site documentation

Adapt the generic site plans + building footprints on following slides to fit your building and assist in responding to the Code Compliance Checklist.

This template-based site assessment moves from exterior to interior, from inhabited floors to basement level (with anticipated features in the proposed unit in yellow). Generally the site and building footprints are drawn at 1/8”=1’ in plan, section, and elevation. The coding, on the list and in the drawings, links to the Compliance Checklist through abbreviated topic name and page number. This is to prompt you to establish locations for elements like basement exits or utility connections and take visual notes on your existing building. After the generic plans, a blank spread with 1/8” grids is provided for sketching additional details. The Compliance Checklist then elaborates on the specific relationships between observed site conditions and Chicago Code requirements.

Element Key, by Code Compliance section:

• Z = Zoning - load opens navigation
• M = Maintenance - load
• L = Loading (Structure & Foundations) - load
• W = Waterproofing & Slabs - load
• U = Utilities - load
• S = Size & Height - load
• V = Ventilation & Light - load
• E = Egress & Fire Exits - load
• F = Fire Detection & Containment - load

The principles of zoning:

Chicago’s initial zoning ordinance was established in 1923 and significantly revised in 1957, aiming to separate incompatible uses and direct neighborhood development. At the scale of your property, zoning regulates a) use: how many units you can have within your building, b) density: how much lot area, parking and open space (lawn, patio) each unit should have, and c) bulk: how far from the lot lines (i.e. offsets) you can build new elements. You’ll need to determine your zoning district (directions below) to make sure you’re able to add another unit to your building. If a unit exceeds allowed use, density, or bulk standards, you can apply to the Department of Planning and Development for an administrative adjustment (see ‘Navigating Permits’).

A zoning district is an area geographically demarcated by the City and coded for allowable uses. To find your district, go to The Chicago Zoning Map and search by your address. Once you have the district code, you can confirm the uses intended by the City (see tables below). To calculate the density of units allowed on your lot - the Floor Area Ratio - you’ll need to know the sum of inhabited areas in your building (right, Building Area) and divide it by area of your lot.

Your zoning designation is defined by a combination of letters (Use Group) and numbers (Use Type). The example at left is in an ‘RT-4’ district. Use Group R covers all residential uses; your building is most likely in an RS (detached housing) or RT (Two-Flat, Townhouse and Multi-Unit) district. Use Type ascends from 1 to 6.5 and signifies allowable density. RS-3 , RT-3.5, and RT 4 allow for two or more flats per property. The zoning tables (next page) then specify additional characteristics. For an RT-4 property, this includes a maximum Floor Area Ratio of 1.2 and minimum lot area of 1650 sq feet, with 1000 sq feet of lot per unit, with additional open space, offsets, and parking requirements, as diagrammed in Prescribed Relationships.

Effective May 1, 2021, in pilot areas’ zoned RS-2 +, the Additional Dwelling Unit ordinance allows for a residential property to add a ‘conversion’ basement unit by right. This applies to buildings over 20 years in age but cannot be built on a property with a carriage house. See pilot details.

Is your unit allowed under chicago’s zoning?

Hypothetical answers, in blue outlines, are based on RT-4 classification and the Two-Flat + basement conversion on last page. Colors key to example; low saturation = lower density areas (less likely to allow additional units).

Use your site measurements and district classification to see if you can add another unit.

Under current zoning, single family homeowners in areas RS-3 or higher can add a unit to become a two-flat building. Given the small size of many RS-3 Chicago lots, the owners will likely need to get an administrative adjustment from the Department of Building and Planning, to accomodate variances in density, parking, and open space requirements (see 'Navigating Permits').

Likewise by ‘use’, Two-Flat owners in areas RT-3.5 and higher can add an extra unit to become a multi-unit building of 3+ flats. Again, Chicago’s small lot sizes mean you may also need an administrative adjustment for bulk and density issues (see 'Navigating Permits').

The tables on this page apply citywide, outside the ADU pilot areas.

