Chimney Cricket: When Code Requires One, How to Build It, and 2026 Install Cost

By The Roofing Brief Team. Last reviewed: October 2026.

Chimney cricket cost is $700 to $1,300 for a framed and flashed cricket in the This Old House chimney repair cost guide (Mar. 2026), and published contractor figures run from $300 to $6,000 depending on whether masonry and flashing work ride along. A chimney cricket is a small framed peak built on the uphill side of a chimney to divert water and debris around the chimney instead of letting it pool against the upper face. 2021 IRC Section R1003.20 requires a cricket where a chimney’s dimension parallel to the ridgeline is greater than 30 inches and the chimney does not intersect the ridgeline. Replacing the flashing around the rest of the chimney at the same time adds to the cricket price. Without one, the back of a wide chimney is prone to leaks however good the flashing is.

Chimney cricket decision table: required, optional, and what to budget

If your chimney or roof has…	Cricket required?	What to do and budget	Source
Width parallel to the ridge of 30 inches or less	No	Optional saddle if the back face collects debris or has leaked	IRC R1003.20
Width over 30 inches, chimney below the ridge	Yes	Size height H from Table R1003.20; budget $700 to $1,300 for the cricket	IRC R1003.20; This Old House, Mar. 2026
Width over 30 inches, chimney intersects the ridgeline	No	Flash the chimney as a ridge penetration	IRC R1003.20
A reroof planned	Same rule	Add the cricket while the deck is open; Yahoo’s March 2026 cost report says that usually costs much less than a later retrofit	Yahoo, Mar. 10, 2026
A stand-alone retrofit with masonry or flashing repairs	Same rule	Expect quotes up to $3,000 to $6,000 from chimney companies that include masonry work	Full Service Chimney
Roof slope under 2:12	Same rule	Build a tapered-insulation cricket under the membrane; asphalt shingles are not allowed below 2:12	IRC R905.2.2

What a chimney cricket actually does

A chimney sitting on a sloped roof acts like a small dam, and on a 48-inch fireplace chimney that dam is 4 feet wide. Water flowing down the roof field hits the uphill face, fans out sideways, and either flows around the chimney corners or pools against the back face. Debris (leaves, twigs, asphalt granules from aging shingles) collects in that pooled water and creates a wet wedge against the brick. Over time, the saturated debris breaks down flashing sealant, drives water sideways through reglet joints, and starts chimney flashing leaks that no amount of caulk will fix.

A cricket eliminates the dam, which is why IRC R1003.20 makes it mandatory past 30 inches of width. Related: Roof cricket design and install (broader). The framed peak takes the water flowing down the roof and splits it into two streams that run past the chimney corners. Debris has less room to collect because there is no flat catchment, and sealant stays drier. A correctly built cricket keeps the back of the chimney flashing out of standing water, which helps it last.

When code requires a cricket

The 30-inch threshold appears in 2021 IRC Section R1003.20, and ICC’s online library shows the same language in the 2015 IRC. The code text reads: “Chimneys shall be provided with crickets where the dimension parallel to the ridgeline is greater than 30 inches (762 mm) and does not intersect the ridgeline. The intersection of the cricket and the chimney shall be flashed and counterflashed in the same manner as normal roof-chimney intersections. Crickets shall be constructed in compliance with Figure R1003.20 and Table R1003.20.” The roofing chapter repeats the rule in Section R903.2.2, which adds: “Cricket or saddle coverings shall be sheet metal or of the same material as the roof covering.”

The measurement is straightforward: stand uphill of the chimney and measure the chimney width parallel to the ridge. If that dimension exceeds 30 inches and the chimney does not meet the ridge, a cricket is required.

Chimney width parallel to the ridge	Cricket required by R1003.20?
30 inches or less	No (a cricket or saddle is optional)
Over 30 inches, chimney below the ridge	Yes
Over 30 inches, chimney intersects the ridgeline	No

Table R1003.20 then sets the cricket height (H) as a share of the chimney width (W), based on roof slope:

Roof slope	Cricket height H (Table R1003.20)	H on a 36 in. chimney	H on a 48 in. chimney
12:12	1/2 of W	18 in.	24 in.
8:12	1/3 of W	12 in.	16 in.
6:12	1/4 of W	9 in.	12 in.
4:12	1/6 of W	6 in.	8 in.
3:12	1/8 of W	4.5 in.	6 in.

Source: 2021 IRC Table R1003.20; the height columns are Roofing Brief arithmetic.

