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Getting to know fire sealants

Fireproof sealants are designed to seal joints and cracks in concrete fireplaces and brick chimneys. Crucially, fireproof sealants must be able to take the heat of a roaring fire, and hold up against high temperatures. Read on to find out more.

Picking the right fire sealant

Your chosen fireproof sealant must be able to bond with all the materials in your fireplace. So check that the sealant can bond with concrete and brick before sealing the joints or cracks between both materials.

Your fireplace will get extremely hot, so your fire sealant must also be able to withstand high temperatures. Maximum temperatures are usually specified on each fire sealant, so read the instructions carefully and aim to use the most heat-resistant sealant you can find.

How to apply fireproof sealant

Application will vary depending on the product, but the following instructions can be used as a general guideline. Before you start, read the manufacturer’s instructions to find out about the fireproof sealant’s maximum temperature resistance, curing time etc.

  1. Gather materials. You will need a sealant gun, a sharp blade, cleaning material, a putty knife, a cloth and some warm water.
  2. Prepare the surface. Surfaces must be free of grease, dust and other contaminants and completely dry. Given the alkaline nature of most fire sealants, everything surrounding the joint – as well as your hands and eyes – must be protected. Check instructions and prepare the surfaces as instructed.
  3. Apply. Insert the fire sealant into the gun and cut off the tip of the nozzle using a sharp blade (e.g. a Stanley knife) and then gently squeeze the trigger to apply the fire sealant evenly. Smooth the fireplace sealant right away using a wet cloth or finger if required.
  4. Finishing up. Remove any remaining stains with a cloth and warm water. Any dried fireproof sealant can be removed by scraping it away with the putty knife.
  5. Let it dry. Allow the fire sealant time to set in accordance with the product instructions.

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