Install Chimney Flashing – Uniflash®

Here are easy instructions to install chimney flashing.  These instructions
are written for shingles, but the process is the same regardless of whether the
roof has wood shakes or is slate, tile, or one of the new “eco-roofing” systems.

Home experts recommend that you install chimney flashing when any new
roofing is put on, since flashing should be as long-lasting as the new roof system.

Before you install chimney flashing, read this to understand how flashing
and counter flashing work together. Most chimneys today are built on a
foundation that is separate from the home, and need to have flashings that
can flex independently, without breeching the important water seal that the
flashing forms with the roofing.

The first part of these instructions shows flashings that are incorporated with
the shingles, and are fastened to the roof,  making sure that they are not fastened
to the chimney at any point, leaving the upper parts free standing.   

The second part discusses counter flashings and how they are used to steer
rainwater and melted snow safely down the roof. Counter flashings are affixed
to the chimney, leaving just the bottom part free-standing. Read these instructions
to install chimney flashing efficiently – and get the perfect result!

Step 1: Uniflash® – Install Chimney Flashing

Apply shingles up to and along the length of the chimney base,
to a place where the tar-line of the shingles is within 4 inches.
Cut the shingle material if needed.

Step 2:

Center the base flashing across the length of the chimney, extending
3-4” inches beyond each end. Remove the notch from each end, and curve
the tabs around the chimney sides.  Nail the base flashing securely, making
sure the nail heads will not be exposed, and will be underneath the
next row of shingles.

Step 3:

Remove the notch from the step flashing and curve the tab toward the front
of the chimney. Usually, step flashings are used to terminate a row of shingles
at a dormer, wall or chimney, and begin at, or close to the tar-line.

The next task is to nail the step flashing only to the roof, and at the point
where the nail head will be protected by the shingle that follows.

Step 4:

The next step to install chimney flashing is to notch and install step flashing
on the other side of the chimney and to nail it into place. Cut the shingle
material so that it fits over the step flashings and leaves a gap of about
1/4" to 1/2" from the chimney to allow water to drain. The shingles that
are installed on the other side of the chimney should be formed so they
maintain the pattern of water slotting.

Step 5:

Keep adding the step flashings, as well as shingle material, on each side of the
chimney until the shingles clear the back, making sure that the shingles merge
with those on the other side of the chimney.  When you nail these shingles down,
a good rule is to position the nail about 1” above the water slot. This helps guard
against weathering of the nail, and the corrosion this would cause.

Step 6:

Shape the final step flashing piece on each side of the chimney and set in place.
It’s an excellent idea to apply a roof cement before finally nailing down.

Step 7:

The next step to install chimney flashing is to cut the shingle to hug the back
of the chimney. This fit should be close, with practically no gap.

Step 8:

Now, you can complete your installation of the shingles along the length
of the chimney.  Nail these in place.

Step 9:

Find the center-point and affix the cricket flashing along the back side
of the chimney, letting each end go beyond each corner by 3 to 4”.
Mark this spot. Trim each end up to the mark you made, and form the
tabs around the sides. Nail to just the roof.

Step 10:

Shingles installation is nearly complete. Just make certain there are
no gaps where weather can destroy your work.

Step 11:

Now, let’s move on to counter flashings.  Install counter flashing with the top
in a straight line, around the chimney perimeter.  For both sides, use chalk
or another temporary marker to mark the tops, allowing a small space at
the shingle line for rain flow.   

Align the tops of both the back and front counter flashings with the top portion
of the side counter flashings.  Mark for reference.  Move on to the next step,
while setting the counter flashings aside for now.

Step 12:

The next step to completing the chimney flashing install is to notch the
counter flashing ends and form them around the chimney sides.

We recommend that you cut the tops evenly with the chimney corners. 
Now, form the tabs around the sides.  This step helps guard against metal
warping when bent.   Now, use masonry fasteners to fasten the counter
flashing to the chimney, making sure the brick is fit snugly to the metal. 

Step 13:

Position the side counter flashing material along the mark you made earlier,
and cut evenly with the counter flashing on the front.  Notch the back corner
and form the tabs toward the back.  Add 2 or 3 additional masonry fasteners.
Side counter flashings sometimes look wider, since they are angle-cut. Keep
the tops in a straight line for the best appearance and performance results.  

Step 14:

The final step to install chimney flashing is to mark the rear counter flashing
evenly with the corners of the chimney and position along the mark you made.
Install additional masonry fasteners.

Click link for a detailed PDF on instructions to install chimney flashing.
Download Uniflash brochure.

MOHECO PRODUCTS COMPANY
26835 West Seven Mile Road
Redford, Michigan 48240
888.814.3721 • 313.531.5630
fax: 313.531.0480
email: sales@moheco.com

© 2010 by Moheco Products Company. 
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We're a manufacturer of roofing safety equipment, construction clean-up products,
and kits to install chimney flashings.
Uniflash® patent number 5,381,632

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