How To Build An Outdoor Fireplace With Cinder Blocks

Upgraded Home Team
by Upgraded Home Team

An outdoor fireplace provides a cozy place to gather with friends and loved ones. Permanent landscape elements like a fireplace will also provide an increase to your home’s value. A properly built fireplace can extend the usable season of your backyard, offering you and your guests a unique outdoor experience, even in the winter.

If you are a do-it-yourselfer looking to build your own outdoor fireplace with cinder blocks, you’ve come to the right place. Building your own fireplace is easier than it seems and can be accomplished over the course of a weekend.

To build an outdoor fireplace, you will need to start by pouring a concrete foundation. Next, build your fireplace up layer by layer with cinder blocks before finally installing a firebox.

If you take the time to prepare your build and invest in quality materials, your project will be a success.

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Preparing the Build

Just like any large construction project, it is important to plan out your build before breaking ground. This involves a few different steps including checking the laws and regulations and determining a proper build site.

Laws and Regulations

Local codes and permit requirements may apply to the fireplace you plan to build. Make sure to check about building and fire codes with your local municipality. There may also be a permit process or fee involved. Some areas may not even allow outdoor fireplaces.

Find the Site

Start envisioning where your outdoor fireplace will be built. You must keep the codes and regulations in mind when doing this. You will want to avoid trees, power lines, gas lines, as well as keeping your distance from buildings and fences.

The site will also need to be level. This ensures a safe foundation for your fireplace. If you’re having trouble finding a level site, you may need to have a section of your yard leveled out.

Why Cinder Blocks?

Cinder blocks provide a cheap and easy way to start building fast. The blocks are pre-formed and widely available, so you should have no problem sourcing the materials. Aside from the standard cinder block, you may also consider using corner units for smooth transitions or jamb blocks for creating an opening.

Foundation First

Most outdoor buildings require a concrete foundation, and a fireplace is no exception. You will need to excavate your site, fill it with gravel, and top it with a poured concrete pad.

Excavate Hole

Measure out your build site. Your foundation should be at least 10 percent larger than the dimensions of your fireplace. Dig out the build site to a depth recommended by your local municipality. This will depend on frost depths in your area.

Before digging, always check with your local utility company to ensure you are avoiding any gas or water lines below your property.

Fill Partway with Gravel

Fill your excavated hole with crushed gravel. The gravel gives the concrete a good base and allows for drainage. Without the gravel, the ground would expand and contract with the seasons and cause damage to the concrete.

Fill with Concrete Pad

Create concrete forms using 2 x 6 boards. The boards should run around the perimeter of your build site. Mix your concrete in a wheelbarrow and pour it in to fill the forms created by the wood boards.

The concrete should be at least 6 inches thick to provide the proper support for a heavy fireplace. Allow the concrete to dry for at least 48-72 hours before removing the forms. Voila! You now have a strong base for your outdoor fireplace.

Laying the Cinder Blocks

Now that you have a solid foundation, you can start with your first layer of cinder blocks. Grab your mortar and a trowel and follow these steps:

Step 1: The First Layer

Begin with a half-inch layer of mortar. Start applying cinder blocks one at a time, keeping them in a neat, orderly row. Use whatever tools you find necessary to ensure that the blocks are level, plumb, and square.

Step 2: Use a Level

Using a level is an essential step. Any mistakes made on the first layers of bricks will continue to cause problems as you work your way up. Take your time when laying each block to ensure that it is perfectly level.

Step 3: Check for Holes

Check for any holes on the exterior of the blocks. Fill these with mortar as you go for a smooth, finished appearance.

Step 4: Repeat

Repeat these steps, working your way up the fireplace. As you begin each new layer, the new cinder blocks should cover the space left by the previous layer. Before moving to a new layer, double-check your previous work to check that it is square, plumb, and level.

Installing the Fireplace

Now that you have built your structure, it is time to install a fire-bearing chamber. This central part of your fireplace is called the “firebox”. The firebox can either be made from fire bricks or stainless steel.

Fire Bricks: Fire bricks are a traditional material used for fireplaces. The bricks line the inside of your fireplace and are built to withstand high temperatures. The fire bricks are a cheap and widely available material. Use high-temperature mortar when installing fire bricks.

Stainless Steel: These days, you can also order a custom stainless steel firebox. These are custom made and easy to install, but they can be rather expensive compared to fire bricks. You will need to build your fireplace opening in accordance with the size of the firebox.

Finishing Touches

Our fireplace has a strong base and a working firebox. Now we just need to add some finishing touches, including a chimney and an exterior finish.

Chimney: Chimney height will likely be regulated by your local building codes, so check there for help. A chimney cap can be installed on top to help keep the rain out of your fireplace. This also is a safety feature, as it stops embers from dispersing into the air.

Finishing the exterior: The exterior finish of your fireplace is one of the most important design elements to consider. A few common options are natural stone and a simple plaster. Whichever finish you choose, follow the manufacturer’s instructions for installation. If you are also redoing your fencing to match your fireplace, check out our guide on fence types.

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Related Questions

How do I build a gas outdoor fireplace with cinder blocks?

For a gas fireplace, most of the construction will follow the same steps. However, you will need to consider how the gas line will enter the fireplace. This may require the assistance of a licensed professional. Also, instead of installing a chimney, you will install a vent or flue pipe.

Can this method be used to build a pizza oven?

Yes! If you build your fireplace opening to the correct size, it can also double as a pizza oven. Pizza ovens require extra hot temperatures, so you may need to alter your design to accommodate this. You may also wish to build a smaller fireplace exclusively for pizza cooking!

Can I use a fireplace building kit?

Yes! A kit can be simpler for those without the tools or know-how to custom build a fireplace. The kit will likely still require a level, solid concrete foundation, so follow our guide to create one.

Upgraded Home Team
Upgraded Home Team

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