When a homeowner in Denver calls about a ceiling stain near the fireplace wall, my first thought isn’t the shingles—it’s the flashing. The intersection where your chimney meets the roof is a complex joint, and it has to work through high winds, ice damming, sun-baked summer days, and winter freeze-thaw cycles. On shingle roofs, that joint relies on a system of step flashing and counterflashing to steer water away. If that system is loose, underlapped, or sealed instead of shingled correctly, leaks follow. Because our climate is unforgiving, flashing details matter more here than almost anywhere else, and getting them right is one of the best favors you can do for your home. If you’re noticing damp drywall, peeling paint, or mysterious attic moisture, start by talking to a local crew that handles chimney repair daily and understands the dance between masonry and shingles.
Flashing, simply put, is the bridge between two materials that move differently. Bricks and mortar expand and contract at a different rate than plywood and asphalt shingles. Denver’s daily temperature swings amplify that movement, which is why a flashing setup built with flexibility in mind lasts longer. The base layer is step flashing—individual metal pieces interlaced with each course of shingles, lapping so water is always directed downhill. Over that sits counterflashing, which is cut into the mortar joints or mechanically fastened to the chimney so it covers the vertical leg of the step flashing. When both are installed correctly, water can’t easily find a path into the home.
Common failure points on shingle roofs
In field visits, we see the same handful of issues. Sometimes the original builder relied on surface-applied sealants rather than proper counterflashing. Those sealants dry, crack, and peel under our UV, leaving open seams. Other times, step flashing pieces are too short or are lapped the wrong way, creating a tiny dam that drives water sideways. We also see nail heads exposed in the flashing line; it only takes one nail hole in the wrong place to invite water into the sheathing.
On the uphill side of wider chimneys, missing crickets are a major culprit. Without a small, peaked diversion, snow and water collect behind the stack, soak the shingles, and work into joints. During spring storms when wind pushes rain uphill, a properly built cricket becomes the difference between a dry attic and a persistent leak.
Diagnosing the leak path
Finding the exact pathway of a leak is as much art as science. From the attic, discoloration on decking and rafters often points to a specific valley where water is tracking. Outside, careful lifting of a shingle tab here and there reveals how step flashing is lapped and whether counterflashing fully covers it. Mortar joints near the base of the chimney may show hairline cracks where sealant was smeared instead of a clean reglet cut and metal insert. We also check the cap and crown because water entering at the top can travel along the chimney’s interior and masquerade as a flashing leak.
In Denver, the weather decides the timeline. On a cold morning after a wet snowfall, a roof can be treacherous. When conditions are safe, a thorough assessment produces a clear plan: rework the step flashing, install new counterflashing ground into the mortar joints, add or rebuild a cricket, and coordinate with any roof repairs that make sense in the same visit.
What a proper flashing repair includes
A durable flashing repair starts by removing the old counterflashing and any step flashing that isn’t correctly lapped. We weave in new step pieces with the shingles so the water always stays on top, never behind. For counterflashing, we cut a neat reglet into the mortar joints and insert new metal that’s bent to shed water, then seal the reglet with a compatible masonry sealant. The result is a clean, layered system that relies on gravity and overlap—not just caulk—to keep water out.
Material choice matters. Heavier-gauge metals resist denting from hail and hold their shape in wind. In many Denver homes, galvanized steel is common, but stainless or other corrosion-resistant options are smart upgrades in high-exposure locations. Fasteners are tucked away from direct water paths. Where the chimney is wider than about thirty inches, a cricket is framed, sheathed, and shingled so water splits and moves around the stack instead of pooling behind it.
One point often overlooked is the transition from flashing to the roof plane at the eaves and ridges. If a roof replacement is on the horizon, coordinating the flashing work with the new roof can save headaches. A good contractor will stage the repair so it integrates seamlessly with new underlayment and shingle courses rather than creating awkward overlaps that may fail later.
Why sealant-only fixes fall short
It’s tempting to smear a bead of sealant along a seam and declare victory, especially when a sudden leak after a storm demands quick action. Sealant has its place as a secondary defense, but in Denver’s sun it ages fast. Without the mechanical interlock of properly installed step and counterflashing, you’ll be back on the roof or calling for help after the next thaw-freeze cycle. The proper fix might take a day or two, but it buys years of dry ceilings in return.
At mid-project, when homeowners ask whether the repair will stand up to wind and hail, I like to point to the details: lapped step pieces, counterflashing that actually lives in the mortar joint, clean bends with no oil-canning, and a cricket that splits the flow. That’s the anatomy of a repair that endures. If you’d like a second set of eyes on a chronic leak, reach out to a Denver team deeply experienced in chimney repair; they’ll distinguish between cosmetic seal jobs and true fixes.
Living with your chimney after the repair
After the last piece of metal is tucked and the final shingle is set, you should expect quiet performance. No drips during the first spring storm, no musty smell after snowmelt, and no new stains creeping across the ceiling. Outside, the flashing line should look intentional and tidy. Through the seasons, a quick glance from the yard after wind events—checking for displaced shingles or bent metal—will catch minor issues early. Most quality flashing repairs outlast the surrounding roof when designed and installed properly.
How do I know if flashing is my problem?
Stains that appear on the ceiling or wall adjacent to the chimney after rain or after snowmelt often point to flashing. If the stain has a sharp edge or tracks along a line, that’s another clue. A professional inspection will confirm by tracing moisture paths and checking how the metal is lapped and sealed.
Do I need a cricket behind my chimney?
If your chimney is wide or sits in a location where snow and water collect, a cricket is a wise addition. It diverts flow and reduces the time water spends sitting against flashing, which drastically lowers leak risk on shingle roofs.
Can new flashing be installed without replacing the roof?
Often, yes. Skilled technicians can lift and weave shingles to install new step flashing and cut in counterflashing without a full reroof. If the shingles are brittle or at the end of life, coordinating with a roof replacement may be more efficient.
What metals are best for Denver?
Heavier-gauge galvanized, stainless, or other corrosion-resistant metals stand up to hail and UV better than thin alternatives. The right choice depends on exposure, roof pitch, and the age of the surrounding roof.
Will sealant alone fix my leak?
Sealant can buy time, but it’s not a substitute for properly lapped metal. Under Denver’s sun and temperature swings, seal-only fixes age quickly and often fail at the worst moment—during the next storm.
If a roof stain has you worried or you’ve been living with a recurring leak season after season, it’s time to solve it for good. Call a local crew that treats flashing as a craft, not an afterthought. For clear diagnosis and long-lasting work tailored to our climate, connect with Denver professionals in chimney repair and give your chimney-to-roof joint the attention it deserves.
