Rock and fieldstone chimney repair in Summerport Beach

Working in hot or dry weather

The same instructions say that in hot or dry weather, the back of each stone should be moistened with a fine spray or wet brush, and a concrete, masonry or scratch coat backing dampened before mortar goes on. Surfaces should look damp but carry no standing water.

Skipping that step lets the stone and backing pull water from the fresh mortar too quickly, weakening the bond. We plan the work and the dampening around the conditions on the day.

A cap that sheds water past the stone

For stone-clad chimney chases, the maker's instructions call for a one-piece cap that extends 1 to 2 inches beyond the finished stone surface, so water drips clear of the stone instead of running down it.

Caps that stop flush with the stone send water straight down the face and into the top joints. When we find that on a chase, the cap goes on the estimate as its own line, next to the stone repair it protects.

How deep to rake out stone joints

The National Park Service's Preservation Brief 2 sets the raking depth at 2 to 2 and a half times the joint width as a minimum, so new mortar bonds and stays put. For stone masonry with wide joints, that can mean several inches.

Loose or crumbling mortar beyond that depth also comes out. The brief shows new mortar falling out of a joint that was not prepared deeply enough. We rake to a sound depth and show you the prepared joints before filling.

• At least 2 to 2 and a half times the joint width
• Deeper where mortar is loose
• Square back so new mortar locks in

Recessing mortar on worn stone

When stones have worn, rounded edges, the brief recommends recessing the final mortar slightly from the face. Filling flush with worn edges makes joints look wider than they are and leaves a thin featheredge of mortar that breaks easily and lets water in.

We set the joint depth to suit your stone. On crisp cut stone, joints can come closer to the face. On weathered fieldstone, a slight recess keeps the repair durable and true to the wall's character.

Hard cement patches on softer stone

Stone chimneys often carry earlier repairs made with a hard, gray portland cement mortar. On soft or medium stone, that kind of patch can trap moisture and push it out through the stone faces beside it, which then flake.

We identify hard patches by look and by scratch, remove them with hand tools where we can to protect the stone edges and repoint with a mortar suited to the stone. Any stones already damaged beside the patch are assessed for replacement.