Measuring windows and doors for a quote: rough opening vs. actual

Window and door quotes go wrong in one of two ways: the unit does not fit the opening, or the opening is not what anyone assumed. Both are caught with a tape measure and ten minutes.

Know which kind of job you are quoting

• Replacement into the existing frame: the new unit builds into the old frame, and the opening stays put. Fastest and cheapest, but only works if the existing frame is sound and square.
• New construction with a nailing fin: the frame is stripped to the sheathing, the unit is nailed and flashed to the structure, and exterior trim is rebuilt. More labor, more weatherproofing, more disposal.
• Insert or pocket installs sit in between, and the term contractors use for them varies by supplier — confirm what the manufacturer's instructions call for.

How to measure an opening

1. 1Width: measure at the top, middle and bottom of the opening. Use the smallest of the three.
2. 2Height: measure at the left, middle and right. Use the smallest.
3. 3Depth: measure the jamb or wall thickness so you know the unit will not sit proud of the interior trim.
4. 4Check for square: measure corner to corner both ways. A difference of more than a quarter inch means shimming, scribing, or a conversation about the frame.
5. 5Note the sill condition — rot under a sill is the single most common surprise in a window job.

Write both numbers down for every opening: what the opening measures, and what the unit is sized to. Manufacturers size windows to the rough opening, and the difference between a unit's stated size and the opening it needs is usually around half an inch to an inch each way. Quote the unit size, and note the opening it fits.

Doors: the details that change the price

• Common exterior doors are 36 by 80 inches; interior doors are typically 24, 28, 30 or 32 inches wide. Confirm yours — older homes are frequently off-standard.
• Slab only, or a full pre-hung unit with frame and trim? Pre-hung is faster to install and slower to deliver.
• Thresholds, sweeps, hardware bore holes, and hand-swing direction all need to be specified before the order goes in.
• Exterior work means the sill pan or flashing detail, the exterior trim, and often a brickmould or casing that has to be matched.
• Fire-rated doors, egress requirements in bedrooms, and hardware that meets your code are not upgrades — they are the job.

What belongs on the quote

A count of openings by type and size, the kind of install (replacement or new construction), the disposal of the old units, the trim and paint work included or excluded, and the flashing and weatherproofing you are performing. If the customer is supplying units, say so and say what you will and will not warranty on them.

Homes built before 1978: removing painted windows and doors disturbs painted surfaces and falls under federal lead-safe work practices, which may require a certified firm. Confirm before you commit to the price.