Installing trim can really take a room from drab to fab. Trim pieces like crown molding, baseboards, and door and window casings add style and polish to any space. However, navigating inside corners while installing trim can be tricky. Inside corners require special attention to detail to get clean, professional results. In this article, we will walk through the entire process of how to do an inside corner with trim from start to finish. We will cover planning and preparation, cutting and fitting the trim pieces, nailing and gluing, caulking and painting, and pro tips and tricks. With the right materials, tools, techniques, and a bit of patience, you can master the art of installing beautiful inside corner trim work.
Page Contents
Planning and Preparation
Before beginning any trim project, proper planning and preparation will make the job go smoother. Here are some key steps to take:
Select Trim Style and Materials
First, decide on the style and type of trim you want to use. Popular options include:
– Crown molding – Installed where the wall meets the ceiling. Provides elegance and visual interest.
– Baseboard – Installed where the wall meets the floor. Gives a finished look.
– Door and window casings – Installed surrounding doors and windows. Finishes openings.
– Chair rail – Installed horizontally mid-wall. Adds detail.
Trim is commonly made from wood materials like pine, poplar, oak, and mahogany or synthetic materials like polyurethane, PVC, or polystyrene. Consider the style and look you want as well as budget when choosing materials.
Measure and Calculate Needed Materials
Measure the length of all your inside corners to determine how much trim you will need to purchase. Remember to account for extra length to allow for mistakes and irregular corners. It’s better to have too much than not enough.
Gather Tools and Materials
You will need the following tools and materials for your inside corner trim project:
Tools:
– Miter saw or compound miter saw
– Table saw or circular saw
– Jigsaw
– Brad nailer and compressor
– Hammer
– Finish nails
– Caulk gun
– Tape measure
– Level
– Stud finder
– Pry bar
– Utility knife
– Wood filler
– Sandpaper
Materials:
– Trim boards
– Wood glue
– Brad nails
– Finish nails
– Wood putty
– Painter’s caulk
– Primer
– Paint
Having all your supplies ready ahead of time will make the installation process go faster.
Cutting and Fitting the Trim
Cutting and fitting the trim pieces precisely is the key to getting clean, tight inside corners. Here is a step-by-step guide:
Cut the Ends at 45 Degree Angles
Use a miter saw to cut each end of the trim boards at a 45 degree mitered angle. This allows the two pieces to fit together snugly to form the 90 degree inside corner. Make test cuts on scrap pieces first to check for accuracy.
Do a Dry Fit
Place the mitered trim pieces into the corner without fastening them. Ensure they form a precise 90 degree angle flush to the wall. Look for any gaps and make adjustments as needed for a tight fit.
Cut to Correct Lengths
If needed, cut the boards to the proper length. Use a miter saw, table saw, or circular saw to make straight cuts. Test fit again and adjust length for a perfect fit into the corner. Leave a 1/4″ gap from the ceiling and baseboard trim.
Make Coped Joints for Tighter Fit
For an ultra-smooth joint, use a coping saw to cut a cope (profile) into the end of one piece that matches the profile of the mating trim piece. Cut the cope on the right side of the left trim piece and the left side of the right trim piece. This helps eliminate gaps.
Check for Level and Plumb
Use a level to confirm the top and bottom edges of the installed trim are level. Check the trim ends with a plumb line to ensure they are vertically straight. Adjust and shim as needed.
Nailing, Gluing, and Filling
To securely fasten the trim and create a seamless inside corner, follow these steps:
Apply Wood Glue
Run a bead of wood glue along the backside of both trim pieces where they meet in the corner. The glue helps adhere them tightly together.
Nail Into Studs
Use a stud finder to mark where wall studs are located behind the corner. Drive 2″ finish nails through the nailing strips on the trim pieces into the studs every 16″. This anchors the trim securely.
Use Adhesive and Fillers
For added strength, run a bead of panel adhesive caulk down the joint where the trim meets in the corner. Drive brads at an angle every 8” into the trim pieces on both sides. Set any protruding nails with a nail set then fill holes with wood filler. Wipe away excess.
Sand Smooth
Once the wood filler fully dries, sand the trim pieces and inside corner smooth. Start with 120 grit sandpaper and work up to 220 grit for a silky finish. Vacuum up all dust when complete.
Caulking, Priming, and Painting
Filling gaps and painting the trim will give your inside corner a flawless finished look:
Caulk Corner Cracks
Run a smooth, thin bead of painter’s caulk down the inside corner seam and gaps. Use a wet fingertip to smooth the caulk into any crevices ensuring it adheres. Let dry completely.
Apply Primer and Paint
Use a small brush to coat all inside and outside corners with primer. This helps the paint stick better to the wood. Once dry, apply at least two coats of topcoat paint in the sheen of your choice with a brush. Lightly sand between coats for best results.
Touch Up as Needed
Check for any drips, thin spots, or imperfections in the paint when dry. Make touch ups with added paint to cover flaws. Clear nail holes can also be touched up with wood filler and sanded again for a perfect corner.
Pro Tips and Tricks
Follow these professional tips and tricks for expert quality inside corner trim work:
– When cutting trim, position it “upside down” flat side down to prevent chipping.
– Use scarf joints for tighter seams on inside corners.
– Pre-drill trim to prevent splitting when nailing into place.
– Cut trim longer to overlap corners and cope ends for tighter joints.
– Install trim on the ceiling first, then baseboard last to meet in the middle.
– For easiest nailing, use a pneumatic finish nailer with a nail set.
– Apply painter’s tape on the walls 1/8” from the trim to prevent paint splatters.
– Back cut the trim top edge to allow it to sit tight to ceiling.
With the right techniques and a careful eye for detail, you can achieve professional quality results installing inside corner trim. The finished look will add style, polish, and value to any room.
Conclusion
Installing inside corner trim for a flawless finish requires careful planning, precision cutting, proper fastening and joining, seamless caulking and painting, and finesse finishing touches. Following the step-by-step process outlined above will help you master the techniques involved and end up with beautiful, clean inside corners every time. Paying close attention to miter angles, tight seams, proper nailing, smooth caulking, and perfect paint coverage are all critical. Take your time, do test runs on scrap pieces, and keep the tips in mind for trim work worthy of a pro. Your newly trimmed out inside corners will add an architectural detail that takes your room to the next level of style and sophistication.