How To Install a Cased Opening Like a Pro | Step-By-Step Guide

Category - Doors

Skill Level - 1

In new construction homes, cased openings serve as a stylish architectural feature that enhances the flow between adjoining rooms without the use of doors. Typically found in areas where a sense of openness is desired, such as between a living room and dining room or a kitchen and family room, these openings allow for easy movement and visibility across different areas while maintaining a sense of separation.

Unlike simple drywall-wrapped openings, which provide a basic passageway between rooms, cased openings are framed with decorative trim that adds depth and character to the space. This trim, or "casing," outlines the perimeter of the opening and is carefully chosen to complement the interior design and architectural style of the home. The casing not only provides a more finished look but also helps protect the edges of the drywall from wear and tear that can occur with regular foot traffic.

Cased openings can vary widely in size and shape, from standard rectangular or square shapes to more elaborate arched or rounded designs, depending on the aesthetic goals of the home. By choosing to case an opening, homeowners and builders can elevate the interior design, making these transitions between spaces not just functional but also visually appealing elements of the home's overall design. The following guide will detail how to professionally install a cased opening, ensuring it is both structurally sound and beautifully integrated into your home.

Tools Needed

• Hand tools

• Miter saw

• 15 gauge nail gun

• 18 gauge staple gun

• 6’ level

• Air compressor

• Air hose

Supplies Needed

• Wood glue

• 2.5” 15 gauge nails

• 1.25” 18 gauge staples

• Wood shims

Materials

• Jamb leg material (pine, poplar, oak, alder, MDF as required), widths of 4 9/16” or 6 9/16”

Quality Check Criteria

• Head of the jamb should be level

• Legs should be plumb and straight

Installation Process for a Cased Opening

Step 1: Measurement and Preparation

• Measure the Jamb Width: Start by determining the width of the jamb based on the type of framing used in the wall where the opening will be located. For walls built with 2x4 studs, you'll need a jamb width of 4-9/16 inches. For walls with 2x6 studs, the jamb width should be 6-9/16 inches. These measurements are crucial as they ensure the jamb fits perfectly within the structure of the wall, maintaining uniformity and structural integrity.

• Measure the Rough Opening: Carefully measure the width of the rough opening where the cased opening will be installed. The inside dimension of the cased opening should be 2 inches narrower than the rough opening width. This allowance ensures that there is sufficient space to properly adjust and shim the jamb for a precise fit. It's important to measure at multiple points—top, middle, and bottom—to account for any variations in the opening due to structural shifts or imperfections.

• Determine the Height: The height of the jamb legs is another critical measurement. These should be the same height as a standard door to ensure aesthetic continuity, especially if the cased opening is in proximity to actual doorways. This standardization helps in creating a harmonious look across the room and ensures that all horizontal lines (like the tops of casings and headers) align perfectly, contributing to a professional finish.

• Plan the Header: For the header, which is the top part of the frame, calculate its length by adding the combined width of the pre-routed notched ends of the jamb legs to the required opening width (which is 2 inches less than the rough opening). This measurement ensures that the header spans the entire width of the assembled jamb, providing a strong, supportive top frame for the cased opening.

By taking the time to accurately measure and prepare based on these guidelines, you establish a solid foundation for the rest of the installation process. Proper preparation in this initial step is key to ensuring that the entire installation goes smoothly and results in a neatly finished cased opening.

Step 2: Assembly

• Prepare the Jamb Pieces: Begin by laying out the two jamb legs on a flat, stable surface. These legs often come pre-built with rabbet jointed top ends, designed for easy assembly. Align the pieces and ensure they are straight and true.

• Measure and Calculate Header Length: Measure the gap between the notched ends of the pre-routed jamb legs. Add this measurement to the required width of your cased opening, which is calculated by subtracting 2 inches from the total width of the rough opening. This total gives you the necessary length for the header piece, ensuring a precise fit within the structure of your opening.

• Cut the Header: Using a miter saw, cut the header piece to the calculated length. Ensure each cut is clean and straight to maintain a snug fit when joined with the jamb legs.

• Assemble the Jamb Frame: Apply wood glue to the rabbeted joints of the jamb legs before attaching the header. This will enhance the structural integrity and durability of the assembled jamb. Align the header with the notched ends of the jamb legs and secure it in place.

• Secure with Staples: While the glue is still wet, use a pneumatic stapler to fasten the header piece to the jamb legs with 1-1/4” staples. Staple at several points along each joint to ensure a solid connection that resists warping or separation over time.

• Check for Square and Alignment: After assembling the jamb, use a carpenter's square to check that the corners are right-angled and that the frame is perfectly square. This is crucial as any misalignment can cause issues during installation and affect the operation of the cased opening.

