Research by DoINeedAPermit Research Team · Updated May 2026
The Short Answer
If you're creating a bedroom, bathroom, or family room, you need a building permit from the City of McHenry Building Department. Storage, utility, or unfinished basement work does not.
McHenry adopts the 2021 Illinois Building Code (aligned with 2021 IBC), which means your basement finishing project is subject to the same egress and habitable-space rules as every Illinois municipality — but McHenry's building department has a reputation for strict enforcement on basement egress compliance and moisture-mitigation documentation, particularly in the older residential neighborhoods north of US-14 where glacial-till soils and groundwater are problematic. The City of McHenry Building Department requires a full permit application, plan review, and inspections for any basement space that will be occupied as a bedroom, living area, or bathroom. If your basement is staying as storage or mechanical space, you can skip the permit. What sets McHenry apart from neighboring jurisdictions like Crystal Lake or Cary is that McHenry's department explicitly requires moisture-intrusion history disclosure on the permit application; if you've ever had water in the basement, they will mandate a perimeter drain system or interior French drain design before approval. Additionally, McHenry is in a radon-prone region (Zone 1), and while radon mitigation is not strictly required by code, the city's department strongly recommends passive radon-ready construction details be shown on your plans (a stub vent rough-in through the rim joist, extending through the roof — cost roughly $300–$800 to add later if omitted). Expect 3–5 weeks for plan review and about $400–$600 in permit fees based on finished square footage and valuation.

What happens if you skip the permit (and you needed one)

McHenry basement finishing permits — the key details

The threshold rule is simple: if the basement space will be occupied and used as a bedroom, bathroom, family room, or any space where people will sleep or spend extended time, you need a permit from the City of McHenry Building Department. The Illinois Building Code (adopted by McHenry) defines habitable space in IRC R202 as 'space in a building for living, sleeping, cooking, or dining purposes, excluding bathrooms, closets, hallways, storage areas, laundry areas, and similar spaces.' Storage rooms, mechanical/utility closets, and workshops in an unfinished basement do not trigger a permit. However, as soon as you add drywall, flooring, electrical outlets, or partition walls to create a finished living area, the assumption shifts to habitable space, and you must get ahead of the inspection process. McHenry's building department processes basement permits under the building permit track, requiring submission of floor plans showing room layout, ceiling heights, and egress routes. If you're also adding electrical circuits (lighting, outlets, HVAC), plumbing (bathroom or wet bar), or HVAC ductwork, those trigger separate electrical and plumbing permits, often bundled into a single 'combo' permit application with a single fee. The permit application fee ranges from $350–$600, typically calculated as 1.5–2% of the project valuation. For a 500-square-foot basement finishing project with drywall, flooring, and partial electrical, expect to estimate valuation at $12,000–$18,000 and budget $200–$350 in permit fees alone.

Egress is the biggest code hurdle and the reason many basement bedrooms fail inspection. IRC R310.1 requires every basement bedroom to have 'at least one outside opening for emergency egress and rescue.' That opening must be an egress window (operable from inside without tools, minimum 5.7 square feet net open area, minimum 24 inches wide and 20 inches tall, with a clear horizontal distance from the bottom of the opening to the finished floor no more than 44 inches). A standard horizontal sliding window below grade will not pass — you must install an egress-rated window in a below-grade opening, usually with an exterior window well, grate, and drainage sump pit. McHenry inspectors are strict on this: they will measure the window opening, check the well installation for proper drainage (a perforated drain pipe running to daylight or sump), and verify that the grate is hinged and releases from inside. Cost to retrofit an egress window (digging the well, installing the window, running drainage) runs $2,500–$5,000 depending on soil, depth, and accessibility. If you're adding a second bedroom to an existing finished basement, or converting a storage room to a bedroom, a second egress becomes required only if the bedroom is deeper than 20 feet from the existing exit or if code-required occupant load exceeds 50; in most single-family homes, one egress per floor satisfies code. Do not attempt to substitute a door opening onto an interior stairwell or into an adjoining room — that is not code-compliant egress.

