Hearth extension repair done right in Airport North

Wood left under a hearth from the original build

Hearths were often poured over wooden forms, and the code is plain about what should happen afterward. Section R1001.9 says combustible material shall not remain against the underside of hearths and hearth extensions after construction.

Sometimes a repair reveals boards or plywood still in place under the slab. That finding changes the job from a surface fix to a support fix. We show you what was found, explain the options for removing it or rebuilding the extension on proper support, and wait for your approval before going further.

Setting materials that belong near a fireplace

Where a noncombustible facing overlaps the front of a factory-built fireplace, one maker's manual calls for noncombustible mortar or adhesive only. The same thinking guides our choice of setting materials around a hearth, where the bed under the tile should suit the heat it will see.

Construction adhesive from a hardware aisle is a poor fit here. We use setting and grouting products suited to the location, follow their makers' curing directions and tell you when the fireplace can be used again.

Small burn pits on the hearth surface

Tiny dark pits or glaze burns on a tiled hearth usually mark where embers landed and cooled. On many finishes they are cosmetic, and they show the extension doing its job.

Where the marks bother you, individual tiles can be replaced. If burn marks sit right at the outer edge of the extension, we also check whether it reaches far enough, since that edge should be well clear of where embers come to rest.

Choosing between a patch and a rebuild

A patch is quick and keeps most of the existing hearth. A rebuild takes longer and costs more, and it resets the base, the size and the finish together.

The right choice depends on what failed. We put both options side by side when both are reasonable, with what each one fixes and what each one leaves as it is. You decide with the facts on paper.

• What each option fixes
• What each option leaves as it is
• How long each one takes
• How each will look when finished