How to block off a fireplace

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While the idea of a fireplace is romantic, it might be a nuisance in practice. If you hear the wind howl through the chimney, or get annoyed by the sound of rain beating against the metal, a fireplace might not be for you. You can follow these easy steps to block off your fireplace or even to close it up completely.

Seal the chimney

Arrange for your fireplace to be professionally cleaned. Since you will not routinely be utilising the space, make sure it is free of any debris.

Locate the chase cap. This is at the top of the chimney and is the pipe that allows the smoke to escape. There is typically a small roof-type structure attached to the cap that prevents rain water from entering.

Remove the roof structure as well as the top of the flue pipe it is connected to. Seal the opening with a piece of scrap metal. Consider placing a barrier over the chimney itself for further sound insulation.

Close the damper inside the firebox opening.

Seal the fireplace

Measure your chimney opening and determine how much brick to buy. Make sure to buy an air brick, a brick specifically designed to allow for air flow.

Set a row of bricks approximately 30 cm (12 inches)inside of the existing opening. In the middle of the second row, set the air brick flush with the existing opening. Continue until opening is blocked. Allow the bricks to set.

Apply a skim coat of concrete over the bricks, leaving the air bricks open. Once this is beginning to dry, take a nail and create scratches. This allows plaster to adhere to the bricks. Allow to dry thoroughly.

Mix up plaster and apply to surface in light coats. Continue this process until surface is covered. Remember to leave the surface of the air brick exposed. Allow it to dry.

Install a decorative grill to cover the air brick. These can be bought at any building supply store and can be attached with screws or glued into place.

Cap off the chimney flue pipe.


Clean the bricks well and allow to dry. Remove any trim from the floor and ceiling area.

Glue furring strips to the bricks. This is the surface you will secure the plasterboard to.

Hang the plasterboard by attaching it to the furring strips. Tape and mud your plasterboard seams.

Prime and paint your surface to match the room. Replace or install the trim to your floor and ceiling.