How To Measure For a Fireplace Mantel

How To Measure For a Fireplace Mantel

Since the mantel is the last piece to be installed during a fireplace installation, measure the width and height of the overall outside of the fireplace and any facing material (marble, slate, brick, etc.) first. This measurement should also accommodate for any mantel overlap that you may want to cover the edge of the facing.

Be sure that there is enough clearance to combustibles, meaning that your local building codes and fireplace model specifications determine how far away combustible materials, such as a wood mantel, must be from the face of the fireplace. Your professional builder and/or installer will know how to determine this and accommodate for it.

Next, depending on what facing material is used, will determine the depth of the inside return of the mantel. By 'return' we mean the depth of the measurement from the back/inside face of the mantel to the wall where it is being installed. We recommend taking three different measurements of the thickness of the facing material and using the largest of the three.

Larger returns are available for thicker facing material applications, for instance brick. The return will simply increase to accommodate the thickness of the facing. The return will always need to be at least ΒΌ" greater than the facing material's thickest point, and this will also ensure accommodations for any walls that are not smooth.

Once you have this information, opening W x H x D, for your mantel, be sure there are no restrictions to accommodate the overall outside measurements of the mantel. Windows placed close to the fireplace, wall outlets/switches, and other obstructions above the fireplace may drastically alter your mantel measurements. It is best to notify us of these restrictions FIRST, before beginning to determine measurements for your mantel.

Congratulations! You now have the full information required and are ready to proceed with purchasing your new mantel.

Measuring for a fireplace mantel

Step-By-Step Mantel Measuring Guide

Before starting, you'll need to check your local building codes and your fireplace's manual to see how much clearance you'll need to combustible material. Because most surround mantels are made of wood, you'll need to make sure that the facing material is sufficiently large to give enough distance away from the firebox. For the most part this is different for every fireplace and in most locations, so take this into consideration and do some research. Discuss it with your contractor or installer -- they should know how to determine the proper amount.

You might want to look at the mantels we have available and use the methods below to make sure it's going to work for you. Make sketches and take notes as you go; ordering a mantel is straightforward but not necessarily simple. Make sure that you have a good idea of what you want and all of the available information before buying.

During any fireplace installation or remodel, the mantel is always the last component to be installed. This means that your fireplace should already have the firebox and surround facing material (brick, stone, marble, tile, etc.) installed.


Diagram showing the firebox, the facing material, and the hearth

First, locate your facing material (also called the fascia) and the hearth. For this example we will be using marble material.


Example diagram showing how to measure the height and width of the fireplace facing material and hearth.

Measure the width of your facing material, and measure width of the hearth (if you have one). Measure the height of the facing material from the floor if there is no hearth, or from the hearth if you have one. if your material is uneven, you'll want to take three measurements on each side and go with the smallest one. In our example the facing material is 40" wide by 38" high, with a hearth width of 52".


Diagram showing the facing material protruding from the wall 1".

Some facing materials are flush with the wall, while others protrude from it. Make sure to measure how much the facing material sticks out from the wall -- you will need this measurement later. If the wall or the facing material seems uneven, take three measurements and use the largest one. In our example the marble protrudes 1" from the wall.

Diagram showing where a mantel might possibly be in relation to the fireplace.



Now that we have the measurements of the facing material, we will need to determine the size of the mantel. Try to visualize where the mantel will go as you work. This will help your to anticipate where you need to take the following measurements, and any possible obstructions that you might find during installation.

Because most of our mantels are custom made some models can't be returned -- be sure to get the right measurements the first time!


Diagram showing the inside width after the half inch is subtracted.

The inside of the mantel surround will need to overlap the facing material on each side to hide the edges. You have some play here, but most builders overlap 1/2" on each side, so you will subtract 1/2" from the facing height, and 1" from the facing width (1/2" from each side). So in our example, our inside width will be 39" and our inside height will be 37-1/2".


Diagram showing the maximum width for the legs.

The outer width will need to fit on the hearth (if you have one). This can affect the maximum width of the mantel's "legs." Check this measurement on the mantel you are considering to make sure that you have enough room that the edges of the mantel legs will not stick out when installed. Because the hearth in our example is 52" wide, we can have legs up to 6-1/2" wide (52" - 40" = 12", or 6" on each side plus 1/2" each for the overlap)

If you don't have a hearth, you're only limited by obstructions on the wall.


Diagram showing possible obstructions to mantel installation.

Next you will need to make sure that there are no architectural obstructions on the wall (light switches, protruding beams, windows, doors, etc.) or on the ground (register grates, shutoff valves, electrical outlets, etc.) that will prevent you from installing a mantel. Remember, the breast of the mantel (the box on top) is usually quite high and the shelf is normally wider than the overall mantel, so you are limited by your fireplace's surroundings.

If you find any obstructions and aren't sure how to proceed, make as detailed a note as you can (measurements from the fireplace surround, the floor, etc.) and give us a call at 1-888-986-1535 so that we can try to find an alternative.

Don't forget: We took a measurement for how much the facing material protrudes from the wall. This measurement is called the "return" of the mantel.


Diagram showing what we mean by the "return" of the mantel.

The return is the measurement from the wall to the back of the mantel surround. In most cases the mantel will not rest against the facing material but sticks out further, giving the mantel some depth.


Diagram showing the return with example measurements.

In order to take this measurement, try to find the thickest point of the facing material and add at least 1/4" (although you can add more if you'd like a deeper frame). So in our example, 1" + 1/4" = 1-1/4" return.


Diagram showing the scribe molding installed.

I know what you're thinking: "Won't this leave a gap between the fireplace facing material and the side of the mantel?"

Actually, no -- surround-style mantels come with a piece of scribe molding for the inside of each leg that you can adjust to fit snugly against the fireplace's facing material.


Check out our Fireplace Mantel selection!

That should just about do it, but if you're unsure at any point as to how to proceed, gather your notes and give us a call at 1-888-986-1535 or email us with your concerns -- we're happy to help!

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