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Plywood Roof Decking being installed before shingles on a new roof

The roof to your family home is composed of much more than just the outer shingles. Instead, it combines different components and materials to protect your home from the elements.

One significant component of your roof is the roof decking or roof sheathing. It is the basis for the roof system. That’s why before considering roof repair or replacement, you should understand the importance of your roof sheathing.

As a homeowner, knowing what exactly makes up your roof is essential in helping you understand why roofing repair can cost so much.

This article discusses everything you need to know about roof decking and its role in the roofing structure. Read on for more information:

What Is Roof Decking?

Roof decking is the system of wooden boards making up the framing of a roof. It is on the roof decking that a contractor installs the shingles. Therefore, roof sheathing is the foundation of the roof.

During a complete roof replacement, it is usually necessary to strip the roof to the decking and rebuild it afresh if it is in good condition.

However, when the damage on the roof deck is extreme, your entire roofing system is compromised. Consequently, it becomes necessary to replace the sheathing.

Types of Roof Decking Material

One of the best ways to know about roof decking is by studying its materials. There is three commonly used roof decking material, including wood, concrete, and steel.


Wood is one of the most common materials used for roof sheathing. Wooden decking may come in the form of sheet decking or plank decking:

  • Plywood: Plywood sheets are factory manufactured with layers of wood pressed together. Plywood usually appears in 3/8-inch, ½-inch, 5/8-inch, and ¾-inch sheets.
  • Oriented Strand Board (OSB): Oriented strand board (OSB) is composed of wood chips or strips that have been compressed together to create a flat 7/16-inch sheet. This roofing material is usually thinner than some plywood sheets.
  • Plank Decking: Before people began manufacturing plywood, the primary type of roof decking was plank decking. The roofing material is usually composed of long, rectangular wood boards that could be either 1×6 or 1×8 in size. Quite a few roofs still use wood boards as a roofing material.


Concrete decking is usually composed of solid concrete, which may come in any of the following varieties:

  • Structural Concrete: This type of concrete material usually has an average weight. It is used during cast-in-place construction on the whole part. The roofing material can handle heavy loads and has an insulated top side.
  • Structural Concrete Composite: This is a steel panel decking system with average structural weight or lightweight concrete.
  • Lightweight Insulating: This low-density, lightweight, non-structural concrete is placed directly on top of a corrugated steel decking.


Steel roof decking may come in the form of a lightweight sheet of metal decking. Compared to the wooden roof sheathing, it is usually durable and capable of resisting hail, storms, and other forms of extreme weather. Besides, steel roof sheathing reflects heat away during the summer, resulting in lower energy costs.

What Causes Roof Decking to Rot?

The primary cause of roof decking is water leaking through the roof. When leaks happen, the result is water pooling on the deck. No matter how well-treated it is, any wood rots when exposed to moisture.

The accumulation of moisture on the decking encourages the growth of bacteria and mold, which produce acidic chemicals that leads to decomposition in the roof decking.

With time, the rot is likely to worsen. The rotten wood accumulates all over the place, causing chemical and weight stress, compromising your roofing system, making the entire structure collapse.

Signs of Roof Decking Rot

Roof decking rot happens to all types of roofing materials, whether steel or other types of shingles. When there is a storm, your shingles get damaged to the extent that they can no longer resist water.

If you fail to identify the damaged areas and have them repaired, water starts to sip into your roof, causing damage to the decking. There are several signs of roof deck rot. These signs usually appear when your roof is almost entering critical disrepair. They include the following:

  • Leaks: A leak is often the clearest sign that your roof decking is damaged. Under normal circumstances, the water may pass through the shingles but not the roof decking.
  • Ceiling Spots: Leaking water may reach your ceiling and cause water spots in different areas.
  • Water Damage: Another sign that you have rotting sheathing is the appearance of signs of water damage. This may include cracked paint, stained interior walls, or peeling wallpaper.
  • Sagging Roofline or Ceiling: The presence of significant problems in the decking and the rest of the roofing structure becomes evident through a sagging roofline or ceiling. The water-logged roof sheathing could warp and lead to a wavy or bowed roofline and ceiling.

Should You Repair or Replace Damaged Roof Decking?

Once you are sure that your roof decking is rotting, you have to decide whether to have it repaired or replaced. However, it is hard to know the extent of the damage. That’s why you can ask a roofing contractor to examine the roof and advise you.

If the roof deck is extensively rotten, you have no option but to call in a roof replacement specialist. That isn’t something that you can wait too long before executing.

If you allow the rot to become widespread, it compromises your roofing system, making it eventually collapse. That would mean doing more extensive roof replacement. As you wait to do that, you have to grapple with mold and mildew.

Of course, roof replacement costs more than repair. However, it is the best option since it makes it possible for you to restore your roof in its entirety.

Trying to repair damaged decking is near impossible. That’s because heating is usually less modular than roofing materials such as shingles. If the rot in the roof decking is severe, your roof is too old to restore through simple repairs.


If your roofing system is extensively damaged, you can have a new roof installed right by Hopkins Custom Roofing. Before installation, we will advise you about everything you need to know about getting a new roof. Call us today for a comprehensive assessment of your home and the steps needed to replacing your roof’s deck and shingles.

Call or Text (903) 387-2344 to Schedule Your Inspection