How to Install Glass Fireplace Doors
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How to Install Glass Fireplace Doors

How to install glass doors for your fireplace.

Nothing is more charming than sitting by a fire on a cold night, but it can be annoying when you have to wait for it to burn completely. Wood fires that are left unattended are not safe. A gas fireplace can be switched off, but the only way to leave a wood fire is to close it off with glass doors.

Most new fireplaces come with glass doors, but you can add this safety feature to an existing fireplace relatively easily. The doors come in standard sizes that fit in any flat firebox opening. Many older fireplaces have surrounds that are undersized so installing glass doors make it safer by blocking the fire from combustible materials such as the wood floor and mantel.

Items you will need

Work light

Phillip's head screwdriver




Socket wrench



Glass Door Kit

These kits come with everything you will need for the installation, including all brackets, screws, anchors, and insulation. The glass doors come in standard sizes, and many stores which distribute fireplace equipment keep popular sizes in stock. If your fireplace is not a standard size, you will need to order a door that may take up to eight weeks. Take the dimensions of your firebox opening, both horizontally and vertically. Make sure to measure in several places and use the smallest measurement for each so the door will slide into the space. You will also need to measure the width and height of your surround between any protruding parts of the mantel. A narrow surround may require a smaller door to accommodate the overlapping firebox edge. It is important to get the proper sized door to prevent any sparks from getting out between gaps along the edge.

Installing a fireplace door is done by fitting the unit into the firebox opening and anchoring it to the masonry. The process is fairly simple when you're dealing with a squared-off brick firebox. If you have a firebox made of rough-textured material, such as

fieldstone, you won't be able to use a standard door because it can't overlap the opening's edge. There are some manufacturers that have glass doors which slip inside the opening without an overlap. You may need to have a custom door made, or square off the opening with a matching stone.  If there are large pieces of loose mortar or protruding stone edge, use a cold chisel to knock them off and even the opening.

Be careful with older fireplaces since drilling into the brittle brick may cause it crack.


1. Attach lintel clamps to door

Stand the door on its bottom edge and remove the screws located on the back of the door where the floor brackets (bottom) and lintel clamps (top) will go. A lintel is a metal angle iron which holds the stone in place. You will need the screws later to attach the brackets and clamps. Assemble the two lintel clamps and attach them to the door at the top.

2. Adjust the clamps

As you tighten the screws that hold the lintel clamps to the upper, rear frame of the doors, the screws fit into a slot in the clamps. This slot allows you to adjust the clamps up or down to precisely align them with the underside of the lintel that runs across the top of the firebox opening.

Now screw the two L-shaped floor brackets in place at the bottom of the door.

You should never lay the unit on the front, it can damage the glass doors.

3. Mark for screw holes

Carefully fit the door into the firebox opening and use caution so as not to scratch the finish. Align the unit into the opening. You may need a portable work light inside the firebox so you can see what you are doing.

While holding the unit in place, reach inside to mark where the bottom brackets meet the floor of the firebox. Use a permanent marker to trace grooves in the brackets.

4. Drill holes for lead anchors

Set aside the door and use a drill with a 5/16-inch masonry bit, drill a 2-inch-deep hole at each of the two bracket marks. Check your instructions that come with the unit to verify the correct size of the drill bit.

5. Insert lead anchors for screws

Use a shop vacuum to remove the dust inside the holes and the surrounding area. Using a hammer, gently tap a lead anchor into each hole until it's flush with the surface of the surrounding brick.

You should always drill into brick, not mortar. The mortar crumbles easily and won't hold the anchor as the screw expands and contracts with temperature changes.

Be sure to drill perpendicular to the surface or you will have trouble getting the screw into the hole and possible misalign the unit.

6. Insulate door

Insert the fiberglass insulation that comes with the door in the channels at the two sides and the top of the unit. It is not necessary to maintain the volume of the insulation as you would in an attic or wall. This insulation is used to seal the door and keep smoke from seeping out, and to protect any finish on the door frame from the heat, not as thermal insulation.

7. Screw door to firebox floor

Carefully slide the door into the firebox opening. Check that no insulation is sticking out around the edge of the frame. Verify that the door is flush to the face of the firebox. By hand, start the screws in the bottom brackets and into the lead anchors. Then tighten with a socket wrench.

If you over tighten the screws you pull the anchor out of the brick or break off the head of the screw.

8. Clamp door to lintel

The clamps that hold the door to the metal lintel bar at the top of the firebox are adjustable. Make sure the clamp is positioned so it can span the depth of the lintel.

Tighten the thumbscrew to clamp the hardware onto the lintel by hand. Use a pair of pliers to give it another quarter-turn.

Over tightening the thumbscrews will bend the clamp.

Final Tips

Make sure that the door unit is square, meaning that the opposite sides are parallel. If the unit becomes racked, it will be difficult to operate the doors. Loosen the screws in the bottom bracket and use the slots to adjust the frame. Tighten when the unit is square.

Many units have slits in the bottom of the frame to allow air to enter the firebox when the doors are closed. This can actually increase the efficiency of the fire place, especially if it is large.

Remember to leave the damper open when you allow the fire to burn down to prevent smoke from entering the living space.

See my Factoid Chimney Inspections and Cleaning to Reduce Fire and Carbon Monoxide Hazards,

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