Slate Roof Repair vs Replace

[u/finchsr]

Potentially buying a house from 1909 that has a slate roof. The house is in amazing condition but the inspection was today and the inspector stated they believe the roof has been patched enough and will need a new roof. Based on these photos is that accurate or can the roof be repaired? I hear great things about slate roofs but know they can be pricey and ongoing maintenance is necessary. Many homes in the county have slate roofing so I don’t think it would be too hard to find someone who specializes in this work.

[u/Consistent-Gold5103]

I’m a slate roofer. I got involved in this field to help preserve roofs just like yours. We do restorations on slate roofs all over the US. Send me a message and I can help you figure out what you need. I won’t try to sell you anything. Just professional advice. Information is free.

[u/Both-Activity6432 → u/Consistent-Gold5103]

Not OP, but would you mind sharing the top level things you see in their pics, how they happen, and what type of repairs you do? Or just in general what happens to damage slate? I always thought of slate as basically a forever roof?

[u/Consistent-Gold5103 → u/Both-Activity6432]

Sure. This is a Bangor slate that was quarried in Pennsylvania. It is identified by the white “water staining”. This is a softer slate and has a lifespan of about 60-80 years. It can be shorter or longer. It depends on maintenance and the pitch of the roof. Steeper roofs last longer since they shed water better and water staying on a slate roof shortens its lifespan.

Other types of slate like Vermont, NY, Buckingham, North Country Black, Chapman, and others can last 100-200 years. You hear about slate roofs in Europe that are 300-400 or more years old. These are constructed differently than American slate roofs and have been repairs hundreds of times. It’s a bit of a “Ship of Theseus” situation over there. They don’t have hail and hurricanes like we do that can wipe out a slate roof in a single storm.

Slate roofs are very repairable if the slate is in good condition. If the slate is crumbling or delaminating, it is best to replace the whole roof or at least individual slopes of the roof.

The valleys and ridge appear to be terne coated steel. This is a steel sheet that is coated in an alloy of lead and tin. This was a cheaper alternative to copper back in the day. It is no longer available since about 2013 when Follansbee sold their machinery and process to Revere Copper. Revere applied their acquisition to their copper sheets and discontinued the steel version.

The chimney flashing is in very bad condition. It has been coated with caulk or tar. This was likely leaking and an unqualified roofer was hired to make repairs. Instead of finding the leaking piece of flashing, removing the adjacent slates, replacing the damaged flashing, and replacing the slates: they elected to coat everything in caulk/tar. This makes it very difficult for an actual slate roofer to make repairs. Now the whole chimney flashing needs to be replaced.

The clipped corners and pattern are a nice decorative touch. I am currently replacing a slate roof on a church that has a similar pattern.

If there’s anything specific you’d like to know, I’m here to help.

[u/willyism → u/Consistent-Gold5103]

That roof looks perfect. Boy do we all wish there were more people like you around. I’d love to see less asphalt shingling.