Measuring Out of Square Openings Without Guessing

Every experienced installer has the same story: a beautiful shade, fabricated exactly to the numbers on the sheet, that leaves a visible light gap on one side because the opening narrowed by three eighths of an inch from top to bottom. The fabrication was correct. The measure was incomplete.

Measure in three places, always

Take width at the top, middle, and bottom of the opening. Take height at the left, center, and right. For an inside mount, the controlling width is the narrowest of the three and the controlling height is the shortest. Record all six numbers on the sheet, not just the number you plan to use. The workroom needs to see the variance to decide how to build.

Check for square before you decide on mount

Measure both diagonals. If they differ by more than a quarter inch, the opening is out of square enough that an inside mount hard treatment will telegraph the problem. An outside mount, or a treatment with a soft bottom edge, forgives what a rigid rail will not.

Depth determines what is even possible

• Roller shades typically need three inches of flat depth for a full inside mount.
• Roman shades need enough depth to clear the stack, and a motorized head rail needs more than a manual one.
• Note obstructions: crank handles, alarm contacts, tile returns, and window stops all reduce usable depth.

Record the finish floor condition

For drapery, the finished length depends on the floor that will exist on install day, not the subfloor under your tape. Note whether carpet, rug, or hard surface is going in and whether the client wants a break, a kiss, or a puddle. Half an inch of hem allowance decided on site beats a remake decided later.

Photograph everything

Three photos per opening, wide and two corners, cost thirty seconds and resolve almost every question the workroom will have. Attach them to the order.

Frequently asked questions

Who is responsible for measurements on a trade order? Whoever measures. If Roseworks measures, we own the fit. If the numbers come from your team, they are fabricated as submitted.

How much deduction is standard for an inside mount? It varies by product. Submit the tight opening size and let the workroom apply the correct deduction rather than deducting yourself.

Can an out of square opening still take an inside mount? Sometimes, with a light gap disclosure to the client. Beyond half an inch of variance, recommend an outside mount.