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Building a Fireplace Mantel Out of MDF Jimmy DiResta shows how to create a mantelpiece out of medium density fiberboard (MDF). Check out more Hammered projects and videos.

In just a few simple steps, Jimmy DiResta fashioned this simple mantelpiece from MDF.

Overview

Using a table saw and radial saw, Jimmy cuts the MDF and assembles the mantelpiece frame using glue and nails. He then uses a router to soften the edges and adds decorative molding details and corbels. Finally he sands the piece, applies wood putty where necessary and finishes things off with a coat of paint.

Below is a summary of the basic steps as seen in this Hammered project, as well as a list of materials and tools used.

Tools and materials:

3/4" medium density fiberboard (MDF) sheets (three 4'x8' sheets)
water-based latex paint, off-white (1 gallon)
paint brushes
wood putty/filler
router
radial arm saw
table saw
chop saw
band saw
wood glue
nail gun/nails
orbital sander / sandpaper
measuring tape
clamps

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The basic framework is formed from three MDF boxes.

Dimensions

Overall: The basic "squared-off horseshoe" shape (sans molding/details) is 5' high x 5' wide, and is formed out of "boxes" made of MDF.

Dimensions of main elements:

(A) Top horizontal pieces (x 2 = back and front): 14.5" high x 5' long
(A) Side vertical pieces (x 4 = back and front, both sides): 41-3/4'" high x 13" wide
(B) Blocks to cover the seam between the vertical sides and the top horizontal piece: 9.5" long x 3-1/4" wide
(C) Height of walls on all edges: 6"; Inner walls: 48" long

Dimensions of detail elements:

(D) Bottom molding/detail (with routed edge): 5 1/8" wide x 14.5" long x 6-1/2" high. (This element is made up of two vertical pieces and one horizontal. Pieces are joined, like a picture frame, at 45-degree angles.)
(E) Top-most piece laying flat (routed): 10" wide x 66" long. Second piece under top (routed): 3.5" wide x 63-1/4" long. Blocks directly under each overhanging side: 2" x 6"
(F) Molding under top pieces (routed; broken up by corbels; see top/bottom molding for construction): 3.5" wide x 5' long x 6-3/4" high.
(G) Top molding/detail (the strip where the horizontal meets the verticals; also with routed edges): 3" wide x 5' long x 6 3/4'" high. (This made following the same configuration as the bottom molding.)
(H) Corbels: 8-3/4" long x 3" wide. These are two identical pieces, glued back to back; set 5" from each side of mantle across strip, leaving a 45" space between.

The corbels are the decorative braces installed beneath the mantel's shelf.

Steps

1. With a table saw and radial arm saw, cut medium density fiberboard (MDF) to the top horizontal pieces (A) and the side vertical pieces (A), per dimensions. Cut up the blocks (B) to hold the verticals and the horizontal, and glue and nail it into place, clamping as necessary.

2. Assemble the walls (C), gluing and nailing them into place. Also glue and nail the top pieces (from step #1) into place to box in the basic shape.

3. With a chop saw, cut out the three pieces that make up each bottom molding detail (D), and then router the top edge. Glue and nail them into place.

4. Cut and glue and nail the top piece (E), the piece under it (E), and the blocks on either side (E), per dimensions. Router the top two pieces similarly. Cut and glue/nail the decorative molding (F) that is under the top pieces, which will hold the corbels. About one inch from the bottom of this molding, cut an indentation across the length as decoration.

5. Cut out the top molding (G) with its three pieces, and glue and nail them into place. Router the top and bottom edges.

6. With a band saw, cut out the 4 corbel pieces (2 per corbel) (H), notching out the back bottom area to accept the molding created in step #4.
   
   
7. Lightly sand the mantle piece using an orbital sander and sandpaper. Apply wood putty to fill any holes as needed.

8. Apply two coats of water-based latex paint.