Flashing is the metal that seals the joints
Ask where flashing goes on a roof and the short answer is: everywhere the roof stops being a plain sheet of shingles. Walls, chimneys, valleys, edges, pipes and skylights all break the surface, and at each one a piece of shaped metal (or a rubber boot) steers water back onto the shingles and down to the gutter.
Because these joints are where two different materials meet, and because they move as the house heats and cools, they are where most roof leaks begin. The shingles around a failed piece of flashing can be in perfect shape. This page shows each place flashing belongs, how a roofer tells it has failed, and what a proper flashing repair involves.
Houston Expert Roofers does not repair flashing. Dial its free number at any hour and an automated assistant connects the call with an independent, locally owned roofing company, which inspects the roof, quotes the repair and does the work.
Every place flashing goes on a roof
A typical Houston house with a two-story wall, a fireplace chimney and a few plumbing vents has most of these. Use the table to match a leak's location to the flashing above it.
| Flashing | Where it goes | How it works | Common failure |
|---|---|---|---|
| Step flashing | Along a sidewall or the sides of a chimney, where the roof slope runs alongside a vertical surface | An L-shaped piece is woven in with each shingle course, so every piece laps over the one below | One long piece face-nailed or caulked instead of individual steps; pieces left out when a roof was redone |
| Counterflashing | Over the top of step or base flashing on chimneys and masonry walls | Set into a cut mortar joint and folded down over the step flashing so water on the brick cannot get behind it | Pulled out of the joint, or replaced by metal caulked to the brick face |
| Apron (headwall) flashing | Where the top of a roof slope butts into a wall, or the front of a chimney | A continuous piece laps over the top course of shingles and up the wall | Seal at the wall fails; siding or stucco installed without covering the upturned leg |
| Chimney cricket (saddle) | On the uphill side of a chimney | A small peaked ridge that splits water around the chimney so it does not pond behind it | Missing on wide chimneys, or its own flashing joints fail |
| Valley flashing | Where two roof slopes meet in a channel | A metal liner (open valley) or woven or cut shingles over a membrane carry water from both slopes | Debris dams the valley; worn metal; nails driven too close to the center |
| Drip edge | Along the eaves (the bottom edges) and rakes (the sloped side edges) | An angled metal edge kicks water away from the fascia and keeps it from wicking back under the shingles | Missing on older roofs, or pieces not lapped, so the fascia and deck edge rot |
| Kickout (diverter) flashing | At the bottom of a roof-to-wall joint, where the eave meets a sidewall | Turns water coming down the wall flashing out into the gutter | Missing, so water runs behind siding or brick and rots the wall below |
| Pipe boots and vent flashing | Around plumbing vents, exhaust vents and other pipes through the roof | A metal flange under the upper shingles with a rubber or lead collar that grips the pipe | Rubber collar cracks in sun and heat; flange lifted by a nail pop |
| Skylight flashing | All four sides of a skylight | Step flashing on the sides, a head piece at the top and an apron at the bottom, usually as a kit | Leaks at the uphill head where water and debris collect |
What the building code says about flashing
The City of Houston adopted the 2021 International Residential Code, with local amendments, for work from January 2024, and many surrounding cities use the same model code. The code sets the minimum, and the shingle maker's installation instructions add their own requirements. A few flashing rules that come up often:
Drip edge on shingle roofs
The residential code requires drip edge at the eaves and rake edges of asphalt shingle roofs (section R905.2.8.5), with adjoining pieces lapped at least two inches, the metal extending at least a quarter inch below the deck edge, and fasteners no more than 12 inches apart. Underlayment laps over the drip edge at the eaves and runs under it at the rakes.
Diverter flashing at roof-to-wall joints
Section R903.2.1 calls for flashing where a roof meets a wall and for a diverter that sends water away where the eave of a sloped roof meets a vertical sidewall. The code does not use the word "kickout", which may be one reason this piece is so often missing.
Sidewall base flashing
Base flashing against a sidewall must be continuous or step flashing at least 4 inches high and 4 inches wide (section R905.2.8.3), directing water onto the roof or into the gutter. Where there is siding, the upturned leg runs up behind it.
Crickets behind wide chimneys
A cricket or saddle is required on the ridge side of any chimney or penetration more than 30 inches wide measured across the slope (section R903.2.2), covered in sheet metal or the same material as the roof.
Code language changes between editions, and cities amend it, so treat this as background. The roofer and your city's permit office decide what applies to a specific job.
Why caulk is not flashing
Flashing keeps water out by overlapping. Each piece sits under the material uphill of it and over the material downhill of it, the way shingles do, so water always runs out across a surface instead of into a seam. That works even when every seal in the joint has failed.
Caulk and roofing cement work the opposite way: they only keep water out while they stay stuck to both surfaces. Houston sun, heat and the daily movement of metal against brick or wood pull them loose over time. That is why a thick bead of sealant at a wall or chimney is usually a sign of an earlier patch over a flashing problem, not a repair.
