Do I need a permit for window replacement in
Westmont, Illinois?

Westmont window replacement permits — the key details

The core exemption in Westmont is the 2021 Illinois Building Code's adoption of IRC R612, which allows like-for-like window replacement without a permit if (1) the opening size remains unchanged, (2) the window type is the same (casement-to-casement, double-hung-to-double-hung), and (3) all egress requirements are met or not altered. The key phrase is 'same size opening' — measured between the rough framing, not the sight line. If you're replacing a 36-inch-wide by 48-inch-tall double-hung on the north wall of your 1970s colonial, and the new window fits in the same rough opening without header work or rough-opening modification, you don't need a permit. But the moment you enlarge the opening, add a window where none existed, or change the operable type (e.g., double-hung to fixed), you cross into permit territory. Westmont Building Department processes these upgrades as a standard permit with $150–$300 fee (based on window count and complexity) and a 2–4 week timeline. One-window replacements sometimes qualify for over-the-counter approval if the opening isn't enlarged; five-window projects almost always go to full plan review.

Historic District overlay rules add a mandatory layer. If your address falls within the Westmont Historic District (check the village's interactive zoning map at westmontil.org or call 630-981-4800 to confirm), you must submit your window specification — including manufacturer, profile image, color chip, and material — to the Westmont Historic Preservation Commission BEFORE filing with Building. This review typically takes 2–3 weeks. The HPC will compare your proposed window against the Secretary of Interior Standards for Historic Preservation and the original window's profile. A 1920s Tudor with casement windows must stay casement; a 1950s ranch with aluminum double-hung can shift to vinyl double-hung if the profile and sightlines match. Vinyl is generally acceptable in Westmont, but the muntin pattern (whether it's true divided lights, faux muntins, or colonial grids) matters. If the HPC rejects your choice, you revise and resubmit (adding 2–3 weeks). Once HPC approves, you file the Building permit with a copy of the HPC letter; the Building Department treats it as administrative approval and issues within days.

Egress window rules are strict and often missed. Under IRC R310, any bedroom — including basement bedrooms — must have an egress window with a sill height no higher than 44 inches above the floor, a net opening of at least 5.7 square feet (or 5 square feet if the egress path is a horizontal exit), and minimum dimensions of 24 inches wide by 37 inches tall. If you're replacing a basement egress window and the new window raises the sill height above 44 inches, you've triggered a permit and a framing inspection. Westmont doesn't grant waivers on egress dimensions; IRC R310 is non-negotiable. On above-grade bedrooms, egress is less stringent if the window isn't the sole emergency exit, but if it is, the same rules apply. A common trap: replacing a single-hung with a casement in a basement bedroom. Both types can be egress-compliant, but if the new casement is mounted higher in the opening (or if the rough-opening sill has settled), the sill height can exceed 44 inches. That requires framing work and a permit.

Energy-code compliance is a silent gatekeeper. The 2021 IECC, adopted by Westmont with no local amendments, requires replacement windows to meet a U-factor of 0.32 or lower in Climate Zone 5A (north of I-88) and 0.35 in Zone 4A (south of I-88). Most modern double-hung and casement windows meet this; single-pane replacements do not. If you're buying a bargain-bin window from a big-box retailer without verifying the NFRC label (look for the gold-and-blue tag with U-factor listed), you risk the window being rejected at final inspection. Building inspectors in Westmont will ask to see the NFRC certificate or manufacturer spec sheet. Westmont's frost depth (42 inches in the north, trending toward 36 inches south of I-88) also means your rough-opening sill should be well above grade to avoid water intrusion; windows installed directly against grade-level siding are flagged as improper drainage.

Timeline and fees: A like-for-like, non-historic-district window replacement typically costs $150–$250 in permit fees (based on the city's fee schedule: roughly $25–$50 per window for the first window, then $15–$25 per additional). Filing is online via the Westmont permit portal or in-person at City Hall (2 South Grant Street, Westmont, IL 60559). Plan review takes 2–4 weeks for full review (multiple openings, enlarged openings) or 1 week for administrative approval (single like-for-like). Final inspection is a visual walk-through; if you're replacing five windows on the same elevation, the inspector typically inspects two or three at random. If any opening was enlarged, framing inspection is required before the window is set, and a final after installation. Owner-builder work is allowed in Westmont for owner-occupied residences, so you can pull the permit and do the installation yourself, though most homeowners hire a licensed contractor to avoid re-inspection delays.

