How big does an egress window need to be?

Per IRC R310, an egress window must have a minimum net clear opening area of 5.7 square feet (basement) or 5.0 square feet (ground floor and above). Additionally, the opening must be at least 24 inches high AND at least 20 inches wide. The sill cannot be more than 44 inches above the floor. Net clear opening means the actual usable space when the window is fully open — not the frame size. Casement windows are ideal because 100% of the opening counts. Hung and slider windows only offer ~50% opening, so they need to be much larger to meet the same requirement. How much does an egress window cost?

How much does an egress window cost?

A complete basement egress window installation (window, well, excavation, labor) costs $1,500-$5,000 for most projects. Budget installations with basic vinyl windows and steel wells run $1,500-$3,000. Mid-range with quality windows and composite wells cost $3,000-$5,000. High-end with premium windows and stone-lined wells can reach $5,000-$8,000+. Major cost factors: foundation type (poured concrete is easier to cut than block), soil conditions (rock increases excavation cost), and depth below grade. Permit fees add $50-$300. Do I need an egress window in a basement bedroom?

Do I need an egress window in a basement bedroom?

Yes. Building code (IRC R310) requires every sleeping room to have at least one egress window that meets minimum size requirements (5.7 sq ft opening area, 24 inches high, 20 inches wide, sill no more than 44 inches from floor). Without a compliant egress window, a basement room cannot legally be called a bedroom. This affects your home's appraised value (bedroom count matters significantly). If you're finishing a basement and adding bedrooms, egress windows are required to get a building permit and pass inspection. What type of window is best for egress?

What type of window is best for egress?

Casement windows are the best choice for egress, especially in basements. A casement window cranks open and swings fully outward, meaning 100% of the window opening counts toward the egress requirement. Hung windows (single or double) and slider windows only open ~50% of their total area, so they need to be much larger to meet the same 5.7 sq ft requirement. For example, a 24x36 inch casement provides 6.0 sq ft of clear opening, while a same-size double hung only provides about 3.0 sq ft. Casement also makes it easier to climb out in an emergency.

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Siding & Exterior

Egress Window Guide: Code Requirements, Cost & Installation

Lumberama Editorial Team, Building Code & Safety Specialists Apr 23, 2026 9 min read

What Is an Egress Window

Definition: An egress window is a window large enough to serve as an emergency exit and rescue opening. Required by building code (IRC) in every bedroom and habitable basement room. Allows occupants to escape during fire and provides firefighter entry.

Where required: Every sleeping room (bedroom) must have at least one egress window. Basements with habitable space (bedrooms, family rooms, home offices). Existing homes: required when finishing a basement or adding a bedroom. New construction: required at time of building.

Why it matters: Without egress windows, a basement bedroom is NOT legally a bedroom. Affects home appraisal and resale value. Life-safety requirement (fire escape). Building inspectors check egress compliance for permits.

IRC Code Requirements

Minimum opening dimensions (IRC R310): Minimum net clear opening area: 5.7 square feet. Minimum net clear opening height: 24 inches. Minimum net clear opening width: 20 inches. Maximum sill height from floor: 44 inches.

Important notes: Net clear opening = actual usable opening when window is fully open. This is NOT the window frame size — it is the OPENING size. Different window types have different opening ratios (casement opens wider than slider). A window can meet the area requirement (5.7 sq ft) with different height/width combos as long as BOTH minimums are met (24 inches height AND 20 inches width).

Example compliant sizes: 24 inches high x 35.8 inches wide = 5.97 sq ft (meets all three). 36 inches high x 24 inches wide = 6.0 sq ft (meets all three). 20 inches wide x 41.1 inches high = 5.7 sq ft (meets width and area but check height).

Grade-floor exception: Ground-floor and above windows: 5.0 sq ft minimum (not 5.7). Same height and width minimums apply. Basement windows: always 5.7 sq ft minimum.

Window well requirements (below grade): Minimum area: 9 square feet. Minimum horizontal projection from window: 36 inches. If well depth exceeds 44 inches: permanent ladder or steps required. Ladder rungs: minimum 12 inches wide, maximum 18 inches apart. Ladder must not encroach more than 6 inches into the required well dimensions.

Window Types for Egress

Casement (best for egress): Crank-open, swings outward. 100% of the window opening is usable. Easiest to meet egress requirements. Best choice for basement egress.

Single/double hung: Slides up and down. Only the bottom sash opens (single hung) or both (double hung). Only ~50% of total window area is usable opening. Need a much larger window to meet egress.

Slider (horizontal): Slides left or right. Only ~50% of total area is usable opening. Need larger window to meet egress.

Awning: Hinges at top, opens outward from bottom. Can meet egress but opening angle may limit net clear area.

Recommendation: Casement windows are the best choice for basement egress because 100% of the opening counts toward the requirement. A smaller casement window can meet egress where a larger hung or slider window would be needed.

Cost

Basement egress window (complete installation): Window unit: $300-$800 (vinyl casement, egress-rated). Window well: $200-$600 (corrugated steel or composite). Well cover: $50-$200 (polycarbonate dome or flat grate). Excavation and concrete cutting: $500-$2,000. Installation labor: $500-$1,500. Waterproofing and drainage: $200-$500.

Total installed cost: Budget (basic vinyl, steel well): $1,500-$3,000. Mid-range (quality vinyl, composite well): $3,000-$5,000. High-end (premium window, stone-lined well): $5,000-$8,000+.

Factors affecting cost: Foundation type: poured concrete (easier to cut) vs block (more labor). Soil conditions: rock increases excavation cost significantly. Depth below grade: deeper = more excavation. Interior finishing: drywall framing around new opening. Permit fees: $50-$300 (varies by jurisdiction).

DIY vs professional: Concrete cutting requires specialized equipment (concrete saw, jackhammer). Waterproofing must be done correctly to prevent leaks. Structural considerations (cutting through foundation). Professional installation recommended for basement egress.

Installation Process

Steps: 1. Check local codes and get permits. 2. Choose window location (consider utility lines, drainage, landscaping). 3. Mark and cut the foundation wall opening from inside. 4. Excavate outside for window well. 5. Install steel lintel or header above opening (load-bearing support). 6. Set window frame and install window. 7. Install window well (corrugated steel, composite, or stone). 8. Add gravel drainage base in well (4-6 inches of gravel). 9. Connect well drain to foundation drain or sump. 10. Waterproof around window and well. 11. Install window well cover. 12. Frame and finish interior (drywall, trim). 13. Schedule inspection.

Timeline: 1-3 days for complete installation. Excavation: half day. Concrete cutting: half day. Window and well installation: 1 day. Interior finishing: additional time.

Permits: Building permit required in most jurisdictions. Some areas require engineering review. Inspection required before covering interior framing. Final inspection after completion.