Assign one ID to one opening
Draw a simple floor or elevation map and number openings consistently. Match the ID on the worksheet, photographs, quote, order confirmation and delivered unit. Two identical bedroom windows still get separate IDs.
Photograph the entire opening from inside and outside, then take closer views of the head, both jambs and sill. Include a scale and a visible reference label where it helps. A photograph of a tape floating across a dark recess is weak evidence; the contact faces must be recognizable.
Complete the condition record
| Inside | Outside |
|---|---|
| Casing, extension jambs, drywall or plaster returns, tile, stool and apron. | Trim, brickmould, capping, J-channel, vinyl, stucco, stone, brick or exposed masonry. |
| Existing frame, sash, liners, tracks, balances and previous inserts. | Flanges, retained metal frame, head flashing, sill projection and drainage exits. |
| Blinds, shutters, handles, furniture and access. | Storms, screens, shutters, awnings, bars, downspouts and work-at-height access. |
| Stains, movement, soft material, cracks and uneven reveals. | Failed sealant, corrosion, deteriorated trim, displaced masonry and signs of leakage. |
Record observations separately from conclusions. “Brown stain below the left sill” is an observation; “window frame leaks” is a diagnosis that still needs evidence.
Record a set, not one convenient dimension
For a rectangular opening, record widths at top, middle and bottom and heights at left, center and right using the selected references. Add readings wherever an obstruction, curve or bow creates a tighter location. Take both diagonals and assess depth and straightness.
The smallest reading is often relevant to a product’s sizing method, but it does not establish that a square, rigid frame can occupy a racked or twisted opening. Preserve all readings, then apply the exact product method.
Reconcile the inside and outside
Make a plan-section sketch showing the interior return, retained frame, proposed new frame and exterior finish. Mark which dimensions were actually exposed and which remain concealed. Add the depth from one named surface to the next.
A window can fit the final cavity yet be unable to pass through a smaller brick throat. It can pass through the exterior but fail against a drywall return when pushed into its intended position. Plan how the frame, flange, handles and installation tools reach their final locations.
Resolve concealed boundaries deliberately
Where hidden geometry controls the order, arrange a targeted investigation. That may involve approved trim removal, access from an existing gap or a supervised exploratory opening, with protection and restoration included in scope.
Never infer every jamb thickness from one exposed window. Use a sample to inform the next inspection, not to certify the rest of the house. If the planned repair or blocking will change the opening, record both the existing observation and the proposed prepared dimension.
Source notes
Manufacturer requirements apply only to the named products and applications. The field procedures and worked examples here are an educational synthesis.
- PNNL / Building America · Complete window and frame replacement ↗
Existing-wall investigation, replacement scope and integration with the wall’s water-management layers.
- Pella · Full-frame replacement without disturbing brick or siding, FF_BFBS ↗
Block-frame details addressing exterior openings, drywall returns, depth, blocking and flashing. Revision March 31, 2023.
- JELD-WEN · Wood/clad pocket measurement guide JMI001 ↗
Pocket and net-frame ordering modes, measuring surfaces, geometry checks and product-specific limitations.