Measuring, Ordering and Installing Double-Glazed Windows

Survey the actual opening

Construction drawings establish intent, but fabrication dimensions should come from the completed or agreed substrate. Measure width and height at multiple points, record diagonals, sill level and wall thickness, and identify the smallest controlling dimension. Note facade projections, shutters, stone returns, blinds, insect screens and access restrictions.

Confirm what the dimensions refer to: structural opening, retained renovation frame, or finished reveal. Mark each opening with a unique code so site notes, quotation, shop drawing and production label refer to the same unit.

Freeze the window schedule before production

The approved schedule should show frame series, divisions, opening symbols, handing, handle heights, glass build-up, safety treatment, color, screens and accessories. Verify that every sash remains within the profile and hardware manufacturer's size and weight limits.

Generic descriptions such as “first-class profile” or “double glass” cannot be inspected at handover. Record identifiable systems and a full insulating-glass build-up. The Persian source gives 4–12–4 as an example notation, not a default for every pane.

Coordinate adjacent work

Agree who prepares the opening and when it is ready. Stone, render, waterproofing, electrical work, suspended ceilings, flooring and curtain pockets can conflict with anchors, frame projections and drainage. Establish tolerances and responsibility for correction before windows arrive.

For replacement work, define removal, protection, debris, repairs and whether the existing frame remains. For new construction, coordinate the window flashing and air barrier with the wall rather than treating the frame as an isolated insert.

Anchor, square and support the frame

Set the frame plumb, level and square on appropriate support blocks. Mechanical fixings must suit the substrate, avoid known services and maintain required edge distances. Fixing should restrain loads without twisting the frame or blocking drainage chambers.

Check diagonals and reveal dimensions before glazing or final tightening. A distorted frame causes uneven gasket pressure, poor sash operation and premature hardware wear.

Build the perimeter joint in layers

The joint typically needs exterior weather control, insulation in the cavity and an interior air seal. Backer rod and correctly proportioned sealant joints help accommodate movement; low-expansion foam can insulate but should not be treated as the only air or water barrier.

Sill flashing and drainage should direct water outward. Keep weep holes open and use materials compatible with the frame, glass and wall finish. Follow sealant preparation and curing requirements rather than exposing fresh joints to movement or cleaning too soon.

Glazing and operation

Support glass on the specified setting blocks so its edge does not bear directly on the frame. Keep edge cover and clearances consistent and place packers according to the window system. After glazing, adjust hinges, keeps and rollers so the sash operates smoothly and seals evenly.

Do not use hardware adjustment to disguise a frame that was installed out of square. Correct the underlying geometry first.

Handover record

Operate every window, confirm locks and restrictors, inspect gasket contact, test drainage where required and photograph concealed perimeter details before closure. Provide cleaning, lubrication and adjustment instructions plus identifiable warranty terms for frames, glass, hardware and installation.

A disciplined measure-to-handover chain reduces costly remakes and makes quality verifiable. The final test is not that the window fits the hole; it is that the complete assembly drains, seals and operates as specified.