By: Melissa Maynard De Kerch | Updated 4:06 PM, October 6, 2021

The roof is one of the important components to protect the house from the harsh environment such as strong wind, ice and snow. If you notice that your roof line sags, bends, or slopes, and the arrow is not straight, your roof may need repairs. Several factors that contribute to roof sagging include age, water damage, overweight, design flaws, low-quality or incorrectly sized materials, and even installation errors.

Although some sagging may not pose an immediate threat of collapse, sagging roofs can be a serious problem and need to be repaired in time. Due to the level of difficulty, only experienced roofers should undertake this project.

Time required: 1 to 2 weeks Difficulty: Expert estimate Cost: US$750 to US$2,000

Repairing sagging roofs is an extensive project, so you need to make sure that you have experience with roofs to avoid major problems or the risk of work mistakes. First, an inspection needs to be carried out to determine the cause of the sagging roof and what is causing the sagging roof. This important step can help you assess damage and plan material costs.

If your roof is sagging, it may be because the trusses or rafters that need repair are damaged. The degree of damage will determine the cost of repairs. If the structural beams are damaged, the price will rise sharply; however, if only a small part of the roof needs repairs, the cost may be lower.

First, you need to check whether the roof is sagging. It's a good idea to see the roof from the street. Next, inspect the roof from inside the house by grabbing the flashlight and heading to the attic. This view can give you an idea of ​​the extent of the damage. Pay attention to your roof truss structure, it is the frame that supports the roof. Look for damage including cracks, rot and breakage. In most cases, the sagging roof is due to the truss or rafters needing repair.

Generally speaking, one of the most challenging aspects of repairing a rafter or truss is to put it back in its original position after damage. The best way to achieve this goal is to obtain a steel "L" channel with a minimum size of 1½ inches x 1½ inches and a length of not less than 2 feet. First drill four ⅜ inch holes on the bottom of the steel "L" channel steel, and drill four holes on the side. The holes should be evenly distributed.

The next step is to remove any wood fragments that may have broken off on the trusses or rafters. Broken wood and debris can interfere with the alignment of the rafters or trusses, so removing debris and debris from the wood is a key step in the process.

Tip: The ideal tool for removing wood fragments is a chisel or reciprocating saw, which is suitable for rough cutting or demolition work.

Locate the damaged part of the truss or rafter, and install the "L" slot with ⅜ inch x 2 inch square head bolts. Next put the carriage bolts and washers (usually ⅜ inches x 2½ inches) into the holes on the side of the steel "L" channel.

It is time to measure the gap between the "L" channel steel and the rafters or trusses. It is recommended to choose a square head bolt whose length is ⅜ inches x 1.5 inches to 2 inches longer than the gap between the "L" channel steel and the bottom of the truss or rafter.

Tip: If you have a 1-inch gap, it is recommended to use 2½-inch to 3-inch lag bolts. However, if your opening is slightly larger, about 2 inches, choose a lag bolt that is 3.5 inches to 4 inches long.

Next, add two lag bolts at the bottom of the "L" groove and start tightening them until they are flush with the steel. It is recommended to tighten the bolt furthest away from the separation until the head of the other bolt is 1/4 inch from the steel. Then you can start tightening the front bolt until it is 1/4 inch from the steel, and then continue the process until the rafters or trusses fit the steel tightly.

If additional bolts are needed, two holes can be drilled in line with the holes on the side of the "L" shaped channel. You can then insert the carriage bolts and make sure that the nuts and washers are snug against the steel and tightened thoroughly until everything is firmly in place.

Tip: Once the rafters or trusses are fixed in place, it is best to add additional supports, such as additional 2x4, to keep the roof in its best condition.

If you have any questions about your own ability to repair sagging roofs, or if you encounter difficulties in DIY this task, you may need to hire a roof professional. Unless you have extensive experience in repairing sagging roofs, it may be difficult to complete the task in a satisfactory and safe manner. Experts can complete tasks effectively while helping you avoid long-term costs and headaches. Experienced roofers know exactly the type of materials and tools needed to complete the process correctly.

There are many aspects to consider when considering whether to repair a sagging roof with your own hands. The first step must be taken to understand why the roof sags, slopes, or bends due to weight, decay, or normal wear and tear. If you think this is not a project that can be easily undertaken, a professional roofer can ensure that the right steps are taken, taking into account expertise and quality materials. After the roof is repaired, it is best to conduct a routine inspection of the roof every year.

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