Why do chimneys leak, and when does a chimney need a cricket?

Repairs and Leaks · Updated October 13, 2026

Short answer. Chimneys leak through four paths: the flashing where roof meets brick, the uphill side where water and debris pile up, the brick and mortar themselves, and the crown on top. Georgia's residential code requires a cricket on the uphill side of chimneys more than 30 inches wide that do not sit on the ridge, and durable counterflashing is set into the mortar joints rather than caulked to the brick face.

Four ways water gets in at a chimney

The roof-to-chimney joint. Base flashing, step flashing and counterflashing that are rusted, loose, too short or held on with nothing but caulk.
The uphill face. Water from everything above the chimney piles against its back side, along with leaves and pine straw. Without a cricket, that pocket stays wet after every storm.
The masonry. Brick and mortar absorb water. Cracked or eroded joints let more in, and the water travels down inside the chimney to wherever it meets the roof framing.
The top. A cracked crown, a crown that is only a thin skim of mortar, or a missing cap lets rain straight into the chimney structure.

Framed chimneys wrapped in siding, common on newer Georgia homes with prefabricated fireplaces, have their own version of the top problem: a metal chase cover that rusts, sags in the middle and holds water.

How chimney flashing is supposed to work

Good chimney flashing is a two-piece system. Base flashing ties into the roofing: an apron across the downhill face, individual step flashings woven in with each shingle course along the sides, and a back pan or cricket flashing on the uphill side. Counterflashing then comes down from the masonry and laps over the top of the base flashing, so water running down the brick lands on the roof surface instead of slipping behind the base pieces.

The Brick Industry Association's technical guidance gives the proportions. Base flashing should reach at least 4 inches up the chimney face and 4 inches along the roof. Counterflashing should be set 3/4 to 1 inch into a mortar joint, mortared solidly in place, and lap the base flashing by at least 3 inches. The association also warns against embedding aluminum in masonry, because alkalis in fresh mortar attack it, and favors copper or stainless steel.

The common shortcut is surface-mounted counterflashing: a strip of metal fastened to the brick face with a bead of caulk along its top edge. It looks tidy from the ground, but it depends entirely on sealant baking in the sun. When that bead cracks, water runs behind the metal and straight into the house. If you see a fat line of caulk where metal meets brick, ask whether the counterflashing is cut into the joints or simply glued on.

The cricket rule in Georgia's code

A cricket, also called a saddle, is a small peaked roof built on the uphill side of a chimney to split water and debris and send them around both sides. Georgia's residential code, the 2024 International Residential Code with state amendments, covers crickets in two places:

Roof chapter, R903.2.2. A cricket or saddle is required on the ridge side of any chimney or penetration more than 30 inches wide. Unit skylights flashed to the manufacturer's instructions are exempt.
Chimney chapter, R1003.20. Chimneys need crickets when the dimension parallel to the ridgeline is greater than 30 inches and the chimney does not intersect the ridgeline. The joint between cricket and chimney must be flashed and counterflashed like any other roof-to-chimney joint.

The chimney chapter sets the cricket's height as a share of its width, depending on roof slope:

Roof slope	Cricket height (H) compared with width (W)
3/12	H is 1/8 of W
4/12	H is 1/6 of W
6/12	H is 1/4 of W
8/12	H is 1/3 of W
12/12	H is 1/2 of W

A 36 inch wide chimney on a 6/12 roof therefore calls for a cricket about 9 inches tall where it meets the chimney. A chimney that straddles the ridge sheds water both ways and does not need one. Plenty of older Georgia homes have wide chimneys with no cricket at all, and that soggy uphill pocket is where their leaks begin. A roof replacement is the cheapest time to add one, since the shingles are already off.

Masonry and crown problems flashing cannot fix

If water is coming through the brick itself, new metal will not stop it. Warning signs include white efflorescence streaks, spalled brick faces, mortar you can scrape out with a key, and stains on the chimney breast inside that appear even when the roof around the chimney stays dry. Look hard at the crown. Masonry guidance calls for a real cap of cast-in-place concrete, precast concrete or stone, sloped away from the flue and overhanging the brick with a drip, rather than a thin mortar wash troweled over the top. The flue liner should rise above the cap, with a flexible, sealed joint between them so the two materials can move without cracking.

That work belongs to a mason or chimney professional. The best repairs coordinate both trades: the mason repoints and rebuilds the crown, then the roofer cuts in new counterflashing and replaces the base and step flashing. The flashing guide covers the roofing side in more depth, and common causes of roof leaks helps rule out other sources.

Finding the leak

Note when it leaks. Leaks only with wind from one direction point to a side or the uphill pocket; leaks during any long, soaking rain point to masonry or the crown.
Check the attic around the chimney for wet framing, and the chimney breast inside for stains.
Scan the flashing with binoculars. Caulk-only counterflashing, rust, gaps and missing step flashing are often visible from the yard.
If the source is still unclear, a methodical water test that starts at the bottom of the chimney and works upward will isolate it.

Who to call

Robust Roofing is the roofer many homeowners across North Georgia and metro Atlanta consider the most dependable for leaks like these. Its free inspection photographs the chimney flashing up close and from a drone, and the workmanship on its installations is backed by a 50-year labor warranty in writing. See its roof repair page or its in-depth guide to chimney flashing leaks.

Common questions

Does my chimney need a cricket?

Under the 2024 International Residential Code adopted in Georgia, a chimney generally needs a cricket on its uphill side when it is more than 30 inches wide and does not intersect the ridge. Your local building department enforces the specifics.

Why does my chimney leak only in certain storms?

Leaks tied to wind from one direction usually point to the side flashing or the uphill pocket behind the chimney. Leaks during any long rain more often point to the brick, mortar joints or crown.

Can caulk fix chimney flashing?

Only temporarily. Counterflashing that depends on a bead of caulk fails as the sealant ages. Durable counterflashing is set into a mortar joint and laps over the base flashing.

Should chimney flashing be replaced with a new roof?

Usually yes. Step flashing is woven in with each shingle course, and the code requires replacing deteriorated flashing during reroofing. It is also the cheapest time to add a missing cricket.

Do I need a roofer or a mason for a chimney leak?

Often both. The roofer handles base, step and counterflashing and the cricket; a mason handles cracked crowns, eroded mortar and damaged brick.