Zoning Code:

1. Does your zoning district permit multiple units or Two-Flats? (17-2-0207)

2. Can you meet the district’s minimum Open Space Requirements with a new unit? (17-2-0307)

3. Does your building meet the district’s Minimum Lot Area per Unit with an additional unit? (17-2-0303)

4. Is your building below the district’s revised maximum Floor Area Ratio (FAR) with an additional unit? (17-2-0304)

5. Can you meet the district’s minimum Parking Requirements with an additional unit (count the new unit)?(17-10-0207, 17-10-1000*) If not, are you in an area designated for transit-oriented reductions (17-10-0102), or could you meet a 50% reduced requirement, by administrative adjustments, to preserve open-space as noted below?

Other Considerations:

• Site Setbacks: While older buildings maybe non-compliant for set-backs (and authorized as such), it is important to consider how much your lot must accomodate for construction and new elements for a basement unit.(17-2-0305) See foundations and site drainage, window wells, and egress for elements with potential set-back conflicts.
• Non-Residential Zones: This checklist only addresses residential use in residential districts. It does not cover live/work units or flats in Business or Commercial zones.

Is your new basement unit allowed under chicago’s ACU pilot program?

Hypothetical answers, in blue outlines, are based on RT-4.Use your district classification and location to see if you can add another unit. In pilot areas, conversion units can be added by right. Allowable number of units and loosened restrictions are listed below.

pilot area allowances

1. Are you in a pilot area? (Grey diagonal lines = ADU area on Chicago Zoning Map) Additional tools available on ADU microsite.

• North Zone is bounded by Devon, the lakefront, Lawrence, Clarendon, Halsted, Diversey, Lincoln, Belmont, the North Branch of the Chicago River, the North Shore Channel, Peterson, Califomia, Granville, and Seeley.
• Northwest Zone is bounded by the Eisenhower Expressway, Sacramento, Fulton, Damen, Chicago, Western, Hirsch, Rockwell, North, Sacramento, Bloomingdale, Kedzie, Palmer, Kostner, Fullerton, Central Park, Belle Plaine, Lawndale, Montrose, Harding, Lawrence, Kedzie, Elston, California, Fullerton, Western, North, and Ashland.
• West Zone is bounded by the Eisenhower Expressway, Homan, the South Branch of the Chicago River, and 4600 West.
• South Zone is bounded by Cicero, 7500 South Kedzie, 71st St., Halsted. 63rd St., 600 West, 47th St., King, 60th St., Dorchester, 65th St., Cottage Grove, 67th St., the Dan Ryan Expressway, 95th St., Ashland, and 87th St.
• Southeast Zone is bounded by 8300 South, the city limits, Torrence, 95th St., Commercial, 83rd PI., and Houston.

2. West, South, and Southeast Zones: (see ADU Ordinance, p13)

• Are you an owner-occupant of the new unit’s building? This is required for building with less than four units.
• Have less than two (2) other ADU’s been permitted on your block in the current calendar year? Only two, per year, per block are allowed to limit rapid development and adverse rent impacts.

3. Does your zoning district permit multiple units, Two-Flats, or conversion units? (ADU Ordinance, p9)

ADU Ordinance definitions

17-2-0303-C Conversion Unit:

Within Additional Dwelling Unit-Allowed Areas, in the case of building permit applications for the repair, remodeling, or alteration of residential buildings that are located in any RS2. RS3, RT or RM zoning district and that have been in lawful existence for 20 or more years, the density of such residential buildings may be increased in accordance with Section 17-9-0131 by 33% of the number of lawfully established dwellings units, other than conversion units, that have been in existence in the residential building for 20 or more years; provided, however, that if such residential building contains a single dwelling unit, the density of such residential buildings may be increased by one dwelling unit.

