We have heard quite a bit about water leaking in through roofs right around where the chimneys are in many homes. Because of all these recent leaks showing up, we thought we would research how home owners can prevent this.
These water leaks are probably due to bad flashing between the chimney and the roof. The reason for chimney flashing is two-fold. First, it seals the joint between the chimney and the roof to protect it against rain and snow. Second, it accommodates movement between the chimney bricks and the roof.
Chimney flashing has four types, and all must be used and installed properly to prevent roof leaks. First is the base flashing that goes on the lower face and covers the front of the chimney and also wraps around the sides. Next is the step flashing. This is nailed to the roof deck and then bent up along the side of the chimney. Next would come the cricket, which is put in behind the chimney. Last is the cap flashing, which is set into the chimney mortar joints and then bent over the step flashing and the sides of the base flashing. Water will run off of the cricket and the cap flashing down the roof and over the step and base flashing.
So if your roof is leaking in the chimney area, you have to check the flashing at the joints of the chimney to try to find the leak. It could be faulty installation, or lack of installation of one of the necessary flashings. We are told that in many instances, cap flashing is missing, most commonly found after re-roofing jobs are done. Roofers tend to use asphalt cement to seal the joint between step flashing and the chimney, and this can cause leaks where the flashing meets the chimney. If this is the problem, you should have a mason correct it, because it is skilled work and must be done properly.
Lastly, the other common cause of leaks is if a cricket was not installed, especially if the width of the chimney is greater than two feet. By the way, a cricket is sometimes also referred to as a saddle. A cricket should be installed and join the roof and chimney. The cricket prevents snow and ice from building up behind the chimney. If this happens, water can build up and get under the shingles and leak into the house. The cricket deflects water around the chimney and down the roof to the gutters.
Hope this little tidbit helps answer those questions about leaks around the chimney!