Some jurisdictions follow IBC (commercial code) instead of IRC for chimneys on multi-family or mixed-use buildings. The IBC’s roofing chapter (Section 1503) carries a similar 30-inch cricket rule. Local amendments can change the requirement, so check your jurisdiction’s adopted code before specifying.

Cricket geometry: how to size it

The cricket has three controlling dimensions, two of them labeled W and H in IRC Figure R1003.20: width (how wide it spans behind the chimney), length (how far it extends uphill from the back face of the chimney), and height, which the code ties to roof slope.

Width

Figure R1003.20 sizes the cricket to the full chimney width (W), so a 36-inch chimney gets a 36-inch cricket base that spans the whole back of the chimney. Any extra width past the corners is a design choice to settle with your roofer and the flashing details.

Length

The classic rule of thumb sets cricket length (uphill projection) equal to half the chimney width, and it lines up with the code. With the heights in Table R1003.20 and a level cricket ridge, the cricket reaches the roof surface about half the chimney width uphill, measured horizontally, at every slope in the table. A 36-inch chimney gets a cricket about 18 inches long. On a 4:12 roof, that cricket is 6 inches tall at the chimney (36 divided by 6). Low-slope roofs get the shortest crickets, so check the shingle manufacturer’s minimum slope for the cricket faces as well.

Height and slope

Rather than a single minimum slope, the IRC sets cricket height by roof slope in Table R1003.20: one-half of W at 12:12, one-third at 8:12, one-quarter at 6:12, one-sixth at 4:12 and one-eighth at 3:12. Follow the table, the shingle manufacturer’s instructions and your local code.

Worked example

A 42-inch wide chimney on an 8:12 main roof.

• Cricket width at base: 42 inches, the chimney width (W)
• Cricket height at the chimney face: one-third of W on an 8:12 roof per Table R1003.20, so 42 divided by 3 = 14 inches
• Cricket length uphill: 14 inches of rise at 8 in 12 needs 21 inches of horizontal run (14 x 12 / 8), which is half the chimney width
• Cricket falls to 0 at the uphill point

Materials list for a typical 36-inch chimney cricket

Material	Spec	Quantity	Notes
Center ridge board	2×6 SPF	1 piece, 24 inches	Cut to cricket length
Hip rafters	2×4 SPF	2 pieces, 30 inches	From ridge to chimney back corners
Sheathing	1/2-inch CDX plywood	1 sheet (use scrap)	Two triangular panels
Underlayment	Ice and water shield	1 roll partial	Full coverage, lapped onto chimney
Step flashing	Aluminum 4×6 inch	8 to 10 pieces	One per shingle course up cricket sides
Head flashing	Aluminum, fabricated	1 piece	Spans uphill cricket peak
Counter flashing	Aluminum or copper	Fabricated to fit	Saw-cut reglet bedded
Sealant	Polyurethane	2 tubes	NPC Solar Seal 900 or similar
Roofing nails	1.5-inch galvanized	1 lb	Deck nailing only

Materials are a small share of the job. The Fixr roof repair cost guide (January 2026) says labor is at least 60% of roof repair cost and can approach 90% on flashing-type jobs, with roofers charging $50 to $120 per hour.

Step by step: how to build a chimney cricket

The ten steps below use a 36-inch chimney on a 6:12 roof as the example: per Table R1003.20 the cricket is 9 inches tall at the chimney (one-quarter of W) and about 18 inches long uphill. Skipping or reordering steps leaves a layer lapped the wrong way.

Step 1: layout

Snap chalk lines on the roof deck for the cricket footprint: a triangle with the base running across the back of the chimney and the apex pointing uphill at the calculated length. Verify the lines are perpendicular to the chimney face and the apex is centered, 18 inches uphill on the 36-inch example.

Step 2: cut and set the ridge board

Cut a 2×6 to cricket length (about 18 inches on the example, plus the plumb cut at the chimney). Set it on edge running from the back face of the chimney to the uphill apex. Toe-nail to the deck on the apex end. The chimney end of the ridge board butts against the brick. Trim the chimney end to match the slope of the main roof so it sits flat against the deck.

Step 3: cut and set hip rafters

Cut two 2×4 hip rafters running from the ridge board down to the back corners of the chimney, each about 25 1/2 inches long in plan on the 36-inch example (the diagonal of an 18 by 18 inch triangle). The bird’s mouth at the corner end should sit flush on the deck. Toe-nail each rafter to the ridge board and to the deck. Verify the hip lines are straight from corner to apex.

