The Delta Slate Co offers a premium slate service, in repair and new roofing.
Every effort is made to match existing slate with new or salvaged material. Slate and copper flashings are installed to the highest industry standards (see The National Slate Association Slate Roof Installation Manual). A variety of snow-guards are offered, and copper gutters installed, specializing in the “Euro” copper gutter system.
Slate repair (why do they break?)
Among the various slate types, some are virtually indestructible, notably Peach Bottom slate from Delta, Pennsylvania and Buckingham slate from Arvonia, Virginia. These might break due to poor installation, though more likely from foot traffic.
Vermont slate are extremely long-lasting (100-150 years), eventually delaminating or rusting due to the iron content. Chapman slate, from Northampton county, PA has a comparable life-span to Vermont slate.
Penn-Black slate from Lehigh County is softer and absorbs more water as they age. The freeze-thaw cycle of winter-time breaks these apart, though only after 80 or more years of good use.
Metal flashings waterproof the area where two roofs intersect, as valleys or hip flashings. They also waterproof through-roof fittings, such as vent pipes, and where structures intersect with the roof, such as end-walls, chimneys and dormers. Due to air-pollution, the metal simply wears out. With slate we are most likely to use copper or lead-coated copper which lasts between 50 and 80 years. Since a slate roof can last twice this time, it is well worth replacing the flashings.
Old flashing and slate are removed, ice and water shield underlayment installed, base flashing is installed. The counter-flashing overlaps the base flashing and is sealed into a mortar joint.
Vent pipe flashing
The steel pipes that vent our plumbing systems were most often sleeved in lead metal to prevent water penetrating. Squirrels like to gnaw at the lead, probably to their detriment, causing leaking, or else the lead wears away over time. Multiple applications of tar are a common fix, but do not last very long as the tar quickly separates from the metal. Vent pipe leaks are hard to detect, since the pipes run inside the house-walls. Water penetrating the vent pipe collar runs down the vent pipe, and is soaked up by plaster and insulation in the walls–a breeding ground for mold.
We flash vent pipes in copper, soldering the copper pipe to a flange around the base-a life time repair that may help our squirrels live a little longer.
Valleys conduct a great deal of water from the roof, so need to be thoroughly constructed.
We first install a heavy underlayment to cushion the copper from the roof decking, then rosin paper as a slip-sheet. The paper permits the copper to move easily as it contracts and expands. Turns on the valley edges prevent leaking from capillary action and a minimum 4-inch overlap of the slate protects against snow and ice penetration.
Between dormer walls and each course of slate, base flashing is installed. The siding then overlaps the base flashing.
The lower side of the dormer is water-proofed by the apron flashing.
When the pitch of a roof changes, the intersection is flashed, a variation of the apron flashing.
Snow and ice sliding down a roof can cause a great deal of damage, destroying gutters and shrubbery, and can also be a danger to pedestrians. Snow-guards trap the snow on the roof until it melts, running off as water. They are made in different styles and are labor-intensive to install, but worth every penny. They can also add a lot of curb appeal.