How do you seal gaps around a fireplace insert?

Sealing gaps around a fireplace insert is an important step to ensure proper functionality and prevent energy loss. There are a few key considerations when sealing these gaps to get an effective air-tight seal.

Why seal gaps around an insert?

There are two main reasons you’ll want to seal any gaps around your fireplace insert:

• Improve efficiency – Sealing gaps prevents heated air from escaping up the chimney when the fireplace isn’t in use. This keeps more warm air in your home, improving efficiency.
• Prevent smoke leakage – Gaps can allow smoke to leak into the room when the fireplace is lit. Properly sealing the gaps contains the smoke in the chimney.

In order to get the most out of your fireplace insert, it’s important that it is properly sealed from the surrounding brickwork or drywall. Even small gaps around the edges can lead to reduced efficiency and smoke issues over time.

Where to look for gaps

There are several common areas to inspect when sealing a fireplace insert:

• Around the entire perimeter – Small gaps can exist between the insert frame and surrounding material like brick or drywall. Run your fingers around the border to feel for gaps or shine a flashlight to spot them.
• Above the insert – Check where the chimney meets the top of the insert for gaps between the two surfaces.
• Below the insert – Depending on the style, there may be an ash lip or space below the base where air can escape.
• Surrounding facings or trim – If there are decorative facings around the insert, check where they meet the face of the insert.
• Blower or vent grilles – Some direct vent inserts have grilles along the bottom or sides that can leak if not properly sealed.

Materials needed

Sealing your fireplace insert gaps properly will require high temperature sealants or cements rated for appliance use. Here are some of the materials to have on hand:

• Fireplace mortar or cement – Special high-heat mortar is designed to withstand temperatures up to 2,000°F.
• Fireblock sealant – Made specifically for sealing gaps and penetrations on hearth appliances.
• Heat-resistant caulk – Choose a caulk rated for at least 500°F to 700°F.
• Steel wool – Can be combined with caulk or cement to help seal irregular gaps.
• Non-combustible backer rod – Placed into large gaps before sealing over top.

Avoid using regular caulking, spackling, orhouseholdsealants as they are not built to withstand high temperatures. Purchase specialty fireplace sealants from your local hardware store or online retailer.

How to seal the gaps

Here are the key steps for properly sealing gaps around a fireplace insert:

1. Clean and prepare the gaps – Remove any old caulk or mortarwitha puttyknife or chisel. Vacuum and wipe down the areas around the gaps.
2. Insert backer rod – For larger gaps, press in a backer rod until it fills about 50% of the space. This provides a base to seal over.
3. Apply sealant or mortar – Use a caulking gun, trowel, or fingertips to apply the sealant. Steel wool can help fill in irregular gaps. Follow product instructions for drying time.
4. Smooth and shape – Tool the sealant with a putty knife or trowel to create a smooth finish. Remove any excess.
5. Allow to fully cure – Give fireplace mortar or cement at least 72 hours to fully set and bond before using the fireplace.
6. Check for leaks – Light a small fire and inspect closely for any remaining smoke or air leaks.

Applying a thorough coating of sealant or mortar to all possible gaps will prevent air leaks. Take care to smooth any messy sealant for a cleaner look.

Tips for an effective seal

Follow these useful tips when sealing gaps around your fireplace insert:

• Read the manufacturer’s instructions – Consult your insert’s manual for any specific sealing recommendations.
• Work in small sections – Seal a few inches at a time to ensure proper coverage and smoothing.
• Wear protective gloves – Fireplace sealant and mortar can irritate exposed skin.
• Check for smoke leaks first – lighting a small fire first will reveal where gaps are present.
• Apply generous amounts – Don’t skimp on sealant in order areas. More is better to get an air-tight seal.
• Inspect annually – Check for new gaps or cracks that may need resealing every year before fireplace season.

Common problem areas

Watch out for these common trouble spots when sealing a fireplace insert:

Location	Potential Issue	Solution
Under the bottom of the insert	Air can leak if underside is not properly sealed to hearth or fireplace floor.	Apply fireplace mortar or high-heat caulk generously underneath insert.
Corner gaps	Tough to reach corners can be overlooked and allow smoke or air leaks.	Use a flexible high-heat sealant and steel wool to pack into corner cracks.
Facings and surrounds	Gaps between the surround and insert can go unnoticed.	Seal with fireblock sealant or caulk where surround meets insert edges.
Chimney at the top	Junction between chimney and insert commonly leaks due to imperfect fit.	Apply fireplace mortar up to create an airtight seal between chimney and insert.

Paying special attention to these prone areas will help ensure you seal any potential gaps that could lead to leaks.

Insert inspection tips

Here are some useful tips for inspecting your fireplace insert for gaps that need sealing:

• Use a bright flashlight – Carefully run the light along all edges and seams to identify gaps.
• Feel with your fingers – Slowly run your fingers around the perimeter to feel for cracks or holes.
• Check fireplace venting – Look for gaps where the chimney meets the top of the insert.
• Inspect under and behind – Pull the insert out slightly if possible to check the back and bottom underside.
• Burn a test fire – Have a helper watch for smoke leaking out around edges when lit.
• Use a mirror – Use a small mirror to check hard to see areas behind or underneath.

Taking the time to thoroughly inspect all sides of the insert will ensure you find any problem areas in need of sealing.

Chimney considerations

When sealing around your fireplace insert, here are some important chimney considerations:

• Check the chimney liner – Make sure it is in good condition before using the insert or sealing gaps.
• Seal the damper area – Prevent air loss by sealing around the damper mechanism at the top of the chimney.
• Seal the terra cotta tiles – Use fireplace mortar to seal cracks between terra cotta flue tiles if needed.
• Install a block-off plate – This seals off the existing damper to prevent leaks up the chimney.
• Insulate the liner – Adding insulation around the liner improves efficiency and draft.

Properly addressing chimney issues and leaks will bolster the performance of your fireplace insert.

Safety warnings

Follow these important safety precautions when sealing gaps around your insert:

• Work carefully when using caulking guns and sealants to avoid accidents.
• Wear eye protection and gloves when working with mortar or sealants.
• Read all product instructions and warning labels thoroughly.
• Ensure the fireplace and chimney are completely cool before beginning any work.
• Provide proper ventilation due to fumes from some sealants and cements.
• Keep all flammable materials away from the fireplace when testing for leaks.
• Check with your local building department for any fireplace or chimney regulations.

Exercising proper safety is paramount when taking on a sealing project around your active fireplace.

Signs you need to reseal gaps

Here are some signs it may be time to reinspect and reseal gaps around your fireplace insert:

• Visible smoke leaking from edges
• Feeling cold air drafting from the fireplace
• Higher energy bills from heat loss
• Excess soot or grime buildup around edges
• Visible cracks, holes, or separation in old sealant
• Burning wood too quickly due to air leaks
• New gaps formed since last sealing

Addressing any leaks or openings in the sealing right away will improve fireplace efficiency.

Conclusion

Sealing gaps properly around your fireplace insert requires using the right high-heat sealants and thoroughly checking for problem areas prone to leaking. Taking the time to seal all openings carefully will pay off through improved efficiency, less risk of smoke escaping, and greater heat output from your insert. Be sure to use appropriate materials for the job and follow all safety precautions when inspecting and sealing the unit.