Three Westmont window replacement (same size opening) scenarios

Historic District overlay: how Westmont's HPC differs from suburban neighbors

Westmont's Historic District (roughly 40% of residential parcels, concentrated along Grand Avenue, Forest Avenue, and Richmond Road) is subject to the Westmont Historic Preservation Commission, which operates under Village Ordinance Chapter 138. This is a pre-permit hurdle that many homeowners don't anticipate. Unlike some suburbs (e.g., Clarendon Hills, which has a lighter-touch HPC), Westmont's HPC requires design-review approval for any exterior alteration, including window replacement. Even a like-for-like swap in material (wood to vinyl) or color change requires HPC sign-off. The HPC meets monthly; if you submit your window spec in early October, approval may not arrive until November. Then you file the Building permit, which adds another 1–2 weeks. Plan ahead for a 6–8 week timeline in the historic district, not the 2–3 weeks you'd expect in non-historic suburbs like Downers Grove or Clarendon Hills to the east.

The HPC evaluates windows against the Secretary of Interior Standards for Historic Preservation, which emphasize matching the original window's visual character: proportions (ratio of width to height), muntin pattern (divided lights vs. picture window), depth (setback from the wall face), material (though vinyl is now accepted), and color. A 1920s bungalow with true divided-light casements needs replacement windows with true or simulated muntins in the same pattern; a bland 1950s ranch with a single-light aluminum slider can accept a vinyl double-hung if proportions match. The confusion arises because 'match' doesn't mean clone — it means 'preserve the historic character.' The HPC's approval letter is your shield; once you have it, the Building Department treats your permit as administratively approved and doesn't reopen the aesthetic question.

One note on expedited approval: If you hire an HPC-registered architect or preservation contractor to prepare your submission (with drawings and specs that demonstrate compliance), the HPC may approve in a single meeting cycle (4 weeks instead of 8). This costs $500–$1,500 in consultant fees but saves 2–3 weeks and reduces the risk of rejection and resubmission. For a five-window project in the historic district, this is worth considering.

Egress windows and frost depth: Westmont's soil and code intersection

Westmont's frost depth — 42 inches in the north, trending toward 36 inches in the south — is driven by glacial till and loess soils that freeze deeply and unevenly. This affects basement window installation and egress sill height enforcement. A basement window sill that sits just above grade (say, 2 inches above the exterior finish) is vulnerable to water intrusion during spring thaw and heavy rain. Westmont Building inspectors will flag a basement window installed too low, and if it serves as an egress window, the violation is serious because water intrusion can degrade egress safety (rotted sill, degraded emergency operability). IRC R310 requires an egress window to be openable by occupants in an emergency; a water-logged, rusted casement is not.

If you're replacing a basement egress window and the existing sill is marginal (say, 3–4 inches above grade), ask your contractor to install a sill pan or raise the rough-opening sill by shimming the header. This costs an extra $200–$400 in labor and materials but prevents future water damage and ensures passing inspection. In south Westmont (Zone 4A), where frost depth is shallower, this is less critical; in north Westmont (Zone 5A, typical 42-inch frost depth), it's essential. One more note: if your basement has a foundation crack or previous water issues, the inspector may recommend (or require) exterior grading and drainage work before approving the window replacement. This is not a permit line item, but it's a cost to budget.

Egress window wells (if your basement is below grade) must also meet code. IRC R310 requires a window well to be at least 10 inches deeper than the sill height and 36 inches in the smallest horizontal dimension. Many Westmont basements have tight window wells that don't meet the 36-inch width; if you're replacing the window and the well is substandard, the Building Department may require well expansion or an alternative egress (e.g., a door to grade or a second window on an above-grade wall). This adds cost and timeline but is non-negotiable for a bedroom window.

Common questions