How to Close Off a Fireplace Opening

The idea of installing a fireplace is literally romantic, and you might have installed for acquiring a fireplace for acquiring an aesthetic look around your room. But as now you have upgraded the overall design of the room or you do not actually need a fireplace anymore, things aren’t going to be as romantic as they should be.

Honestly, removing a fireplace is the hardest task, especially when you have dust issues. It creates a lot of mess, and you end up with a big mess if you don’t follow the proper process. So, how to close off a fireplace opening in the appropriate ways? Let’s show you how you can do that.


Some of the most annoying things of the fireplace is the wind howling sound that comes through enters through the chimney and the rain beating sound against the metal. While most of the users get used to these sounds but some just don’t want to tolerate them anymore.

One reason you might want to close off your fireplace is to prevent any complications. But don’t worry, with the simple steps below you can easily block off your fireplace. So take a few minutes to focus on the steps and leave all your other tasks behind.

How to Close Off a Fireplace Opening

Method 1: Block the Chimney Flue

Step 1

Put on gloves, safety goggles, and a dust mask. Place a small block of insulation against the damper. Tape it in place with duct tape. Open the door to the furnace. Carefully slide the insulation block into the furnace until it is touching the damper. Close the door and turn on the furnace.

Let the furnace run for about 15 minutes. Check the insulation block. If it is hot, the damper is open. If it is not hot, the damper is closed.

Step 2

This method is used to close off an unused flue after removing the old fireplace insert or refractory brick. You can use this for an outside wall or inside wall chimney; if an inside wall chimney, place a small block of insulation between the flue pipe and the masonry.

Block the Chimney Flue

Step 3

If you simply stuff fiberglass insulation into an unused fireplace or wood-burning stove chimney flue, this will not serve as a good firestop. However, if you do it this way, use plenty of water-resistant tapes, such as fiberglass tape or aluminum foil caulk strip tape to seal the edges of the insulation at all joints.

Method 2: Block the Flue with Furring Strips

1. If you have an unused flue that has never had a fireplace insert, you can close off the entire chimney with furring strips (1×2 or 1×3 lumber).

2. To make a chimney, you will need to get wood furring strips and nail them vertically into the sides of the chimney at all joints. This is the cheapest way to do it.

3. At the top of the chimney, you’ll need to cut out some of this vertical furring strip away at the corners on both sides so that you will be able to attach the horizontal strips that complete the closure.

4. You can also use HVAC metal ductwork or aluminum flashing if you have them available. Just seal the joints with firestop caulking or other water-resistant materials, such as fiberglass tape.

5. You should check with your local building code enforcement office to see if building a box around your chimney will meet safety standards before you start the project.

Method 3: Caulk the Flue Against Weather

1. For this method, you will need caulk that is either silicone or butyl rubber caulking that can be used between -40 to 600 degrees Fahrenheit. All you need to do is cut out the damper and apply the caulking to the flue and sides of the fireplace.

2. Then, put a piece of galvanized sheet metal over the hole and screw it into place with drywall screws or other wood screws that will not rust. You can then paint or varnish the metal to match the trim of your fireplace.

Use HVAC Metal Paper

3. Don’t apply the caulking too tightly against any flue liner insulation you might have placed inside either, as this can compress it over time. Instead, just seal off the cracks between the damper and sides of your fireplace opening.

Method 4: Closing the Fireplace

Step 1

To begin, you must take an accurate measurement of the chimney and determine how many bricks you will need for the project. For this, it would be best to bring along air bricks. These bricks are designed to maintain airflow and will be essential for the success of the project.

 Step 2

Now, start setting a row of bricks. This row should be 12 inches from the existing opening. Make sure to put the air bricks in the middle of the row. Continue making these rows until the opening is completely blocked. After putting all of the bricks properly, let them set.

Step 3

Next, you have to apply a skim coat of concrete. While doing this, make sure to leave the air bricks open. After accomplishing this process, inspect the concrete, and when you will find that it is starting to dry, create some scratches on its surface with a nail. By doing this, you will be able to adhere to the plaster with the bricks properly. Then let the concrete dry thoroughly. D

Step 4

Now prepare the plaster and then start applying it on the surface of the brick. At first, you should apply a light coat. Continue this process until you have covered the entire surface properly. Don’t forget to let the air bricks be exposed. Once you have accomplished the process, let it dry.

Step 5

Okay, then bring a grill to cover the air bricks. In this case, you can use a decorative grill to extend the stylish appearance. You can simply buy this type of grills from any building supply store or from the only shops. Once you bring them, you have to attach it by using some screws. You can also glue it on the respective place.

Use a Decorative Grill

You can also add drywall and attach it with several furring strips. If you are using drywall, make sure to mud and tape the seams of the drywall. That’s it; if you can follow these simple steps, you can close off the fireplace opening conveniently.

Method 4: Closing the Fireplace with Sealent Pens

1. If you have a fireplace insert but don’t want to use it, you can close off the chimney flue with a caulk sealant pen. This will allow some heat to disperse into your living area without having to rebuild anything.

2. Just remove the old fireplace insert and the damper once all of the old caulk and glue have been scraped off your fireplace’s flue and sides.

3. Then, use a utility knife or putty knife to remove any existing caulking from the insert opening and clean it out with paper towels until it is completely free of all debris. Use some mineral spirits if necessary to get rid of any remaining residue.

