A slate roof does not need much. That is the whole point of the material. But the small amount it does need has to happen on a schedule, because the failures that end up costing real money almost always start as something a homeowner could have seen from the driveway two seasons earlier. A slipped slate sitting in a gutter. A gutter that has not drained since October. A line of dark staining down a chimney that was not there last year.
The stone itself will outlast most of the people reading this. Depending on the quarry and the thickness, slate commonly gives somewhere between 75 and 150 years of service, and some of the harder Virginia and Pennsylvania stone goes longer. What fails first is everything around the stone: the nails, the flashings, the underlayment, the gutters, the mortar at the chimney. Those parts have service lives measured in decades, not centuries, and they fail quietly.
What follows is a seasonal pass you can run on an older Lynchburg house. Some of it you can do from the ground with binoculars and a flashlight. Some of it needs someone on the roof who knows how to move across slate without breaking it, which is most of the reason slate roofs get damaged during maintenance in the first place.
Fall: clear the water paths before the leaves stop falling
Fall is the most important pass of the year, and the reason is simple. Every problem a slate roof has in winter is a water problem, and every water problem starts where water is supposed to leave and cannot.
Work from the top down. The valleys go first. A slate roof valley is a metal channel, usually copper or terne-coated stainless on the better old houses, and it has to stay clear from the ridge all the way to the eave. Oak and maple litter packs into valleys and holds moisture against the metal year round. On an open valley you should be able to see a clean strip of metal between the two slate courses. If you cannot see metal, the valley is not draining, and in January it will not drain at all.
Then the gutters and downspouts. Clean them twice in fall if you have mature hardwoods, once in early October and again after the last drop. A full gutter in freezing weather is a block of ice sitting against your eave slates and your fascia. Check that every downspout actually runs when you put a hose in the top. A downspout that is blocked at the elbow will back the whole gutter up even when the trough looks clean.
Last, walk the perimeter of the house and look up at the roof plane from several angles, ideally with low afternoon light raking across it. That light shows displaced slates, cracked slates, and slates that have slid down an inch or two much better than midday sun does. Note anything that looks out of line and where it is. You are building a record, not fixing anything yet.
Winter: watch from the ground and stay off the roof
Nobody should be on a slate roof in winter. Wet slate is slick, cold slate is brittle, and a slate that gets stepped on wrong in January will not show up as a leak until March. The winter pass is a watching pass.
After the first hard freeze and after every snow that sticks, look at the eaves. Icicles hanging off a gutter are normal in a cold snap. Ice building back up under the first two or three courses of slate, or a ridge of ice sitting on the roof plane above the gutter line, is an ice dam, and it means meltwater is running down the roof, hitting the cold overhang, and refreezing. That water backs up under the slate and gets into the deck. Ice dams are usually an attic insulation and ventilation problem rather than a roofing problem, but the roof is where the damage lands.
Inside, go into the attic with a flashlight on a bright cold day. Look for daylight. Look for dark stains on the underside of the sheathing, particularly along valleys and around the chimney. Feel the sheathing near the eaves for damp. Wet sheathing in February tells you exactly where to start looking in April.
Spring: find what winter broke
Spring is when the damage shows itself. Water absorbed into weathered slate freezes, expands, and splits the stone along its natural layers, so the slates that were marginal in November are the ones lying in your flower beds in March. Start there. Walk the ground line around the whole house and pick up every fragment you find. A pile of slate chips under one corner of the house tells you which slope is deteriorating and roughly how fast.
This is the right season to book a proper look at the roof. A full slate roof inspection in spring catches the slipped and cracked slates while the weather is still mild enough to set replacements properly, and before summer storms drive water through the gaps winter opened.
Spring is also when to look hard at metal. Snow and ice move flashing. Check the chimney, the sidewalls where a dormer meets the main roof plane, and any pipe penetration. Rust streaks, lifted counterflashing, or an open joint at a chimney corner are all reasons to get slate roof flashing repair scheduled before the summer thunderstorm season rather than after it.