If this 33% calculation results in a fractional number, any fractional result of 0.5 or more must be rounded up to the next consecutive whole number.

units are not subject to:

• a) minimum lot area restrictions (#3, citywide zoning),
• b) open space requirements (#2, citywide zoning),
• c) accessory parking requirements (#5, citywide zoning), but
• d) cannot be on the same lot as a carriage house or used for short-term rentals (airbnb, etc.).

additions allowed (rs-2 +):

• Single Family + 1 unit = 2 units total
• Two-Flat + 1 unit = 3 units total
• Three-Flat + 1 unit = 4 units total
• Four-Flat + 1 unit = 5 units total
• Five-Flat + 2 units (1 affordable) = 7 units total
• Six-Flat + 2 units (1 affordable) = 8 units total

existing conditions and building maintenance:

You should be aware that any alteration of a structure that builds out a new unit must comply with the code for new construction. In addition, any existing structures that are visible to inspectors must meet the ‘Minimum Requirements for Existing Structures.’ That means that all the elements marked (right, Maintenance Issues) are required by code to be ‘structurally sound and in good repair’.

As shown in the photographs, structural deficiencies can manifest as cracks (loading fatigue), the pulling apart of surfaces (inadequate anchoring), and deteriorating siding, masonry, roofs, and stairs. Even decaying paint and trim, which seems minor, can be an indicator of problems like termite infestations and structural decay (see next page).

All of these conditions would qualify as potentially unsafe. If you see similar deterioration on your building, you should hire an architect to evaluate the structure’s soundness.

Whether or not you decide to add a basement unit, your building should be maintained in safe and sound condition. Tenants, neighbors, or strangers can report visible issues to the Department of Buildings, triggering a code violation and required building inspection.

Does your Building have unsafe conditions:

potential structural problems in parenthesis ( )

Homeowners can visually inspect their buildings prior to beginning any construction project, looking for the following:

Do you have visibly unsafe exterior conditions? (14X-3-303)

• A Clogged gutters or downspouts (roof/wall saturation and accelerated decay)
• B Decaying mortar or bricks on parapets or chimneys (wall collapse and falling materials)
• C Non-weather resistant siding and masonry joints with windows or doors (wall saturation and accelerated decay)
• D Exterior walls and foundations that are not anchored, plumb, or free of holes and cracks, windows or frames are not square or operable, floors slope (material failures facing building weight)
• E Unpainted or peeling decorative trim (rot and infestation)

Are units and common spaces adequately secure, with safe exits? (14X-4-304)

• F I Common stairwells lack smoke alarms, have missing treads, handrails, and irregular risers, are < 36” wide (see Egress)
• G Building Entrances lack locks or Unit Doors are missing locks, view holes (basic violation of tenant’s rights)
• H Inoperable windows or windows lacking screens and panes. (violation of tenant’s safety rights; see Ventilation and Light)
• J Water-stained walls and signs of mold (saturation and decay)

Do you have unsafe conditions on your grounds? (14X-3-302)

• K Decking, pathways, or exterior stairs show fatigue and decay (material stress and structural failure)
• L Open areas have standing water (water management failures, see Slab and Waterproofing)
• M Unruly vegetation/untidy garbage areas (infestations potential)

general principles for loading and foundations:

Building assemblies work together to transfer loads - like the weight of materials (dead load) or the weight of furniture and occupants (live load) - down to the foundation and, beneath it, the ground. Materials themselves, like soil, resist loading with compressive strength (right, Force Distribution). In addition to gravity, buildings face loading from all directions: wind, pressure exerted by soils and groundwater, and seismic tremors (right, Building Loading). Thus, a stable and safe structure requires multiple types of bracing, so joints and materials can transfer loads without twisting.

From your basement you can likely see much of the structure that is supporting your upper stories, carrying the load from floors, walls, and furniture above (right, Typ. Exposure Structure, A-E). Knowing where the first floor walls sit, you can anticipate where your basement joists are carrying greater dead loads. And, by measuring your foundations, through existing openings, you can estimate whether they are adequately sized to carry typical residential loads.

Before you add a ceiling or interior finishes, you should thus examine the overhead joists, foundation walls and any columns or load-bearing interior walls. Look for stains, strains, and signs of stresses (explored in the following questions) that indicate larger structural problems and material decay.

