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How to Fix a Sagging Roof?


If you have just stepped outside your house and realized that your roof is no longer straight, this could signal a problem. Fixing a sagging roof as soon as you spot it is very important, otherwise, you could find that the problem will only worsen over time.

In the end, you may need to have the entire roof replaced, which could be extremely costly, not to mention a lot of hassle. If you having a sagging roof, you will not be able to even begin to think about repairing it before you take some time to investigate why the problem has occurred in the first place.

There can be several reasons why your roof is no longer arrow straight, although some reasons are more common than others.

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. Take a look at our range of roof repairs Melbourne.

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. 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):

How to Fix a Sagging Roof Line

Step 1 – Check the Beams

Before you start, check the beams to make sure what kind of state they are in. If they are not infested with things like termites, you are in for a fairly easy task. When doing garage roof repairs, you will usually have open beams enabling you to have easy access.

You will need two ladders and some scaffolding planks. This enables you to walk along the beam’s line on the scaffolding and work on beams without continually climbing a ladder.

Step 2 – Buy the Right Lengths of Timber

Measure the beams’ lengths that you require for the bolstering and buy the right lengths in 2×6-inch lumber.

You will require the same numbers of lengths as there are trusses on the roof. Make double sure of your measurements before ordering the wood for your garage roof.

Step 3 – Start at The Eaves

Lay your wood out under each beam, and lifting up the eaves side, put a 6-inch nail underneath the beam to temporarily hold it in position. If you have a friendly helper, it’s a lot easier.

Do the same to the other end of the beam, and once in place, you can screw it into the old beam with 4-inch brass screws.

Use brass, so they do not rust. Make sure that as you are working, you are pushing the roof up. If necessary, use something to force the roof up while you work the beams into place and fasten them.

Gradually work along all the beams, pushing the roof up as you go. Any sagging will gradually be lifted, and by the time you have finished the garage roof repair, your roof should but upright again.

Step 4 – Strengthen the Beams

While you are doing the job, you might as well do it properly, so the beams do not sag again.

To do this, use a few lengths of timber the garage’s length and move them into position under all the beams and secure to each beam. This will prevent the beams from sagging again. 

In this article, we will take a look at the main reasons you could be experiencing this issue with your roof.

We will then look at some of the best ways of rectifying the problem so that you can restore your roof to its original condition before further damage is caused.

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.

How To Fix A Sagging Roof 1

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.

Rooflines should be arrow straight. If you can see a dip, curve or swag on the peak when standing in the street, your roof has a problem. It might be something basic you can handle yourself, but it’s likely to be more complicated and require intervention by a professional.

It’s Above Your Head

Climb into the attic and familiarize yourself with your roof’s structural anatomy. Framing terminology for a roofline can be reduced to a simple triangle. When crouched or standing in the attic, the horizontal boards below your feet are the ceiling or roof joists.

The sloped boards above your head are the rafters. The rafters attach to another beam, the ridgeline at the top.

The shape of the three panels forms the familiar triangle of the roof. This shape is capable of supporting a large amount of weight. It’s typically enough to keep the accumulated weight of the roof, including roof sheathing and shingles and other external forces such as snow and ice.

The rafters transfer the weight to the joists, and the joists transfer the weight to the exterior walls. When everything works together properly, the roofline should be straight.

Lapping It Up

Sagging roof lines can originate with the horizontal ceiling rafters: When the roof framing is assembled, two ceiling rafters are often joined together to create a longer span. They are typically lapped and toe-nailed together in the centre to achieve the needed length.

As the accumulated weight of the roof and/or heavy snow exerts pressure on the roof, it pushes the rafters outward; in turn, the rafters push on the exterior walls on both sides. If the joints are not lapped and instead butted together, they can pull apart.

If the weight and pressure are sufficient, even properly lapped joints can loosen. When the joints pull apart, it causes the ridgeline to drop or sag as the exterior walls tilt slightly outward.

Even if the sagging is not noticeable from the exterior, there may still be signs of sagging inside your home. Look for cracks in the drywall on the ceiling.

Beam Me Up

Another type of roof framing includes the use of a central beam.

The system is similar to lapped ceiling joists, but instead of lapping two joists together, two individual beams join onto a larger beam running perpendicular to the joists.

The joists are attached on both sides of the beam via metal hangers.

As the accumulated weight of the roof creates pressure, the hangers pull loose from the beam and the exterior walls to move outward, resulting in the sagging roofline at the top.

It’s a Tie

Depending on the design of the framing, another component is sometimes added to the triangle shape of two sloping rafters.

