Chimney Flashing Repair in Kansas City

A chimney is a big box sticking up through the roof, and water hits it from every side. Four separate pieces of flashing deal with that.

Step flashing runs up both sides. Each piece is an L-shaped bend tucked under one shingle course and turned up against the brick, overlapping the piece below it like the shingles themselves.

Counterflashing covers the top edge of that step flashing. It's cut into a mortar joint, bent down over the steps and sealed into the joint. Without it, water runs down the face of the brick and straight behind the step flashing.

On the uphill side, a back pan or a cricket keeps water from piling up against the chimney. Across the front, an apron laps over the shingles below and sheds everything back onto the roof.

Plenty of homes in the older parts of the metro have brick chimneys that are older than anyone living in the house. Every winter the mortar joints take on water, freeze and thaw. Over enough years they soften and crumble. Counterflashing that was set into those joints loosens, and water gets in behind it.

The second pattern is shortcuts from an earlier roof job. We see counterflashing that was never cut into the brick at all, just laid flat against the face with a strip of caulk along the top. We see old step flashing reused under new shingles. Both can look fine for a few years. Neither lasts.

Then there's the wide chimney with nothing on the uphill side. Snow and debris build up against it, water backs up under the shingles, and the leak shows up on the ceiling a few feet downhill from where it started.

Not every wet chimney is a roofing problem, and we'll tell you when yours isn't.

A cracked concrete crown on top of the chimney lets water into the brick from above. A missing or rusted cap lets rain fall straight down the flue. Old, porous brick can soak up water on a long rainy day and release it inside. Gas appliances venting into an unlined or oversized flue can produce condensation that stains the wall. None of those are fixed by new flashing.

If we find one of those, it goes in the photos and the write-up, and we'll tell you it's work for a chimney mason. Paying for new flashing when the crown is the problem just means you'll still have the leak.

We take up the shingles around the chimney and remove the old metal and any tar. Ice-and-water membrane goes onto the deck and turns up the brick. New step flashing goes in with each course of shingles, then new counterflashing is cut into a ground mortar joint and sealed there, not glued to the face.

On the uphill side, a chimney wide enough to dam water gets a cricket, a small framed ridge that splits runoff around the chimney. The residential code requires one on chimneys more than 30 inches wide across the slope, and we build it even where an older roof never had one. Smaller chimneys get a formed back pan.

The front apron goes on last and laps over the shingles below. When we're done you get photos of each layer before it's covered, since none of it is visible once the shingles are back.

Roofing cement smeared over the joint between the roof and the brick is the most common chimney repair we find. It's also the one we end up tearing out most often. Tar dries, shrinks and cracks after a summer or two of sun. Worse, it hides whatever is underneath, so the next person can't see how bad the metal or the decking has gotten.

If you have a tar patch that has held for years, fine. If it's leaking again, more tar isn't the answer. The metal behind it is.

When we replace a roof, the chimney gets new step flashing, new counterflashing and a new apron as part of the job. It's in the written scope, line by line. We also look at the mortar joints before we price it, since counterflashing needs a sound joint to sit in.

If you have a chimney you no longer use, some owners have it taken down below the roof line during a replacement. Once the masonry is removed, the opening is framed, decked and shingled with the rest of the roof, and there's one less thing to leak.