Sealant still has a place. It is used at exposed fastener heads and in the reglet where counterflashing meets brick, and a roofer may smear it on as a temporary measure after a storm. If an estimate says "seal" or "caulk" at a leaking joint, ask whether that is the whole repair or a stopgap until the flashing can be replaced.
Signs a flashing joint has failed
- A ceiling or wall stain near an outside wall, a chimney or a skylight, keeping in mind water can run several feet before it drips.
- Leaks that appear in wind-driven rain but not in a steady, straight-down rain.
- Rust streaks on the shingles below a chimney, vent or wall joint.
- Thick caulk or black tar visible at a joint from the ground, meaning someone has already patched it.
- Stained, swollen or soft siding or trim below the bottom of a roof-to-wall joint, which points to a missing kickout.
- Damp or stained drywall around a fireplace, often blamed on the chimney itself.
Look from the ground or through a window only. Binoculars help. Do not climb onto the roof or lean a ladder against a gutter to look, and leave the close inspection to the roofer.
Stay off the roof. Wet, storm-damaged roofs are slick and the decking may be weak, so leave the ladder in the garage. Keep well away from downed power lines and report them to CenterPoint Energy or 911. Indoors, move belongings away from the leak, put a bucket or towels under the drip and keep people out of any room where the ceiling sags. Photograph the damage from the ground and inside the house, then call your insurer and a roofer.
How a careful roofer repairs flashing
- Confirm the source. The roofer checks the attic or the inside of the wall and the joint itself to make sure the water starts at the flashing, not at a nearby boot or valley.
- Lift the shingles around the joint. Step flashing is woven into the shingle courses, so the shingles next to the wall or chimney have to come up, carefully, to reach it.
- Check the wood underneath. Long-running flashing leaks often rot the deck edge or the wall sheathing. Soft wood should be replaced before new metal goes in.
- Install new metal the right way. Individual step pieces with each course, counterflashing cut into the mortar on masonry, a kickout at the bottom of wall joints, and new boots on vents.
- Relay and match the shingles. The roofer should say beforehand whether it can reuse or match your shingles, and should photograph the work before the shingles cover it.
On a roof with years of life left, replacing flashing alone is usually the right call. If the roof is close to replacement anyway, ask whether it makes more sense to fold the flashing into a new roof, since a full replacement should include new flashing. The roof leak repair page covers leaks from other sources.
Water near a wall, a chimney or a skylight? Call and describe where it shows up and in what kind of rain. The local roofing company you are put through to inspects the joint and puts its repair and price in writing.
What drives the cost of a flashing repair
The line does not quote prices, and a figure without seeing the roof would not be honest. These are the things a roofer weighs when it prices the job, so you can understand why two flashing repairs on the same street can cost very different amounts.
Location and access
A pipe boot on a low, walkable slope is quicker than a chimney on a steep second-story roof, which may need extra safety gear and time.
How much roofing comes up
Step flashing along a long wall means lifting and relaying many courses of shingles, and brittle older shingles may need replacing rather than relaying.
Masonry and siding
Counterflashing on brick means cutting and sealing mortar joints. On walls, siding or trim may have to come off to fit the flashing behind it.
Hidden rot
Rotten decking or wall sheathing found under the old flashing adds to the job. Ask for a unit price for any wood replaced.
Materials
Galvanized steel, aluminum, copper and lead behave and cost differently, and matching existing metal on an older home can matter.
Matching shingles
If your shingle is discontinued, the roofer may need to discuss alternatives before it starts lifting courses.
How a flashing call works
- Call the numberAn automated assistant answers (832) 662-4107 at any hour and asks which service you need, since the line also takes heating, cooling, pressure washing and water damage calls.
- Describe the roofA leak, missing shingles, hail, a limb on the roof or an old roof you want looked at, plus your part of greater Houston and how urgent it is.
- Get put throughYour call is transferred to an independent, locally owned roofing company, which hears a short summary before it picks up.
- Deal with the roofer directlyIt inspects, quotes and does the work, and you pay it (or your insurer does, as you arrange). If it misses the call, it gets your name, number, city and need to call you back.
Texas has no state roofing license. No state agency licenses roofing contractors in Texas, and a 2025 bill to create one (HB 3344) did not reach a vote of the full House before the session ended. So check what you can: a certificate of liability insurance sent to you, a written contract with the full scope, a permit where your city requires one, local addresses you can drive past, and the shingle maker's warranty registration. Some cities also ask roofers to register. The line does not check any of this for you. How to check a roofer before you hire.
About this line: Houston Expert Roofers is a free phone line, not a roofing contractor. It answers your call and connects you with an independent local roofing company, which inspects, quotes and does the work, and which you pay directly. Companies may pay a referral fee. The line never charges you. Read how the line works.
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