Roof flashing is thin metal (or a similar waterproof material) that sits wherever your roof meets something else: a wall, a chimney, a pipe, a skylight, another roof plane or the roof edge. The main types are step, counter (continuous), base, kick-out, valley, drip edge, vent pipe, chimney and skylight flashing. Each one handles a different joint, and a leak usually starts at the joint, not in the middle of the shingles.
Below you will find what each type does, where it belongs, how to tell whether yours is failing, and the practical next step if it is.
TL;DR
- Flashing directs water down and out, away from your walls. Shingles shed water on open slopes, and flashing protects the joints and edges.
- Step flashing, kick-out flashing and valley flashing handle most roof-to-wall and roof-to-roof joints. Counter flashing covers the top edge of other flashings.
- Drip edge protects the eaves and rakes, and vent, chimney and skylight flashing seal the openings.
- Leaks at flashing often show up as stained ceilings, rotted trim or peeling paint near the roofline, and siding can hide the damage for years.
- When you replace a roof, the flashing should be replaced with it, not reused.
Table of Contents
- What roof flashing does
- Roof flashing types at a glance
- Step flashing
- Counter flashing and continuous flashing
- Base flashing
- Kick-out flashing
- Valley flashing
- Drip edge
- Vent pipe, chimney and skylight flashing
- Which flashing material should you expect?
- Signs your flashing is failing
- What to do next
- Flashing in Central Texas
- Perspective: our view on flashing
- Get your flashing checked
- FAQ
- Sources
What roof flashing does
The job is simple to state. The U.S. Department of Energy's Building America program describes the basic principle of rainwater control as directing water downward and outward, over the cladding or drainage plane and away from the building. The same publication calls flashings arguably the most important component of the building enclosure.
Think of flashing as a set of small gutters and overlapping shields. Each piece lets water run over the one below it, so water never has a path behind the roof or wall. Shingles do this on a plain slope. The trouble comes where the plane changes: a chimney, a dormer, a pipe, a valley. Those spots need metal that is shaped for the joint.
Roof flashing types at a glance
| Type | Where it goes | What it does |
|---|---|---|
| Step flashing | Where a sloped roof meets a vertical wall | Overlaps with each shingle course to carry water onto the roof |
| Counter flashing | Over the top edge of step or base flashing | Shields the upper edge and completes the seal |
| Base flashing | At the bottom of a wall, chimney or curb | Directs water onto the roof surface |
| Kick-out flashing | At the lower end of a roof-wall joint | Sends water into the gutter instead of behind the siding |
| Valley flashing | Where two roof planes meet | Channels water off the roof |
| Drip edge | Along eaves and rakes | Guides water off the edge and protects the decking |
| Vent pipe flashing | Around plumbing vents and similar pipes | Seals the opening |
| Chimney flashing | Around the chimney base and sides | Combines base, step and counter pieces |
| Skylight flashing | Around the skylight frame | Seals and sheds water around the opening |
Step flashing
Step flashing is the workhorse of roof-to-wall joints. Building America guidance says it is used where a sloped shingled roof intersects a vertical wall, and it is interwoven with the shingles so the wall's drainage plane hands off to the roof's drainage plane.
In practice, installers use small bent pieces of metal, one per shingle course. Each piece laps over the one below it, like the steps of a staircase. The shingle manufacturers' trade association says step flashing units are installed with each course of shingles, fastened to the roof and not nailed to the wall. Fastening to the roof matters because the wall and roof move at different rates, and a piece nailed to both can tear.
One point that surprises many homeowners: on a re-roof, the best practice is to remove and replace the step flashing, with each piece overlapping the piece below it. Reusing old pieces is a common shortcut and a common source of later leaks.
Counter flashing and continuous flashing
Counter flashing goes over the top of another flashing. You will also see it called cap flashing, and "continuous flashing" often refers to a single long piece used in a similar way along a wall. The idea is the same: one layer shields the upper edge of the layer beneath.
Step flashing vs. counter flashing
They are partners, not alternatives. On a chimney, step flashing runs up the sides as L-shaped pieces overlapped by shingles. Counter flashing is tucked into the mortar joints and overlaps the base flashing. Fine Homebuilding explains that the pieces are not joined together, so they can move independently as the house and chimney settle at different rates, which helps prevent tearing and leaks.