Ceiling height in McHenry basements must meet IRC R305.1: a minimum of 7 feet 0 inches measured from the finished floor to the lowest point of the ceiling or ductwork. In areas with beams, pipes, or HVAC ducts, you may drop to 6 feet 8 inches under a single beam (but the majority of the room must be 7 feet). If your basement has a header beam or steel post that will remain in the finished space, and the clearance under that beam is less than 6 feet 8 inches, you cannot legally finish the space under that beam as habitable area; you must designate it as a storage alcove or relocate/raise the beam (expensive). McHenry's building inspector will bring a measuring tape to the rough-framing inspection and will reject a permit if ceiling height falls short. This is not negotiable — there is no variance process for ceiling height in residential basement finishing. Many homeowners discover mid-project that their basement slab elevation and the main-floor beam location create an impossible ceiling height; this is why getting a pre-permit consultation with the building department (often free or $50) is worthwhile.

Moisture and drainage are McHenry-specific pain points because the city sits on glacial till and loess soils with high groundwater in spring. The Illinois Building Code adopts IRC R406, which requires below-grade walls and slabs to be protected from water intrusion by 'a damp-proof membrane or moisture barrier.' McHenry's building department interprets this strictly: if your permit application mentions any history of water intrusion, wet stains, or mold, the inspector will require either an interior or exterior perimeter French drain system, a sump pump, and a vapor barrier under any new concrete or flooring. Many homeowners think they can skip this if water hasn't been a problem in the past five years — incorrect. The city requires proactive moisture control; if you finish over a bare concrete slab without a vapor barrier and moisture wicks up into the drywall, that's on you. Cost for a basic interior French drain and sump pump runs $1,500–$3,500. If you're installing below-grade plumbing (bathroom in the basement), an ejector pump is required by IRC P3103.2 if the fixture drain is below the sanitary sewer line; that's another $800–$1,500. McHenry's sewer connections are predominantly gravity-fed, so most basement bathrooms will need an ejector pump. Do not omit this from your plan or assume the contractor will 'figure it out' — the plumbing inspector will red-tag it.

The inspection sequence in McHenry typically unfolds as: (1) permit application and plan review (3–5 weeks), (2) rough-framing inspection (after framing and before insulation, checking ceiling heights, egress windows, and rough electrical/plumbing runs), (3) insulation and moisture-barrier inspection (verifying vapor barriers under slab, around rim joists, and on exterior walls), (4) drywall and fire-sealing inspection (checking that any separation walls to furnace/utility areas are sealed, fire-rated if required), and (5) final inspection (electrical outlets, lighting, smoke/CO detectors, and overall compliance). Each inspection must pass before you move to the next phase; a failed rough-framing inspection for ceiling height or egress means you halt the project, correct the issue, and call for a re-inspection (no additional fee, but it delays your timeline by 1–2 weeks). Plan for 6–10 weeks from permit pull to final sign-off if everything goes smoothly. Electrical and plumbing inspections are often bundled into the same appointment as building rough-framing; coordinate with your contractors so electricians, plumbers, and framers finish their rough work in tandem.