4. Apply the sealant pen over the flue and sides of your fireplace opening, squeezing out the air bubbles to get an even coating. Applying it evenly is key for this method to work correctly. Then wait overnight until it has dried completely before using your fireplace again to see if you like the results.

Method 6: Closing Off Unused Chimney Flue with Masonry Firestop Materials

1. If any of the above methods didn’t work out for you, your best bet is to have a professional help you rebuild the fireplace opening with fireproof materials that will close off the flue permanently.

Rebuild the Fireplace

2. This insulation has to be strong enough to withstand any updrafts from chimney fires and remain pliable enough so that it doesn’t crack over time. In addition, it will need to be water-resistant so that it doesn’t fall into the opening and block it off even more over time.

3. The firestop material should also be easy to cut and moldable enough to close off your fireplace opening without having to rebuild the entire structure around the flue itself. Of course, you’ll probably need to replace the damper and glass doors in your fireplace.

4. This material can be one of two types: fiberglass batts, which is solid insulation that you can install yourself; or spray-in fireproofing insulation, which has a high compressive strength when dry and can be applied by an experienced professional contractor who is licensed to work with this kind of material.

5. Again, before you do anything, make sure that all codes and regulations regarding fireplace inserts and any attached flues have been met and that no one will come knocking at your door to tell you differently later on down the road.

6. If you’re sure that it’s up to code and don’t need to alter or rebuild anything, you can seal the flue off with the fireproof insulation of your choice.

Method 7: Closing Off Fireplace Opening by Adding a Gas Log Set

1. If you want to completely close off an unused fireplace opening without having to use any caulk or sealant and still be able to use the fireplace for warmth and ambiance, then a gas log set is your best bet.

2. The flue deflector will close off the unused fireplace opening and reflect the heat from the fire back into your living area so that it feels more like natural burning wood than gas logs.

Use Any Caulk or Sealant

3. This type of gas log is also easy to install by dropping it into the existing fireplace opening and hooking up the necessary components underneath your fireplace’s mantel.

4. This means you don’t need to remove your old fireplace insert to get this setup, which makes closing off the unused flue on an insert that much easier.

5. Make sure you get a gas line installed for this if it doesn’t already have one hooked up to it, and make sure you read all the instructions provided with your new fireplace set to keep everything running smoothly before you attempt to turn on your hearth’s gas supply.

6. Again, if you have your doubts about being able to do this type of project by yourself, hire a professional contractor to help you with the gas line installation and placement of the logs.

Frequently Asked Questions

Can You Permanently Close Off a Fireplace?

Yes, you can permanently close off a fireplace using proper techniques.

The first step is to identify the location of the fireplace and mark it with a flag or sign. Next, use wire mesh or metal screening to cover the fireplace’s opening completely. Ensure that there is no gap between the screening and the brick or masonry wall surrounding the fireplace. Finally, use a sealant to protect the screening from weathering and deterioration.

What Is the Best Way to Cover a Fireplace?

There are many ways to cover a fireplace. One way is to use a traditional fireplace cover. This type of cover is made from materials such as wood, metal, or plastic and is designed to protect the fireplace from rain, snow, and debris. Another way to cover your fireplace is with a modern fireplace cover. These covers are made from materials such as glass or stainless steel and are designed to protect your fireplace from the elements.

Another way to cover a fireplace is to use an artificial fireplace cover. These covers are made from vinyl, fabric, or plastic materials and can be installed in minutes. They come in different shapes and sizes and can be used with any artificial fire.

Finally, you can also use an outdoor fireplace screen. This screen is made from mesh material and is designed to keep bugs and other insects out of the fire area.

Can I Block Up My Chimney?

There is no definitive answer as to whether or not you can block up your chimney. It all depends on the type of chimney and the materials that are used to build it.

If you have a traditional masonry chimney, then it is unlikely that you can block it up. This type of chimney is made from clay, brick, or stone, and each material has its own set of limitations when it comes to blocking up a chimney.

If you have a metal chimney, it may be possible to use an obstruction device like a gas vent cap or a grille. However, if the obstruction device is not installed correctly, it could cause serious damage to your chimney.

Cover a Fireplace

If you are unsure whether or not you can block up your chimney, then it is best to contact a professional installer who will be able to inspect the situation and provide an accurate estimate for the cost of blocking up your chimney.

What Is the Code for Fireplace Surround?

1. If you are looking for a fireplace surround code, you can use this online tool to find the code.

2. You can also find the code for a fireplace surround by contacting a local home improvement store or contractor who specializes in fireplaces and surrounds.

Final Thoughts

How to close off a fireplace opening? Is it clear to you now, or are you still confused? Hopefully, the steps will clear all your complications. But in case, if you need further support, you can contact me through the comment section below.

you may read also –

  1. How to Build a Brick Smoker and Pizza Oven
  2. How To Put Out Tiki Torches
Angela Ervin

Angela Ervin

Angela is the executive editor of DIY quickly. She began her career as an interior designer before applying her strategic and creative passion to lifestyle and home. She has close to 15 years of experience in creative writing and online content strategy for housekeeping, home decorations as well as other niche efforts. She loves her job and has the privilege of working with an extraordinary team. She lives with her husband, two sons, and daughter in Petersburg. When she's not busy working she spent time with her family.

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