Aitkin Heritage Home — Natural Slate Restoration

Aitkin sits on the Mississippi River, upstream from where it starts picking up size on its way south, and this house a few blocks from downtown was built in the 1920s with a slate roof that had been doing its job for nearly a hundred years. That's the thing about slate — it doesn't really fail, not the way asphalt does. What fails first is the flashing.

By the time we got the call, the copper step flashing at the two dormers and the chimney saddle had corroded through, and the valley liners were pinholing. The slate itself was 80 to 90 percent sound. This was a selective restoration, not a tear-off: pull and stack the existing slates by course, strip the failed flashing and valleys, run new 20-ounce copper throughout, set the original slates back in place, and replace the estimated 15 to 20 percent that had cracked or gone soft.

Slate at a 12/12 pitch is not general-crew work. Our crew lead running this job has 14 years in slate specifically — you sort every slate by thickness before it goes back up, set them on copper slater's hooks instead of nailing through, and check every course with a raking light before the next one goes over it. Anything that doesn't ring true when tapped comes out.

The replacement slates came from a Vermont quarry, matched to the existing grey-purple tint. The chimney saddle was rebuilt in copper. The house will carry this roof through another generation before anyone has to think about it again.