Introduction: Window Trimming the Easy Way

About: My name is Troy. I'm a Mechatronics and Aerospace Engineer. I make things out of wood and electronics and spend time outdoors (especially SCUBA diving).

There's nothing warmer than the morning sun coming through an open window. After many winter months with the house being closed up, the fresh air of spring is a welcome guest. When my sister moved into her house, she was a little indifferent about her basic window trimmings.

After some poking and prodding she enlisted my help in putting the finishing touches on those boring old windows.

Now, let's get to adding some trim to those naked windows!

Step 1: Parts and Tools

Depending on how many windows you are looking to frame, you will need different quantities of wood. We framed six windows on one Saturday and used three 4' x 8' sheets of 3/4 inch MDF cut lengthwise using a table saw. We have prospects of doing more window framing in the future, so cutting the wood to specific quantities wasn't a top priority.


  • 3/4" MDF
  • 7/16" x 1/2"
  • 1 1/2" upper trim


  • Table Saw
  • Air Compressor
  • Nail Gun
  • 16 Gauge 2" Nails
  • Jig Saw
  • Combination Square

Step 2: Window Sill

Measure the opening of the window from left to right and add 7 inches.

Take the 5 1/2 inch boards and cut to the length mentioned above.

Note: 5 1/2 inches was chosen because it is 2 1/2 inches wider than the original widow sill. If yours is different, a change here might be in order.

Measure 3 1/2 inches in from each end and mark the depth of the window sill to make a square (See picture 4).

Using the jig saw, cut out the two squares from each end and test fit in the window sill. If everything looks good, sand and nail in place.

Step 3: Sides

Measure from the top of the window sill to the top of the window on each side. Knowing that houses are never perfectly square, remember to measure both sides.

Take the 2 1/2 inch wide boards and cut both sides to length.

Sand and nail in place.

Step 4: Top

Measure across the top of the window on the outside of the MDF.

Cut the 7 1/2 inch boards to the above length.

Sand and nail in place.

Step 5: Bottom

Measure the window sill from MDF to MDF on the respective side pieces.

Take the 2 1/2 board and cut to length.

Sand and nail in place.

Step 6: Lower Trim

Measure for the lower trim.

Measure across the top and add the thickness x 2.

For example, the thickness of my trim piece was 7/16 inch so I added 7/8 inch to the width across the top and cut my trim to length.

Sand and nail trim in place.

Cut two pieces of trim to a length of 3/4 inch (the thickness of the MDF).

Sand and nail in place

Step 7: Upper Trim

Do the same for the upper trim.

The only difference is to make 45° cuts on the trim.

Nail in place.

If the nail is sticking out like shown in picture 3, use a nail set to sink the nail.

Step 8: Fill and Caulk

Fill the nail holes and caulk the joints.

Sand smooth.

Step 9: Tape

Using painters tape, cover the wall where you don't want to paint.

Step 10: Painting and Done

How you paint is up to you. Pick a nice accent color that will go well with the rest of your home. My sister is a fan of the lovely white accents shown here.

Some thoughts about painting. Using brushes could leave brush marks, but rollers have a tendency to "fling" paint. Use whatever method you choose and enjoy.

This style of window trimmings was inspired from here, but we used an MDF board and different sizes than what they recommended.