Three McHenry basement finishing scenarios

Scenario A
Family room finish, 300 sq ft, no bathroom or bedroom, 7'2" ceiling, Crystal Lake Road corridor
You're converting an unfinished basement storage area into a family room / media room with new drywall, flooring (engineered hardwood over the concrete slab), and recessed lighting. No bathroom, no bedroom, no plumbing. The ceiling height is 7 feet 2 inches, well above code minimum. This DOES require a building permit because the finished space qualifies as a habitable room (occupied space for living purposes per IRC R202). You'll need to submit floor plans showing room dimensions, ceiling heights, electrical outlet locations, and smoke/CO detector placement. The basement concrete slab has a faint water stain near the southwest corner from a storm five years ago, now dry. McHenry's building department will flag this moisture history and require you to install a vapor barrier (polyethylene 6-mil sheeting) under the new flooring and extend it 6 inches up the exterior walls before drywall is installed. Cost for vapor barrier material and installation: $400–$600. Electrical permit will be required for the new circuits and outlets (expect $100–$150 in electrical permit fees). Permit fee for the building portion: roughly $300–$400 based on $10,000 project valuation. Rough-framing inspection verifies ceiling height, vapor barrier installation, and electrical rough-in. No egress window required because this is not a bedroom. Total timeline: 4–6 weeks plan review, then 1–2 weeks for construction and inspections. Expect to spend $800–$1,200 in permit fees and inspection prep.
Permit required | Building permit $300–$400 | Electrical permit $100–$150 | Vapor barrier under flooring $400–$600 | No egress window required | Smoke/CO detectors interconnected | Total project cost $10,000–$15,000 | Timeline 4–6 weeks plan review
Scenario B
Master bedroom addition with egress window, 250 sq ft, 6'10" ceiling, with en-suite bathroom, north McHenry (older home, frost depth 42 inches)
You're finishing a basement corner as a second master bedroom with attached bathroom. The ceiling height is 6 feet 10 inches, which clears the 6-foot-8-inch minimum under an existing beam but falls short of the preferred 7 feet. McHenry code enforcement accepts 6'8" under beams, so you're legal, but you must note on the floor plan exactly where the beam is and its clearance. Because this is a bedroom, IRC R310.1 requires an egress window. The exterior wall faces a paved patio, so you'll need to excavate a window well roughly 3 feet wide by 4 feet deep (frost depth in McHenry north is 42 inches, so the bottom of the well must be below that frost line — your contractor will dig to ~48 inches and backfill with gravel and perforated drain). The egress window itself (a horizontal slider, 24 inches wide by 20 inches tall minimum, operable from inside) costs $600–$1,000; the well excavation and drainage installation add $2,000–$3,500. You're also adding a bathroom (toilet, sink, shower) in the adjacent 80 square feet. The bathroom drain connects to the main sanitary line, which runs uphill from the basement, so you'll need an ejector pump (submersible sump-pit pump, $800–$1,200 installed) to lift waste water to the main line. Permit requirements: building permit (bedroom + bathroom, $400–$500), plumbing permit (bathroom rough-in + ejector pump, $150–$250), electrical permit (bathroom circuits, ventilation fan, GFCI outlets, $100–$150). Moisture: the basement has no history of water intrusion, but the new excavation for the egress well may expose groundwater. You'll install a perforated drain pipe around the well sump and tie it to the sump pump discharge. McHenry's inspector will require the sump pump to discharge to daylight or to the storm drain (not the sanitary line). Inspections: rough-framing (ceiling height, egress window opening framed correctly, bathroom rough plumbing/electrical), rough mechanical (ejector pump installation and venting), insulation/moisture barrier, drywall, final (plumbing fixtures, electrical outlets and switches, lighting, smoke/CO detectors). This is a complex project with multiple trades. Plan for 6–8 weeks plan review (bathroom + egress + ejector pump adds complexity) and 4–6 weeks of construction with 5–6 inspections. Total permit and related costs: $1,200–$2,000. Total project cost (labor + materials + permits): $20,000–$35,000. The egress window and ejector pump are the non-negotiable items; do not proceed without them.
Building permit $400–$500 | Plumbing permit $150–$250 | Electrical permit $100–$150 | Egress window (materials + install) $2,600–$4,500 | Ejector pump $800–$1,200 | Moisture barrier and drainage $600–$1,000 | Total permits $650–$900 | Total project $20,000–$35,000 | Timeline 6–8 weeks plan review + 4–6 weeks build
Scenario C
Finished recreation space, 400 sq ft, 7'4" ceiling, no plumbing or sleeping area, known moisture history, west side glacial soils
You're finishing a basement rec room (ping-pong, fitness area, game table) — a habitable space but not a bedroom or bathroom. The ceiling is 7 feet 4 inches, well above code. No new plumbing or HVAC is needed. However, your basement has a documented history of water intrusion: the previous owner disclosed that the northwest corner experienced seepage during heavy rains (2015, 2018), and you see old water stains on the rim joist and concrete blocks. McHenry's building department will require moisture-intrusion documentation on the permit application. The inspector will not approve plans without a moisture-mitigation strategy. Your options: (1) install an interior French drain (perimeter trench with perforated pipe running to a sump pump, ~$2,000–$3,000), (2) install an exterior perimeter drain (excavation around the foundation perimeter, exterior membrane, interior or daylight discharge, $5,000–$8,000), or (3) use a combination approach (interior drain in the wettest areas, exterior in the high-risk corner, $3,000–$4,500). McHenry's inspector prefers the exterior drain for long-term reliability, but will accept interior if the cost/disruption is prohibitive. Your plan: interior French drain along the northwest corner and west wall, discharging to a new sump pit with a 1/2-hp pump. This addresses the code-required moisture barrier (IRC R406) and gives you confidence for drywall and flooring. Cost: $2,200–$3,000. Building permit ($350–$450) and electrical permit for the sump pump circuit ($75–$100). Rough-framing inspection will check ceiling heights, verify vapor barriers over the slab (6-mil polyethylene extending 6 inches up walls), and inspect the French drain installation (perforated pipe, gravel backfill, sump pit). Plumbing inspector will verify sump pump discharge route (must exit above grade to the daylight or storm drain, not the sanitary line — McHenry is strict on this). No egress window required (not a bedroom). Smoke and CO detectors required, interconnected with the rest of the house per IRC R314.4 (hardwired, wireless, or battery-powered if hardwiring is infeasible). Timeline: 4–6 weeks plan review (moisture mitigation adds scrutiny), 4–5 weeks construction and inspections. Total permit costs: $450–$550. Total project (including moisture mitigation, flooring, drywall, electrical, permits): $15,000–$22,000. The moisture mitigation is non-optional here; do not skip it or hide it from the inspector.
Building permit $350–$450 | Electrical permit $75–$100 | Interior French drain and sump $2,200–$3,000 | Vapor barrier and insulation $500–$800 | No egress window or plumbing required | Smoke/CO detectors $100–$200 | Total permits $425–$550 | Total project $15,000–$22,000 | Timeline 4–6 weeks plan review

