What Are The Common Causes of a Sagging Roof?


A sagging roof is among the most common shortcomings of a roofing system. Unfortunately, you have to stop the problem as soon as possible or find yourself footing roof replacement costs. Sagging mainly occurs in the wet months of fall and winter, and even new roofs are not spared. Homeowners, therefore, need to conduct a regular roof inspection.

If you have been brooding over the same question, here are some causes.

Common Causes of a Sagging Roof


Old age is the most common cause of a sagging roof. Given proper care and maintenance, most roofs can last well over ten years.  But constant exposure to rough all type weather finally takes its toll. The materials begin to rust, and other roofing constructions weaken, causing the roof to sag, which calls for a roof replacement every decade.

Water Damage

One of the roof’s primary purposes is protecting the house interior from weather elements such as water and snow. Water runs down the top when it rains or due to melting snow during winter.

And water has an ingenious way of detecting defects in your roofing system. It then uses these imperfections probably left during installation and seeps into the inner sections. Excessive moisture encourages the growth of molds and mildew causing respiratory allergies. It also causes the rotting in the wooden parts and rust in the supporting structures, causing them to weaken and sag under the roof’s weight.

Water impenetrability indicates the strength of a roof, and it is advisable to conduct a regular roof inspection or have a professional do it for you.

Roof May Sag Because of Heavy Snow

Roofs may sag because of bearing excessive weight. There are two ways to explain it. The first one is poor installation. The contractor who initially installed the roofing was not careful to build the roof to drain all the water. Some roof parts may not be level enough to drain water fast, causing the roof to sag under the weight.

The second reason is piling snow during winter. Minnesota and Michigan top the list with the worst snowfalls and extended periods of ice. Most of the roofs in these states are constructed strong enough to withstand winter precipitation, but prolonged exposure can get a chink in the armor.

Excess ice may cause the roof to sag if left there for too long. It is advisable to remove some of the extra ice though you should do this with caution. You may accidentally break brittle exposed shingles in the process. Better have a professional remove it if it is a must.

Insufficient Roof Rafters and Roof Joints

Most residential roofs are triangular. Rafters rest on the roof joint or the ceiling and slant diagonally, ending in a ridgeline.

This construction design distributes your roof’s weight from the ridgeline, along the rafters to the roof joints, and finally, channel down the walls of your home.

Improper construction or architectural flows mean that the roof cannot bear all the weight from the water, shingles, snow, other roof construction materials, and ice bringing structural instability and sagging over time.

Use of Low-Grade Roofing Materials

Some uncouth contractors use inferior materials when installing or replacing a roof to woo potential clients. Once the deal goes through, they use low-grade materials such as untreated lumber to reduce the costs. The materials will do an excellent job for a few years but deteriorate fast compared to genuine materials, and thus your roof will sag sooner.

Roof Inspection Tips

  1. The easiest way is to walk around the house in a position where you can see the roof from the ground. Look out for any noticeable sagging, damage, or aging signs.
  2. Look out for areas with water damage indicated by algae and the growth of weeds. Algae indicate a breach in the roof, causing leakage.
  3. Inspect the shingles. Look out for distorted or curled shingles. Attics sometimes produce hot air, which damages the shingles, causing sagging of the roof.
  4. Inspect your roof after a snowfall or snow meltdown. Your roof may have curved inward due to the weight.
  5. Check out the attic for signs of water leakage.
  6. Lastly, have a professional inspect your roof regularly.

Bottom Line

Sagging is familiar with roofing and is caused by structural defects or the weight of piled-up snow. Other causes are using low-grade roofing materials and insufficient roof joints and rafters.

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