How to Repair Roof Flashing

Introduction

Whenever it's practical to replace damaged roof flashing, do so. In an emergency or when replacement is too difficult or expensive, use a patch and inspect it annually. Typically, you can use this method for step flashing, which interlaces with shingles where they meet a wall or other vertical surface. However, it's not practical to repair flashing at the valley where two roof planes intersect.

By: eHow Home & Garden Editor

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Instructions

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Difficulty: Moderately Challenging

Tips & Warnings:

Step flashing should extend at least 4 inches (10 cm) out onto the roof and ideally 2 to 4 inches (5 to 10 cm) up behind the siding, trim or counter flashing.
To avoid injury or roof damage, observe proper ladder and roof safety, and use a roof ladder (a rental item) where possible.
Don't mix metals when nailing flashing or where new and existing flashing contact. The electrolysis generated causes rapid corrosion.
The cut edges of metal flashing are very sharp, so wear work gloves.

Insert new step flashing

Step1

Install new step flashing over the damaged step flashing (you'll likely need a ladder). Cut the flashing with tin snips, bend it in half at a 90-degree angle; slip the vertical half up under the siding or trim on the wall; slide it up the roof under the shingle and on top of or under the damaged piece. Adhere it using dabs of asphalt flashing cement under and over it.

Replace plumbing-vent flashing

Step1

Look for the leak. A plumbing vent can leak between the collar and the pipe, through the collar, or through the plastic or metal pan that fits under the course of shingles above the pipe and on top of the course below.

Step2

For leaks between the pipe and collar or through the collar, replace the collar or slip a repair collar over the pipe on top of the existing one.

Step3

For flashing leaks, install new vent flashing. Remove the shingles above the flashing, and install it according to the manufacturer's instructions, usually with finishing nails.

Repair chimney flashing

Step1

If the step flashing is corroded, insert step flashing as described in "Insert new step flashing," above. If the counter flashing is corroded, patch it until you can have it replaced professionally.

Step2

If the mortar joint where counter flashing is embedded is deteriorating, repoint the joint.