How to Build An Outdoor Fireplace Step-by-Step Guide

You can build my fireplace kit in a weekend. It is that simple.

-Roman Stone

So, you have decided to take your backyard to the next level? Maybe you’re wondering how to build a fireplace. Is it a good fit for your family and lifestyle? The great thing about the Fremont outdoor fireplace kit is that it isn’t just a beautiful piece of patio décor, it is a relaxation centerpiece. Just picture gathering your friends and family outside to share stories by the crackling of the fire.

However, even though cuddling up next to an outdoor fireplace seems like a great way to de-stress and forget about the world, people often hesitate on whether they want to build an outdoor fireplace in their backyard. They hear “DIY” and instantly think there is no way I can do that. My Fremont outdoor fireplace kit is designed to be quick and simple. You won’t be messing with special tools or cutting any material. Stack and glue the pieces together as I have shown in the step by step instructions.

Step 1: Check local codes

Be sure to check any State, Local, or HOA codes and restrictions for an outdoor fireplace. Usually, these are as simple as meeting clearance requirements from structures and property lines. You may need to add a simple spark arrestor. Unfortunately, open fires could be banned. Be sure to check with your local municipality to ensure a compliant build.

Step 2: Develop A Plan of Action

The first step is to go in the backyard and see if you have the right amount of space. The Fremont fireplace kits dimensions without add-ons will need a 52” W x 48” D x 91” T space. Are you going to want to burn wood or use gas logs? Will you need extra chimney clearance? Ask yourself these questions now so that you won’t be caught off-guard later. Whether you want a taller chimney height, wood storage on the side, or go with gas logs, I offer plenty of options to modify the kit to your liking. If you need help planning your outdoor living space, check out my article on it here.

Step 3: Build your foundation

You will need to spend some time preparing for the foundation. You can find the guide here.

I know your eager to get started but having a solid foundation to put the fireplace on top of is the first and most important step! I cannot overemphasize this so watch my quick video guide and get your shovel ready!

Many people build on concrete, and there is nothing extraordinary to do outside of using standard best practices. There are only a few things to consider. Concrete still needs a 4"-8" crushed aggregate base on which to rest.  Don't pour it directly on the soil.  The concrete also needs steel reinforcement.  Be sure to build it properly according to local codes.  You will want a minimum 4" thick -up to 8" thick reinforced concrete pad.  If you are building on a pre-existing concrete pad, or one much larger than your fireplace footprint, be sure to form or cut expansion joints around the fireplace.  Expansion joints will ensure that the weight of your structure does not crack your concrete pad.  You can practically hide the expansion joints if you choose.  Lay out the first course of blocks.  Tightly mark around them with a permanent marker.  Remove the blocks.  Use a concrete saw to cut along the lines outlining where the blocks will go.  When you reposition the first course, the blocks should hide the expansion joints. Cutting or forming these expansion joints will give your fireplace its own separate pad.  When movement or settling occurs, this pad will move independently of your main slab.  The isolated pad will minimize or eliminate cracking of your main pad due to the constant weight of the fireplace.

Step 4: Gather your tools

Tools Needed:

Not needed but definitely recommended is Romanstone now infamous "Big Ass Square."

  • Dead Blow Hammer
  • Hammer
  • Caulk Gun
  • 4 Foot Level
  • Torpedo Level
  • Square (Big Ass if possible)
  • 2 Ladders (6 Ft Min)

Step 5:Build your Fireplace

Here is an overview of building a fireplace and wood boxes. This video shows the older model, but I believe it is still helpful to get a good idea of what is involved. Realize the new model is even easier to build.

Lay your foundation block

Alright, the hardest part is over! As you start to lay your foundational blocks, I recommend you begin from the center because the middle of the base aligns at the middle of a full block helping you center your fireplace for optimal placement.

Note: As you construct your kit, be sure to keep it all level, square, and plumb. Use a four-foot level and check often. Starting on a level foundation is key. When gluing blocks together, be sure not to use too much adhesive – this will cause the blocks to “swim.” Just a small bead of glue is ideal as the gravity of the blocks themselves will hold the fireplace together, the glue is just insurance.

