Although a fireplace is a beautiful home feature, occasionally it becomes necessary to brick it closed, so knowing how to is crucial. This complicated task is not well suited to the beginning do-it-yourselfer and should be handled by a professional. Those more experienced in home renovation will be able to achieve the project on their own but it will require a good deal of planning and hard work.
The first step to closing a fireplace is ensuring that it is clean and free of debris. Measure the opening of your fireplace to determine how much brick you'll need to complete the project. If the opening is wide than four feet across, you'll need to use a tooth-in method to ensure that the new brick is secured to the older brick, providing more stability for the structure.
A vital part of bricking up a fireplace is inserting an air brick, which allows airflow into the space and prevents moisture from collecting inside the chimney. The air brick should be positioned in the second or third row and installed flush against the rest of the brick. After the air brick has been installed, continue bricking in the rest of the fireplace using standard brick laying procedures.
If there is a gap when you reach the top of the opening and it's too small to fit a regular shaped brick, then you can fill the space with tiles or partial bricks. After the brick and mortar has been given sufficient time to dry, apply plaster over the brick to mask the fireplace completely within the room. Don't forget to leave the air brick exposed, however, as the plaster will prevent air from circulating within the chimney.
Once you've successfully bricked up the interior of the fireplace, don't forget to fit a cowl to your chimney cape. This will prevent debris and animals from making their way into your chimney, while also allowing plenty of air circulation.