# DIY Firebox Mortar Repair
Things You'll Need
- Safety glasses
- Shop light or head lamp
- Fireplace cleaner, if needed
- Mortar raking tool
- Masonry chisel
- Hammer
- Stiff-bristled brush
- Refractory mortar
- Trowel
- Joint filler
- Jointing tool
- Sponge
Instructions
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1
Clean the firebox so that all of the joints can be visibly inspected. Use a fireplace cleaner according to the manufacturer's instructions to remove soot.
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2
Remove faulty mortar to a depth at which sound mortar is reached. Attempt mortar removal first with a mortar raking tool. If the mortar is stubborn, use a masonry chisel and hammer to chip mortar out.
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3
Brush the joints with a stiff-bristled brush to remove any remaining mortar still attached to firebricks, and clean debris out of the empty spaces.
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4
Dampen the surfaces of the firebricks where mortar will be placed. The brick surfaces should be moist but not have standing water.
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5
Prepare a refractory mortar. Use a hydraulic-setting refractory mortar, preparing it according to manufacturer's directions if it was not purchased in a ready-to-use form. Consider purchasing a mortar with admixtures that are mixed into the mortar to reduce shrinkage and improve bonding.
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6
Apply refractory mortar to the joints in layers using joint filler. Each layer should be no thicker than 1/4-inch to limit air pockets. Let each layer of refractory mortar sit for 30 minutes before the next layer is applied.
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7
Smooth the joints with a suitable jointing tool once the final layer of mortar is applied. Use a jointing tool that matches the existing joints for aesthetic purposes.
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8
Brush any excess mortar off the surfaces of the bricks using a stiff-bristled brush. Allow the mortar to cure for several weeks if possible before utilizing the firebox unless the mortar manufacturer provides a more specific curing time requirement.
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