• Let the Assembly Set: Allow sufficient time for the wood glue to dry according to the manufacturer’s recommendations before moving the assembled jamb. This waiting period ensures the adhesive fully cures, providing additional strength to the assembly.

This methodical approach to assembling the jamb ensures that the structural components of your cased opening are accurately prepared, leading to a smoother installation process and a more refined finish.

Step 3: Install the Assembled Jamb

• Position the Jamb Assembly: Carefully lift the assembled jamb into the rough opening. Make sure it's centered and properly aligned before proceeding. Place thick shims under each leg to raise the jamb off the subfloor by approximately ¼ inch. This small elevation is crucial as it prevents the wood from direct contact with the subfloor, which could lead to moisture-related issues and ensures that there's room for flooring adjustments if needed.

• Level and Center the Header: Before securing the jamb in place, adjust the header's position. Use shims about 2 inches from the top of the header to hold it centered within the rough opening. This step is vital to ensure that the header remains level across the top of the opening. Use a 6-foot level to check the header for levelness from one end to the other. Adjust the shims as necessary to achieve perfect horizontal alignment.

• Secure the Top of the Jamb: Once you've confirmed that the header is level and the jamb is correctly positioned, you can begin to secure the jamb to the framing. This is done by driving nails through the jamb and into the framing at the points where the shims are located. Start by nailing at the center shim points to stabilize the setup, then secure the sides. This method helps maintain the level and position of the header as you work.

• Check Alignment: After securing the header, take a moment to check the alignment of the entire assembly. The sides of the jamb should be flush with the interior wall surfaces or as close as possible. Variations in wall thickness and framing can sometimes lead to the jamb not being perfectly flush; however, adjustments can often be made by manipulating the shims or slightly altering the position of the jamb within the rough opening.

• Secure the Entire Assembly: Finish securing the assembly by nailing through the jamb legs into the framing at all shim points. Be sure to nail at an angle that maximizes the hold and provides the most stability to the jamb. This step solidifies the placement of the jamb, ensuring that it is sturdy and well-supported within the wall.

By carefully positioning, leveling, and securing the jamb assembly in this manner, you ensure that the cased opening will be structurally sound and aesthetically pleasing. This foundation is essential for the successful completion of the cased opening, providing a robust framework that enhances the architectural flow between rooms.

Step 4: Adjusting and Securing the Legs

Securing the legs of the jamb accurately is crucial for the stability and visual alignment of the cased opening. Follow these detailed steps to ensure the legs are perfectly plumb and free from any twisting:

• Plumb the Legs: Begin by placing a shim near the bottom of each jamb leg, about 6” from the floor. This step is critical as it sets the foundation for a vertically straight jamb. Use a 6’ level to confirm that each leg is perfectly plumb. Make slight adjustments by tapping the shims. Once aligned correctly, tack the jamb in place using a few nails, but do not fully drive them in yet as you may need to make further adjustments.

• Check for Twisting: To ensure that the legs are not twisted and remain perpendicular to the walls, use a framing square or take measurements at several points along the height of the opening. Measure the distance of the opening at the top and bottom to check they are consistent. A visual check can also be helpful; look along the edge of the jamb from top to bottom to see if it lines up straight without any warping. If you notice any discrepancies, adjust by flipping the thick side of the shims to the opposite side as necessary. This fine-tuning is vital for achieving a flawless finish.

• Final Securing: Once you are satisfied that the legs are both plumb and straight, proceed to securely nail through the bottom shims. This will anchor the legs firmly at the base. Move upwards, placing additional shims at strategic points along the height of the jamb — typically at one-quarter, one-half, and three-quarter heights. Each point should be carefully leveled before securing. Ensure that each shim is snug and supports the jamb without forcing it out of alignment. Nail through each shim point to permanently secure the legs.

• Ensure Consistency and Straightness: After securing the base and intermediate points, use the 6’ level again to check the entire length of each leg. The level should just barely touch the jamb along its entire length, indicating a straight and plumb installation. Make any minor adjustments needed by adding or adjusting shims. Once every part of the leg is confirmed to be straight and level, drive in all nails fully to lock the position.

By meticulously adjusting and securing the legs as described, you ensure that the entire frame of the cased opening is stable, straight, and properly aligned, setting a solid foundation for the finishing touches.

Step 5: Finishing

This completes the installation specific to the cased opening. From here, you can proceed to trim or case the opening similar to casing one side of a door, following appropriate instructions for trimming and finishing.

By following these steps, you can professionally install a cased opening that not only enhances the flow between rooms but also elevates the overall aesthetic of your home.