When it comes to home maintenance the chimney is often overlooked. After all its way up on the roof and often times it’s simply not accessible for a homeowner to inspect thoroughly without the proper equipment and/or climbing experience. In this series, we will address some common chimney issues like Chimney Leak and how to properly address these potential water penetration concerns.
Chimney leaks can develop from a number of situations but let’s start with the most common type of leaks associated with chimneys which are poor flashing details. A chimney can be cosmetically appealing and still have problems that could have been avoided if certain steps had been taken during the construction or reroofing process. When siding is being replaced on a chimney that coincides with a reflashing project it’s a good idea to install an ice and water shield underlayment at the base of the chimney on all sides with the ice and water shield is turned up the wall a minimum of 4” behind where the siding will be reinstalled. This is a great backup to the flashing that will follow. This application is also effective on brick chimneys. Simply turning the ice and water shield up the brick 4-6” will create the same secondary defence against water leaks. Ice and Water Shield is a 36” wide underlayment so that leaves 30-32” of protection on the roof deck as well. There are several brands of Ice and Water Shield on the market. We use WinterGuard made by CertainTeed or StormGuard by GAF. We find that while WinterGuard has great elastomeric properties and a finely granulated finish for terrific walkability, the StormGuard has the superior adhesive ability.
Now that we have peace of mind with our Ice and Water Shield underlayment we can focus on the flashing. We begin the low point of the chimney by installing an open-wall flashing which typically comes formed at 120 degrees so that it fits nicely against the vertical wall of the chimney face and then out onto the roof where it should cover the shingle by 5”. The vertical portion of this open-wall flashing will extend up behind the siding or on the outside of the brick on a masonry chimney. The sides of the chimney should be step flashed when possible using galvanized pieces. Step flashing comes in standard sizes of 8” x 8” or 7” x 8” but custom sizes are sometimes required depending on unique situations. These pieces are hand bent in half on-site at a 90-degree angle. Step flashings are installed, again, behind the siding or on the exterior of the brick. Each shingle that meets the wall will have its own piece of step flashing that sits on the shingle headlap and which will be hidden by the next shingle installed. Where the step flashings are fastened is important. Fastening on the roof deck side is typically all that is necessary and the fasteners should be placed halfway up and as far from the wall as possible to avoid water contact with the nail head which could eventually rust and leak. The topside of the chimney can vary in the flashing requirements. Where applicable a chimney cricket should be installed. A chimney cricket is a small ridge that meets the back of the chimney horizontally from the roof deck that forms a valley on either side in which evacuating water is directed around the chimney to prevent damming. Once the cricket is in place the same step flashing technique should be applied.
To finish off the flashing project the siding is simply replaced on a wooden chimney. Check the siding caulking before it’s painted for shrinkage or gaps but otherwise, you should be done. As for our brick chimney, we have a few more steps. After the step flashing and shingles have been installed we need to prevent water from running down behind our step flashing since we turned them up on the outside of the brick. This is accomplished with counterflashing. Counterflashing comes standard 6” tall and 10’ long but, again, custom sizes can be necessary. The most common application of counterflashing is the cut method. Using a saw or grinder with a diamond blade the brick wall will be cut leaving a shallow groove to accommodate the “V” bend at the top of the counterflashing. This will allow for the “V” to be tapped snuggly in place and is then caulked with an elastomeric polyurethane sealant for additional water prevention.
Attention to detail is extremely important when flashing chimneys. The simplest oversight can become a homeowner’s headache and can be costly in damage repair resulting from leaks. At Discount Roofing, we focus on each step during installation. We strive to continue discovering innovation so that our customers rest well in the assurance that we’ve combined the best products and years of experience to provide the best roofing service available in Conroe and Southeast Texas.
1110 North Loop 336 West, Conroe, Texas 77301
|Oak Ridge North|
|San Jacinto County|