Discovering rotted wood under shingles can be a stressful situation for any homeowner. Left unaddressed, it can lead to further structural damage and costly repairs. Fortunately, with the right tools, materials, and techniques, repairing rotted wood under shingles is a manageable task. This guide will walk you through the necessary steps of how to repair rotted wood under shingles from future deterioration.

What Causes Wood Rot under Shingles?

Wood rot under shingles is typically caused by prolonged exposure to moisture, creating the perfect breeding ground for fungi. Common sources of moisture include roof leaks, poor ventilation, and clogged gutters that allow water to pool. Once water penetrates the shingles and reaches the wooden structure below, it can remain trapped, unable to dry out effectively. Over time, this persistent dampness leads to decay and weakens the wood.

Additionally, inadequate or aging flashing around chimneys, skylights, or vents can contribute to water infiltration, increasing the risk of rot. Understanding these causes is essential to preventing future damage and maintaining the structural integrity of your roof.

Signs of Rotted Wood under Shingles

Detecting rotted wood under shingles early can help mitigate further damage to your roof and home. One of the most obvious signs is a sagging or uneven roofline, which often indicates compromised wood beneath the shingles.

Other signs include soft spots that can be felt when walking on the roof, as well as visible cracks or breakage in the shingles themselves. Inside the home, water stains or discoloration on ceilings and walls may point to leaking and potential wood rot.

Additionally, the presence of mold or a musty odor in the attic can signal trapped moisture degrading the underlying wood. Regular inspections and prompt attention to these warning signs can help address issues before they escalate.

Tools and Materials You’ll Need

To address roofing issues effectively, having the right tools and materials on hand is essential. Here’s a checklist of commonly needed items:

• Ladder – A sturdy, extendable ladder to safely access the roof. 
• Roofing Nails – For securing replacement shingles or other roofing materials. 
• Hammer or Nail Gun – Essential for driving nails quickly and securely. 
• Replacement Shingles – To replace damaged or missing pieces. 
• Roofing Cement – Useful for sealing small cracks and gaps to prevent water from seeping through. 
• Utility Knife – For cutting shingles and other materials to size. 
• Measuring Tape – To accurately measure damaged areas and ensure proper material placement. 
• Safety Harness and Gear – Critical for personal safety when working at heights. 
• Tarp – To cover exposed roof sections during repairs or inclement weather. 
• Sealants and Caulking Gun – For filling gaps and providing additional waterproofing. 

Having these tools and materials readily available will not only make the repair process smoother but also ensure the job is completed efficiently and safely.

Safety Precautions Before Repairing

Before beginning any roof repair work, safety should be the top priority. Here are some essential precautions to follow:

1. Inspect the Weather Conditions – Only perform repairs in dry, calm weather. Wet or windy conditions increase the risk of slips and falls. 
2. Use Proper Safety Gear – Always wear a safety harness, non-slip boots, and gloves to minimize potential injuries. 
3. Secure the Ladder – Ensure the ladder is stable, positioned on level ground, and properly secured before climbing. 
4. Work with a Partner – Having someone nearby to assist or call for help in case of an emergency can prevent dangerous situations from escalating. 
5. Be Aware of Power Lines – Keep tools, materials, and your body at a safe distance from overhead power lines. 
6. Assess Roof Stability – Check the roof’s integrity and avoid walking on areas that appear structurally weak or damaged. 

Taking these precautions will help reduce the risk of accidents and injuries, creating a safer environment for roof repair work.

10 Methods How to Repair Rotted Wood under Shingles

1. Inspect and Identify the Extent of the Damage

The first step in repairing rotted wood under shingles is conducting a thorough inspection. Start by visually examining the roof for signs of sagging, dark patches, or areas where shingles appear loose or warped. Lift shingles gently in suspicious areas to check the condition of the wood underneath.

Use a screwdriver or awl to press into the wood; if it sinks easily, the wood is rotted and must be replaced. Identifying the full scope of damage ensures that repairs are targeted and effective. Without proper assessment, hidden decay may continue spreading unnoticed.

2. Remove Damaged Shingles Carefully

Before repairing the wood, the shingles covering the rotted area must be removed. Use a pry bar or roofing shovel to lift the shingles, starting from the edge and working upward. Be cautious not to break surrounding shingles that are still in good condition, as they may be reused.