Step 4: sheath the cricket

Cut two triangular plywood panels from 1/2-inch CDX. Each panel covers one slope of the cricket. Nail to the ridge, hip rafters, and deck with 8d nails at 6 inches on edges and 12 inches in the field. Sheathing should butt tight against the brick face at the chimney end and end flush with the deck at the apex.

Step 5: ice and water shield

This is the most critical step and the one most often skipped. Apply self-adhered ice and water shield (Grace Ice and Water Shield, Henry Blueskin, GAF StormGuard, or equivalent) to cover the entire cricket sheathing, lapping at least 6 inches onto the main roof deck downhill, 4 inches up the chimney face on all sides, and extending past the cricket apex onto the deck above by at least 12 inches. See ice and water shield for membrane specs and application detail.

Step 6: install apron flashing across the back face of the chimney

This is the metal that catches the divided water streams coming off the two cricket faces and routes them around the chimney corners. Hem the lower edge to prevent capillary creep. Lap onto each cricket face by at least 4 inches.

Step 7: install step flashing up the cricket sides

Each shingle course up the cricket side gets one piece of step flashing, lapped 2 inches over the piece below, nailed only to the deck and only on the high side. Same detail as standard sidewall step flashing installation. The flashing turns up 4 inches onto the brick.

Step 8: install head flashing at the cricket apex

At the uphill apex, a head flashing piece spans across the peak of the cricket and runs up under the shingles above. Lap onto the membrane below. The apex is a change in roof slope, one of the locations where IRC R903.2.1 requires flashing.

Step 9: shingle the cricket

Shingles installed up the cricket faces in matched courses, woven into the main roof shingles at the cricket base. Cut shingles tight along the chimney face. Hand-seal all cut edges with asphalt sealant. IRC R905.2.2 allows asphalt shingles down to a 2:12 slope, with double underlayment from 2:12 to 4:12, so check the slope of each cricket face before choosing shingles over metal.

Step 10: counter flashing

Saw-cut a reglet groove into a mortar joint of the chimney face along the cricket sides and apex line. Fabricate counter flashing to fold into the reglet and turn down over the step flashing. Bed in polyurethane sealant. See counter flashing for the install detail.

Cricket install cost 2026

Scope	Typical cost	Source
Chimney cricket, framed and flashed	$700 to $1,300	This Old House, Mar. 12, 2026
Cricket quoted by a Cincinnati roofer	$300 to $700	Weller Roofing, cited by Yahoo, Mar. 10, 2026
Cricket installed by a chimney company, all told	$3,000 to $6,000	Full Service Chimney (Kansas City)
Chimney flashing replacement plus a new cricket, galvanized or aluminum	About $1,100 to $3,000	Roofing Brief estimate: Angi’s $400 to $1,600 flashing range plus This Old House’s cricket range
Full rebuild with cricket on a 40-inch chimney, in copper	About $1,800 to $4,100	Roofing Brief worked example built from This Old House cricket pricing and retail copper prices

For a line-by-line view of what a cricket adds to chimney flashing cost, see our what a cricket adds to chimney flashing cost breakdown.

Retrofit installs can cost more because the existing shingles around the chimney have to come up, the job is billed at the $50 to $120 hourly labor rates Fixr reports, the deck has to be exposed, and matching shingles to the existing field is harder. A Yahoo cost report (Mar. 10, 2026) quotes Weller Roofing, a Cincinnati roofer, at $300 to $700 and Full Service Chimney, a Kansas City chimney company, at $3,000 to $6,000. If your chimney needs a cricket and a reroof is coming up, evaluate doing it as part of a full reroof rather than a stand-alone retrofit. See roof repair cost guide for broader context on bundling repairs.

Three common build mistakes that cause leaks

Mistake 1: cricket too short

A cricket built shorter than Table R1003.20 calls for can hold water against the chimney. On a 6:12 roof the table sets cricket height at one-quarter of the chimney width, or 9 inches on a 36-inch chimney, so a 4-inch-tall cricket there is undersized. Check the height against the table for your roof slope.

Mistake 2: no membrane wrap

Building a cricket with felt underlayment instead of self-adhered ice and water shield (an ASTM D1970 membrane) is a common shortcut. The cricket valleys see concentrated water flow and ice accumulation in northern climates. Felt is more vulnerable there, so self-adhered ice and water shield is the safer choice for a cricket; follow the shingle manufacturer’s instructions and local code.

