Pocket-Screwed Panels Are the Building Blocks
Pocket-screw joinery is the foundation for all my mantel projects. Most of my mantel details are based on frame-and-panel construction, which I assemble on site with pocket screws.
Because pocket-screw joints go together quickly and require little clamping or sanding, the author uses them to build the frame-and-panel assemblies that make up the mantel.
To add depth to the pilasters, he glues and pocket-screws 1-by rippings to the frames, pinning them them in place first so that they are inset slightly from the edges of the panel.
Later, he will trim the panel edges flush with a router.
Next, after fastening the plywood panel to the frame, he fills in voids and dings with wood glue mixed with sawdust.
Then he cleans up the joinery with a few passes of a belt sander.
For example, the lower pilasters on this project are basically frames built with poplar stiles and rails glued and pocket-screwed together. The panels are cut from 3/4-inch birch plywood and are simply nailed to the back of the frames. In cases where the panels are mounted directly on the wall, such as this surround's three-panel overmantel, I cut the panels from 1/4-inch plywood.
Because the pilasters project from the wall, I build out the frames with 1-by rippings pocket-screwed along both outside edges at right angles to the stiles. All of the dimensions for these pieces are derived from my story pole.
I trim the insides of the frames with panel molding.
The pilaster panels are trimmed out with an imprinted panel molding. To help size the panels so that the pattern remains continuous as it turns the corners.
The author lays out the stiles and rails using a precut section of molding as a spacing jig.
He back-cuts the miters slightly with a block plane so they'll slip easily into place during installation.
For these pilasters, I used a 2-inch-wide molding with a beaded edge and an applied lamb's tongue overlay, a repeating pattern that requires a little extra care in layout. I like the pattern on this molding to run continuously around the miters rather than meet haphazardly at the corners, which means I have to fine-tune the panel size. Since this particular pattern repeated about every 1 1/4 inches, the panel dimensions had to be adjusted by 1 1/4-inch increments; otherwise, the pattern would be interrupted as it turned the corners.
Once I've determined a panel's approximate dimensions, I can cut its molding to the exact lengths required by the pattern. When I assemble the stiles and rails, I lay the actual cut pieces of molding in place along the stile or rail to indicate each component's exact position.
The lower pilasters here are topped with carved corbels, while the bases are built out with additional moldings. To make sure the glued corbels wouldn't move after I positioned them, I used my 23-gauge pinner to initially secure them to the pilasters, then drove screws through the backs of the panels and into the corbels.
After applying glue and carefully positioning the corbels, the author pins each in place to make sure it won't move, then screws into it through the back of the panel for a strong connection.
When installing the pilaster bases, he is careful to place the molding so that the repeating pattern turns the mitered corners symmetrically.
My pinner is also handy for securing all of the various moldings in this kind of project; it won't split some of the more delicate pieces, and the holes left by the fasteners are so small they may not even need filling.
Building the Boxed Mantel
The mantelshelf is really a simple plywood box with moldings covering the joints. It's sized so that the plywood bottom is 1/2 inch wider than the projection of the corbels it sits on, while the length equals the outside-to-outside measurement of the lower pilasters.
The mantelshelf begins as a plywood box, butt-jointed along the bottom edge and with the front and sides mitered together. A few cleats pocket-screwed inside reinforce the box.
The butt joint is covered with molding.
Both measurements are taken from the story pole.
To make the top of the box shown, I used two layers of 3/4-inch plywood, with a bullnose panel molding covering the end joint. Because the crown molding that finishes the shelf also has an applied architectural overlay with a repeating pattern, I was careful to install it so that the pattern remained continuous as it turned the corner.
The top of the box — the actual shelf — consists of two layers of 3/4-inch plywood. The bed molding that conceals the end joint is securely fastened from behind with pocket screws through the underside of the top layer of plywood.
Glued into place, the second layer of plywood adds mass to the shelf and conceals the pocket screws.
The cutouts will accommodate an electrical box. The author fastens the top to the box.
Then the author finishes the mantelshelf with crown molding.
Of course, the size of the mantelshelf can't be as easily tweaked to accommodate the molding as the size of the panels can be, so I shifted the crown molding until it was exactly centered along the shelf. Then I marked and cut the end miters, and cut the returns to match.
Assembling the Pieces
After the upper and lower pilasters, the mantelshelf, and the overmantel have been made, it's time to put the parts together.
I like to start in the middle and work up and out. I also like to keep my saw close at hand for minor adjustments so that the pieces go together cleanly.
I begin by checking the floor for level. The pilaster on the highest side should be set first; the second pilaster can be brought up level with it.
To help ensure that the assembly will be plumb and level, the author pins and then pocket-screws the lower pilasters to the plywood frieze before installing them.
MDF cleats glued and nailed to the wall provide secure fastening for the pilasters.
To provide nailing for the pilasters, I glue and nail plywood rippings to the wall; they're sized to fit just inside the pilaster returns. Although I try to hit the studs, I know that I can always nail at least the bottom edge of the cleat to the bottom plate of the wall; glue does a good job of holding the rest.
The important thing is that the cleats are plumb and positioned correctly so that the mantelshelf will sit level on the pilasters.
Before installing the shelf on top of the pilasters and frieze, I glue and nail another horizontal cleat to the wall. I nail the mantelshelf to this cleat and to the supporting pilasters and then fasten the three-panel overmantel and the two upper pilasters directly to the wall.
A horizontal cleat provides nailing for the box mantelshelf.
This is installed after the lower pilasters.
The author installs the paneled overmantel.
The author completes the basic surround by installing cleats and the upper pilasters.
Then it's time for the finishing details, such as the dentils and moldings that hide the upper shelf joint.
With the main components installed, I cover all the joints with moldings. Once I've dressed up the undermantel frieze with various carvings and moldings — which I install with my pinner — all that remains is to run the room's moldings either over to or around the mantel; after that I can turn the project over to the finisher.Gary Striegleris a builder in Springdale, Ark.