How to Install a Fireplace Insert in an Unconventional Opening | Ask This Old House

20January 2020


Spade bit []
Caulking gun []
Pliers []
Screwdriver []

Shopping List:
Electric fireplace insert []
2×4 dimensional lumber []
Pocket screws []
Granite slab
Construction adhesive []
Wire nuts []

1. Start by identifying an insert that’s the closest fit to the opening. Be sure that it is suited for zero clearance and no venting.
2. Fill in the rest of the opening with a fake hearth. Cut to size some 2×4” dimensional lumber and assemble a frame using pocket screws.
3. Secure the frame to the floor with more screws.
4. Cut a hole in the floor behind the frame for the wiring using a spade bit.
5. Shut the power off at the breaker. Fish the wires for the insert through the basement at the panel and through the floor and through the wood frame for the fake hearth.
6. With the wiring pulled through, secure the granite piece to the top of the frame using construction adhesive.
7. Wire the fireplace insert to the wiring coming up through the floor.
8. Secure the insert to the wall on top of the new fake hearth.
9. Turn the power back on.

Heath installed an Allure 32 Wall Hanging Electric Fireplace Insert, which is manufactured by Napoleon Fireplaces (

Since Heath was unable to find an insert that perfectly matched the strange dimensions of the opening at the house, he built up a frame for a “fake hearth” to fill in the rest of the hole. For this, he used regular pocket screws and 2×4” lumber, which can be found at any home center. Heath got the granite cutoff from LA Tiles | Marble and Granite Design (, though he mentioned that any stone yard would most likely be willing to cut and edge a piece of stone if they were provided with the correct dimensions.

The other tools and materials Heath used to install and connect the electric fireplace insert, including the wiring, fish tape, wire nuts, and screwdriver, can all be found at home centers and electrical supply houses.

Expert assistance with this segment was provided by Eaton and Eastman Electric (

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