Summer: the working season
Summer is when the actual work happens. Slate is easiest to handle warm and dry, mortar cures properly, and a roofer can take the time to do a repair right instead of racing weather.
Use the summer pass for the jobs that need a person on the roof: resetting slipped slates, replacing broken ones with matching stone, repointing the chimney crown, renewing sealant at counterflashing, and clearing any growth that has taken hold on the north slope. Regular slate roof maintenance done in a single summer visit is usually the cheapest hour anyone spends on an old roof, because it catches the twelve small things before one of them turns into a deck repair.
Summer is also the season to deal with trees. Overhanging limbs drop debris into valleys, hold shade that feeds moss, and scrape slate in wind. Cutting limbs back from the roof plane removes three problems at once.
The gutter, valley, and chimney checklist
These three areas account for the large majority of slate roof leaks we are called out to. Run through them at every seasonal pass.
- Gutters: Free of debris along the full run. No standing water after rain. Every downspout flowing. Hangers tight, with no section pulling away from the fascia. No granular grit or slate fragments in the trough, which would mean the stone above is shedding.
- Valleys: Clear metal visible end to end. No leaf pack at the bottom where the valley meets the gutter. No rust perforation, which is common on older galvanized valleys and shows up as dark pinholes. Slates along the valley edge cut clean and sitting flat, not lifted or chipped.
- Chimney: Crown intact with no open cracks. Mortar joints in the upper courses sound rather than crumbling. Counterflashing still let into the mortar joint and not pulled loose. The cricket, if there is one, shedding water to both sides instead of holding a wet patch of debris behind the stack.
- Eaves and rakes: Starter course complete. No slates missing at the corners, which take the most wind. Drip edge present and not curled.
- Penetrations: Plumbing vents, bath fans, and old chimney thimbles all still flashed and sealed, with no gap you can see light through from the attic.
Older housing stock makes this more relevant here than it would be elsewhere. Plenty of the slate we work on around older homes in Amherst was laid before 1930 on cut nails and skip sheathing, and those roofs are now in the stretch of life where the fasteners fail before the stone does. The same is true of a good deal of slate roof work in Madison Heights, where mature hardwoods and north-facing slopes keep valleys damp for most of the year.
Common questions
How often should a slate roof be inspected?
Once a year is a reasonable baseline for a roof under about 60 years old that is not showing problems. For a roof past 75 years, or one that has already had slipped slates, twice a year makes more sense: once in spring after the freeze cycles and once in fall before them.
The visits matter more than the interval. An inspection that is a walk around the yard with binoculars is not the same as someone getting eyes on the flashings and the underside of the deck.
Can I walk on my own slate roof to clean the gutters?
We would not. Slate breaks under point loads, and it breaks in ways you cannot see from above: a hairline split that only leaks in driving rain. Even experienced roofers use hook ladders and staging on slate rather than walking the field freely. Clean gutters from a ladder set on the ground, and keep your weight off the roof plane entirely.
Is moss on my slate roof actually a problem?
Moss itself does not eat stone, but it holds water against the slate and against the nail heads, and it lifts the bottom edge of the course above. On a weathered roof that extra moisture accelerates delamination. It is worth removing, gently, but pressure washing a slate roof will do far more damage than the moss ever would.
What does a slipped slate mean?
Almost always that the nail holding it has corroded through or that the slate has broken around the nail hole. One slipped slate is a repair. A dozen slipped slates across different slopes is a sign the whole fastening system is at the end of its life, and that is a different conversation about the roof as a whole.
Book the seasonal pass
The seasonal rhythm only works if somebody actually runs it. We handle the parts that require being on the roof, and we tell you plainly what we found and what can wait until next year. Call +15555555555 to schedule an inspection or to get on the maintenance schedule for the coming season.
