Because the primary cost of a high-end slate roof can be considerable, it is wise to conduct timely and thorough maintenance. Even though slate is an extremely durable and resistant material, there are several key points to keep an eye out for as you enjoy your roof over time. For safety reasons it is always wise to observe the roof from the ground with binoculars or from a boom lift. Although slate is a walkable roof surface, inexperienced foot traffic could result in unnecessary breakage. While performing these routine checks, it’s a good idea to document your findings. Bringing a camera and a notebook is the easiest way to keep very accurate records of your roof. Organize all your findings and roof related bills so that they are accessible for future use. Proper roof maintenance includes regular gutter cleaning, normally twice a year in the spring and in the fall, to prevent problems caused by inadequate drainage. Every five to seven years you should have a professional that is familiar with slate and steep sloped roofs perform the check in detail.
With routine checks and professional repairs (when needed), a slate roof will accent your home or building for many years to come. The first and easiest points on the roof to look for would be cracked, damaged, or missing pieces of slate. Over time, slight defects in the stone can cause a small percentage of pieces to crack, which eventually leads to part of the slate falling off or out of place. Slate can also come loose from the nail holes, allowing the full piece slide a little, or completely out of its location. Both of these scenarios are not out of the usual and require little time and effort to repair. Any knowledgeable slater or contractor can fix a broken or loose piece of slate in minutes. They simply match the broken slate with a same size and color new piece and secure it in place. This is called a “nail and bib” repair. First the old piece is removed and the new one is slipped into place. Then the slater marks a point on the new piece that is between the two pieces above it in the side laps. He then punches a hole and nails the new piece of slate in its final position. After that, the slater installs the “bib” on the new nail location to ensure proper drainage. There is no need to remove or change any of the surrounding pieces as the procedure is designed to only work with the piece that needs repaired. When surveying the roof, you should also check for any abnormal weathering or delamination. Delamination is when a piece of slate starts to deteriorate or flake apart. Obviously lower grade slate will have much more delamination than the higher grade stone. Other than the slate itself, failed flashings also need to be accounted for. Keep an eye out for pin holes, open seams, loose or misaligned elements, and broken or clogged downspouts. Inside of the attic, on the underside of the roof, is very important to check for any water or stains from possible leaks. Most often leaks will form where two roof planes connect like in valleys or hips. Rafters, truces, and the roof sheeting should also be checked for leaks and water rot.