Build the firebox

The firebox is the heart of your fireplace. In essence it is exactly what it is called- a box.  Be sure to keep your box flush, level and plumb. Using a Big Ass Square will definitely help. Start building from this outside corner. Keep your structure flush, level, and plumb.

There is nothing particularly difficult about the firebox construction. It only has a two key features that you will keep in mind when building. It is lined with firebrick, and it has an opening which will require a lintel. Both are relatively simple build. The instructions will guide you every step of the way.

The fire brick are an additional layer of masonry that keeps fire from attacking your structure. All the firebrick are included in the kit. Be sure to note the cut pieces. Note the  airgap in the corner of the firebox. 

Next, you will be placing your lintel block at the top of the firebox opening. It is important to do this exactly as shown ensuring to glue these blocks as they will be supporting your angle iron.

Place your angle iron such that the top of the angle leg is flush with the top of the lintel blocks. You may need to use coins as shims or add sand under the angle iron to make it flush. Be sure to center the iron to the firebox opening roughly. The extra room will allow for the angle iron to expand.
To complete the rest of the firebox, you will need to set up TEMPORARY support blocks. Be sure just to catch the corner of the support block as it will be easier to remove later.
The firebox portion of the build is complete!

Build Your Smoke Chamber

Now that your firebox is complete, this is a good time to take a break and allow the glue to set-up.

As you begin to build the smoke chamber, rack the block in approximately 2” from each side and about 4” from the front. Due to the tumbled nature of the blocks, it might be difficult to get a good measurement without a special jig.  You can make a jig, or just use the finger method as shown below. Its as accurate as you need to be.  Remember: If it looks good to your eye, it looks good.

Here you can see the smoke chamber being built. As you continue building the smoke chamber, you will keep the back wall of the fireplace plumb while racking the block in approximately 2” from each side. Always use a straight edge to keep your runs straight.

Build the Chimney

With the smoke chamber complete, you will move on to the chimney. This is a simple process of stacking your block while ensuring everything stays level, square, and plumb just like before. The chimney is the same size all the way up. This will ease construction. If you have wood boxes, please build those so you can stand on them when constructing your chimney. Not only is it safer than ladders, it is easier, too. You can always extend the height of the chimney up to an extra 48" using our Chimney Extension kits. This will ensure your chimney can clear any obstacles or structures as needed.

Chimney Extension of Fremont Bethany Ledge blend

Add Your Cap

I know you are ready to relax by the fire and I promise we are almost there. Be sure to take your time and be well rested. If you follow the instructions, this will be done the following day after you finish the fireplace, so the rested part should be taken care of. Outside of getting your foundation level, placing the cap is the next hardest part of the entire build, use ladders, and a friend. Be sure to go over your plan. Have a safety escape planned in case the final cap gets dropped. Your fireplace parts are not as important as your body parts! Be safe and take your time. You can also use the ledges created by the racked block as a “stairway” to move the block up until the final heave. Again, having wood boxes installed makes this much easier and safer.  If you don't have enough man power, WAIT. Plan to install this when you can do it safely.

Add the Finishing Touches

Last but not least, we need to add all of our finishing blocks. These block are the lightest and smallest pieces in the build. They are used for trimming the top of the chimney, and creating a mantle. Glue these trim pieces down well as they are the only block that isn’t locked into place.

Allow the fireplace to cure for 72 hours before building your first fire.

Congratulations! Your outdoor fireplace is complete. I’d tell you to pat yourself on the back, but your shoulders may be sore. I hope you enjoy your new fireplace and relaxation centerpiece. If you can build this, you can build any of my kits. Come to think of it; you could use a new grill

Patrick Vu

related posts:

Measurement for putting a fireplace and wood boxes kit into a corner

How to Build a Fireplace in a Corner

How to raise your Fireplace Kit

9 Small Patio Designs with BIG Impact

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