Installing Chimney Flashing Systems - Flashing Chimneys

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When installing a chimney flashing system there are many different ways to flash a chimney. Chimneys are the most common leak source in the residential roofing industry. The chimney leak areas are commonly caused by many things, one way is by ponding water in the area behind the chimney, which is prone to serious leaks due to the non-moving water aspect. Flashing leaks, which normally are at the seams at the chimney sides are leak roof flashing as well. And finally ice dams, when snow and ice get stuck behind the chimneys, a leak can occur.

One way to keep chimneys free from leakage is to install a chimney cricket. Chimney crickets make very good sense, they divert the water, and crickets keep water flowing around the chimneys instead of the water flowing through the chimneys causing major water damage. Installing chimney crickets can reduce ponding issues, reducing the ponding of water from behind the chimney itself. They reduce ice back-up; crickets keep the ice from building up behind chimneys. They also deflect water away from seams, properly installed chimney crickets keep any water flowing away from the chimney seam.

Chimney crickets are needed on all roofs steeper than 6/12 to handle water volume on the roof. On all chimneys that are wider than 24" to reduce ponding water problems. And on all chimneys in the north due to ice dams, snow loads, and the freeze-thaw cycle. Making chimney crickets can be somewhat a tedious job. They are manufactured from either wood or metal. Wood crickets are easy to manufacture, are available on site, finish with shingles to match the roof. Metal crickets are custom made using non-corroding metal which is required. They conform to lower slope roofs, require no finishing and are also easy to install.

Cricket sizes differ depending on what size roof you are working on. They can extend from 6" up the chimney back at a minimum, to handle the splash and volume of water exposure. They can also extend 12" up the roof plane to create a wide enough water diverter.

Another way to flash a chimney is to use the underlayment at chimney system. Install a shingle-mate or deck armor roof deck protection all around the chimney sides, over wood crickets. Do not run the shingle-mate or deck armor up the chimney sides so that the leak barrier can be sealed to the chimney sides. Install weather watch or storm guard leak barrier over the shingle-mate or the deck armor roof underlayment to waterproof this area. Seal to the chimney sides at least 5" up the walls to completely seal off any water infiltration. This protects form any movement or settling, chimneys and roof decks move independently so this makes sense since the leak barrier adhered to both could split or crack with structural movement.