Is there any leakage in your roof? Often leaks in the roof are caused by leakage in flashing and the flashing is used to protect chimneys, dormers, and vents. So, you may want to know how to seal a metal roof around a chimney.

It requires a lot of work to seal a metal roof around a chimney. But, no worries. It’s not that tough. You need to focus on the step-by-step guideline and do all the steps properly.

Read this article to get your work done.

How To Seal A Metal Roof Around A Chimney: Step To Follow

Sheet metal flashings are nearly always to blame for chimney leaks. And, leaking flashing can channel streams into a home since flashing is typically utilized where there is a lot of water flow.

So, knowing how to seal a metal roof around a chimney will be a great help. Before starting the sealing techniques, you should take proper safety measures. Then, following the steps one by one will lead to your success.

Necessary Tools To Seal A Metal Roof Around A Chimney

It will be easier to seal if all the necessary tools are gathered before starting the process. Necessary tools to seal. The required tools are as follows:  

Safety Equipment

Your safety is our priority. So, gather all the safety equipment and wear the necessary safety gear. Necessary safety equipment are;

  • A sturdy extension ladder
  • Roof brackets
  • 2×10 planks
  • A safety harness
  • Lanyard
  • Rope-grab
  • Rope, and 
  • Roof anchor.
  • Hand gloves
  • Goggles
  • Dust masks
  • Hearing protection

The step-by-step guideline is explained in the rest of the article.

Step 1

Before starting, determine the roof’s slope. Then, Place a piece of prebent bottom flashing to cover the front of the chimney and make sure it fits. To curve around aside, make a 45-degree bend.

Step 2

On the opposite end of the chimney, mark the edge and cut and bend the flashing end. Then put the flashing and to keep the flashing in place, pound four equally spaced 1-in. galvanized roofing nails into the front edge.

After you’ve finished tearing out and cleaning up, shingle up completely to the tip of the chimney and seal it with 12-inch wide ice-and-water barrier strips. Across the top of the chimney, run a 36-inch-wide strip. Stick this portion to the roof panels and 8 inches up the chimney’s rear. 

Complete the installation of the first flashing piece of the base.

How To Seal A Metal Roof Around A Chimney? [Step-By-Step Guide]

Step 3

To fit 1-1/2 in. in the front side, cut and twist a portion of prebent 8-in. square step flashing. Apply a dab of caulk the size of a jelly bean to the corner where the chimney joins the roof. Nail the corner step flashing to the roof with two roofing nails after embedding it in the caulk.

Step 4

Over the first step flashing, place the next shingle in place. Then, over this shingle, nail a new step flashing. Continue climbing the chimney until you reach the top corner. The final step flashing all around top should be cut and bent.

Step 5

Nail the saddle to the roof and seal it with extra membrane strips to finish the base flashing. Cut the shingles precisely along the valley, leaving approximately 2 inches of metal exposed. Shingle over the section of the saddle that sits on the roof.

Step 6

To accommodate the L-shaped cap flashing, cut 1-inch deep slots in the mortar. Use a circular saw or a grinder with a dry-cut diamond blade. 

Step 7

Extend the front cap flashing 8 inches longer than the chimney’s width and twist it around the chimney’s front corners.

Step 8

Push the cap flashing’s flange into the mortar joint’s groove. To avoid denting the flashing, use a piece of wood.

Step 9

On every side of the chimney, drill a 3/16-in. x 1-1/2-in. big hole via the metal and towards the bricks. Then, to expand the anchor and attach the flashing, squeeze the expanding plastic anchors further into holes then hammer in the drooping nail.

Step 10

Snip the side cap flashing to match the roof’s angle and overlap every lower cap flashing by at least 2 inches. Drive in the extending anchors and hammer the flashing into the holes. 

Bend and install the cap flashing around the rear of the chimney.

Step 11

Fill the gap with polyurethane caulk once all of the cap flashings have been installed.


I hope you’ve understood how to seal a metal roof around a chimney. So, follow the step-by-step guideline and get your work done.

Don’t skip or miss any step. Skipping any steps will be a pain later. Make sure to be safe.

All the best.


As a civil engineer and roofer, I love to share the experience that I have gained through the last couple of years. In the roofing industry, practical experience is a very crucial fact that can help you a lot. Hence, I want to help you with my blog.

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