Technical Information: Garage Doors

Measuring Techniques for Radius and Template Creation

When making a door that will be installed in a curved opening, there are some important considerations to take into account.  

If there are no trim boards (i.e. just t&g running vertical, or just mdf) then matching the curve is irrelevant.  The door will be built as a square top, and the curved opening will fall wherever it may.

When there are trim boards, then the offset or reveal from the curve is important to maintain an equal spacing around the opening that matches the sides of the door.

When measuring a curved opening to determine the drop, please note the correct and incorrect procedures below:

The spring line is defined as the point at which the vertical sides meet the arch of the top opening.  The easiest way to measure the drop is to run a string from the left to the right side to that point and then measure from the tallest point in the arch to that string at a 90 degree angle to the spring line.  This is your drop.


Opening Width 6" Drop 9" Drop 12" Drop
8 Feet 195 Inches 132.5 Inches 102 Inches
9 Feet 246 Inches 166.5 Inches 127.5 Inches
10 Feet 303 Inches 204.5 Inches 156 Inches
16 Feet 771 Inches 516.5 Inches 390 Inches


Templates allow the designer to maintain a uniform reveal around a curved or elliptical opening.  Templates are only necessary when the door has trim boards across the top of the door.  If the arch is thought to be tipped (not level), elliptical, or uneven a template should be provided.  If the requirements are such that Designer Doors needs to match a critical dimension, then it would be ideal for the builder to supply a template.  The templates are used by the factory to design the product and to actually build the top of the door to match the opening.  To do that, the template needs to meet certain requirements outlined below.

Acceptable Materials to Use For a Template:
Tyvek, kraft paper, or similar single piece non-stretchable material.  Taped pieces together are not acceptable.  Templates should be rolled up, not folded, to prevent distortion when placed on the door.

Do not use cardboard, plywood, tarpaper, sheetrock or similar materials

Recommended Procedure:
Stretch the material across the interior side of the opening with 4” overlap across the top and down the sides.  Securely fasten with tape or other fastener.  Standing outside the garage, looking in, trace the opening with a waterproof marker in a contrasting color.  The template should look like below.  Do not cut out the template.

A seperate template is required for each opening if the openings are different.  You can use the first template to verify the other openings.

Additional information required on the template include:

  • A job number, proposal number, or job name
  • An identification number for each door if more than one door (A, B, C).  This letter should match the same letter in the proposal for the door intended for that opening.
  • Include the dimensions shown below:

The Spring line is the intersection point where the side of the opening meets the arched top of the opening.

There will be a template fee charged to the customer for each door for this service.

Send the rolled up template(s) to :

Designer Doors, Inc
Customer Service Department
702 Troy Street
River Falls, WI 54022