How to Make Fireplace Opening Smaller

If you have recently installed a new fireplace, you may find that the opening is larger than your previous one. This can be problematic if you want to keep the same surround or mantel, as it may not fit properly.

One option is to install a fireplace insert. Inserts are designed to fit into existing fireplaces and can help to reduce the size of the opening. They are typically made from cast iron or steel and can be used with wood, gas, or electric fireplaces.

Inserts can be a great option if you want to maintain the look of your existing fireplace while also making it more efficient.

Another option is to build a new surround. A surround is the decorative frame that surrounds the fireplace and can be made from a variety of materials, including wood, stone, or tile.

If you want to keep your existing mantel, you may need to build a new surround that fits around the smaller opening. This can be a DIY project or you can hire a professional to do it for you.

Understanding Fireplace Dimensions

When it comes to making a fireplace opening smaller, it is essential to understand the dimensions of your fireplace. In this section, I will cover the two main dimensions that you need to consider when making your fireplace opening smaller.

Height and Width

The height and width of your fireplace are the two most important dimensions to consider when making your fireplace opening smaller.

Most fireplaces are 42 inches wide, while some smaller designs can have as little as a width of 36 inches. Some somewhat bigger models can even be 48 inches wide.

With the height, generally, a mantle should be at least 12 inches above the opening. For a standard fireplace with a 36 inches width, it should be 29 inches tall.


The depth of your fireplace is also an important dimension to consider when making your fireplace opening smaller.

The depth of your fireplace will determine how far back your firebox will sit in your fireplace. Typically, the depth of a fireplace is around 20 inches. However, some models can be deeper, and some can be shallower.

To make your fireplace opening smaller, you will need to measure the height, width, and depth of your fireplace. You can then use these measurements to determine how much you need to cut from your surround to make your fireplace opening smaller.

It is important to note that you should always consult a professional before making any changes to your fireplace.

Materials Needed for Reducing Fireplace Opening

Reducing the size of a fireplace opening requires careful planning and the right materials. Here are the materials you’ll need to make your fireplace opening smaller.


Bricks are the primary material used to reduce the size of a fireplace opening. You’ll need enough bricks to build a new wall inside the existing opening.

The number of bricks you’ll need will depend on the size of the opening you’re working with. You can purchase bricks from a local home improvement store or brickyard.


Mortar is the binding material used to hold the bricks together. You’ll need enough mortar to cover the surface area of each brick and create a strong bond between them.

Mortar can be purchased pre-mixed or as a powder that you’ll need to mix yourself. Be sure to follow the manufacturer’s instructions when mixing and applying the mortar.

Fireplace Doors

Fireplace doors are optional, but they can help improve the efficiency of your fireplace and prevent drafts.

You can purchase fireplace doors from a local home improvement store or online. Be sure to measure your fireplace opening carefully to ensure that the doors you purchase will fit properly.

By using these materials, you can successfully reduce the size of your fireplace opening. However, if you’re not comfortable working with bricks and mortar, it’s best to hire a professional to do the job for you.

The Process of Making Fireplace Opening Smaller

When it comes to making a fireplace opening smaller, there are a few steps you need to follow. Here are the three main steps to follow:

Removing Old Bricks

Before you can make the fireplace opening smaller, you need to remove the old bricks. This can be a messy and time-consuming process, but it’s necessary to ensure that you have a clean slate to work with.

You can use a hammer and chisel to carefully remove the bricks, or you can use a demolition hammer for larger areas. Be sure to wear safety goggles and gloves to protect yourself from flying debris.

Laying New Bricks

Once you have removed the old bricks, you can start laying the new ones. You will need to measure the new opening carefully to ensure that the bricks fit snugly.

You can use a level to ensure that the bricks are straight and even. You can use a mortar mix to secure the bricks in place, and you can use a trowel to spread the mortar evenly.

Be sure to let the mortar dry completely before moving on to the next step.

Installing Fireplace Doors

After you have laid the new bricks, you can install the fireplace doors. This is an important step, as it will help to regulate the airflow and prevent drafts.

You can choose from a variety of different styles and materials, including glass, metal, and wood. Be sure to measure the opening carefully to ensure that the doors fit properly.

You can use a drill to attach the hinges and handles, and you can use a sealant to ensure that the doors are airtight.

Safety Precautions

As with any DIY project, it is important to take safety precautions when making the fireplace opening smaller. Here are some tips to ensure a safe and successful project:

Working with Tools

When working with tools, always wear appropriate safety gear such as gloves and goggles.

Use caution when handling power tools and make sure they are in good working condition before use. When cutting or drilling into the fireplace, be mindful of the surrounding area and take care not to damage any nearby surfaces.

Dealing with Ash and Soot

Before beginning the project, make sure the fireplace is completely cool and free of ash and soot.

Wear a dust mask and gloves when cleaning out the fireplace to avoid inhaling any harmful particles. Dispose of the ash and soot in a metal container and keep it away from any flammable materials.

In addition, it is important to have a fire extinguisher nearby in case of any accidental fires. Keep a carbon monoxide detector in your home to ensure proper ventilation and air quality.

Maintaining a Smaller Fireplace

As a homeowner with a smaller fireplace opening, it is important to maintain it properly to ensure its longevity and safety. Here are some tips on how to maintain your smaller fireplace.

Regular Cleaning

Cleaning your smaller fireplace regularly is crucial to prevent the buildup of soot and debris, which can cause blockages and increase the risk of chimney fires.

I recommend cleaning your fireplace at least once a year, preferably before the start of the winter season.

To clean your fireplace, you will need a few tools, including a chimney brush, a vacuum cleaner, and a dustpan and brush.

Start by removing any debris and ash from the fireplace using the dustpan and brush. Next, use the chimney brush to clean the inside of the chimney flue. Finally, use the vacuum cleaner to remove any remaining debris.

Inspection and Repair

Regular inspection and repair of your smaller fireplace is also essential to ensure its safety and efficiency.

I recommend having your fireplace inspected by a professional at least once a year, preferably before the start of the winter season.

During the inspection, the professional will check for any signs of damage or wear and tear, such as cracks in the chimney flue or damaged bricks.

If any issues are found, they should be repaired immediately to prevent further damage and ensure the safety of your home.

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