Are you changing the moving slab or the whole frame?

A slab-only replacement leaves the jambs, threshold and sidelights in place. Replacing the door's frame beside existing sidelights is a different job, especially when the components share a sill or connecting frame members. Ask the supplier to mark the proposed removal line on a photograph. 'Keep the glass' is not a complete installation scope.

Find the brand, product line, labels and any original order information. Photograph the hinges, latch edge, threshold and the vertical joints beside each sidelight. The narrow member between door and glass may form part of the entry system; do not assume it is ordinary trim that can be removed without affecting support, alignment or sealing.

Therma-Tru's prehung installation instructions distinguish single, sidelight and double-door configurations and include configuration-specific fastening and alignment details Therma-Tru: Prehung door system installation.

Good-looking sidelights do not prove the sill is sound

Inspect for soft frame bottoms, failed finishes, water staining, fogged glass and movement at the hinges. Check how the existing slab seals at all four edges. If the entry has a history of water under the threshold, replacing only the slab needs a clear explanation of how that work resolves the leak. New glass and paint can leave a failing concealed joint untouched.

Choose the scope from the assembly's condition

  • Sound frame; damaged slab

    Ask for a compatible slab and matching preparation.

  • Sound sidelights; failed door frame

    Have the supplier assess shared sill and mullion connections.

  • Leak or decay crosses the assembly

    Compare repair with complete entry replacement.

  • Changing opening or layout

    Assess framing and approvals as a separate project.

Nominal size is not enough

Record actual height, width, thickness, handing, hinge positions and hardware preparation. Exterior edge profiles, weatherstrip contact and door-bottom fit must work together. A multipoint lock adds further compatibility requirements. Do not order an interior-style slab swap based only on the old door's width. Ask the supplier to confirm the proposed replacement in writing.

Appearance also deserves a deliberate choice. A new finish may not match weathered sidelights exactly, and a different glass style can look unrelated. Compare samples in the entry's daylight rather than assuming identical colour names guarantee a match. This is a design consideration alongside performance, not a reason to discard sound components automatically.

Compare a completed partial repair with a completed new entry

Include custom machining, compatible seals, threshold work, trim repairs, finishing and warranty responsibility in both prices. Clarify who measures and who owns a fit error. If replacing the assembly changes the rough opening or affects surrounding structure, obtain appropriate assessment and local approval requirements before removal.

At completion, check ordinary opening, closing and locking, consistent seal contact and the drainage details included in the scope. Inspect the bottom corners for daylight, then verify rain performance when conditions allow. Keeping the sidelights is a useful option when the system supports it; the decision should follow the entry's actual construction.