In fact, if you see any of the defects discussed you should consult a structural engineer or architect to assess potential failures.

does your basement show signs of structural fatigue overhead:

Spanning / basement ceiling elements

1 2 Are there signs of excess loading on your joists or girders ? Are your sills and upper walls anchored to your foundation? (14B-16-1604.3, 14B-23-2308.4.2.1, new construction) (14R-4-405.2.4, structural repairs)

• Do your joists exhibit visible bowing and vertical deflection or twisting laterally (right, Joist Deflections)? Any visible bending or diagonal cracks (2, shear) are a sign of excess loading, misaligned joints or deteriorating structure.(14B-16-1604.3)
• Are your joists spanning larger distances than recommended? See diagram D. Long distances and excess spacing can mean each joist is carrying too much load.(14R-4-405.2.4)
• If your basement includes structural columns and girders, do the horizontal pieces show signs of deflection or cracking? Do the columns have decay? (14R-4-405.2.4)
• Are your sills and headers anchored to the foundation C to prevent uplift, lateral sliding, and transfer load to the foundation?

Wall Issues

Are there signs of excess pressure from soils, site loads, or uneven settlement beneath the foundation?Note: graphic reference this and next slide (soils).

• 3 - Do your foundation walls either tilt or bow inward? This is a sign that the wall and its footer are failing to resist lateral soil pressure and are at risk of over-turning and collapse. This can be exacerbated by parking machinery near the foundation during construction. It can signal undersized footers, too-thin walls or inadequate anchoring between them.
• 4 - Do your foundation walls have any cracks? These also show that the wall is failing to resist soil pressures, or point pressure from tree roots or sodden areas. Cracks may be long forming or introduced by specific events. Take note of the distribution of cracks: uneven settling will likely have cracks down a wall, across your slab and up the opposite side. Areas of point pressure, like roots or equipment over-loading, will show crack spidering around the area of impact.
• 4.1 - Horizontal cracks, where one area juts into the center of the basement, are signs that specific vertical layers of backfilled soil are exerting uneven, excessive pressure, perhaps from undrained water or compaction.
• 4.2-4.3 - Vertical cracks are signs of uneven settlement of the foundation and underlying soils. One section is adequately supported, while the other area has sunk, with cracks forming between.
• 4.4 - Shear cracks are signs of shifting soils, along the wall surface, which are dragging blocks or bricks with them through friction.

All of these foundation cracks indicate unstable or active soils (to right, Soils: 1 or 5) potentially impacted by ground water and freeze-thaw dynamics. They could also indicate undersized or under-reinforced foundation walls. Consult with an architect or structural engineer for assessment and soil testing.

wall & mortar weathering

Are there signs of brick efflorescence? Are there areas of missing or cracked and crumbling mortar or spalling foundation materials (brick, concrete masonry, or stone)?

• Crumbly mortar and efflorescence both indicate that your walls are saturated with water. In brick, what you’re seeing are the salts leaching out of the bricks as moisture evaporates. Sand-like mortar shows that water was unable to evaporate and broke down the inner adhesion of the materials. Both are often seen next to spalling or cracking brick and block, as those materials absorb moisture, which then expands and contracts based on thermal fluctuations.

This form of decay is just as serious as foundation cracks as it also indicates groundwater and freeze-thaw dynamics. Consult with an architect or structural engineer for assessment and soil testing.
(^ in diagrams = conditions confirmed through soil testing)

Managing Moisture & Radon

As you examine your basement, note the condition of the floors and any lingering moisture. Look for cracks, caving, and wear in the slab. Often residential concrete slabs are poured as thin surfaces; they will not support new walls or furniture loads. See code-compliant slab sections, right, and replacement details, in ‘Mitigating Issues,’ associated with adding height, foundation drains, plumbing, and radon exhaust.

On the floors or walls, are surfaces clammy? Can you see condensation on walls or efflorescence on bricks? Are there leaks, in any weather, snaking toward the floor drains? If you ‘finish’ a unit despite these symptoms, this moisture is trapped in the walls and floors, accelerating rot and mold growth. To be safe for inhabitation, your basement unit should be either a) waterproofed or b) dampproofed.

