Types of roof flashing: what each one does and where it goes
Most roofs use five or six kinds of flashing. Knowing the names helps you read a quote and find where a leak really starts.
There are several types of roof flashing, and each one belongs to a specific joint. A roofer who says "it's the flashing" could mean any of them. Here is how to tell them apart.
Step flashing
Small bent pieces of metal laid in a row where a roof meets a side wall. Each piece overlaps the one below it, like stairs. See what is step flashing.
Base and counter flashing
Base flashing runs up the wall and under the shingles. Counter flashing hangs over its top edge. They are a pair, and they are not joined. We explain each in base flashing and counter flashing.
Valley flashing
A long metal channel where two roof slopes meet at an inward angle. It carries the most water on the roof. Open and closed versions look different from the ground, as our page on valley flashing shows.
Chimney flashing
A layered set that combines base, step and counter pieces, plus a back piece called a cricket on wide chimneys. It is one of the commonest leak spots. See chimney flashing.
Drip edge and vent boots
Drip edge is the thin metal strip along the roof edge that kicks water off into the gutter. Vent boots are the collars around plumbing pipes. The rubber on a boot cracks long before the metal does, so it fails more often than people expect.
Which one fails most
In plain terms, the ones with the most joints and the least slope: chimneys, valleys and wall joints. A long, plain drip edge rarely leaks. A vent boot with a cracked collar often does.
What to check from the ground
With binoculars, scan each joint you can name: chimney, valleys, wall lines and pipes. Look for rust, gaps and tar smears. Inside, trace any stain along the attic rafters with a flashlight, staying on the joists.
Why we do not show the repair
Every type of flashing is fixed at a roof edge, joint or slope. That is work at height, and we do not publish the steps. Learn the names, take photos and ask a roofer which type needs work. The overview is in what is roof flashing.
Frequently asked questions
What are the main types of roof flashing?
Step, base, counter, valley, chimney, drip edge and vent boot flashing cover most roofs.
What is the difference between base and counter flashing?
Base flashing runs up the wall under the shingles. Counter flashing covers its top edge. They overlap but are not attached.
Which type of flashing leaks most often?
The ones at chimneys, valleys and wall joints, because they have the most seams and take the most water.
Is a vent boot a type of flashing?
Yes. It seals a pipe where it passes through the roof, and its rubber collar often cracks first.
Can I identify my flashing from the ground?
Often yes. Use binoculars to find each joint and note what it looks like. Do not go on the roof.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NRCA. National Roofing Contractors Association
- US OSHA. 1926.501 — Duty to have fall protection (OSHA)