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How To Build A Fireplace: The Ultimate Guide For Beginners

The winters are getting colder, and many are looking for new heat sources. One option for homeowners is building a fireplace, but I know what you want to ask.

How do you build a fireplace? Where do you build it? With the help of this guide, you’ll know how to build a fireplace and what you need to make one.

How To Build A Fireplace: The Ultimate Guide For Beginners

Before you build your fireplace, you should find out your local building codes. Consult a professional for guidance if you need to. There are several different types of fireplaces that may need you to build according to code. But adding a fireplace to an existing home can be a challenging task.

Building Codes

Building codes can vary depending on where you live. Generally, I have a few requirements you should keep in mind.

Your chimney wall should be 4 inches/100 mm thick unless you don’t use a flue liner. Using a flue liner, your chimney wall should be 8 inches/200 mm thick.

As a rule, if your chimney or flue liner changes shape, it should be within 6 inches of your floor or ceiling.

The smallest height for a chimney should be greater than 3 feet/1 m above the highest point of your roof. If you have adjoining buildings within 10 feet/3 m, your chimney should be 2 feet/600 mm higher than them.

Your chimney should also not have any combustible material within 2 inches/50 mm of it. You can ignore this rule if your chimney is outside.

If your chimney’s outside, a distance of 1 inch/ 25 mm is fine. I would put non-combustible materials between them.

For example, leave them within 1 inch/15 mm between the chimney to prevent fire from spreading.

Remember to seal your chimney’s exterior so no debris falls in. The best way to seal exterior spaces is by flashing and caulking.

If you have a masonry chimney, it shouldn’t stick out more than 6 inches/150 mm from any walls.

Likewise, they shouldn’t stick out from walls less than 12 inches/300 mm thick. This is only acceptable if it projects on each side of your wall equally.

These are the best rules to stick to when you’re building your chimney and fireplace. I recommend always consulting your local authority first before you start your project.

Types Of Fireplaces

How To Build A Fireplace: The Ultimate Guide For Beginners

Before we start, let’s consider the different types of fireplaces around. Masonry is one of the most expensive options, but it looks the best.

Typically these consist of a brick or stone firebox, a chimney, and a hardwood mantel. These are also the most challenging to add to an existing home.

Zero-clearance fireplaces are easier to add to an existing home. These fireplaces are lightweight, more affordable, and need less construction work.

Zero-clearance fireboxes always remain cool, and they can sit over hardwood floors. They don’t even need to go too deep into your walls. These are better for smaller homes, and you can find different fuel types.

Gas fireplaces are the best for the environment and have a lower fire risk. Like zero-clearance fireplaces, they don’t take up much room either.

All you need for a standard unit is a gas supply line and a decent venting mechanism. So, you can either put it where your chimney is or make a new one.

How To Build An Indoor Fireplace

I recommend consulting a professional to build a fireplace at home. If you have an idea, handing the reins over to someone else can be difficult.

That’s why I’ve found a basic outline of how you can build your own fireplace. Remember that all fireplaces are different, and you may seek a specialized approach.

It’s pretty easy to build your own stone and brick fireplace. But if you’re adding to an existing home, it’s a little complicated.

You first need to build your foundation. The foundation is the most important part of your fireplace. Many people forget how heavy fireplaces are and forget you need to reinforce them.

Your base should be 100 mm below your floor level and needs to be thick and wide enough to support everything.

Your frame will be metal, and you’ll usually place it roughly 2 inches to the side of your fireplace. Remember that your wall should be 4 inches wider than your masonry opening. Your header should then be 3 inches above it.

If using a firebox, your hearth must consist of firebrick and refractory mortars. Remember the smallest width of each joint should be 1 sixteenth of an inch. If you don’t have a firebox, you should cover all sides with the above materials.

Your firebox will come with a steel frame glass door which you can use as a guide for the height and width. All you need to do is layer the edges with a firebrick and nine-inch refractory mortar.

You need backup masonry to prevent your firebrick from cracking. This should be at least 8 inches thick. Reinforce your base with 4 inches of solid concrete. Also, leave a little air space since your firebox will expand with heat.

You can also get a premade throat or build one yourself. They are usually 300 mm and made from refractory mortars and firebrick. I have to admit the size may vary depending on your fireplace.

Of course, you also need your chimney for ventilation. Your chimney needs to be 4 inches larger than your flue. Don’t leave combustible materials within 2 inches of your chimney wall, either. Consult your local building codes to ensure your chimney abides by regulations.


There are many different types of fireplaces for indoor and outdoor use. You always need to ask for permission before building an outdoor fireplace. When you’re building an indoor fireplace, always consider your local building codes.

If you have any questions about building your own fireplace, don’t be afraid to ask an expert. It’s a lot more difficult to put a fireplace in an existing house than a newly-built one.

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