how to build a fireplace mantel

[This is Part 2 of my How to Build FIREPLACE MANTEL-102 series.]

Build the Pilaster Cores

Your pilaster cores must be very square, so don’t rush this part.  I can’t emphasize this enough.

Wrapping the core with all the other materials will be an exercise in frustration if your pilaster cores are not square.

My Very Helpful Tip

Read through the entire installation sequence before you start cutting, gluing and nailing.

I do my best to be very systematic on how I write these step by step tutorials — and in my mind they are perfectly clear — but it may not always be clear to you.

So just read through all the steps first so you’re sure it all makes sense.  If something doesn’t make sense, you can always ask me questions in the comment section below.

Now let’s build the pilasters.

how to build a fireplace mantel

Before building your pilaster cores, it’s best to work out a rough sketch of all the mdf and molding layers with their dimensions.

Below  I’ve cut all the pieces I need to wrap the core.  The end result will be a paneled pilaster, room for mounting the corbel, and room for a baseboard to be wrapped around the base.

how to build a fireplace mantel

The Short Side

I want the base cap to return on top of the marble slip, so that meant having a short side.

how to build a diy fireplace mantel

Corbel Space

If the corbel you buy for your fireplace mantel is longer or shorter than the one I used, then all you need to do is adjust this part of the pilaster.

how to build a fireplace mantel

Pilaster Base

I chose to install a different base cap around the pilaster than what I installed in the rest of this condo, but you don’t have to do that.  You can wrap your own baseboard right around the base of your pilaster if you want.

how to install moldings

fireplaces direct

Wrapping Order

I like to wrap the pilaster pieces in this order.

how to install moldings


I don’t use Liquid Nails for this part of the assembly, I use a thinner wood glue so all the panels sit flush up against their mating surface.

23 Gauge Micro Pinner

The beauty of using a 23 gauge micro pinner to hold these panels in place with is that micro pinners have no recoil at all.  Recoil on larger nail guns can knock your perfectly placed panels out of place.

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Test Fit Pieces

Long before I ever get to this stage I test fit all the pieces together to make sure there are no surprises at assembly time.

easy to install moldings

how to build a fireplace surround

how to install moldings

how to install mdf moldings

how to make a fireplace surround

See how easy that was?  The hardest part is cutting all the pieces so that they fit together all nice and snug like this.

Below  I used Liquid Nails and a few 18 gauge brad nails to attach the corbels to the pilasters.

how to install corbels

Pilaster Base

The pilaster bases are just made from 3/4″ mdf board.  You could use 1/2″ mdf if that would work better with your base cap.

how to build a fireplace mantel surround

Install Screen Molding Inside Panels

I love how deep and refined this combination of screen molding and 1/2″ mdf is.  Molding too big for this purpose are often used in this situation, and the grace is lost for the sake of bulk.

corbel on fireplace

Nailer Blocks

Attaching the pilasters to the wall is as simple as making a nailer block that fits inside the core.

how to install moldings

Scribe the inside dimension so you know how wide to make your block, and then make it just a hair narrower so the pilaster slips on snugly but does not need to be forced on.

corbel on fireplace

Glue and nail your pilaster nailer block in place.

how to install a fireplace surround

Add some Liquid nails to make it that much stronger.

how to build a fireplace mantel

How to Build FIREPLACE-102 Series Posts

1.  How to Build FIREPLACE MANTEL-102 for c. $162.00: Part 1

2.  How to Build FIREPLACE MANTEL-102 Part 2: Make the Pilasters

3.  How to Build FIREPLACE MANTEL-102 Part 3: Make the Collar & Capitals

4.  How to Build FIREPLACE MANTEL-102 Part 4: Make the Frieze

5.  How to Build FIREPLACE MANTEL-102 Part 5: Make the Hood

6.  FIREPLACE MANTEL-102 Gallery