Materials

Part	Qty	Dimensions	Link
Frame & Face/Surround (Steps 1 & 4)	2	1x4x8	Maple Plywood
Outer Frame Part 1 (Step 2)	3	1x6x8	Pine
Outer Frame Part 2 (Step 2)	3	1x4x8	Pine
Internal Blocking (Step 3)	3	1x2x8	Pine
Inner Frame (Step 4)	3	5/4x4x8	Pine
Crown Molding (Step 5)	3		Crown Molding

Tools & SUPPLIES

• Miter Saw
• Table Saw
• Biscuit Joiner
• Wood Glue
• Brad Nailer
• Brad Nails
• Trim Screws
• Positioning Squares
• Drydex Spackle
• Bessey Clamps
• Dewalt Quick Clamps

Rough sketch

1. Build the Frame

Building a frame for the fireplace mantel is the first step for the mantel. It will provide the foundation and general height and width of our finished mantel. We used measurements that worked with the size of our fireplace as well as referencing industry standards when it comes to mantel sizing. As shown below in 2nd image, we used maple plywood and cut 3 rectangular pieces with our table saw (ignore the miter 45 degree angles on the sketch, I was feeling a bit ambitious on paper). A track saw or circular saw with a straight edge jig would also work great for this step. For our fireplace, we went with the sizes listed below. Once the cuts were made, we then assembled them using a biscuit joiner to ensure alignment with wood glue. Once complete, it should look like the images below.

TIP: If you plan to paint your mantel, we recommend a closed grain plywood such as maple. This will ensure a smooth paint finish as the grain will not show through the topcoat.

Also, I highly recommend the Bessey clamps (red clamps in 2nd image below) in order to apply the proper pressure for the strongest joints. You could also use pocket hole screws as an alternative option.

2. Build outer frame

Now that we have our foundational base frame, the next step is to add the outer frame which will provide the finished depth of our mantel. For our mantel, we opted for 5 1/2″ depth by using standard 1×6 boards.

To start, we cut 3 1×6’s with a 45.5 degree angle to match the height and width of our base frame plus 3/4″. Once these pieces were cut, we also ripped a bevel on the boards through the table saw on a 45.5 degree angle. We then glued and trim nailed them into the base frame, ensuring that the pieces sat perfectly square by using these square positioning jigs. Once complete, it should look like the image below.

In order to give the illusion of a thicker mantel, we also cut and ripped corresponding inner boards on the inside of our outer frame with a 45.5 degree bevel. To cover the triangular slot, we then ripped a triangular piece that matched the width of our triangular. We found this clever hack through Coco & Jack’s fireplace mantel tutorial. Take a look at this video for more details. Otherwise, you can simply buy thicker boards as well. After these steps, our mantel’s outer frame has a depth of 5.5″ and a thickness of 1.5″ through the triangular illusion hack mentioned above. Props to Coco & Jack!

At this point, your mantel should look like this:

TIP: It is best to set your table saw slightly past 45 degrees in order to ensure that your seams are tight and the glue has space to sit on the joint.

3. Add Internal Blocking to pack out the inside of the mantel

To fatten up our mantel, we added 1.5″ boards (also known as 1×2’s) on the face of the base frame as shown in the cross-section view below (see segments labeled 1.5″). To orient you, the base frame is on the bottom of this diagram and the outer frame is on the left. This would allow our mantel to thicken up and finish at the appropriate depth for our face frame and crown molding which we will install in a later step.

4. BUILD face and inner frame

Next, we essentially repeated Step 1 in order to the build the face of the mantel. Again, we cut this using our miter saw but you can use a circular saw with a straight edge or a table saw. We then biscuit joined and glues this as well to ensure coplanarity. We then laid this upon the 1x2s as shown in the images below.

Next, we also added 5/4 boards for the inner frame. We simply mitered these to tightly fit the outer dimensions of our fireplace window. You can see these as the white boards in the 2nd image below.

At this point, your mantel should look like the below. Now you can leave this as is if you want a more modern look. But if you’d like to dress it up a bit more, you can proceed to the next step to add some crown molding.

5. ADD CROWN MOLDING

To add the finishing touch, we added crown molding to the inside part of the frame. This required us to cut 3 pieces that nestled the inside of the outer frame as shown below. We brad nailed them flush with the outer frame and spackled/sanded the seam in order to make the seam disappear.

FINISHED PRODUCT

I hope you all enjoyed this tutorial! Please reach out if you have any questions!

Sincerely,