Specialty shapes, bays & bows.

Define the whole shape

For an arch, document base width, overall height, straight-leg heights, the springline and the curve. A semicircle, segmental arch, ellipse and an irregular existing curve can share some of those dimensions without matching each other.

For trapezoids and other polygons, identify each edge, angle or diagonal requested by the supplier. Label the exterior viewpoint and the high side. Confirm whether all dimensions describe the opening, net frame or another template boundary.

Request the supplier’s shape form before the survey. If a full-size template is required, use the specified material, orientation and reference marks. Mark opening ID, top, interior/exterior face and the exact boundary traced. Do not trim the template by an assumed clearance unless the supplier tells you to.

Control the template handoff

1. Verify that the traced boundary is the one that will remain after preparation.
2. Record independent dimensions so the template can be checked for distortion.
3. Photograph the template in position with its reference marks visible.
4. Confirm how the supplier translates the template into frame size.
5. Review the resulting dimensioned shop drawing before fabrication.

A photograph has perspective distortion and is not a full-size template. A digital survey can be useful when the supplier accepts the method and its calibration; a phone image alone does not establish manufacturing dimensions.

A bay or bow is an assembly

Establish whether the job replaces individual windows inside an existing bay structure or removes the entire projecting assembly, including head and seat boards. Those are different surveys.

For a complete assembly, obtain the supplier’s measurement sheet and record the overall wall opening, projection, panel arrangement, angles, head/seat dimensions, wall depth and surrounding roof or soffit geometry. Check interior seat height and depth, outside clearances and how the unit reaches the opening.

Do not reconstruct a bay from guessed standard angles or the width of its center light. A bow’s segment arrangement and projection likewise require a complete drawing.

Coordinate support and weather protection

Projecting units require their specified support system and weather protection. Determine the required support/anchor locations, the condition of the receiving structure and the flashing/roof interface. Decorative brackets are not automatically structural support.

Simonton’s 5500 product information describes a cable support system; that is one example, not a universal solution. Use the selected assembly’s installation instructions and any required structural design.

Include garden windows, greenhouse units and unusual projections in this more detailed review. Their weight, drainage, roof glazing and support needs differ from a flat fixed window.

Release from a coordinated drawing

• The drawing matches the actual opening ID and viewing direction.
• The overall assembly and individual component dimensions are identified.
• The shape or template boundary and deductions are explicit.
• Support, anchorage, water management and access are resolved.
• The supplier and responsible contractor have reviewed the same revision.

When a shop drawing changes, compare the new revision against the site survey again. Approval of a previous drawing does not approve a different geometry.