How to build a Wood Fireplace Mantel

By Pam Wynne June 7, 2023 1 mins read 131 Views

If you recently installed a gas fireplace in your home, or you’re looking to update the decor in your living area, installing a new mantel is a great way to make your fireplace the centerpiece of your room.

The following steps should enable a confident DIYer with a few power tools to create a beautiful custom fireplace mantel in just a few days.

Solid Lumber Cutting List

KEY	QTY.	PART	DIMENSIONS
A	2	Stiles	3/4″ x 2-1/4″ x 8-3/4″
B	1	Bottom rail	3/4″ x 2-1/4″ x 64-1/2″
C	1	Top rail	3/4″ x 3-1/2″ x 64-1/2″
D	2	Mullion	3/4″ x 2-1/4″ x 4″
E	2	Top pieces	3/4″ x 4″ x 71″

1/4-in. Plywood Cutting List

KEY	QTY.	PART	DIMENSIONS
F	1	Center panel	3-15/16″ x 29-15/16″
G	2	Outside Panels	3-15/16″ x 15-15/16″

3/4-in. Plywood Cutting List

KEY	QTY.	PART	DIMENSIONS
H	2	Box top/bottom	5-3/4″ x 66-1/2″
J	2	Sides	5-3/4″ x 8-3/4″
K	1	French cleat – wall	2″ x 64-1/2″
L	1	French cleat – mantel	2″ x 66-1/2″

Determine Its Size

The first step, and perhaps the most important, is determining the size of the mantel. There’s no one-size-fits-all rule or formula, though a few components of your fireplace can guide your decision.

Choosing crown molding played a major role in determining the height of our mantel. I designed it with readily available bed molding available at most home centers. To accommodate larger crown molding, simply adjust the top rail height and mantel top to suit.

For width, often you’ll see mantels one to two feet longer on each side than the firebox or gas fireplace insert. It’s also common to make it the same width as the fireplace’s hearth.

I suggest cutting a few strips of cardboard 9-1/2-in. wide (the height of our mantel) and asking a helper to hold the cardboard above the fireplace, cutting off or bending over pieces until you find the right size for your eye. In my case, I settled on 71 inches, which is 20-1/2-in. larger than my firebox on each side and the exact width of my hearth.

Fireplace Components