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Egress windows: the code requirement that will make or break your basement bedroom

Every basement bedroom must have at least one egress window complying with IRC R310.1. The window must be operable from the inside without tools, have a net open area of at least 5.7 square feet, and have minimum dimensions of 24 inches wide and 20 inches tall. The bottom of the opening must be no more than 44 inches from the finished floor. In practice, this means a standard horizontal slider (24 inches wide, 24 inches tall, roughly 6 square feet net open area when fully opened) fits the requirement; a small casement or single-hung window likely does not. McHenry inspectors measure this precisely at rough-framing inspection.

The exterior opening must be protected by a window well or similar structure to prevent dirt, leaves, and rain from accumulating. The well itself must slope away from the foundation, have a drain (perforated pipe running to a sump or daylight), and if it's deeper than 44 inches below grade, must include a ladder or steps for emergency egress. In McHenry's glacial-till soils (north of US-14) and loess soils (south), frost depth is 42 inches; your window well must extend below that, typically to 48–50 inches. The well bottom connects to a sump pit (3 feet by 3 feet, roughly, lined with plastic), which is then drained by a submersible pump or a perforated pipe discharging to daylight. If daylight discharge is not feasible, the pit gravity-drains to the sanitary sewer (with a one-way valve to prevent backflow), but McHenry's inspector may push back on this — best practice is daylight discharge or a separate sump system.

Cost to retrofit an egress window in an existing basement runs $2,500–$5,000: excavation ($800–$1,500), window ($600–$1,200), well structure and grating ($400–$1,000), and drainage installation ($700–$1,500). If the wall is brick or block, additional cutting may be required ($200–$500). This is why many homeowners add egress windows during the original finish; installing one mid-project is messier and more expensive. Do not attempt a secondary egress as an interior door (e.g., a door opening into an adjoining room or hallway) — that is not code-compliant; exterior egress only.

McHenry permits will not be issued for a basement bedroom without an egress window shown on the plans. If you pull a permit without showing the window, the inspector will red-tag the rough-framing and will not sign off until the window is installed and the well is functional. This can delay your project by 4–6 weeks if the window is a retrofit. Plan for it upfront.