Mistake 3: caulking instead of cutting a reglet

IRC R1003.20 requires the cricket-to-chimney intersection to be flashed and counterflashed like any roof-chimney intersection, so the counter flashing has to be bedded into a saw-cut reglet groove in the masonry. Turning the metal up against the brick and caulking the top edge to the face relies on caulk alone and is likely to leak once the caulk ages. Always insist on a saw-cut reglet for counter flashing on a cricket.

Alternatives to a true framed cricket

Two alternatives show up on smaller chimneys where a full framed cricket is overkill.

Built-up roofing cricket

Instead of framing, the roofer builds up a cricket shape using stacked layers of self-adhered membrane and tapered insulation board. Works on low-slope or flat roofs below 2:12, where IRC R905.2.2 rules out asphalt shingles anyway. Not appropriate on shingle roofs at residential scale.

Pre-formed metal saddle

For chimneys at the 24 to 30-inch threshold where a full framed cricket is not required, pre-formed copper or aluminum saddles can be ordered to size. These are folded metal triangles that sit on top of the deck without framing. Some manufacturers sell pre-formed saddles in stock chimney widths. Effective but limited in scale. See our roof saddle installation guide for the pre-formed detail.

Can you build a cricket yourself?

If you are comfortable on a steep-slope roof (paid crews need fall protection from 6 feet up under OSHA 1926.501(b)(13)), can read framing layouts, and have done at least one full shingle install, a small cricket on an accessible roof is within reach. The framing and sheathing are basic carpentry. The membrane work requires care but is forgiving. The metal work is where DIY attempts go wrong: fabricating step and counter flashing without a metal brake, cutting a clean reglet with a grinder, and bedding sealant cleanly are all skills that take practice.

Realistic DIY scope: frame and sheath the cricket, install ice and water shield, shingle the cricket faces. Bring in a sheet metal pro for the flashing work, which is where Fixr’s 60% to 90% labor share lands.

Cricket vs no cricket: what happens long term

Without a cricket, the back of a chimney wider than 30 inches holds water, snow and debris against the flashing. That keeps the back flashing and its sealant wet, which is the pattern behind many back-face leaks, and it can speed wear on the masonry above.

With a correctly built cricket, water and debris split around the chimney and the back flashing stays drier.

We have not found a published study that puts a dollar figure on the repairs a cricket prevents, so weigh it against your own leak history. A cricket costs $700 to $1,300 per This Old House, and on a chimney wider than 30 inches parallel to the ridge it is a code requirement anyway.

Frequently asked questions

Does every chimney need a cricket?

No. 2021 IRC Section R1003.20 requires a cricket only where the chimney is wider than 30 inches parallel to the ridge and does not intersect the ridgeline. A typical 16×16 single-flue chimney does not need one. A wider double-flue or fireplace chimney does.

Can a cricket be added without tearing off the roof?

Yes, but it costs more. The roofer will pull shingles in the cricket footprint plus a margin around it to integrate the new membrane and step flashing into the existing field. Matching new shingles to an older, weathered roof is the main challenge. This Old House prices the cricket itself at $700 to $1,300.

What slope should a cricket be?

2021 IRC Table R1003.20 sets cricket height by roof slope rather than a single minimum: one-half of the chimney width at 12:12, one-third at 8:12, one-quarter at 6:12, one-sixth at 4:12 and one-eighth at 3:12. A cricket built shorter than the table calls for can hold water and debris against the chimney.

Is a cricket the same as a saddle?

The terms are used interchangeably in residential roofing. Some pros reserve “saddle” for pre-formed metal pieces and “cricket” for framed structures. The IRC treats them as one: Section R903.2.2 is titled “Crickets and saddles” and applies the same 30-inch rule to both.

Should I add a cricket if my chimney is exactly 30 inches wide?

Code requires a cricket only when the width parallel to the ridge exceeds 30 inches. At exactly 30 inches it is optional. If the back of the chimney already collects debris or snow, or has leaked before, a cricket is worth pricing; This Old House puts the cost at $700 to $1,300.

Bottom line

The chimney cricket is one of the most effective upgrades on a roof with a wide chimney. 2021 IRC Section R1003.20 requires it once the chimney is wider than 30 inches parallel to the ridge and does not meet the ridgeline, and it addresses a leak pattern that flashing alone cannot fix. Build it during a reroof if possible, since Angi notes that bundling flashing work with a reroof can cut labor. Insist on a cricket height that meets Table R1003.20, a full ice and water shield wrap, and saw-cut reglet counter flashing. If your roofer wants to skip any of those three, get another quote. For broader flashing context, see what is flashing on a roof and roof flashing.