Chimney Crickets (Saddles): When a Roof Needs One

A chimney needs a cricket, a small peaked roof framed on the chimney’s uphill side, when the chimney is wide enough that water, leaves and snow would pile up against it instead of flowing around. Local codes set the width that triggers one; in Lincoln, Nebraska, for example, the city’s re-roof policy requires a cricket on chimneys 30 inches or wider.

So the question has two parts: how wide your chimney is on the side that faces up the roof, and what your town’s code says about that width. If the answer is yes, a re-roof is the practical time to build it, because the shingles and flashing around the chimney come off anyway.

What a Cricket Does Behind a Chimney

Water running down a roof slope hits the uphill face of a chimney and has to go somewhere. On a narrow chimney it splits and flows around both sides. On a wide one, the water slows and collects in a flat pocket between the chimney and the roof, along with leaves, granules and, in winter, snow and ice. The flashing at that joint can then sit under standing water and wet debris instead of shedding it.

A cricket changes the geometry. Its ridge points up the slope and splits the flow, and its two small valleys carry water and debris around the chimney’s sides. Flashing seals the joint between chimney and roof; only shape moves water away from it. That is why new flashing or a bead of sealant on a wide chimney does not solve a pocket that keeps refilling.

Masonry pays for the water that stays. The Chimney Safety Institute of America wrote in a 2010 article on preventing major chimney water damage that “water causes more damage to masonry chimneys than fire.” The crown, cap and counterflashing above the roof line are a separate set of defenses, covered in flashing, crown and cap.

Your Local Width Trigger and How to Measure Your Chimney Safely

The 30-inch example comes from Lincoln’s Re-Roof Policy, dated December 10, 2021 and written against the 2018 edition of the International Residential Code (IRC), the model code the city builds its local rules on. It requires what it calls “chimney flashing (also referred to as a cricket or saddle)” on chimneys that are 30 inches or wider.

Measure the face of the chimney that looks up the slope, the side water runs into. Then ask your building department to confirm that is the dimension its code measures.

You do not need to go on the roof to get the number:

• From the attic. Where the chimney passes up through the roof framing, measure its width with a tape on the uphill side. Step only on framing or a walkway, wear a headlamp and a dust mask, and do not disturb insulation or fire-stopping around the chimney. If the insulation is loose, pebble-like vermiculite, EPA’s page on vermiculite attic insulation advises treating it as possibly containing asbestos and leaving it undisturbed, so look from the hatch, leave that attic to a professional, and use one of the other two methods.
• From the ground. If the chimney rises along an outside wall at the same width from the foundation up, measure it at the base. Chimneys can narrow above the roof line, so confirm with one of the other methods if the shape changes.
• From the roofer. Ask the estimator to photograph a tape measure held across the chimney’s uphill face during the inspection and to write the width on the estimate.

If the chimney is close to the trigger, a photo with the tape in frame settles the question better than an estimate from the yard.

Why Your Town’s Code Wording Matters

The 2021 IRC has a section titled R1003.20 Chimney crickets. Treat Lincoln’s 30-inch rule as one jurisdiction’s adopted version of that requirement, not as the national wording, and read the text your own town enforces.

Three questions decide how the rule applies to your house, and the building department can answer each:

1. Which code edition is in force, and has the city or state amended the chimney cricket section?
2. Which chimney dimension does the code measure, and is the trigger “30 inches or wider” or “more than 30 inches”?
3. Does the rule treat a chimney that straddles the ridge differently? A chimney sitting on the ridge has little or no roof uphill of it, so ask whether it still needs a cricket.

The wording matters most when the chimney measures right at the trigger, or when a roofer and an inspector read the rule differently. Get the answer from the department rather than from either party. For the other code items that come up on a re-roof, see other re-roof code items.

How a Cricket Is Framed, Covered, and Flashed

Your roofer’s method and the roofing maker’s instructions govern the dimensions and specifications, so what follows names the parts you should see in photos. The basic components are defined in the guide to roof parts and their jobs.

A cricket starts as framing: a small ridge set against the chimney’s uphill face, sloping down to the main roof on both sides, with sheathing on its two faces tied into the existing deck. Some are built entirely from lumber and sheathing; some are formed from sheet metal. Either way, the cricket’s slopes create two short valleys where they meet the main roof.

Over the framing go underlayment, the roof covering or sheet metal, and flashing. The flashing where the cricket meets the chimney face has to turn up the masonry and be covered by counterflashing, the same way flashing works elsewhere on the chimney. The guide to flashing types explains how step, counter and valley flashing lap, and the chimney flashing guide covers the masonry side.

Ask for these photos before each stage is covered:

• The framed cricket with sheathing in place, showing how it ties into the deck.
• Underlayment lapped over the cricket and turned up the chimney face.
• Valley treatment where the cricket meets the main roof.
• Flashing and counterflashing at the chimney face after the covering is on.

Adding a Cricket During a Re-Roof

Shingles and flashing at the chimney come off during tear-off, so the added cost is mostly framing, sheathing and the extra flashing, not a second disturbance of finished roofing. Lincoln’s rule sits in a re-roof policy, which shows that at least one jurisdiction applies the requirement at replacement time.

Put it in the scope in plain words. The estimate should name the cricket, what it is built from, how it is covered and flashed, and whether new counterflashing is part of the job or left for a mason. If the chimney measures at or above your local trigger and the estimate is silent, ask why before you sign.

A cricket can also be added without a full re-roof, but then the shingles and flashing on the chimney’s uphill side have to come off and be woven back into the existing roof. If you are pricing it as a repair, ask how the cricket’s two valleys will tie into the old shingles and whether matching shingles are available.

Where a re-roof is part of an insurance claim and the cricket is a code requirement the old roof did not have, coverage for that upgrade depends on your policy; who pays for code upgrades explains the endorsement to look for. For where the cricket fits in the order of work, see the re-roof sequence, and keep the cricket photos with your final inspection papers.

Does Your Chimney Need a Cricket Before the New Roof Goes On?

If the uphill face of your chimney measures at or above your local trigger, and the chimney does not straddle the ridge, plan on a cricket and make sure it is a named line item in the re-roof scope. If the chimney measures under the trigger but leaves, ice or stains keep showing up behind it, ask the roofer whether a cricket would solve a drainage problem the code does not require you to fix. If the chimney sits on the ridge, ask the building department before anyone builds or skips one.

Get the uphill width first, from the attic or a roofer’s tape photo; then call the building department to confirm how it measures width and which edition applies, and check that the quote and the walkthrough photos show cricket framing, covering and flashing.

This guide is general information for U.S. homeowners, not legal, insurance, tax, or engineering advice. Codes, laws, and policy terms vary by location and change over time; confirm details with your local building department, your insurer, or a licensed professional.

Sources

• Four Low-Cost Recommendations to Prevent Major Water Damage, Chimney Safety Institute of America
• Re-Roof Policy (City of Lincoln, NE Building and Safety), City of Lincoln, Nebraska
• 2021 International Residential Code (IRC) – R1003.20 Chimney crickets, International Code Council
• My attic has vermiculite insulation in it. Am I at risk? Should I take it out?, U.S. Environmental Protection Agency