Moisture mitigation in McHenry basements: why the inspector will ask about water in the basement, and what you must do about it

McHenry sits at the intersection of glacial till (north) and loess (south) soils, both of which are fine-grained and prone to retaining water. In spring (April–June) and during heavy rain events, groundwater rises into the basement perimeter, especially in older homes built on shallow foundations (pre-1970s). The Illinois Building Code, adopted by McHenry, requires IRC R406 compliance: 'Exterior walls of foundation shall be dampproofed or waterproofed to prevent the entry of ground water and water-soaked soil.' This means a moisture barrier — typically a polyethylene sheet (6-mil minimum) between the concrete/block and the interior insulation and drywall.

McHenry's building department interprets this strictly: if your permit application or conversation with the inspector reveals any history of basement water (stains, seepage, mold, efflorescence on concrete), the department will require either an interior or exterior perimeter drain system. An interior French drain (a perforated PVC pipe in a gravel trench around the interior perimeter, draining to a sump pump) costs $1,500–$3,500 and can be retrofitted into an existing basement with moderate disruption. An exterior drain (excavation around the foundation, a perimeter footer drain, exterior membrane, and daylight or sump discharge) costs $4,000–$8,000 and is more invasive but more reliable. McHenry's inspector prefers the exterior solution; many homeowners choose the interior for budget reasons. Either way, you cannot finish the basement without addressing moisture if there is any documented history of water.

Beyond the perimeter drain, the vapor barrier under the slab is mandatory. If you're installing new flooring (wood, vinyl, tile) over the concrete slab, you must install a 6-mil polyethylene sheet directly on the slab, extend it 6 inches up all walls (where it will be covered by the drywall), and seal seams with acoustic sealant. This barrier prevents capillary moisture rise, which can damage flooring and promote mold. Cost: $300–$600 for materials and labor. McHenry's inspector will verify this at the insulation inspection (before drywall is hung).

If you have a sump pump in the basement (existing or new), it must discharge to daylight (a trench or splash block at least 4 feet from the foundation) or to the storm drain (if available). Discharging to the sanitary sewer is permitted but disfavored by McHenry's department; if you do, the outlet must include a one-way valve to prevent backflow. Many homeowners forget to address sump pump discharge and end up with water pooling near the foundation; the inspector will catch this at final inspection and will not sign off until it is corrected.

City of McHenry Building Department
2213 North Seminary Avenue, McHenry, IL 60050 (City Hall main line; Building Dept. extension varies)
Phone: (815) 363-2100 (main) — ask for Building and Zoning Department | https://www.mchenryil.gov (check 'Permits and Licenses' or 'Building and Zoning' for online portal and application forms; some permits may require in-person submission)
Monday–Friday, 8:00 AM–5:00 PM (call to confirm; some cities maintain reduced hours or appointment-only reviews)

Common questions

Do I need a permit to finish my basement if I'm not adding a bathroom or bedroom?

If the finished space will be occupied as a living area (family room, rec room, office, den), you need a building permit because it qualifies as a habitable room under the Illinois Building Code. If it is remaining as storage or mechanical space, no permit is required. The key test is: will people spend extended time in this room, or is it purely for equipment/stuff? Once you add drywall, flooring, and lighting to create a finished room, assume you need a permit.

What is the minimum ceiling height in a McHenry basement, and can I get a variance if mine is only 6'6"?

IRC R305.1, adopted by McHenry, requires a minimum of 7 feet 0 inches from the finished floor to the lowest point of the ceiling. Under a single beam, you may drop to 6 feet 8 inches. There is no variance process for ceiling height in residential basement finishing — it is a safety and habitability rule that cannot be waived. If your basement ceiling is lower, you cannot legally finish the space as a habitable area. Your only option is to raise or relocate the structural member (expensive) or leave that area unfinished or as storage (unfinished basement below 6'8" is not restricted by code).

My basement has never had water problems. Do I still need to install a moisture barrier and vapor sealing?

Yes. IRC R406 requires moisture barriers and vapor control on all below-grade walls and slabs, regardless of current water history. McHenry's inspector will require a 6-mil polyethylene vapor barrier under any new flooring and on the exterior side of exterior walls before insulation. This is proactive protection; even if you have not had problems in the past, groundwater in spring or a heavy rain can cause moisture wicking. Do not skip this step; damp basements often develop mold and damage to flooring and drywall, and moisture can void some flooring warranties.

