A slate roof is worth it for the right house: it can last a century or more and it resists fire, but it costs several times what asphalt does and it is heavy. Many houses built for asphalt need extra framing before slate can go on. If you may sell within a decade or two, the math rarely works.
The short version
- Natural slate can last 60 to 125 years or longer (opens in a new tab), depending on the stone and the setting.
- It typically costs 3 to 5 times as much as asphalt.
- It is heavy, so the roof framing may need to be checked and strengthened.
- Slate is brittle: walking on it and fixing it both take care.
- The nails and flashing often give out long before the stone does.
What are the pros of a slate roof?
The big advantages are life, fire resistance and a look nothing else matches. This Old House lists slate as fire-resistant and low maintenance (opens in a new tab), and says a carefully installed slate roof can last 100 years or more (opens in a new tab).
The National Park Service, which looks after historic slate roofs, says slate is one of the most durable of all roofing materials (opens in a new tab). It also notes the life span depends on the kind of slate: Vermont and New York slates last about 125 years, while Pennsylvania soft-vein slates last in excess of 60.
That gap matters. “Slate” is not one product, and a cheap slate can wear out in a lifetime.
What are the cons of a slate roof?
The cons are price, weight and how hard it is to work on. This Old House calls slate one of the most expensive roofing materials (opens in a new tab) and says it needs professional installation.
Slate is also brittle. This Old House points out that it does not support weight well (opens in a new tab), so walking across it breaks tiles. That includes the gutter cleaner, the chimney sweep and the satellite installer. Every one of them is a possible repair.
Our own read is that the stone is rarely the problem. What fails is everything around it, which is the next section.
How much does a slate roof cost compared with asphalt?
Around Ellicott City, a full architectural asphalt roof typically runs $6.00 to $9.00 per square foot installed. Natural slate typically runs 3 to 5 times that. This Old House puts natural slate at $10 to $30 per square foot (opens in a new tab) nationally, with synthetic slate far lower.
| Architectural asphalt | Natural slate | |
|---|---|---|
| Typical cost | $6.00 to $9.00 per square foot around Ellicott City | 3 to 5 times asphalt |
| How long it lasts | 18 to 25 years in Maryland | 60 to 125 years or longer (opens in a new tab) |
| Weight on the framing | Standard for most houses | Heavy, may need extra support |
| If one tile breaks | Quick, cheap repair | Needs care and a roofer who knows slate |
The price gap closes if you stay long enough to skip two or three asphalt roofs. It does not close if you sell in ten years, because a buyer may not pay for what you spent.
For the cheaper end of the market, see how metal compares in is it cheaper to roof with shingles or metal.
Can your house hold a slate roof?
Often not without checking. This Old House says the weight of slate often calls for additional structural support (opens in a new tab), which adds to the cost.
When we tear off a roof and find framing trouble, an engineer’s letter typically runs $600 to $1,500 and can add $3,000 to $15,000 or more and days to weeks of delay. For slate, that check should happen before you sign, not after the old roof is off.
In Old Ellicott City, the Historic Preservation Commission can add months and limit which materials you may use. In covenant-controlled neighborhoods like Turf Valley, Font Hill and the Columbia villages, review can add 30 to 45 days.
What fails on a slate roof before the slate?
The nails and the flashing fail first. The National Park Service says plain steel and galvanized nails will usually rust out long before the slate itself (opens in a new tab) begins to deteriorate, and that copper or stainless steel nails should always be used.
Flashing is the metal that seals the roof where it meets a chimney, wall or valley. We see it as the place roofs leak, on any material. Caulk is a consumable with a 5 to 10 year life, so any detail that leans on sealant is a leak waiting its turn. A slate roof needs metal that lasts as long as the slate does.
Can you repair a slate roof, or must you replace it?
A few broken tiles can be fixed, but a roof past a point should be replaced. The National Park Service says that if 20% or more of the slates (opens in a new tab) on a roof or slope are broken, cracked, missing or sliding out of position, it is usually less expensive to replace the roof than to repair it piece by piece.
This Old House adds that cracked or chipped tiles are easy to fix (opens in a new tab) if caught quickly, but extensive damage gets expensive fast. Slate repair is its own skill, and not every crew does it. Ask before you book.
A free look first tells you which side of that 20% line you are on. Our free roof inspection includes a walk on the roof and a written report, and we will say plainly if a repair is enough.
Is slate right for a Maryland home?
Slate suits a house that was built for it, owned by someone staying for decades. It suits an old stone or brick house where the look is part of the home’s value. It suits poorly a modern frame house with a simple roof and a tight budget.
If you want a long-lived roof without the weight, metal shingles can copy the slate look at lower cost and a fraction of the load. Standing seam metal typically runs 2 to 2.5 times asphalt.
Common questions
How long does a slate roof last in Maryland?
The National Park Service gives 60 to 125 years or longer, depending on the type of slate. Nothing in the sources says Maryland changes that, but the nails, flashing and gutters around it will need attention long before then.
Is a slate roof worth the money?
It is when you plan to stay and the house can carry it. This Old House says a slate roof costs more than most other materials (opens in a new tab) but adds value to your home. Compare that with how long asphalt lasts in how long do roof shingles last.
Can you walk on a slate roof?
You should avoid it. The National Park Service recommends keeping foot traffic off a slate roof and says workers who must go up should hook ladders over the ridge (opens in a new tab) and walk on the ladders to spread their weight.
What to do next
If you are weighing slate against asphalt or metal, start with the numbers for your own roof. We measure it, check the deck and the flashing, and tell you what it would take to replace it. Our roof installation page covers what a full replacement includes, and you can call us any time to book the free inspection.
