How to Attach Roof Flashing to Masonry Walls

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  • 46 hours
  • Intermediate
  • 40-60
What You'll Need
Metal flashing
Mortar sealer
Roof cement
Caulking gun
Tin snips

When you are building something that has masonry walls and wants to put a roof in it, then you will need to install the flashing over the brick. You will also need to install flashing to masonry in the event of sealing the roof near the chimney. This is an especially critical area as there are plenty of places where leaks can form. To install roof flashing to a masonry wall, or to a chimney, you will need to follow specific instructions to ensure a leak-proof seal. Here are some step by step directions to installing this roof flashing yourself.

Step 1 - Clean the Masonry First

Give the masonry walls a good rinse with some soap and water. Just go over it with a sponge and rinse the soap off of it. You do not need to do a huge cleaning job. You only want to remove things like sap, dirt, and other things that accumulate on the bricks.

Step 2 - Cut Flashing to Fit

According to where you are going to put the metal flashing you will need to cut it to fit that specific area. Mark out the measurements on the metal itself and cut out with tin snips. Use thick gloves and long sleeves for this step. The edges of the flashing can be very sharp.

Step 3 - Seal Masonry Wall

Use a good masonry sealer and spread it over the area where you are going to place the metal roof flashing. Use a regular paintbrush to apply the sealer to the brick. This sealer will help the adhesive stick to the mortar much better. Wait until the sealant becomes hard before you proceed to the next step.

Step 4 - Spread Roof Cement

Once the sealant has dried and has a hard coating to it, you can now spread out the roofing cement over the area. Make sure it covers the entire area without any gaps or air bubbles. Use a smooth spreader for this roof cement. Work carefully as it is very sticky and can end up all over the place if you are not watching out.

Step 5 - Embed Flashing

Place your flashing into the roofing cement and press it into the masonry. Smooth it out to make sure there are no bubbles or bulges. Leave some of the flashings to overhang a little.

Step 6 - Joining Two Pieces

If you have the need to join 2 pieces of flashing together, you can do this by spreading roof cement on the seams where they will meet. Spread the cement wider than the seam to make a watertight seal.

Step 7 - Install Flashing Cap

To better protect your masonry, or roof structure, from the water you should install a flashing cap. This small piece of metal will cover over the seams and create a way for water to run off. Spread out mortar on the masonry with a caulking gun. Press the cap into the mortar and seal by running your finger along the edges. Make sure there are no gaps in the mortar and there is a constant bead along the edge.