A chimney that is wider than a few shingle courses sits in the path of water running down the roof. The small peaked saddle built on its uphill side, called a cricket, splits that flow and sends it around the chimney instead of letting it pile up behind the masonry. When a cricket is missing, undersized, or flashed poorly, the leak often shows up in a ceiling in a room that has nothing to do with the chimney, which is why so many homeowners look in the wrong place first.
What the cricket is supposed to do
Water that runs down a steep slope hits the chimney and has to go somewhere. Without a cricket, it stalls against the upslope face of the masonry, soaks into the flashing seam, and works its way along the framing. A properly built cricket is a short ridge of sheathing covered with metal or membrane, pitched so that water leaves the chimney on both sides. Many building codes call for one when the chimney is wider than about 30 inches, because a chimney that narrow will not block much of the flow on its own.
The cricket only works if its flashing is tied into the shingles on both sides and into the chimney base. The sealant that holds the flashing to the masonry is the part that wears out first, because it sits in direct sun and then in freeze and thaw. In St. Louis, that means a joint that looked tight after a summer can open up by late winter, and the first heavy spring rain is often when the stain appears.
Why the stain lands in the wrong room
Water that gets past a failed cricket does not drop straight down. It follows the back of the chimney, runs along the top plate or rafter, and comes out wherever the framing gives it a path. That path is often a hallway, a closet, or a bedroom wall on the side of the house opposite the chimney. A homeowner who sees a stain there may check the bathroom vent, the attic hatch, or the window above it, and never think about the chimney.
This is the same pattern that shows up with other roof details. The leak point and the stain are separated by framing, insulation, and gravity, so the place you see water is rarely the place it entered. If you are trying to decide whether to call someone, the useful question is not where the stain is but whether anything on the roof sits uphill of that stain, and a chimney almost always does if it stands on the upper slope of the roof.
Signs that point to the cricket
- The stain shows up only during or right after heavy rain from the upslope direction, and stays dry during light drizzle.
- There is staining or dark, damp wood on the uphill side of the chimney framing when you look from the attic.
- Sealant or caulk along the chimney base is cracked, peeling, or pulled away from the masonry.
- The metal flashing at the chimney has lifted, or the shingles directly uphill of the chimney are cupped, split, or missing.
- There is no cricket at all. Some older chimneys were built without one, and the flashing was simply laid against the brick.
Hail season adds another test. Hail that strikes the upslope face of a chimney and its cricket can bend the metal or crack the sealant without leaving any obvious shingle damage. If the leak began after a spring storm, the cricket metal is worth a close look in the same walk-around that covers the shingles.
How to check it without climbing on a wet roof
Do not go onto a wet or frosted roof to look for this. Shingles are slick when wet, and the cricket sits on the steepest part of the slope. Instead, go to the attic on a dry day and look at the framing on the uphill side of the chimney with a flashlight. Look for dark wood, rust on nails, water lines on the sheathing, or old mineral staining. Mark what you find with painter's tape so you can compare it after the next rain.
If it is raining, take a second look from inside during the storm. Put a flashlight on the framing and watch for drips or fresh wetting. Photograph the area with a timestamp. That record is useful for a roofer, and it is also the kind of dated evidence an insurer will ask for if the damage came from a storm. Keys Roofing can be reached at (314) 220-2333 if you want a second look at what you have photographed.
What a proper repair line should name
A cricket repair is not the same as a bead of sealant on the chimney base. A written scope should say whether the existing cricket is being rebuilt, re-flashed, or left in place, and it should name the metal, the gauge, and how the flashing is tied into the shingles. If the sheathing under the cricket is soft, the scope should say so, because a cricket on rotten decking will keep failing no matter how well the metal is sealed.
- Whether the cricket is new, rebuilt, or the original kept with new flashing.
- The metal type and thickness used for the cricket and the step flashing.
- Whether the sheathing under the cricket was checked and what was found.
- How the flashing is woven into the shingle courses on both sides of the chimney.
- What sealant is used at the masonry, and whether counterflashing is set into the mortar joint.
- Photos of the cricket before and after the work, taken from the same spot.
What to ask the roofer
- Does the chimney need a cricket, and if one exists, is it sized for the chimney width?
- What do you see in the attic on the uphill side, and can you show me the photos?
- Will the repair change the shingle layout around the chimney, or only the flashing?
- Who will look at the cricket again after the first heavy rain following the repair?
Missouri does not license roofers, so a roofer's registration is not a stand-in for these answers. The written scope and the photos are what you keep. Keys documents what it finds, puts the written scope with photos and measurements in your hands, and attends as the contractor while you deal with your own insurer, if a claim is involved. Keys does not represent or negotiate a homeowner's insurance claim, and Missouri law (RSMo 407.725) bars a roofing contractor from doing that, so any insurer conversation stays with you.
When the cricket is not the cause
Not every stain beside a chimney comes from the cricket. The flue cap, the crown of the chimney masonry, and the step flashing along the sidewalls can all send water in the same general direction. If the stain is near the chimney but the attic framing on the uphill side is dry, look higher, at the crown and the cap. If the attic framing is wet on the sidewall side instead, the step flashing is the likelier suspect. The point of checking is to match the wet framing to the water source, and a single rain test with a dated photo often separates these faster than another round of guessing.
A cricket that is built correctly and flashed well should last as long as the surrounding shingles, but only if someone checks the sealant after the freeze and thaw cycles of a St. Louis winter. Put it on the list for the same spring walk that covers the rest of the roof, and do not wait for the next stain to show up in a room you did not expect.