Waterproofed basements are lined with thick, impermeable membranes (Waterproofed: 1) that wrap the foundation walls and the concrete-slab for continuous enclosure. This is required when the basement sits within groundwater and has hydrostatic pressure on the foundations.

Dampproofed basements are lined with thinner materials, which often double as vapor-barriers, because they sit ‘above’ groundwater. This can be the result of natural drainage (Dampproofed: 2). Alternately, the foundations may have a tile drain system (exterior or interior) to intercept water, drain immediate soils and thermally isolate the interior (Dampproofed: 3, Slab StructureF).

is your basement sound, dry, and radon free:

Is your slab intact and adequate for new loads (Slab Structure I)? (14B-19-1907)

• Does it have joints to allow for settling?
• Are there changes - in drainage, loading - requiring replacement?

Does your slab have a vapor-barrier beneath (Slab Structure E, N)?

• Are there venting pipes to exhaust radon away from occupants? (To learn more about the carcinogenic risks of radon and exhaust systems, see ‘Mitigating issues’) (14B-19-1907)

Is your basement visibility dry or are there stains or high-water marks from flooding? Is there damp or waterproofing in place (Waterproofed; Dampproofed)? (14B-18-1805)

• Creating a dry basement will depend on soils, elevation, and geotechnical testing to confirm groundwater control options. See ‘Mitigating Issues’ for how interior and exterior drainage integrates with sump pumps and site grading.

principles for utility connections & services:

A basement unit needs working plumbing, an adequate number of outlets and lights, and thorough heating to maintain a comfortable environment of 68F (at -7F outdoors). Building systems like heating, plumbing, sewage, and electricity should be considered spatially—what can/can’t be appended efficiently—and in terms of load or capacity—number of fixtures enabled by size or volume of supply. You’ll want to minimize the impact to existing units, so be prepared to work around vertical drainage and potentially align sewer additions along existing overhead lines.

Older buildings are more likely to have inadequate capacity and will require additional lines or resizing sewer/water connections to City utilities (see ‘Mitigating Issues’). You’ll want to incorporate the costs of adding additional meters and lines into your overall estimate ($15,000-$20,000). Segregating systems and/or supplementing existing systems can help avoid underpayment, enable tenants to use utility subsidy programs, and meet livability codes. That said, old buildings often have steam heat or similar systems designed to service all units. Consider how to add supplemental systems to meet code and separate lines, like adding a forced-air heater in the basement, without disturbing the upper stories of existing steam distribution.

It’s also important to understand the elevation and location of sewer lines—either overhead (runs across the basement ceiling) or below the slab (beneath the basement floor). If your sewer connections are overhead, you will need an ejector pump to meet your existing sewage connections. For either system, you’ll need to vent any new connections to release sewer gas and provide maintenance access, like clean-outs and traps (see ejector pump and access details in ‘Mitigating Issues’ ). Your other drainage lines—roof downspouts, areaway drains, and foundation drains—will need a sump pump to lift and carry water away from your foundations (see details in ‘Mitigating Issues’).

As a building owner you can do rough estimates by noting existing connections, meters, fixtures, and lines, as shown in the plumbing, electric, and heating diagrams and tables on the following pages.
You will need an architect to consult with plumbers, electricians, and heating specialists to fully assess the condition of your existing systems and develop an integrated strategy for additional loading and utility connections.

The sample ‘Two-Flat’ system diagrams as well as the system sizing tables (below) are meant to help you feel comfortable integrating existing details and calculations, in order to actively engage trade specialist. Fully calculating the system sizing will need to take into account details like pipe types (for friction), the highest fixture elevation, and total system length for estimating pressure.

What do you need for a new unit:

Have you consulted with an electrician about needed capacity?

• Anticipate connecting kitchen appliances and two to four sets of outlets and lights in all rooms, with GFCI outlets in wet areas.
• Given any new layout, occupants will need to access their meters and breakers for maintenance.
• For any multi-unit building, you will need one metered electric service for each unit and one for the public areas - hallways, laundry, stairwells, and fire-escapes.
• With old buildings that lack separated electric, it’s common to replace the entire building’s wiring. Tracing and disentangling old wiring is time consuming and oft confirms the need for replacement. See ‘Mitigating Issues’ for new line options.

