Egress Window Installation Thornton CO
Code-compliant egress windows for finished basement bedrooms — engineered window wells, proper drainage, and permits pulled for every job. Serving Thornton, Westminster, Northglenn, and Adams County.
Call (720) 740-6511 — Free InspectionAn egress window isn't optional for a finished basement bedroom in Colorado — it's a life-safety requirement under the International Residential Code adopted by Adams County and the City of Thornton. A basement bedroom without a code-compliant egress window cannot be listed as a bedroom on an MLS listing, doesn't count toward appraised square footage as finished living space, and creates liability for sellers who don't disclose it. More importantly, it traps occupants during a fire.
We handle the complete egress window installation: wall saw cutting through the foundation, engineered window well with gravel drainage base, code-compliant window unit (minimum 5.7 sq ft net clear opening, 24" clear height, 20" clear width), and the permit from Adams County or the City of Thornton, depending on your address. You don't manage the permit — we do.
Egress Windows in Adams County — Code Requirements
IRC Section R310 requires that every sleeping room below grade have at least one egress window meeting these minimums: net clear opening of 5.7 square feet (or 5.0 sq ft at grade level), minimum clear opening height of 24 inches, minimum clear opening width of 20 inches, and maximum sill height of 44 inches above the finished floor. Window wells must have a horizontal area of at least 9 square feet with a minimum 36-inch horizontal dimension.
Adams County Building Department enforces these requirements at permit inspection. The City of Thornton's building division is the applicable authority for addresses within city limits — permit fees and inspection timelines differ slightly. We know both jurisdictions and file under the correct authority based on your address. Inspections are typically scheduled within 5–10 business days of installation completion.
Many Northglenn and Westminster basement bedrooms were finished before current codes were adopted and have undersized windows or no window at all. These rooms are routinely flagged by home inspectors and appraisers. Retrofitting a proper egress window before listing adds the square footage back to the appraisal and removes the safety disclosure issue entirely.
Project Details
| Timeline | Inspection + permit application: 1–3 days. Installation: 1 day. Permit inspection: typically 5–10 business days after rough-in. |
|---|---|
| Window Sizing | Minimum IRC R310 compliant (5.7 sq ft net clear opening). Standard install is a 3040 or 3048 casement or single-hung unit from Andersen, Pella, or equivalent. |
| Window Well | Pre-fabricated galvanized steel or polyethylene well, minimum 36" horizontal projection, anchored to foundation. Gravel drainage bed minimum 6 inches deep at well floor. |
| Foundation Cut | Diamond blade wall saw — clean, precise cut through poured concrete or block foundation without jackhammer vibration damage to adjacent wall sections. |
| Lintel | Steel lintel beam installed above the opening to transfer load around the window opening. Required for all poured concrete and block foundation cuts. |
| Permit | Pulled for every job. We file with Adams County or City of Thornton Building Division as applicable, manage the inspection schedule, and provide the final permit card for your records. |
| Pricing | Quoted per job after free on-site inspection — itemized by foundation wall thickness, window unit, well size, and permit fees. |
Our Egress Window Installation Process
- 1Site Assessment & Permit Application — We measure the proposed window location, check exterior grade for well depth calculation, confirm there are no utilities in the cut zone (we call 811 before any excavation), and file the permit application. We also assess whether the location requires waterproofing coordination — a new window well that lacks proper drainage can become a water entry point if not installed correctly.
- 2Exterior Excavation — We excavate outside the foundation at the window location to the depth needed for the window well floor — typically 18–24 inches below interior finished floor level. Excavated soil is removed from site or stockpiled as directed.
- 3Foundation Wall Cut — A diamond blade wall saw cuts the opening to exact dimension. The cut is made from the exterior for concrete walls; from both faces for block walls to prevent block face spalling. The core is removed in sections.
- 4Lintel Installation — A steel angle or beam lintel is set above the opening and grouted or bolted in place to carry the wall load around the new opening. This step is non-negotiable for structural integrity — openings without proper lintels develop diagonal cracks at the corners within 1–3 years.
- 5Window & Well Set — The window unit is set and shimmed in the rough opening, flashed at the sill and jambs, and sealed with low-expansion foam and exterior waterproof caulk. The window well is anchored to the foundation wall above the window with stainless fasteners. A 6-inch gravel drainage layer is installed at the well floor with a drain tile connection to daylight or the interior sump system where practical.
- 6Interior Finish & Permit Inspection — Interior rough framing is installed around the window opening, and we schedule the permit inspection. After inspection sign-off, you receive the permit card and our installation documentation for your records.
Common Egress Window Scenarios in Adams County
Pre-Code Basement Bedrooms
The most common scenario in Northglenn and Westminster — a basement bedroom finished in the 1980s or 1990s with a small hopper window that doesn't meet current egress requirements. The fix is a full egress window installation with a new, larger opening cut through the foundation. The existing hopper window location may or may not be usable depending on its size and the well depth needed.
