Slate roof repair in St. Louis: how a proper tile swap works

A damaged slate tile rarely leaves cleanly. Bits of stone stay tucked under the course above, and the old nails are still in the deck. The first tool out of the bag is a slate ripper: it slides up under the surrounding tiles, hooks each hidden nail, and a hammer strike on the ripper's end pops the nail out or cuts it. Until that cavity is clean, no replacement tile goes in.

Sizing is the step that separates a repair that disappears from one you can spot from the street. The replacement tile is laid over the opening and checked against its neighbors, and if it runs big it gets trimmed on a slate cutter. When the original tile came out whole, it becomes the template for the new one, matched for thickness and color.

Setting the tile is deliberately gentle. It slides up under the course above until its bottom edge sits flush with the tiles on either side, then it is fastened with copper roofing nails, two of them so the tile cannot rotate. The nails are driven flush and no tighter. Overdriving a nail into slate is how one broken tile becomes three.

The finishing move is a copper bib: a slip of sheet copper four to five inches wide with a slight bend put into it. The bend springs tension against the slate so it stays put, and the bib slides under the joint above the repair so water crosses over the fresh nail heads instead of finding them. Done right, the repair is invisible from the ground and watertight for decades.

The reason to call rather than climb: wet slate is nearly as slippery as ice, natural stone grows moss, and foot traffic from an inexperienced walker breaks more tiles than it fixes. We repair and restore slate roofs across the historic St. Louis neighborhoods, and a regular slate roof inspection is the cheapest maintenance a hundred-year roof will ever get.