The purpose of chimney flashing is to create a waterproof barrier between the front, back and sides of the roof structure. When you begin to notice leaks around your chimney or stains on your ceiling from moisture it may be time to replace the flashing.
All the materials you will need for this job can be purchased from your local hardware store. To help you with this process we have compiled a comprehensive 6 step how to guide.
The first thing you will want to do is to remove the old flashing from the chimney. This can be done by using a chisel and hammer to scrape away any cement and other materials.
The next step is to cut the base flashing, you can either do this yourself or have a hardware shop cut them down to size. If they are cut correctly they should fold down around the edge of the chimney.
Once you are confident that the flashing fits around the chimney well you will need to secure it. You will know that it fits when all areas are flat against the surface and the area the lies straight with the roof should overlap the shingles. In order to secure it you will need to bend the clipped flashing around the chimney and then hammer in 4 galvanised roofing nails in the areas lying against the roof.
You will then need to work on attaching the corner and step flashing. Check that the piece of flashing neatly fits into the front corner- it should be around 8 inches. Once you are confident it will fit, put it to one side and place a small amount of caulk onto the corner where the roof and chimney meet. You should then place the flashing onto this and hold it in place for a minute. After it is in place, you will need to hammer 2 roofing nails into the flashing/roof. Secure a shingle over the corner flashing using a hammer and nail. You will then place another piece of flashing against the chimney which overlaps the shingle. Then secure another shingle over this piece and continue to repeat this process until all around the chimney is covered.
In this step you will need to secure the chimney saddle which starts by fitting it around the back of the chimney. Once you are happy with the positioning you will need to use a hammer and roofing nails to attach the saddle into the roof with a nail being every 6 inches. You then place shingles over the flat part of the saddle and nail them and the saddle into the roof.
The final step is to install cap flashing all around the chimney starting by using a circular saw to cut small groves around 2.5cm deep into the mortar joints. The height of this should match your pre-cut cap flashing. Once this is done proceed to fit the cap flashing around the chimney and secure it by inserting the flashings flange into the groove in the mortar. To finish it off you will need to drill a hole on each side of the chimney and hammer in plastic anchors, ensuring that each piece of flashing overlaps the next. Finally, to secure everything you should use caulk to seal the mortar joints.
In following these 6 simple steps you should be able to successfully reinstall your chimney flashing, securing your home and increasing the longevity of your chimney and fireplace.