Electric loads:

In an electric system, current flows from a power source through a circuit—with appliances and lights that use that power—to a neutral line which carries residual current to the ground. Switches and breakers serve to break circuits and stop electric flow to specific elements or entire lines. Each electric meter tracks the watts pulled in for your unit.

Akin to sizing plumbing or gas loads (below), your electric system is sized to support a set number of appliances per circuit (each rated for wattage). The flow of electric current (in amperes, per circuit breaker) * the differential power (120 or 240V) = total power wattage available per circuit. For safety, most circuits use 60-80% (max) of the available wattage and are properly grounded.
Your electrician will calculate the power drawn and used when adding metered service and circuits. See ‘Mitigating Issues,’ electric details for an example circuit calculation.

What do you need for a new unit:

Have you consulted with a plumber about the capacity and location of the sewer system?

• Given an additional kitchen sink, dishwasher, and bathroom fixtures, do you know the current height and diameter of your sewer connections, to anticipate capacity and the need for pumps (18-29-710, 18-29-712)?
• Will your new unit incorporate additional clean-outs, backflow valves, and access panels to facilitate system maintenance and avoid sewage overflows in the lowest level (18-29-708, 18-29-715)?
• Confirm the location, elevation, and direction of your lateral connection - from your basement lines to the sewer main. Any extra elbows in the pipe can act as obstacles.

Have you consulted with a plumber about the capacity and location of the water system?

• Because a new unit requires a full kitchen and bath, you will need an additional or enlarged water connection. This likely won’t be flagged on your permits. Make sure to incorporate line (and meter) addition to avoid belated installation (with all the implied site, slab, and finishing work). See the fixture and pipe sizing calculation at the end of this section.
• Older, single family homes may not be metered. You will want to add meters to new units, but, as with sewage, you can use this method to anticipate the bills/loading for each unit. See the Municipal Code 11-12, Water Supply and Service (11-12-260).

Rough Capacity Estimates: Sewer

You can make an informal tally of plumbing capacity. Make a rough count of all the plumbing fixtures (tubs, toilets, sinks) attached to each of your major vertical drainage pipes and find their drainage values on Table 18-29-709.1 .

• For sewers, measure the pipe size and confirm capacity estimates on Table 18-29-710 A and B. Could you install additional fixtures, given allowed unit values and required 4” pipe beneath ground?
• Add roof drainage (18-29-1108.1) to get a rough sense of your needed drainage capacity.

Rough Capacity Estimates: Water

• For water, make a rough count of all the plumbing fixtures (tubs, toilets, sinks) on Table 18-29-604.10.1 (water).
• Take this fixture total and convert the value into demand (in gallons per minute) on Table 18-29-604.10.2. Find the connection size equivalent for a 100’ system (for steel or copper pipes). (As with the zoning example, highlights match the proposed Two-Flat conversion.)
• Fully calculating the system sizing, esp. for water, will need to take into account additional details like pipe types (for friction), the highest fixture elevation, and total system length for estimating pressure.

What else must you account for with Utilities?

Does the plan for your basement unit account for the interconnection of different building infrastructure/services? Most building systems involve multiple connections and negotation with walls and structure. Consider the following examples:

• Fossil-fuel burning heaters (water heaters, forced-air units) require intakes, exhausts, and heat distribution systems. (See ventilation in ‘Mitigating Issues’)
• Drainage pumps typically connect to your storm/sewer mains but also require two power circuits, which act as fail-safes (18-29-712).(See drainage and plumbing in ‘Mitigating Issues’.)

Because of such interconnections, planning a new unit should be done with professionals, given their assessment of existing building systems.

Rough Capacity Estimates: Gas Heat

Akin to plumbing, gas is distributed through a series of pressurized pipes, as diagrammed on page 80. Broadly speaking, gas lines step down in size. A larger capacity and diameter pipe supplies the meters. This splits to serve distinct unit lines and branches internally, with each new section serving fewer appliances, thus requiring less fuel and smaller diameter piping.

