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Masonry - vs - Zero Clearance
How To Tell the Difference

Masonry Fireplace
Zero Clearance Fireplace

Before you begin shopping for fireplace doors, it is critical that you determine whether you have a masonry or prefabricated fireplace (also referred to as: "zero clearance", "zc", "prefab", "manufactured" or "metal" fireplace). Masonry fireplaces are built from non-combustible materials that insulate the fireplace from the rest of your home, so there are no special requirements for Masonry Fireplace Doors to keep the firebox cool. A zero clearance fireplace is a metal box with a metal flue that is framed into your home. There are built-in air passageways that keep the outer casing of the firebox cool so that the framing members do not catch fire. If the airflow is restricted by installing the wrong type of fireplace doors, the fireplace can overheat and result in a potential fire hazard. ZC Fireplace Doors are specifically designed to allow air to pass through these vents and keep the fireplace cool. The information on this page will help you identify which type of fireplace you have

Email Your Pictures

The best way to determine the type of fireplace you have is to email us some pictures. Our experts will likely be able to make the determination at a glance and help you find the right doors.

Use this link for: Instructions on Emailing Pictures!

How To Identify Masonry Fireplaces:

Fig. #1
Fig. #2
Fig. #3
Fig. #4
Fig. #5

A masonry fireplace is built by a mason from ground up using completely non-combustible materials such as Brick or Stone. The inside the fireplace is lined with real firebrick on the floor and sides (Fig. #1) and there is not any visible black metal inside, with the exception of some older heat-form fireplaces. The chimney outside the house is commonly made of brick (Fig. #2) or stone, but in some cases the masonry chimney is covered with some other material such as siding or stucco (Fig #3). The inside of the chimney is usually lined with an oval shaped ceramic flue liner that can often be seen protruding from the top of the chimney (Fig. #4). The damper is normally rectangular in shape and will have a large lever that you push back to close or pull forward to open (Fig. #5).

Shop For: Masonry Fireplace Doors

How To Identify Zero Clearance Fireplaces:

Fig. #6
Fig. #7
Fig. #8
Fig. #9
Fig. #10

The most obvious way of identifying a zero clearance fireplace is the existence of black metal, either exposed on the face or inside the firebox (Fig. #6). Some fireplace manufacturers are doing a better job of hiding the metal and making fireplaces that look more like masonry (Fig. #7). Prefab fireplaces will almost always have fake brick panels lining the inside of the fireplace that are made of a cast refractory material (Fig. #8). They will also have a round metal damper and flue, which you will see if you look up inside the fireplace (Fig. #9). The flue is usually 8" or 10" in diameter, but sometimes larger. The exterior chimney (or chase) is typically covered with stucco or siding (Fig. #10), but is sometimes covered with brick or stone veneer. There will also be a metal cap, sometimes covered with a shroud (Fig. #10).

Shop For: Zero Clearance Fireplace Doors

Fig. #11

Look For a Label

Most prefabricated fireplaces will have a metal label inside the fireplace somewhere near the opening (Fig. #11 to right). If you find such a label, take a picture of it and email it to us, it will help us identify the fireplace and make it easier to find the right doors.

If you have any question about what type of fireplace you have, just give us a call at: 1-800-201-1193

Choosing Doors for Masonry Fireplaces:

Shop For: Masonry Fireplace Doors

If you have a masonry fireplace you can use normal glass doors that overlap the opening or fit inside depending on the application. With brick fireplaces, the amount the frame overlaps the opening is more or less important depending on the width and depth of the mortar joints between the bricks. When it comes to stock size glass doors, the amount of overlap is determined by the size of your opening compared to the stock size that most closely fits your opening, so in some cases, even though a size chart determines that a door will fit your opening, it may not sufficiently overlap to cover wider mortar joints. Also, there is a metal bar that extends across the top of the fireplace opening called the Lintel bar. The lintel bar is set in place during the construction of the fireplace facing so as to support the upper row of bricks as the mason lays them across the top. The thickness of this bar as well as how far back from the opening it is placed must also be accounted for to ensure that it is not in the way of any sub-frame that extends behind the face of your fireplace door frame. These are the types of things that our fireplace glass door experts will look at to make sure the doors you order will fit correctly.


Choosing Doors for Prefabricated Fireplaces:

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Prefabricated fireplaces have air vents that allow room air to circulate through the hollow space between the inner and outer casing of the metal firebox. This keeps the outer metal casing cool enough to prevent the framing members of your home from catching fire. So you must only install fireplace doors that are specifically made for your type of zc fireplace, otherwise you run the risk of creating a fire hazard. Prefab fireplace doors are specifically designed to allow more air to flow into the fireplace as needed so that it does not overheat, whether it be larger gaps between the glass or air gaps around the frame. Conventional doors made for masonry fireplaces would potentially block this necessary airflow. We suggest you email us pictures of your fireplace so we can determine the type of doors you will need.

Read instructions for emailing your pictures here: Fireplace Design Service