Chimney repair with a free inspection in Clear Lake

The mortar used to repoint matters

Stronger mortar is not necessarily better mortar. BIA guidance on mortar says no single mortar is best for all purposes and advises choosing the lowest compressive strength that meets the needs of the job. For repointing, it names compatibility between the existing brick and mortar as the most important consideration.

Mortars laid before the early twentieth century were mostly lime and have lower strength, so older brickwork likely needs a weaker repointing mortar than new construction would use. BIA maintenance guidance wants repointing mortar no stronger than the original, and it cautions that a mismatched mortar can make the old brick spall and crack.

The reason is stress. A repointing mortar stronger than the original concentrates stress where brick meets mortar, and the brick faces can spall. The mortar is chosen for the chimney in front of us, and its type is named on the estimate.

Factory-built chimneys take their own listed parts

A factory-built chimney is a tested system. The Florida Building Code requires it to be listed and labeled, and installed and terminated per the manufacturer's instructions. The listing belongs to the whole system, which in one maker's instructions runs from the pipe and supports through firestops and shields to the chase top and cap.

That is why a generic part is a problem even when it fits. Those instructions, DuraVent's for its DuraChimney II chimney, say to use only its authorized parts, not to mix parts from other systems and not to improvise. A section borrowed from another brand or a cap bent up from sheet metal leaves the chimney outside the conditions it was tested under.

Before any part is quoted, the chimney's maker and model have to be known. On a chimney in Clear Lake, our technicians read the label where it can be reached and write the maker and model on the estimate, so each replacement matches the system already in the house. If the system can no longer be matched, that is said plainly.

Changing the appliance means checking the flue

A flue is sized and lined for what it vents. Under the Florida Building Code, a chimney flue may not be smaller in area than the connector from the appliance, and a flue that served an open fireplace is not automatically right for a stove or an insert.

Swapping appliances is where mismatches start. Because the code ties the lining to the terms of the appliance listing and the maker's instructions, the new appliance's own manual carries part of the answer, and the chimney has to satisfy both the manual and the code.

If you can, bring the new appliance's model and manual into the conversation before it is bought. Our crew in Clear Lake compares its flue requirements with the chimney you have, and the estimate spells out whether the existing lining can stay, needs repair or has to be replaced to suit it.

Splitting a long repair list into phases

An inspection on a neglected chimney can turn up a long list. Doing everything at once is not always possible, and it is not always necessary. The list can usually be split into phases without leaving the house at risk.

Some items cannot be split. Counterflashing is set into mortar joints, so repointing and flashing on the same face go together, and a new crown goes on after any rebuild of the courses below it, not before. The estimate marks which lines depend on each other, so the phases you pick still work as a sequence. Within those limits, the order usually runs like this.

• Safety first, such as loose masonry or a damaged flue
• Water entry next, at the crown, cap, flashing and joints
• Working parts after that, like the damper and cleanout
• Finish work last, such as cleaning and color matching