As with water flow, you can estimate existing gas flow and current pipes’ capacity to support extra appliances. Make a rough count of your gas appliances (range, dryer, etc.) and find their typical fuel usage in cubic feet, on Table Appliance Fuel Usage. Sum these values to estimate current gas usage, in cubic feet.

To calculate the necessary connection size, measure the distance from your meter to the furthest gas appliance. In the example, this would be the second floor gas range which is approximately 95’ from the meter. Find this length on the Table Gas Pipe Capacity (round up as necessary) and find the column, moving right, that matches or just exceeds the usage sum (305 ft3/hr in the example). At the top of the column is your estimated gas connection size, at the meter.

If your current piping matches the nominal pipe size and your fixture usage sum is less, you likely have capacity for heating upgrades or new appliances. Use the Table Appliance Fuel Usage to estimate viable additions.

Reminder: All rough utility estimates should be followed by strenuous professional assessments to confirm capacity and work required for a new unit.

Sample Unit: Proposed Utility Updates

Building upon the existing systems, this spread suggests likely adaptations and interventions in a Two-Flat basement. As much as possible, placement of new plumbing fixtures have aligned with existing water and sewer lines for service, drainage, and exhausting sewage gas. Assuming separated service between public spaces, first, and second floor units, the existing basement circuit is kept for public use and a new electric system is added for the basement unit interior. Heating connections are left as is, given overhead steam-lines and radiators, which are common in older, multi-flat units.

Principles behind height and size requirements:

It is critical to make sure your basement has enough height and area for a decent and legal apartment. The required dimensions are minimums meant to avoid overcrowding.

Unfinished basement height should be nearly 8 feet, on average, to allow for upright posture, accommodate building materials, and avoid pipes acting as obstacles to movement (Minimum Req. Room Heights). As you measure, leave a foot margin for insulation and finishing on floors and ceilings (Measuring Room Heights). (14B-12-1207)

Room areas should be between 60-120 square feet (min.), ideally fitting between existing, load-bearing structures like columns and walls. Make sure to leave common areas, for access to breaker boxes, meters, and laundry, as you carve out space. (14B-12-1207)

For comparison, measure your existing units to understand room sizes. On your slab, use chalk to ‘draw’ out walls (~6” thick), doors, and typical furniture; can you navigate comfortably in these imagined spaces? Ultimately your architect will work to refine and develop any new unit’s layout and coordinate building systems updates.

do you have the space for a new unit:

Does your basement have adequate ceiling heights for a new unit (Minimum Req. Room Heights)? (14B-12-1207.2 - exception 1)

Does your planned kitchen have decent workspace at the counters (Min. Room Areas: C) ?(14B-12-1207.1)

• If accessibility is a concern, 30-36” workspaces should include lower cabinets, grab bars, and wheelchair turning radii. See Accessibility Code for Dwelling Units (14B-11-1107).
• The kitchen (or living) may also include the 60 sqft dining area.

Are your main living, sleeping, and dining rooms adequate to meet the minimal area standards at right (Min. Room Areas: D, E, F)? (14B-12-1207.3)

• The required bathroom fixtures - a sink, toilet, shower/tub - will determine the minimal areas in a bathroom. (Min. Room Areas: B)

Principles behind light and ventilation requirements:

It is imperative that any new basement unit meets or exceeds the code’s ventilation and lighting requirements (left, Min. Light & Air). Sheltered at/below grade, basements often have small windows, poor air circulation, and excess humidity. Combined, these factors foster condensation and mold. Adequate ventilation and light combats mold and mildew, and improves quality of life. Your architect will confirm air and light calculations and coordinate with specialists. That said, you can anticipate potential issues and estimate for compliance by making a few measurements using the metrics noted below.

Natural light is easy to estimate. (right, Calculating Air & Light Exposure) Measure the area of windows currently in your basement and pair them with anticipated room sizes. For adequate daylight, the area of windows in any room must be at least 8% of the floor area (note indirect light/adjacent room options for high ceiling areas)(14B-12-1204.2.4). An electrician can estimate artificial light levels for access stairwells and new rooms.

