recommend for your home.

How much does it cost to fix a sagging roof?

The cost to fix a sagging roof will depend on a variety of factors, most notably—the type and extent of the damage. For example, the price may rise significantly if the structural beams have been damaged. On average, its repair can cost anywhere between $750 and $2,000. A full replacement will be higher, but it may be worth it in the long run.

What could cause a roof to sag?

Sagging roofs are typically caused by a buildup of water or snow that weighs down the shingles and boards underneath. An excessive load of weight can weaken your roof’s structure, especially if it happens repeatedly or over a certain length of time. Too many layers of shingles can also cause sagging especially if your roof is getting up there in age or has been improperly designed or constructed.

Is a sagging roof covered by insurance?

Whether your insurance will cover the repair or replacement of your roof will depend on what has caused it to sag. Insurance companies will typically pay for damage caused by sudden accidents, including storms and falling objects. However, if the roof is getting old or hasn’t been properly maintained, the insurance company will most likely not cover the costs of the damages.

How do you strengthen a sagging roof?

Understanding why your roof is sagging in the first place is the key to repairing and strengthening it. In many cases, you’ll either need to repair trusses/rafters, a gusset plate, or the roof decking. In other cases, the roof may require a full replacement. We recommend hiring a professional roofer to help determine what your home needs and take care of the job for you. You can also check out our “How To” sections above.

How do I keep my roof from sagging?

Sagging roofs are typically caused by insufficient internal bracing or undersized rafters/trusses combined with excessive loads of weight. Snow, ice, wind, and even too many layers of shingles can add stress to your roof and cause sagging. The best way to prevent it from sagging is to make sure it’s properly installed by hiring a trustworthy company that offers warranties.

Contact Us to Learn More!

If your roof is sagging between trusses, there are multiple ways you can go about repairing it. The one thing you don’t want to do, though, is leave it alone. We believe that your roof should protect your home and family, and that means taking care of it throughout its entire lifespan. We’ll also provide service (including installation and replacement) for siding, windows, doors, and gutters. No matter what you need for your home exterior, our team will be able to help you. Learn more about roofing replacement by giving us a call at 215-798-9790 or filling out a contact form here.