How to Build a DIY Fireplace Mantel: A Step-by-Step Guide with Bold Paint Makeover

A DIY fireplace mantel with stained wood and a black brick paint.

When we bought our house, the fireplace was a focal point in the living room but desperately needed some love. The insert was rusted, outdated, and, according to our house inspector, a fire hazard. Living in the South and moving in June, we never needed a fire anyway. Instead, we focused on giving this space a complete makeover with a rustic DIY fireplace mantel and a bold black paint finish.

The results? A fireplace that not only complements our home’s color scheme but also covers up an awkward strip of tile left from a previous kitchen countertop project. Here’s how we tackled this DIY project and turned a potential eyesore into a stylish centerpiece.

Before image of the fireplace in a living room.

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Materials and Tools for Your DIY Fireplace Mantel

Before diving in, make sure to measure your fireplace dimensions and adjust the materials as needed for a snug fit.

Materials:

1×6 boards: 1 cut at 68.25 inches (front), 2 cut at 11.25 inches (sides)
1×12 board: 1 cut at 66.5 inches (top piece)
1×2 board: 1 cut at 66.5 inches (underside)
1×3 boards: 2 cut at 8.5 inches (end underside pieces)
Wood stain (we used Varathane Provincial)
Polycrylic for sealing
Wood glue
Wood filler
Optional: Paintable cord cover for TV wires

Tools:

Nail gun and nails
Sander (120 grit sandpaper)
Paintbrushes

(This is assuming you already have everything in our Getting Started with DIY Toolbox)

Cut list and assembly guide for DIY fireplace mantel

Step-by-Step Guide to Building a Rustic DIY Fireplace Mantel

Assemble the Fireplace Mantel Box

To create the mantel box, start by laying out the top piece (1×12) upside down. Attach the side pieces (1×6) to either end using wood glue and nails. Secure the front piece (1×6) to the sides in the same manner.

Next, attach the underside pieces:

Glue and nail the 1×2 piece to the back of the front board.
Attach the two 1×3 pieces to the shorter side boards.

This process creates a clean, seamless box with one open end. Fill any gaps with wood filler for a polished finish, then allow it to dry.

Note: We deliberately made the top piece of the box not quite as deep as the mantel so there would be a little sunken strip for our TV cords to sit out of sight.

Sand and Stain the Mantel

Use 120-grit sandpaper to smooth the entire surface, paying extra attention to areas with wood filler. Softening the edges can give your mantel a more rustic charm. Once sanded, apply a coat of Provincial wood stain and let it dry. Finish with a layer of Polycrylic for durability and easy cleaning.

Install Your DIY Fireplace Mantel

Once your mantel is dry, it’s time to install it:

Apply wood glue to the top of your existing mantel and slide your new box into place. Weigh it down with heavy objects for a few hours to secure it.
For a removable option (perfect for renters), screw the mantel into place instead.

Painting the Fireplace: A Bold Black Statement

Choosing the Right Black Paint

After completing the mantel, we decided to give the entire fireplace a bold makeover with black paint. The transformation started with removing the old, rusted insert and capping off the gas line—a task we wisely left to a professional.

I did one coat of the black (SEE THE CUSTOM PAINT COLOR HERE) but did touchups, ran out of paint and left it splotchy for a shameful SIX WEEKS.

Initially, we debated tiling over the uneven brick, but leveling it seemed daunting. Instead, I painted the brick and tile black. For added texture, I mixed a stone paint additive with the second coat to blend the tile seamlessly with the brick.

A stained DIY fireplace mantel with a gap for a TV cord to fit behind hidden.

DIY Fireplace Mantel Final Touches

To hide our TV and PlayStation cords, we used a paintable cord cover. It’s one of those details that subtly elevates the overall look without drawing attention.

Now, our DIY fireplace mantel and bold black paint job have transformed the living room. It’s the perfect mix of rustic and modern, standing out beautifully in our otherwise neutral space.

FAQs About DIY Fireplace Mantels

What type of wood is best for a fireplace mantel?
Pine is a budget-friendly option that’s easy to work with, but hardwoods like oak or maple offer more durability.

Can you paint over a brick fireplace?
Yes! Painting brick with a high-quality interior paint creates a fresh, modern look.

How do I remove an old fireplace insert?
It’s best to hire a professional for this task, especially if gas lines or electrical components are involved.

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