What a Chimney Cricket Does and Which Chimneys Need One

You have had the flashing on your chimney redone once, maybe twice, and the same stain came back on the same side of the ceiling. Or you got up on the roof and found a wedge of leaves, pine needles and shingle grit packed solid against the uphill wall of the chimney. That is usually not sloppy flashing work. That is a chimney that needs a cricket.

What a cricket actually is

A cricket, which some people call a saddle, is a small peaked structure built onto the roof on the uphill side of the chimney. Picture a short ridge running away from the back of the chimney with two sloped faces angling down to either side, framed in wood and covered with roofing that ties into the surrounding shingles.

Its job is simple. On a sloped roof, everything running down the slope hits the back wall of the chimney and stops there: rainwater, melting ice, leaves, twigs, the grit that washes off asphalt shingles. The chimney is a dam. A cricket turns that dam into a wedge, so water and debris meet a peak, split, and travel around both sides of the chimney instead of collecting behind it.

A cricket is not flashing, and flashing is not a cricket

These two get mixed up constantly, so here is the difference. Flashing is metal that seals the joint between the chimney and the roof. A cricket is structure that changes where the water goes before it ever reaches that joint. Flashing is the seal. The cricket is the diversion.

A cricket has its own flashing where it meets the chimney and where it meets the roof, so the two work together rather than replacing one another. That is also why a chimney can have brand new flashing and still leak: the new metal is being asked to sit in standing water and wet debris every time it rains. Metal in a puddle fails. Metal that stays dry lasts. If nobody addresses why water is pooling there, the next flashing job has the same short life as the last one.

Which chimneys need one

Two things decide it: how wide the chimney is across the slope, and how much roof drains onto it.

• Wide chimneys on a sloped roof. The wider the chimney measured across the slope, the more water it dams up and the further that water has to travel sideways to get around it. Standard residential building code calls for a cricket where a chimney more than 30 inches wide passes through a sloped roof.
• Steeper pitches make it worse. More pitch means more speed and more volume arriving at the back wall at once.
• Chimneys low on the slope. If there is a lot of roof above the chimney, all of it drains down onto that one spot.
• Trees overhead. Debris is the quiet half of this problem. Leaves and needles pack in behind the stack, hold water like a sponge against the brick and the flashing, and never get a chance to dry.

A narrow chimney near the ridge, or a chimney coming up through a flat roof, generally does not need one. There is almost nothing for it to dam.

Signs a missing or failed cricket is your problem

• Flashing that keeps failing on the same side. Repeat repairs on the uphill face are the clearest signal there is.
• Debris packed behind the stack. If someone shows you a photo of the back of your chimney and it looks like a compost pile, water has been sitting there for a long time.
• Ceiling staining on the chimney’s uphill side. Where the stain sits relative to the slope tells you more than how big it is.
• Shingles curled, worn thin or rotted in that pocket while the rest of the roof still looks fine.
• Rust marks or a chalky white bloom on the back brick, which is masonry that stays wet longer than the rest of the chimney.
• A cricket that exists but was built too shallow, or one whose flashing has separated. A cricket with too little slope holds water in its own valleys and creates the problem it was meant to solve.

If that describes your roof, a chimney cricket installation deals with the cause instead of resealing the symptom every couple of years.

What I look at before I tell you that you need one

I measure the chimney across the slope, look at how much roof drains onto it, and check what is already sitting behind it. Then I photograph the uphill face: the debris line, the shingles in that pocket, the flashing, the condition of the brick. When I come down, I show you those pictures on my screen so you are looking at your own roof rather than a description of it.

Sometimes the honest answer is that your chimney is narrow enough, or high enough on the slope, that a cricket is not warranted and the flashing simply needs to be done properly. I would rather tell you that than sell you a structure you do not need. Either way, you get a written estimate for what I actually recommend and nothing else.

If the same corner of your ceiling keeps staining after the same repair, call or text me at 214-300-5295. I will get up there and show you what is happening behind your chimney.