DIY Carriage Doors for Your Garage

Carriage door builds have gotten complicated with all the hardware options, frame joinery debates, and questions about whether tongue-and-groove or shiplap boards look more authentic. As someone who built a set of carriage doors for a detached garage using cedar and a period-appropriate Z-brace design, and learned two things the hard way about wood movement in exterior applications, I learned everything there is to know about what makes these doors work long-term. Today, I will share it all with you.

Carriage doors are heavier and more structurally demanding than they look. The opening is large, the doors swing outward on hinges rather than rolling overhead, and they’re exposed to weather year-round. That combination means any shortcuts in materials or joinery will show up as sagging, warping, or hardware failure within a season or two. Build them right the first time and they’ll last for decades.

Materials: Wood Species and Hardware Selection

Cedar is my first choice for carriage door construction — it’s dimensionally stable, naturally rot-resistant, light for its strength, and takes paint and stain well. Redwood is equivalent in performance but more expensive and less available. Douglas fir works and costs less, but requires more careful finishing to prevent weathering. Avoid pine for exterior doors — it’s soft, prone to rot, and will need replacement within 10 years in most climates without excellent paint maintenance.

Hardware is where a lot of DIY carriage doors fail. The hinges need to support the full weight of the door through decades of cycles; undersized hinges are the most common reason carriage doors sag. For a typical two-panel door set where each panel weighs 60 to 90 pounds, use heavy-duty strap hinges or carriage bolt-through hinges rated for the actual door weight. Don’t guess — calculate the door weight and match the hardware rating.

Measuring and Planning

Measure the opening in three places — top, middle, and bottom of each dimension. Garage openings are rarely perfectly square, and building the door to the largest measurement with a gap at the smaller dimension is better than building to the smallest and having the door bind. Carriage doors typically split into two equal halves that meet in the center. Allow 1/4-inch clearance on each side and at the top; at the bottom, allow clearance for your threshold or a door sweep.

Sketch the door design before building. A classic Z-brace uses two horizontal rails, two stiles on the outside edges, and a diagonal brace running from the hinge-side upper corner to the latch-side lower corner. The diagonal is critical — it’s what prevents the door from racking and sagging over time. Without a proper diagonal brace, even a well-built door will develop a lean within a few years.

Building the Frame

Mill your frame lumber flat and straight — twisted or cupped frame members will transfer those defects to the finished door. Cut the stiles and rails to length, check them for straightness, and discard any piece that won’t lie flat. Join the frame with mortise-and-tenon or bridle joints at the corners; pocket screws work but aren’t ideal for an exterior door that will cycle through temperature and humidity extremes for decades. A glue-and-peg mortise-and-tenon joint is what traditional carriage doors used and what holds up best.

Check the assembled frame for square using diagonal measurements. The diagonals should match within 1/16 inch. Clamp and let dry fully before adding the panel boards. An out-of-square frame produces a finished door that won’t hang true and won’t close properly against its mate.

Attaching Boards and Managing Wood Movement

Vertical boards on an exterior door expand and contract across their width with seasonal moisture changes. If you nail each board solidly to every crossing rail, the movement is constrained, and the boards will split, cup, or push the frame apart within a few years.

The solution is to nail each board at the center of each crossing rail with one fastener and allow the edges to move. Face nailing at the edges — or worse, screwing directly into each board edge-to-edge — creates the movement constraint that causes failures. Use narrow boards to reduce movement per piece; 4-inch to 5-inch boards move less than 8-inch or wider boards, and the visual effect is authentic to traditional carriage door aesthetics.

Finishing for Exterior Durability

Finish all six faces of every board before assembly — end grain especially. End grain absorbs moisture faster than face grain and is where rot starts. Two coats of a quality exterior primer on all surfaces, then two coats of a 100% acrylic exterior topcoat, is the minimum for a paint finish that will last. For a natural look, an exterior-rated penetrating oil finish or a semitransparent stain works, but plan on reapplication every 2 to 3 years; penetrating finishes don’t provide the same longevity as a full paint system.

Hardware Installation

Mount the hinges to the door first with all fasteners, then hang the door and adjust. Use 3/8-inch or larger stainless or galvanized lag screws into the door frame’s structural members — screwing into the garage cladding rather than a structural member behind it is another common failure point. The door handle hardware should be weather-rated; interior-grade hardware corrodes rapidly in exterior exposure and the finish fails within a season or two.