So you have found a lovely home with a gorgeous slate roof. In most cases, this will be a historic home. The roof is beautiful, but you are concerned because you have heard that slate roofs can be expensive to repair and replace. And you are right to be concerned. Slate is a very high-end roofing material. It is prized for its unique look and historical beauty, plus it can last for centuries if well maintained. But before you sign the papers, there are some factors to consider when buying a home with a slate roof.
What is the Current Status of the Roof
First of all, congratulations on your consideration of a home with a slate roof. You have already avoided the most costly part of owning a slate roof, the installation. But like any home, it is important to consider all aspects of the home’s current condition. This is true of the roof, as well.
A well-maintained slate roof can last for hundreds of years. In fact, many slate roofs are still sheltering homes that date from the 19th century and earlier. The biggest factor is maintenance.
You can think of maintenance on a slate roof like maintenance of your dental hygiene. Slate roofs, like your teeth, can and should last a lifetime. Slate is stone, so it is impervious to much of the rot and other damage that can slowly eat away at other types of roofs. But problems can arise. Just like you may get a small cavity in your teeth, a slate roof may have one or two tiles that become damaged or cracked. While the damaged tiles may not immediately result in a leak, leaving them unrepaired would be like leaving a cavity unfilled. The damage is due to spread, and as it does the repairs become more costly, and the damage is much worse.
Replacing an Individual Slate
The easiest and cheapest bit of maintenance is replacing one or two damaged slates. The repair can cost as little as $50 or as much as a couple of hundred dollars, but rarely more. Broken slates should be replaced as soon as they are noticed to avoid spreading damage.
There are several ways to replace a broken slate. The first thing to be done is to remove the damaged slate. To do this, the roofer will use a ripper, a long, flat, metal tool with a slightly wider bit on top that can act as a hook to catch a nail. The roofer will slight the ripper up under the damaged slate, keeping the ripper flat and parallel to the roof to avoid damaging any other slates. Then they will use the hooker to latch onto the nail holding in the broken slate and tap the ripper with a hammer until the nail pulls loose. The slate can then be carefully slipped out and removed.
Installing a Replacement Slate
Once the slate is removed, a new slate has to be installed. This can be done with a hook or with a nail. If a hook will be used, a small hook in hammered directly into the sheathing where the slate has been removed. The new slate is slid into place, with its upper portion sliding under the slate above it. The bottom of the slate is then rested on the hook, which holds it in place.
If the slate is going to be nailed it, the roofer must first make a small hole for the nail. Using a pin tool, the roofer breaks a small hole in the area where the two slates above the missing one meet. The new slate is slid into place, and a nail is hammered into the slot between the two upper slates, going into the small space that was opened for it. Then, a small sheet of copper or stainless steel is slipped into place on top of the new slate and underneath the slate above, covering the newly installed nail.
Replacing Flashing on a Slate Roof
One of the weak points on any slate roof is the flashing. Flashing is sheet metal that is used for waterproofing areas prone to gathering water or leaking. These include valleys and the areas around chimneys, vents, skylights, or other openings in the roof. Depending on the material used, flashing can last up to 75 years or as little as 15 to 20 years. In any case, this is usually less than the lifetime of the slate. So the flashing will have to be replaced before the rest of the roof.
Replacing the flashing can be a big job. The cost depends on the size of the roof and the material used for the new flashing. It can cost anywhere from several hundred dollars to tens of thousands of dollars. What makes replacing flashing on a slate roof a big job is that the slate covering the edges of the flashing must be removed. Once the slate around the flashing is removed, the new flashing is installed as with any other roof. Then the removed slate must be reinstalled over the edge of the flashing.
Slate roofs are usually installed with nails, though some methods use hooks. In most cases, if the roof is installed properly, the fasteners should not need replacement. However, if the roof is exposed to excessive moisture, the fasteners can begin to fail. If the fasteners are failing, immediate action is necessary to prevent extensive damage.
Restoring a Slate Roof
A well cared for slate roof should only need the minor repairs mentioned above. But if a roof has been neglected, it may require restoration. This is more common in historic homes that are stretching into the century-plus age range. Restoration is really just a more extensive type of repair. It may include fixing a large number of slates. It can also mean replacing flashing or fasteners, or both. If you purchase an aging historic home in the hopes of fixing it up and returning it to its former glory, it is likely the roof will need some work, too.
The general rule with restoration is that it should only be undertaken if 70%-80% of the slates are still in good condition. The damaged slates should ideally be scattered around the roof. This would be the result of poor maintenance. If the damage is concentrated in one area of the roof, the damage may be more severe, and a full roof replacement could be necessary.
Replacing a Slate Roof
If more than 20%-30% of the slates are damaged, most slaters will recommend a full roof replacement. At that point, you are faced with a tough decision. Do you install new slate, a costly proposition, or go with a different roofing material? A large part of this decision will depend on the type of house you have. If you are in a historic home, a large part of the value of the home is its slate roof. In that case, it may be unwise to use other more modern materials. In other cases, with newer homes, there are more options. If you like the look of slate but not the expense, there are modern synthetic shingles that replicate the look of slate. But for a historic home, that method would significantly decrease the value.
If you are purchasing a historic home, it may be good to save up for a roof replacement. Unless your roof is in great condition when you purchase it, replacement may be in your future. Of course, proper maintenance can delay or even prevent replacement. That’s why it is essential to have your slate roof inspected annually by a slater, a roofer who specializes in slate. You should never walk on slate, so having an inexperienced roofer inspect your roof could do much more damage than good. But with regular maintenance and cleaning, your slate roof could last another century.
If you are considering purchasing a home with a slate roof, check in with the professionals at Eagle Watch Roofing. We can help you assess the quality of the roof and determine any future problems that may arise.