A simple way to remember it:
- Step flashing sits under the shingles and against the wall. It sheds water onto the roof.
- Counter flashing sits over the step or base flashing. It covers the top edge so water cannot get behind it.
Base flashing
Base flashing is the lower layer at a roof-to-wall or roof-to-chimney joint. It lies on the roof and turns up the vertical surface. Counter flashing then covers its upper edge. On a chimney, the base flashing is typically the front apron and the step pieces on the sides. If you want to see how these pieces fail around a chimney in particular, our guide to roof leaks around a chimney walks through the four causes to inspect.
Kick-out flashing
Kick-out flashing is a small, angled piece at the bottom edge of a roof-wall joint. Its job is to direct water out from below the cladding and away from the wall, preventing water from draining into the wall system below.
It is also the piece most often missing. Building America guidance notes that without it, water can overflow the gutter and run down the wall, eventually rotting window trim and causing water damage inside the wall. If you have a roof that ends against a second-story wall, look at that lower corner. Dark streaks on the siding right below it are a classic sign.
Valley flashing
A valley is where two roof planes meet, and it carries a lot of water. Valley flashing collects rainwater and channels it off the roof. Building America recommends a peel-and-stick membrane in all valleys and roof-wall intersections, with metal flashing over the membrane.
Valleys can be open (metal visible) or closed (covered by shingles). Both can work when installed properly. For a deeper look at the options and how leaks get repaired, see our article on roof valley flashing.
Drip edge
Drip edge is metal along the eaves and rakes. It is the flashing you can see from the ground, and it is often missing on older homes. In high-wind zones, drip edges are recommended at eaves and rakes, and installing them over the underlayment can help lock the roof in and protect it from moisture.
Details matter here. Building America guidance says drip edge should sit about a half-inch out from the fascia board, with the bottom edge flared outward, so water does not wick back behind it into the wood. Our page on drip edge roofing covers why most roofs need it. And if the fascia and soffit behind it already show moisture damage, read about fascia and soffit repair.
Vent pipe, chimney and skylight flashing
Anything that pokes through the roof needs its own flashing.
- Vent pipe flashing seals plumbing vents and similar protrusions. Most are a metal or plastic base with a rubber collar. The rubber collar is the part that tends to crack in the sun, so it is a common small leak.
- Chimney flashing is a system: base flashing, step flashing on the sides and counter flashing set into the mortar. A leak here may be flashing, or it may be the mortar, the crown or the cap.
- Skylight flashing is usually a kit made for the specific skylight model. Mixing parts from other products is a frequent cause of leaks.
When these openings are surrounded by shingles, a cracked seal or a lifted shingle edge can let water in even though the metal itself looks intact.
Which flashing material should you expect?
Common materials include galvanized steel, aluminum, copper and rubberized or plastic products for specific uses. The rule to know is code-related: the 2018 International Residential Code section R903.2.1 calls for metal flashing that is corrosion-resistant and at least 0.019 inches thick. Local codes can differ, so your contractor should confirm what your city requires.
Two practical points. First, pick one that suits your roof: metal roofs use matching metal flashing and trim, and noise or deck questions should be raised early. Our piece on metal roof noise in rain explains what to ask. Second, avoid mixing metals that react with each other. Your roofer should match fasteners and flashing.
Signs your flashing is failing
Check from the ground and from the attic after a hard rain.
- Brown stains on ceilings or walls near a chimney, dormer or exterior wall.
- Water marks or damp insulation on the attic side of the roof deck near a joint.
- Rusted, bent, lifted or visibly gapped metal at the chimney, wall or valley.
- Dark streaks on siding below a roof edge, especially at a roof-wall corner.
- Peeling paint or soft, rotted trim around windows near the roofline.
- Sealant (caulk) that has cracked or pulled away. Caulk is a patch, not a flashing.
The quiet danger is that damage can stay hidden. Building America notes that missing or inadequate flashing can let water into walls, damaging sheathing, framing and insulation and causing mold, and that newer siding can hide the intrusion for years. Fiber cement and brick veneer are among the claddings that can mask it. If your home has siding, our article on house wrap under siding explains why flashing is the first priority behind it.
