A fireplace is a natural focal point in any room. But if your fireplace surround isn’t up to par, it may not be making the statement you want it to. Fortunately, upgrading it doesn’t have to be expensive. With this DIY tutorial, learn how to build a fireplace mantel with crown molding and MDF.
This post is another in the “upgrades to my builder grade house” saga.
Let me start by saying I love my fireplace.
This is the first time that I have ever had a gas fireplace and I love being able to turn it on with the flip of a switch.
And there is nothing quite like curling up in comfy chair in front of the fire on a rainy day.
Having said that, the look of my builder grade fire place wasn’t exactly what I wanted, and I didn’t want to spend much money to upgrade it.
The “Before” fireplace
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Here is the fireplace that I started with. There were 3 basic issues:
1. All that surrounded the fireplace were some moldings. There was no mantel…and I think all traditional fireplaces should have a mantel of some kind.
2, The front of the fireplace also had that really ugly brass trim (I have never been able to figure out why they make fireplaces with that trim).
3, The proportions seemed wrong…the fireplace looked too small for the size of the room.
Step 1: Find inspiration
I always start by making a list of what I want the new piece of furniture or room design to have. So here’s what I decided I wanted in my mantel:
- A surround that would add some dimension to the fireplace so that it wasn’t so flat and filled the space better
- A mantel that was wide enough to be able to hold candles…or Halloween decorations 🙂
- A somewhat traditional design (since the fireplace design is fairly traditional), but not too ornate
- No brass!
And I didn’t want to spend too much money…
After looking at pre-made mantels, I decided to make it myself. The already built ones were just too expensive and I couldn’t find anything that I liked (they were all either the wrong size or too fancy for my tastes).
Step 2: Make a plan
First step in building a new mantel? Know the dimensions of the fireplace! Since I was planning on keeping the slate that surrounds the fireplace, I measured it, too.
Using my inspiration picture as guidance, I came up with the following plan:
- I wanted to create 2 plain columns, one for each side of the fireplace. Since the slate was 6″ wide, I decided to make the columns 9″ wide and 3″ deep. I always look at the existing measurements and use an even multiple to come up with a proportional looking build.
- Since I wanted to add some height, I decided to make the columns 12″ higher than the top of the slate.
- I wanted the mantel to extend about 6″ on either side of the fireplace, so that meant it had to be 72″ long, and I wanted it to be 9″ wide (partly because I had a board in the garage that would fit that width).
- That meant that the board which stretches between the columns underneath the mantel would be 12″ wide and 44″ long.
- To add a little interest, I would add moulding…spefically, crown molding under the mantel, chair rail molding just above the top of the slate, some panel molding around the columns (just under the cross board) and baseboard molding around the bottom of the columns
- The last step is to paint
Step 3: Get the supplies
- 4′ x 8′ x 3/4″ MDF panel
- 6 foot length of crown moulding
- 6 foot length of chair rail moulding
- 3 foot length of panel moulding
- 3 foot length of baseboard moulding
- Black Spray Paint
- Circular Saw (or table saw) – I love my cordless circular saw for these types of projects.
- Hammer and nails (or a nail gun if you happen to have one)
- Miter Saw or Miter Box*
- Caulking Gun*
Step 4: Cut the MDF
Use your circular saw or table saw to cut the pieces from the MDF using the measurements from above (if you are using MDF for everything including the mantel) or from below (if you have a separate piece of wood that you want to use for the mantel).
Step 5: Assemble the fireplace surround columns
1. Put half of the columns together by nailing one of the 3″ x 48″ column sides to the 7.5″ x 48″ column back
2. Nail the column back to the wall so that the column side is right next to the slate surround.
3. Assemble the other half of the columns by nailing the other 3″ x 48″ column side to the 9″ x 48″ column front
4. Attach the second half of the column to the part that is already attached to the wall to form a column box.
5. Repeat 1 – 4 for the column on the other side of the fireplace
Step 6: Add the mantel and joining board
1 Nail the joining board to the wall above the slate and between the 2 columns.
2 Center the mantel board over top of the columns and nail it to the tops of the columns.
Step 7: Add crown molding under the mantel board
1 Cut the first piece of crown molding to cover one side of the column with a 45 degree outside angle on the free end. The backside dimension should be 3¾”. Using a molding guard on the miter saw will make sure that the angle is cut correctly for crown molding.
2. Cut the next piece with a 9″ length along the back of the molding and 45 degree outside angles on both free ends.
3. The next molding will fit the inside of the column. One end will be an outside 45 degree angle and the other will be an inside 45 degree angle. The inside length should be 3″ long.
4. Next cut the crown molding to be installed over the joining board. This will be 44″ long on the back side of the crown molding. Both ends have a 45 degree inside angle.
5. The inside of the other column will be 3″ on the backside of the crown molding. One end will be an outside 45 degree angle and the other will be an inside 45 degree angle.
6. The front of the other column will be 9″ on the backside of the crown molding. Both ends will have 45 degree outside angles.
7. The last piece of crown molding will cover the outside of the other column. The backside of the crown molding should be 3¾” long. The end closest to the wall will be a straight cut. The other end is an outside 45 degree angle.
Step 8: Add chair rail and panel molding
1. Install the Chair Rail Molding about 1″ above the bottom of the joining board. This will use the same measurements as the crown molding in Step 8.
2. Add the Panel Molding around the columns just below the edge of the joining board.
a. The panel molding that covers the outside edge of the column will be 3¾” long on the back side with an outside 45 degree angle.
b. The panel molding the goes across the front of the column will be 9″ long on the back side with both ends having outside 45 degree angle cuts.
c. The panel molding that covers the inside edge of the column will be approximately 3″ long on the back side with one straight cut (for the section next to the wall) and one 45 degree outside angle. Make sure to double-check this measurement since the exact size will depend on how thick your slate is.
d. Repeat for the panel molding on the other column.
Step 9: Add base board molding and caulk
1. Cut the base board molding that covers the outside edge of the column to 3¾” long on the back side with an outside 45 degree angle.
2. The base board molding the goes across the front of the column will be 9″ long on the back side with both ends having outside 45 degree angle cuts.
3. The base board molding that covers the inside edge of the column will be approximately 3″ long on the back side with one straight cut (for the section next to the wall) and one 45 degree outside angle. Make sure to double-check this measurement since the exact size will depend on how thick your slate is.
4. Repeat the same cuts for the base board molding on the other column.
5. Now that you are finished with building the mantel, use the caulk to fill in an nail holes and smooth out the edges of your surround and mantel.
Step 10: Paint the mantel
I have alternated between having a white mantel and a black one…but whatever color you choose, painting it is the next step.
And then I finally got rid of the brass on the fireplace (the easiest step of all!) by spray painting it black.
The finished DIY fireplace mantel
The finished mantel makes the statement I was hoping for.
In the current version, I have painted the fireplace surround white and given up trying to hide the TV (mostly because the TV got bigger and was harder to hide).
In any case, the finished product make me happier than what I started with. And the process of building my own mantel was easier than I thought it would be (and cost less than $75).
Other living room decor ideas you might like
- Living room focal point ideas
- Living room layout ideas with a TV and a fireplace
- How to decorate a coffee table
Comments or questions about how to build a fireplace mantel? Tell us in the section below.
This post was originally published on September 29, 2015 but was updated with new content on February 28, 2022.