I want to add a bedroom to my basement. What is the single most important thing I must do?

Install an egress window (and the surrounding well and drainage) before framing walls. IRC R310.1 requires an operable window with at least 5.7 square feet net open area, sized 24 inches wide and 20 inches tall minimum, with the bottom no more than 44 inches from the floor. Without this window, you cannot legally have a basement bedroom. Cost is $2,500–$5,000; plan for it as a line item in your budget and coordinate the installation early in the project.

What inspections do I need for a basement finishing project in McHenry?

Typically: (1) rough-framing (after framing, before insulation — ceiling heights, egress windows, electrical rough-in, plumbing rough-in), (2) insulation and moisture barrier (vapor barriers, rim joist sealing, drain systems), (3) drywall and fire-rating (if applicable, e.g., separation walls to furnace areas), (4) electrical final (outlets, switches, lighting, AFCI/GFCI compliance), and (5) building final (smoke/CO detectors, ceiling height re-check, overall compliance). If you're adding plumbing, the plumbing inspector may combine with the rough-framing inspection. Plan for 5–6 separate inspections spread over 4–6 weeks of construction.

I am finishing my basement myself (owner-builder). Do I need a licensed contractor, or can I do the work?

Illinois permits owner-builders to do work on owner-occupied homes, including basement finishing. However, electrical work above 15 amps and plumbing below-grade work must typically be done by a licensed contractor (or you must become licensed yourself, which is not practical for a one-off project). Framing, insulation, drywall, and painting can be owner-done. The permit and inspections still apply; the inspector will red-tag work that does not meet code, regardless of who did it. Hiring a licensed general contractor or subcontractors for electrical and plumbing is the most straightforward path.

How much will the permit cost for my basement finishing project in McHenry?

Building permit fees in McHenry are typically 1.5–2% of the project valuation (labor + materials). For a 400-square-foot basement finish without plumbing, expect $300–$500 valuation of $15,000–$25,000). Add $100–$150 for electrical permit, $150–$250 for plumbing permit (if applicable), and any required plan review deposits (if the city charges them separately; many do not). Total permit costs usually fall in the $500–$900 range for a standard basement project. Speak with the building department for a specific estimate based on your scope.

If I don't get a permit and the work passes, will I be okay?

Probably not. Unpermitted basement work can surface when you sell (disclosure requirement under the Illinois Residential Real Estate Disclosure Act), when you refinance (lender's appraisal inspector flags non-permitted square footage), or when you file an insurance claim (insurer may deny coverage for injury or fire in an unpermitted space). A stop-work order from McHenry's building department carries a $500–$1,500 fine, plus you will owe double permit fees when you finally get it permitted. The costs and hassles of retroactive permitting or resale disclosure far exceed the cost of doing it right upfront.

Do I need to install radon mitigation in my finished basement?

Radon mitigation is not required by code in Illinois, but McHenry is in EPA Zone 1 (radon-prone). Many builders include a passive radon-ready system (a stub vent rough-in through the rim joist and rim board, extending through the roof) at the framing stage; cost is $300–$800. This allows you to install an active radon-mitigation fan later if radon testing shows elevated levels. If you omit the stub vent at framing, retrofitting it is disruptive and more expensive. Ask your contractor to include the passive system as a matter of best practice; most permits and inspections do not flag it as required, but it is a smart precaution for resale value.

What is an ejector pump, and when do I need one in a basement bathroom?

An ejector pump is a submersible sump pump installed in a pit below the basement bathroom fixtures (toilet, sink, shower/tub). It lifts waste water from below the main sanitary sewer line to the line so gravity can carry it away. If your basement is below the sanitary sewer (which is common in McHenry), the bathroom drain cannot drain by gravity; it must be pumped. IRC P3103.2 requires an ejector pump for any fixture drain lower than the sewer main. Cost is $800–$1,500 installed. If you are adding any plumbing fixture in the basement (including a wet bar sink), check with your plumber and the building inspector to see if an ejector pump is required for your specific sewer connection.

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Disclaimer: This guide is based on research conducted in May 2026 using publicly available sources. Always verify current basement finishing permit requirements with the City of McHenry Building Department before starting your project.

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