How to Inspect a Slate Roof

Position a ladder next to the house and climb up onto it so that you can easily see the entire slate roof surface.

Scan the roof visually and identify any areas where the slate tiles have broken off completely and the underlying roof wood is visible. These tiles may also be visible on the ground along the sides of the building. A sound slate roof has no holes or gaps.

Look at the overlapping pattern on the slate roof to ensure that is is perfectly consistent over the entire roof. If you see an area where the pattern is slightly skewed, it means that one of the tiles has dislodged and shifted at an angle. These tiles need repair to prevent water seepage.

Look carefully at the slate tiles to ensure that they are not cracked or chipped, especially around the edges of the roof line. Any tiles that are visibly damaged need replacement.

Grasp the corners of some of the slate tiles with your fingers and try to break them off. If you can break them with your fingers, they are not strong enough to withstand impact from hail or tree limbs and need replacement.

Identify any white stains on the slate tiles, which are typically in a half-moon shapes but may also streak down the length of the tiles. These stains indicate the layers of slate are separating. If the slates are 1/2-inch thick, they do not require replacement. If the slates are only 1/4-inch thick, they do not have much life left.