Remove nails or fasteners securing the shingles to the wood, and set salvageable pieces aside. By clearing the area completely, you gain full access to the rotted wood underneath, making the repair process more accurate and thorough.

3. Cut Away Rotted Wood Sections

Once the shingles have been removed, the rotted wood itself must be dealt with. Using a circular saw or oscillating tool, cut out the rotted sections of the decking or sheathing. Ensure that you cut at least one to two inches beyond the visibly damaged area to reach solid, healthy wood. Dispose of the rotted pieces immediately to prevent mold spores or insects from spreading. This method not only eliminates compromised wood but also creates a clean, solid foundation for replacement material.

4. Replace with New Plywood or Sheathing

After removing the damaged wood, the area must be rebuilt using new material. Select plywood or oriented strand board (OSB) of the same thickness as the original sheathing to maintain a consistent roof surface.

Cut the replacement piece to fit snugly into the opening, ensuring the edges align with the surrounding wood. Secure the new sheathing with galvanized nails or decking screws spaced six to eight inches apart. This creates a strong, stable base ready to support shingles and resist future water damage.

5. Reinforce with Sistering Boards

If rot has affected rafters or structural members beneath the shingles, sistering boards can provide reinforcement. Sistering involves attaching new lumber alongside damaged rafters or joists to restore strength and stability.

Cut treated boards to the same length as the damaged section and secure them tightly using construction adhesive and nails or bolts. This method distributes the load evenly, ensuring that the roof structure remains strong and capable of supporting both shingles and weather conditions.

6. Apply Wood Hardener to Slightly Damaged Areas

In cases where the wood is only mildly rotted and not completely compromised, applying a wood hardener can be an effective solution. First, clean the surface and remove any loose fibers or debris.

Then apply a commercial wood hardener with a brush or spray, allowing it to soak into the weakened area. The resin penetrates the wood, reinforcing fibers and preventing further decay. This method is ideal for small, localized areas where replacement is not yet necessary but reinforcement is still critical.

7. Use Epoxy Wood Filler for Small Repairs

When rot is limited to small holes or surface depressions, epoxy wood filler can restore strength and integrity. Begin by cleaning out the decayed area and applying a liquid consolidant to solidify the remaining wood. Once dry, mix and apply the epoxy filler, shaping it to match the surrounding surface.

After curing, sand the area smooth and level with the rest of the wood. Epoxy repairs provide a durable, weather-resistant solution that prevents water intrusion and maintains the structural quality of the wood beneath shingles.

8. Install an Ice and Water Shield Barrier

Prevention is an essential part of repairing rotted wood under shingles. Once the damaged wood has been replaced or repaired, installing an ice and water shield membrane provides long-term protection. This self-adhesive barrier is applied directly over the wood decking before reinstalling shingles.

It creates a waterproof layer that prevents moisture from seeping into the wood, especially in valleys, eaves, and other vulnerable areas. This added protection ensures that your repair work remains intact for many years to come.

9. Replace and Seal the Shingles Properly

After repairing the wood and applying protective barriers, the shingles must be reinstalled. Begin by positioning the salvaged or new shingles in place, securing them with roofing nails driven just above the shingle tabs. Ensure that each shingle overlaps correctly to create a watertight barrier.

Apply roofing cement under the tabs of the last row to secure them against wind uplift. Properly sealing shingles is critical to preventing water from re-entering and causing the same rot issue all over again.

10. Perform Regular Maintenance and Inspections

Repairing Rotted Wood is not just about fixing existing damage; it also requires preventing future occurrences. Regular roof inspections, especially after storms or during seasonal changes, help catch early signs of shingle damage or wood decay.

Clean gutters to prevent water buildup, replace missing shingles promptly, and trim overhanging branches that may cause water pooling. By maintaining the roof diligently, you extend its life and reduce the likelihood of wood rot recurring under shingles.

Conclusion

Rotted wood under shingles is a serious issue that, if left untreated, can compromise the structural integrity of a roof and even lead to interior damage. Fortunately, with the right methods, homeowners can effectively repair the problem and restore the strength of their roofing system. Follow these simple instructions outlined in this blog post about how to repair rotted wood under shingles, and you’ll be able to get the job done with ease.