Goal: You will
be able to calculate the linear feet of window trim needed for any dimension
window.
Interior window trim (casing) is a
molding that is nailed to the finished window frame to give the window a
“finished” look. The trim is
located on the inside of the home around the perimeter of the window frame and
is often cut at a 45º angle. See
picture. You can think of it
as a picture frame around the window.
The same idea is also used around doors.
Problem 1:
Your window frame (inside edge) is
38” wide by 54”. There is to be a
3/16” reveal on all edges. Your
corners are mitered at 45º. The
trim (casing) is 2 1/4” wide. How
many inches of trim do you need?
You can ignore saw blade width but do need to consider casing profile.
Problem 2:
Problem 2 is a generalization of
problem 1. What is a formula
(shortcut) for finding the length of trim needed if the window size is “w”
inches wide and “h” high with a trim width of “t”? Again, assume you have a casing profile to consider.
Teacher Notes:
Students may need to research
terms such as reveal, casing, and casing profile unless you provide a
demo. You will need to decide if
you need to give hints regarding 45-45-90 special right triangles. You can extend this to building a
octagonal frame using 30-60-90 special triangles. Trim carpenters know the rule by heart but do not call it a
“formula”.
