Hearth extension repair done right in Audubon Park

Larger fireplace openings need a larger hearth

When the fireplace opening is 6 square feet or larger, section R1001.10 asks for more coverage, at least 20 inches in front of the opening and at least 12 inches beyond each side. A wide or tall opening crosses that line sooner than many homeowners expect.

We work out the area from the opening's width and height at the free inspection. If your fireplace falls into the larger class and the extension was built for the smaller one, the estimate shows how far it has to grow and which materials can extend it cleanly.

Hearths in front of factory-built fireplaces follow the listing

A factory-built fireplace plays by different rules. Section R1004.2 says its hearth extension is installed in accordance with the listing of the fireplace, so the manual that came with the unit sets the size and the materials.

One maker's wood-burning model, for example, calls for an extension reaching at least 20 inches in front of the opening and 12 inches beyond each side, and another model can differ. We find the model on its rating plate before measuring, so the repair follows the right document.

• Model found on the rating plate
• Manual read for hearth size and layers
• Repair matched to that document

Keeping a hearth extension from sliding

A hearth built as a panel or from loose units on top of the floor can creep away from the fireplace over time. One maker's instructions call for a means to prevent the hearth extension from shifting, together with the sealed gap at the fireplace front.

Movement shows up as a widening joint at the firebox edge or a finish sitting off square. We find what lets it move, secure it and reset the edge so the extension stays tight against the fireplace.

Why a flush hearth needs its full extension

A fireplace whose firebox floor sits at the height of the room floor has nothing to stop a rolling log or a spray of embers. The hearth extension in front of it is the only barrier between the fire and the floor.

That is why the code keeps the full thickness rule for flush fireplaces, and why we measure their extensions closely. If a flush hearth is short or thin, we treat it as a priority item on the estimate.