No Window at All
Basement bedrooms on below-grade walls with no existing window opening are common in older Brighton and Commerce City homes. A fresh cut through the foundation is required. We assess the exterior grade and utility clearances at the free inspection before committing to a location.
Pre-Sale Compliance
Sellers who want to count basement bedrooms in their listing price and square footage before closing need egress windows installed and permitted before the appraisal. We work on compressed timelines for pre-sale installs — most jobs complete within 5–7 business days of permit filing.
Well Drainage Failure
An existing egress window with a well that fills with water after every rain event is a common Broomfield and Thornton Crossroads issue — the original well had no gravel drainage layer and sits in compacted clay. We can add a drain tile from the well floor to the interior sump or daylight without replacing the window itself.
Warranty in Detail
Installation workmanship: 10-year transferable warranty on the foundation cut, lintel, window well anchoring, and flashing. If the window leaks, the lintel cracks, or the well detaches from the wall within 10 years due to installation workmanship, we repair it at no charge.
Window unit: Window manufacturer's warranty covers the unit itself (typically 10–20 years on hardware, 10 years on glass seal). We register the window at installation and provide the warranty card.
What the warranty does NOT cover: window well drainage failure caused by exterior grade changes after installation (e.g., new landscaping that redirects runoff into the well); window glass breakage; screen damage; seal failure in window glass unit (covered by manufacturer's separate warranty).
Permits and records: We provide the signed permit card, inspection sign-off, installation photos, and window spec sheet. Include these in your property file — they're required documentation for any future sale that includes the basement bedroom in the square footage.
Egress Window FAQ — Thornton, CO
Do I need a permit for egress window installation in Thornton?
Yes — Adams County and the City of Thornton both require a building permit for egress window installation. We pull the permit for every job, manage the inspection schedule, and give you the final permit card. Don't hire a contractor who skips the permit — an unpermitted egress window creates a disclosure issue at resale and may not pass a buyer's inspection.
How much does egress window installation cost in Thornton, CO?
Cost depends on foundation wall thickness (poured concrete costs more to cut than block), window unit spec, well size, and whether drain tile is needed at the well floor. Call (720) 740-6511 for a free on-site inspection and written itemized quote.
Can my existing window opening be used for egress?
Possibly — if the existing rough opening is large enough to accommodate a code-compliant unit. We measure the existing opening at the free inspection. If it's too small, we widen the cut. If it's in the wrong location (e.g., too close to a corner or over a utility), we'll find a better location.
How deep will the window well be?
Well depth depends on your interior finished floor level relative to exterior grade. Most Adams County homes need wells 18–36 inches deep. Wells over 44 inches deep require a built-in ladder or step by code — we note this in the written quote when applicable.
Will cutting the foundation wall weaken my house?
Not when done correctly. A steel lintel above the opening transfers the wall load around the new window — the same engineering principle used in every above-grade window in your home. We install the lintel as part of every foundation cut. Skipping the lintel is what causes corner cracks — that's a contractor quality issue, not an inherent structural concern.
How long does egress window installation take?
The physical installation — excavation, cut, window set, well anchor, interior rough framing — typically completes in one day. The permit inspection is scheduled 5–10 business days after rough-in completion. Total project timeline from permit filing to final inspection sign-off is typically 2–3 weeks.
Will the window well collect water?
A properly installed well with a gravel drainage bed and a drain tile connection to daylight or the sump system will drain within minutes of a rain event. Wells without drainage fill up. We include proper well drainage in every installation — it's not an add-on.
Does egress window installation increase my home's value?
In Adams County, adding a compliant egress window to a non-conforming basement bedroom allows that room to be counted as a legal bedroom on your MLS listing and in the appraisal. The value increase is typically 3–5x the installation cost in the current Thornton market — it's one of the highest-return improvements available in a finished basement.
Make Your Basement Bedroom Legal and Safe
Free on-site inspection, permit included, same-week scheduling in Thornton, Westminster, Northglenn, and Brighton.
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What You Get in Our Quote vs. the Lowball Bid
We don't compete on the lowest sticker price — we compete on the quote that gets the job actually done. Here is what is included in every quote we write, and the cut-corners that show up in cheaper bids.
Included in our written quote
- Engineer-style elevation + crack assessment
- Soil and drainage evaluation
- Written quote with pier counts + warranty terms
- Photo documentation of every crack/movement
- Permit-pulling where required
- Post-install elevation re-check
Cut corners in the lowball bid
- Free-quote with no actual inspection
- Pier-count guesses without measurements
- Subcontracted installation crews
- Warranties that exclude common failure modes
- Pressure to sign at the kitchen table
- Same-day pricing tricks