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CHIMNEY INSPECTION DIAGNOSIS REPAIR
BACKDRAFTING HEATING EQUIPMENT
CARBON MONOXIDE - CO
CHIMNEY COMPONENT DEFINITIONS
CHIMNEY FIRE ACTION / PREVENTION
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
FLAME COLOR, BLUE vs YELLOW COMBUSTION
HOME HEATING SAFETY
Moisture / Frost Damaged Chimney
ODORS & SMELLS DIAGNOSIS & CURE
Safety Recalls, Chimneys, Vents, Heaters
STAIN DIAGNOSIS on BUILDING EXTERIORS
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
Chimney inspection from the rooftop: this article describes chimney inspection on the roof, reporting on flashing and leak problems, and inspecting and diagnosing cracks in the sides of a brick chimney. Page top sketch of chimney flashing defect checkpoints provided courtesy Carson Dunlop Associates.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
This article series on chimneys, chimney construction, and chimney safety provide detailed suggestions describing how to perform a thorough visual inspection of chimneys for safety and other defects. Chimney inspection methods and chimney repair methods are also discussed.
Horrible chimney flashing at the roof surface is shown in these photos which are remarkable for the number of errors, the leak history at this home, and the chances of related damage to the surrounding wood structure from insects or rot, or damage to the chimney itself from frost.
The new roof was installed with a bare half-inch of vertical side flashing along the chimney and no counter flashing. The previous roof or chimney flashing was installed with no counter flashing, relying on roofing mastic to seal this juncture. Cracks and openings at chimney flashing admit wind-blown rain into the structure.
An inspector with binocular vision might have found this crazy
flashing installation from the ground. Maybe.
Watch out: older asphalt-based roofing mastics and sealants may contain asbestos. See MASTIC, CUTBACK ADHESIVE, FLASHING CEMENT ASBESTOS.
The illustrations below, courtesy of Carson Dunlop Associates, show chimney flashing details when there is NOT a chimney saddle or cricket as well as where some of the trouble spots occur.
Question: How about some details on roof saddle construction?
[Paraphrasing: On a messy re-roof job that includes a roof section with lots of penetrations, we are cleaning up the roof design to reduce the leak risk by constructing a roof saddle or cricket.]
I see reference to "crickets" all over... your site mentions them on "Flashing & Sealing Specifications for Exposed Fastener Metal Roof Systems" page. But I have been unable to find specific instruction... models, diagrams etc., on how to build these things. What I do see around here is a lot of metal roofs.
The roofs I've checked out with the same issues that I'm asking about (vertical wall on downside slope of a roof) all were done without crickets. And every winter, I see a bucket of Henry's tar up there trying to patch the leaks. So if you have a reference for building crickets or a good book I'd sure appreciate it. -- Jim McKay, November 2010
Reply: Build a Tiny Intersecting Roof Gable, Standard Chimney Step & Counter Flashing, Valley Flashing, careful sealing
We hadn't previously thought about giving specific build instructions for a chimney cricket or roof saddle, perhaps because building a saddle is a duplication of the framing for roof construction of a tiny intersecting gable - standard carpentry.
As you'll see in our photos of chimney saddles above, the cricket or saddle will form an intersecting gable that butts against the up-roof side of the chimney.The devil is once again, in the details of forming and sealing flashing to avoid leaks from water or in some climates melting snow on the up-roof side of the chimney. A chimney saddle also avoids the accumulation of debris, leaves, etc. that shorten roof life in that area.
The length of the ridge of your cricket (or saddle) will determine the height of the cricket at the chimney and the point at which that ridge contacts the main roof slope. We make sure that the cricket ridge is long enough that the height above the roof at the chimney is high enough that we have a decent slope, 6 in 12 or more, to assure good drainage around the chimney. Of course the total length of the saddle ridge is limited if you don't have a lot of roof distance up-slope from the chimney itself. In that case the ridge of the cricket will come to the ridge of the main roof. And of course your cricket (saddle) ridge is framed level.
If the total cricket size is small, just a few feet or less, it's probably easiest to simply construct the entire supporting structure for the cricket out of 1x lumber.
Larger crickets would be framed using 2x lumber and roof sheathing. Remember that maybe not you, but someone is likely to step on the cricket sooner or later, perhaps while repairing or cleaning the chimney. So flimsy saddles and crickets are a bad idea.
Once the chimney saddle has been built and nailed into place on the main roof slope, you can proceed to cover it with metal flashing, ice and water shield etc. and then a metal cover or roof shingles or another covering that matches what's on the main slope. Some roofers cover large crickets with shingles or roll roofing, but we prefer solid metal or a membrane such as modified bitumen.
If you're covering the whole cricket with shingles, then the cricket ridge is shingled like a roof ridge, with the last ridge cap shingle where the cricket ridge meets the main roof slope done the same way as a lower roof ridge would meet a main upper slope - the last shingle has to be split, and sealed, before the shingle on the main roof slope course covers it up.
Make your flashing the feature that keeps water out of the roof. Don't rely on caulks and sealants.
Thin Cracks in Brick or Masonry Block Chimneys
Cracked chimney masonry such as shown in this photo of cracks in a brick chimney exterior, may a safety concern if the flue liner or chimney are not intact and fire/gas safe.
Cracks in a brick masonry chimney such as shown in these photographs may be caused by improper original chimney construction. This damage also appears on concrete block constructed chimneys.
See Chimney Crack Detection & Diagnosis for details about inspecting and diagnosing types of chimney cracks and movement.
WARNING: Cracks in a chimney can be very significant and dangerous, risking fire or chimney collapse. Be sure to review the articles at CHIMNEY CRACK & COLLAPSE HAZARDS.
Frequently Asked Questions (FAQs)
Questions & answers or comments about chimney flashing leaks & defects that are found by an on-roof inspection.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.