Glossary / All About Arches

 
 
Casing
also referred to as “trim” or “molding"; the piece of wood attached to the jamb that will show
on the face of a wall.
   
   
Elliptical
a standard CurveMakers Arch shape.
     
     
Finished Opening Height
the measure from the finished floor to the inside highest point of the arch AFTER it has been installed.
   
   
Finished Opening Width
the measure from left to right of the inside of the arch AFTER it has been installed.
 
 
Finished
Jamb Measure
the total thickness of the wall with sheetrock (drywall) or plaster hung.
 
 
Header
the structure over the opening that supports the ceiling.
   
   
Jamb
vertical side piece of a door frame or window.
   
Molding
also referred to as “trim” or “casing”; the piece of wood attached to the jamb that will show on the face of the wall.
   
   
Rise
the measure of how high the arch curves up to its highest point from the spring line.
     
     
Round
Top
a standard CurveMakers shape; a true half-circle.
     
Rough Opening Height
measure from the floor to the top of the opening BEFORE arch is installed; is always larger than the finished opening height because jamb material has thickness.
   
Rough Opening Width
measure from the left to the right of the opening BEFORE the arch is installed; will always be larger than the finished opening width because jamb material has thickness.
     
     
Segment
a standard CurveMakers shape; commonly referred to as “eyebrow” and “arc”.
     
     
Spring
Line
the point at which the curve begins.
     
     
Trim
also referred to as “casing” or “molding”; the piece of wood attached to the jamb that will show on the face of a wall.
   

 

Why Choose One Arch Shape Over Another?

 

All Arch shapes look nice; however, the shape you choose will greatly affect the spring lines.

Elliptical Shapes

ELLIPTICAL ARCHES can have the same spring line, rise, and finished
opening height no matter what the finished opening width measures.

These consistent measures, no matter the widths of the opening,
provide for a consistent and attractive installation.

Round Top Shapes

ROUND TOP ARCHES are also called TRUE RADIUS
or HALF CIRCLE.

Because Round Top Arches are made from a single radius measure, the rise varies as the finished opening width varies. (see diagrams below)

It is geometrically impossible to have constant spring lines and constant finished opening heights with Round Top Cased Openings. This should be considered when choosing Round Tops as your arch shape.

Diagram 1 demonstrates that if different width Round Tops are made with the same spring line, the finished opening height will vary. (The wider the arch, the
taller the finished opening.)

Diagram 2 demonstrates that if
the finished opening heights are the same, the spring line will vary with different width arches. (The wider the arch, the lower the
spring line.)

Segment Shapes

SEGMENT ARCHES are sometimes called ARCS.

Segment Arches are gentle curves. They are simply part of a circle and are made from a single radius measure like Round Tops.

Segment Arch shapes should be made so that they all have the same spring line and rise like Ellipticals. This also provides for a pleasing look when using different finished opening widths as demonstrated below.

Segments are good to use when a wide finished
opening width is desired, but the ceiling is too low for an Elliptical or Round Top.

There is one situation to avoid when using Segment Arch shapes. If the finished opening width is small, and the rise is large, then the arch shape begins to look like an incomplete Round Top, as shown at right.

This may not be a pleasing shape and should be
considered when choosing a rise measure for Segment shape arches. This is why we use a standard 6" rise with Segment shape arches.


Parts Of An Arched Cased Opening

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