As we noted in a previous post, a slate roof that’s been properly installed can last at least 100 years. However, that doesn’t mean your slate roof is indestructible. Routine inspections and maintenance as well as prompt and expert repairs can go a long way to preserving the beauty and durability of your slate roof.
Roof inspection
Given the relatively high initial cost of installing a new slate roof, it pays to inspect its overall condition annually and after severe storms. For safety reasons, it is a good idea for building owners and maintenance personnel to carry out roof surveys from the ground using binoculars or from a cherry picker.
During the inspection, cracked, broken, misaligned, and missing slates and the degree to which delamination has occurred should be noted, along with failed flashings (pin holes, open seams, loose and misaligned elements, etc.) and broken or clogged downspouts.
A roof plan or sketch and a camera can aid in recording problems and discussing them with contractors. In the attic, wood rafters and sheathing should be checked for water stains and rot. Critical areas are typically near the roof plate and at the intersection of roof planes, such as at valleys and hips.
Every five to seven years, building owners should get an inspection by professionals experienced in working with slate and steep slopes. Good record keeping, in the form of a log book and the systematic filing of all bills and samples, can help in piecing together a roof’s repair history and is an important part of maintenance.
Routine maintenance
Regular maintenance should include cleaning gutters at least twice during the fall and once in early spring, and replacing damaged slates promptly.
Keep foot traffic off the roof. If maintenance personnel, chimney sweeps, painters, or others must walk on the roof, they should hook ladders over the ridge and walk on these ladders to better distribute their weight. If slates are to be walked on, it is best to wear soft-soled shoes and to step on the lower middle of the exposed portion of the slate unit.
Basic roof repair
Broken, cracked, and missing slates should be repaired promptly by an experienced slater to prevent water damage to interior finishes, accelerated deterioration of the roof and roof sheathing, and possible structural degradation to framing members.
Roof slates are categorized by where they are positioned, from starters at the bottom to valley or flashing slates that are cut to fit against the top of the flashing, to ridge and hip slates. Specialty nails are used to hold slates in place and these nails must be tapped into place with great care and precision to avoid slate damage or leaks. Cement may be needed to secure slates in certain positions or circumstances, such as roofs exposed to chronic high winds.
An experienced slate roof contractor will have all the appropriate tools and materials to correctly remove and replace any of the slates, regardless of size or position on the roof.
Leading cause of slate roof repair – improper gutter installation
Often, repairs are needed on the drip edge at the bottom where rainwater drips off the roof and the sheathing beneath the slate. This often happens when the roofing contractor takes the easy route and fasten the gutters to the house by nailing through the slate with strap hangers. This damages the slate, which must then be repaired or replaced.
Strap hangers, if used, must be fastened under the slate unless they can be installed on the fascia—the board installed at the edge or face of the overhang. However, on a very old home, the fascia may not be plumb along the same line as the dripping rainwater. In that case, the contractor may have to rebuild the fascia before hanging gutters.
Asphalt shingles don’t belong there either!
If a home had a built-in gutter that was replaced at some point, there may be several layers of asphalt shingles along the bottom edge to cover exposed sheathing (instead of slate). An experienced slate roof contractor will remove these asphalt shingles and re-slate the roof along the drip edge.
Work with a professional slate roof contractor
Inspecting and repairing a slate roof is a specialty and requires the expertise of a seasoned slate roofing contractor. Contact Slate Roof Professionals for an evaluation of your slate roof in Northern and Central Jersey as well as Westchester County, NY.