What to do next
- Look, safely. Use binoculars from the ground. Do not walk a wet or steep roof.
- Photograph the signs. Date the photos of stains and damaged metal. They help with a contractor or an insurance claim.
- Do not rely on caulk. A tube of sealant may hold briefly, but the joint still needs correct metal.
- Get an inspection. A roofer can check every joint in one visit.
- Compare estimates. Ask each contractor to list which flashings they will replace, not just "flashing" as a line item.
- Ask about the whole roof. If the roof is near the end of its life, repairing flashing alone may not be the best use of money. Compare the options in our reroof vs. tear-off guide.
What a good estimate lists
A clear estimate names the flashing types: drip edge, step, kick-out, valley, pipe boots and chimney or skylight work. It states whether old pieces are removed, which underlayment or membrane goes under them, and what material is used. If two quotes differ widely, vague flashing scope is often the reason. For what a full job involves, see the roof replacement process and the roof replacement timeline.
Flashing in Central Texas
Central Texas roofs deal with intense sun, sudden heavy rain and hail. Sun ages rubber pipe collars and sealants. Storms can bend or lift edge metal and dent exposed flashing. After a storm, flashing is easy to overlook because the shingles get the attention, yet a bent drip edge or a displaced valley piece can start a leak months later. If a storm is involved, document everything and have the flashing checked along with the shingles.
Perspective: our view on flashing
We see the same pattern on roofs across Central Texas: the shingles look fine and the leak is at a joint. A chimney, a wall, a valley, a missing kick-out. That is why we tell homeowners to judge a roof estimate by what it says about flashing.
Our advice is simple. Get more than one estimate, and ask every contractor to list each flashing piece they plan to replace. We encourage that comparison because we stand behind our Best Price Guarantee and would rather you choose with full information.
If a storm damaged your roof, flashing belongs in the inspection and in the claim conversation. We guide homeowners through insurance claims so the damaged metal is documented along with the shingles, and we use durable materials suited to Texas weather.
Dan
Get your flashing checked
If you spotted stains, rusted metal or a missing kick-out, we can inspect the roof, explain what is failing and give you a free estimate for repair or replacement. We handle asphalt shingle and metal roofs, storm damage restoration and insurance claim guidance for homes in Central Texas. See our roofing repair and replacement services, or learn how insurance claims made easy works if you have received a payout.
If flashing problems have reached your walls, our siding repair and replacement team can also repair the damage behind them.
FAQ
What is roof flashing?
Roof flashing is waterproof material, usually metal, installed at joints and edges where shingles alone cannot keep water out. It directs water down and away from the roof and walls. Common spots are walls, chimneys, valleys, vents, skylights and roof edges.
What is the difference between step flashing and counter flashing?
Step flashing is a series of small pieces woven into the shingles along a wall or chimney side. Counter flashing goes over the top of step or base flashing to cover its upper edge. They work as a pair and are not fastened together.
Can I fix roof flashing with caulk?
Caulk can slow a small leak for a short time, but it is not a lasting repair. Sealants crack in sun and heat, and the joint still lacks proper overlapping metal. A roofer can tell you whether a repair or replacement is the right fix.
Does flashing need to be replaced when the roof is replaced?
Usually yes. Building America guidance says that on a re-roof it is best to remove and replace step flashing. Ask your contractor to list which flashings they will replace, so you can compare estimates fairly.
How do I know if my kick-out flashing is missing?
Look at the bottom of any roof edge that ends against a wall. If you see no angled metal piece there, or you see stains on the siding and rot on the trim below it, it may be missing. A roofer can confirm.
Sources
- BSC Information Sheet 303: Common Flashing Details
- Water Management Residential, Building America
- Step and Kick-Out Flashing at Roof-Wall Intersections, Building America Solution Center
- Look for Missing Roof and Wall Flashing, Building America Solution Center
- Drip Edge at Roof Eaves and Rakes, Building Science
- Moisture Barrier and Flashing on the Roof
- Critical Roof Flashings Keep Water Out, Fine Homebuilding
- Installing Chimney Flashing, Fine Homebuilding
- Applying Shingles at Valleys, Asphalt Roofing Manufacturers Association