The rafter tie or collar is a horizontal piece that connects the two rafters on either side. It’s typically nailed to both rafters about halfway up.

The rafter tie is designed to prevent rafters from moving away from each other. If the placement of the rafter ties is not correct, the idea is to form a perfect triangle at the top with the tie.

It can be compromised and becomes insufficient to stop rafters from spreading. Other problems occur when rafter ties are insufficiently nailed to the rafters. The nails pull loose, and the rafters spread apart.

Struts Are Us

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Some roof framing designs include the use of a strut or beam that runs perpendicular across the bottom of the rafters inside the attic. The shaft is attached to both exterior walls and to the bottom of each sloping rafter to give the roof strength.

If the beam is not properly nailed, it can also pull loose, and this contributes to roof sagging. Problems may also occur if the shaft or strut is the wrong size or defective with cracks or splits. Top Glaze has the best range of help if you’re looking for Melbourne roof repairs.

Water Damage to a Weak Roof Surface

Rain and snow can quickly damage a roof that isn’t optimally designed and well maintained. Shingles and other roofing material must be in good condition to allow water to run off. Metal flashing should be installed on the valleys and junctions of your roof to direct water away. Damage to any part of the roof’s surface gives water a way to get in and weaken the underlying structure.

A damaged or poorly designed gutter system can also lead to water issues. If water runoff isn’t safely directed away via the gutters, it can pool on the roof and eventually seep in.

Poor ventilation in the attic exacerbates water problems. Without enough airflow in the attic, moisture builds upon the underside of the roof, making it easier for water to permeate the roof’s surface. It also allows summer heat to build up, speeding up the deterioration of your shingles.

If water damage is causing your roof to sag, your first step will be to correct the problems that allowed the damage to occur. That might mean replacing the shingles and flashing, repairing your gutters, and improving the attic ventilation.

To correct the sagging itself, angled braces can be installed to shore up the rafters. Another approach is to give more support to the walls by installing chains attached to the wall plates and linked in the middle with a turnbuckle. Depending on the degree of sagging, your contractor might need to use jack posts to raise the roof before installing any reinforcement.

Sheathed and Rotten

In some cases, roof sagging problems are not caused by framing issues. Rotten or saturated sheathing can also cause roof lines to sag.

This is the easiest problem to repair. If the framing is sound and issues are not found elsewhere, but the roof still sags, the problem might have originated because of poor installation of the plywood sheathing or shingles.

When water penetrates through the shingles it causes the plywood to warp, weaken or rot, causing the roof to appear as if it’s sagging between rafters.

Professionals Needed

Problems with and repairs to a sagging roof should be evaluated by professionals. It might be a simple fix that can be done by jacking up loose rafters, adding struts or, more economically, simply by replacing sheathing and shingles.

The extent of repair can be somewhat difficult to determine, but if you see obvious broken rafters, joists or beams, consult with a professional to ensure that your roof is repaired properly. Looking for roof repairs? Look no further! Top Glaze has you covered.

What Do I Need to Be Aware of When I Repair My Roof?

There are a few things that you need to bear in mind when you are preparing to repair your sagging roof.

1. Safety – your safety and the safety of those around you are absolutely paramount when you are carrying out any form of repair on your home, but especially when you are working on your roof as it is very high up and one false move could lead to you falling. Also, if you make a mistake when repairing your roof, you do run the risk of making your roof structurally unstable and unsound, which could eventually result in your roof giving way and collapsing – not an ideal scenario for anyone.

2. Measurements – if you are using new beams, it is always important to measure them properly to make sure that they are the right size to offer appropriate support. If you use beams that are too short, the level of support will not be adequate to take the weight of your roof, especially if snow or ice lies on it during the winter season, and you could end up causing further damage.

3. Access – before you try to carry out any work on your roof, you need to be sure that you will be able to gain access to all of the areas that you need to reach in order to carry out the repairs safely and easily. Remember that you will also need room to move and use tools in the space to need adequate room to achieve this. If you feel that there is not sufficient room for you to do the job properly, you should seek professional help.

4. Identify the problem – you should never assume that a particular issue is a problem that your roof is experiencing. Assuming that you have rotten sheathing when you have truss damage will waste your time and money and delay the essential repair that needs to be carried out. It could be much longer before you finally determine what the real problem is, and by then, the problem could have got out of hand and may need a much more extensive and expensive repair. By simply carrying out a few simple checks in your attic, you can pinpoint the source of the problem so that you can get the right solution the first time. If you are unsure what the problem is even after checking, it is always important to see professional guidance so that you can make sure that the problem is properly identified so that it can be fixed.


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