Separate opening size from usable clearance
The existing door, finished opening and clear space available to a vehicle are related measurements, but they are not interchangeable. Describe what you are trying to accommodate, such as an existing tall vehicle, and keep accessories included in that discussion. A field measurement establishes the proposed fit.
Check the actual model options
Clopay’s published range includes custom sizing for selected products. That does not establish that every style, window layout or wind-rated assembly is available in every dimension. Compare a named product in the proposed size with the applicable documentation before a deposit or production order.
Identify changes outside the door scope
If the opening needs rebuilding, the framing and project approvals require their own review. The installation quote should state whether it assumes the present opening will remain. Ask how the existing door will be secured while measurements, product selection and any surrounding work are completed.
Your questions
Can a sectional door just be cut narrower?
Do not alter sections to force a fit. Use a manufacturer-supported size and assembly.
Will an unusual width automatically cost a fixed percentage more?
No reliable percentage applies to every project. Construction, size, hardware and product availability all affect the quote.
