How to Repair a Firebox Made With Prefab

Prefab fireplaces are now more popular than masonry fireplaces.
Prefab fireplaces are now more popular than masonry fireplaces. (Image: Jupiterimages/Polka Dot/Getty Images)

Repairing a firebox made of prefab materials is a realistic do-it-yourself project that can save up to 2/3 of professional repair costs. A repaired firebox saves energy, reduces heating costs and maintains the value of property, particularly when it is time to sell. There are two types of prefab fireplaces: the wood-burning fireplace and the gas-burning fireplace. Prefab fireplaces are also sometimes called manufactured fireplaces or zero-clearance fireplaces. Knowing these basics, along with understanding the basic parts of a fireplace, helps avoid costly — even fatal — mistakes.

Things You'll Need

  • Screwdriver
  • Internet or phone directory
  • Telephone
  • Work gloves
  • Refractory panels, pre-ordered from manufacturer

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Replacing panels

Remove the front portion of the fireplace to access the panels properly. Remove the clips that hold the panels in place. Prefab refractory panels are the concrete sides, back and bottom of the firebox and are replaceable.

Find the necessary information under the firebox where the fan is: model number, serial number, and manufacturer should be found in metal information tags or on a data plate.

Contact the firebox manufacturer and confirm if the model is still available. Alternatively, find a store that sells fireplace units and chat up the owner or manager. Sometimes, the model number changes only because of updated model colors or some other cosmetic reason while the basic model remains the same; only further inquiry can reveal this.

Ensure that the panels are properly packed for shipment or delivery as panels can break easily in transit. Use a courier that provides insurance for the panels.

Panels can break easily in transit; use a reliable, insured courier.
Panels can break easily in transit; use a reliable, insured courier. (Image: Jupiterimages/liquidlibrary/Getty Images)

Follow manufacturer’s instructions strictly during actual installation. Clip panels into place.

Get a certified chimney sweep to ensure that you have complied with all fire safety standards. This consultation fee should last an hour at most and should cost a lot less than a whole installation fee.

Get a professional chimney sweep to certify your work.
Get a professional chimney sweep to certify your work. (Image: Edwina Gnika/Valueline/Getty Images)

Repairing Cracks

Check how wide the cracks are. If a toothpick can pass through, then panel replacement is needed. If the crack is smaller, original panels can still be repaired. If it is a metal panel, then panel replacement is also needed.

Mix hydraulic refractory cement according to instructions. Find this specialty cement in mason supplies shops.

Layer a thick coat over the cracks, gradually smoothing down the cement layer.

Create brick impressions over the layer while cement is still damp. Score appropriate vertical and horizontal lines to simulate bricks by using a trowel tip or barbecue stick. Clean the trowel tip/barbecue stick every so often to avoid any build-up and achieve clean lines, but hand-drawn imperfections are fine. Wipe off excess cement on walls with a damp rag; let dry for 3 to 7 days.

Fire up the hearth to “age” brick lines and create a rustic look.


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