Expert stone chimney repair in Monterey

Three ways a chimney ends up stone

A stone chimney can be built of solid stone masonry, with thick units that make up the wall itself. It can be natural stone veneer, thinner stone set against a masonry or framed backing. Or it can be manufactured stone veneer, a lightweight cast product adhered over a layered backing.

From the street, all three can look alike. Their repairs do not. We identify the construction first, because the right mortar, the right method and the right questions about water all depend on it.

• Solid stone masonry
• Natural stone veneer on a backing
• Manufactured stone over lath and barrier

Two layers of barrier behind the lath

Behind the lath, the barrier matters most. The instructions we follow call for the water-resistive barrier to be installed as two separate layers, lapped shingle fashion so water runs down and out instead of in. The layers wrap continuously around inside and outside corners.

Where veneer has been removed for repair, we look at the barrier closely. Torn, missing or reverse-lapped barrier is replaced before new lath goes up. It is hidden work, and it is the work that keeps the framing behind a stone chase dry.

Tooling timing and joint color

When the last layer is thumbprint hard, the joint is tooled to match the existing profile. According to the brief, early tooling dries paler and risks fine cracks, and late tooling marks the joint with dark tool burning and fails to seal tight to the stone.

Our masons check joints by hand as they go, so each area is tooled at the right moment. Consistent timing is how the joint color stays even across a repair.

Why repointing mortar is softer than the stone

Preservation Brief 2 sets out that new mortar must have greater vapor permeability and be softer, measured in compressive strength, than the masonry units, and be as permeable and as soft or softer than the historic mortar.

The reasoning is practical. Joints are meant to be the part that wears and gets repointed. A mortar harder and tighter than the stone forces moisture and stress into the stone faces instead, and the stone pays for it. We choose the mix with that rule in mind.

Cutting stone safely around your home

Cutting and grinding stone raises fine dust. One maker's instructions caution that dust from cutting its product contains crystalline silica and call for eye protection and a properly fitted respirator when cutting.

We cut outdoors, away from open windows and doors, with wet cutting or dust collection where practical, and keep children and pets well away from the cutting area. Dust is cleaned from walkways and surfaces before we leave.