A brickmould replacement removes the old window right back to the brick, and the new unit arrives with brickmould already attached — it fills the masonry opening in one piece. It's the standard full-frame replacement for brick and stone homes.
From outside, the number that matters is the overall size of the existing unit: outside edge of the brickmould trim to outside edge, both ways. The new window is built with brickmould attached, sized so its overall footprint matches what's coming out — it drops into the same masonry opening with the same clearances.
Record every measurement in inches, to the nearest 1/16″, and always write width before height (W × H). Measure every opening — even the ones that look identical rarely are.
Measure from the outside edge of the brickmould on the left to the outside edge on the right — at the top of the window, the middle, and just above the sill. Openings settle; smallest wins.
Measure from the top outside edge of the brickmould down to the bottom of the trim — if there's a sloped sill nosing at the bottom instead of brickmould, measure to the bottom of the nosing where it meets the brick. Take it at the left, centre, and right.
Your overall size is the smallest of the three widths by the smallest of the three heights. Write both down before you take another measurement.
Measure both diagonals, corner to corner of the unit. Within 1/4″ of each other is a healthy opening. More than that, send us photos with your numbers — settled openings usually still work, but the unit gets sized to the true rectangle that fits.
Measure the face width of your existing brickmould — the flat exterior trim between the window frame and the brick. Panes brickmould comes in 3/4″, 1″, 1-1/4″, 1-1/2″, 2″, and 2-1/4″ profiles. Matching it keeps the new windows looking original to the house.
The window frame inside the brickmould is your outside measurement minus two profile widths — one each side. Example: 38″ outside with 1-1/4″ brickmould is a 35-1/2″ frame. In our configurator, choose "Brickmould" as what you measured and pick your profile — the frame math is automatic.
Bottom finished with a sill nosing instead of brickmould? On height, subtract one profile width plus 3/4″ (the nosing) rather than two profile widths. If the old unit is already gone, measure the bare brick opening instead and treat it as a rough opening: subtract 3/4″ both ways to get the overall unit size.
Full-frame replacements need the wall depth: from your interior drywall or plaster face to the exterior face of the wall. With brickmould attached, the frame body is 4-5/8″ deep — extension jambs make up the rest. Our jamb depth guide shows exactly where to hook the tape.