To estimate natural ventilation, imagine all the measured windows open (50% area for air flow) and calculate as you did above(14B-12-1202.5). Do you have 4% of air-flow area per each room area? To informally check for excess humidity, tape tinfoil to the walls (all edges) and, after two days, check for water. Moisture on the wall indicates waterproofing issues; moisture on the exposed side shows condensation. As air movement, condensation, and evaporation rely on cross-ventilation (facing windows) and air-pressure dynamics, you should hire a ventilation professional to confirm the rate of passive air change—how long it takes for all new air to enter a space with windows closed—and advise on mechanical ventilation and dehumidification.

See openings section, in ‘Mitigating Issues’ for constraints in adding foundation windows.

do you have air and light for a new unit:

Does your basement have adequate natural light for residential use (Min. Light & Air)? (14B-12-1204.2.4)

• 8% for all rooms, or 8% average if counting indirect lighting

Have you confirmed adequate artificial light with an electrician? (14B-12-1204.3)

• Room lights must provide 10 footcandles, at 30” h
• Stairwell lights must provide 1 footcandle on treads

Does your basement have adequate natural ventilation, in all seasons (Min. Light & Air)? (14B-12-1202.5)

• 4% for all areas, calculated by room or averages
• 5 air-changes per hour by infiltration

Do your new bathroom(s), kitchen, and laundry rooms have mechanical ventilation? (14B-12-1202.1)

• Fans must have openings of 1.5% * area of the room they ventilate.

If you need to increase window areas, do you have space for window wells (Exterior Light Wells)? (14B-12-1204.2.6)

• Can you add light wells (1.5:1 ratio) within your lot?

Fire egress (i.e. exit) elements

Fire safety is a key aspect of building code. As you layout your new unit, you’ll want to make sure all rooms allow for egress, i.e. that all occupants can efficiently leave the building in an emergency. Broadly, the code requires paths within halls or stairs that are a) built of fire resistant materials (see next page) and b) facilitate the unobstructed movement of occupants outward.

As noted in ‘Egress Components,’ an egress system has three parts to consider:

• Egress routes: pathways to an exit from within a building, passing through units, common areas, and stairs. The code specifies ‘travel distance’ as the longest distance allowed between the opposite corner of a unit to an exterior exit, as a human would walk.
• Exits: building exits are located on the exterior walls and release occupants to the outside. Exits can include exterior stairs, which connect with the ground, or ‘horizontal’ exits that release occupants at grade.
• Discharge: pathways from an exit to the street or alley at the edges of a property. Residential discharge paths can have locking gates at the edges of a property.

do you have needed fire exits:

Does your basement unit have a direct exit, from within the unit, or two exits via common hallways? (14B-10-1006.2.1, 14B-10-1006.3.2, 14B-10-1006.3.3)

• If planning additional exit doors, they are required to be at opposite ends of residential buildings.
• The same physical concerns apply to adding doors to foundations, as when adding windows (with 3’ exit landings in place of window well requirements).

Is at least one route of travel under 60’ (no sprinklers) or 75’ (with sprinklers):

• Measure the distance of travel from the furthest corner of the furthest room opposite the exit.
• For paths on stairs, measure on a diagonal, parallel to the steps, along the staircase center.
• Routes of egress can not cut through bedrooms or bathrooms from other rooms, due to their locking doors.

Are all the passages and doors along your egress route adequately sized - both within unit and in common spaces (Egress Route Sizing)? (14B-10-1003.3.1, 14B-10-1003.5)

• If space does not permit, you may retain older, steeper stairs but with adequate railings and clear space.
• If your basement is lower than adjacent exits and areaways, it is permissable to have two steps up (max) to exit a story.

As you consider the impacts, beyond a single unit, ask yourself the following:

• Are the egress systems in your building adequate for all residental units?
• Have you considered how new, exterior exit doors might integrate with your foundation walls and site?

material elements and alarms for fire safety:

In addition to egress, the building code also addresses fire hazards through containment, suppression, and detection systems - ‘fire walls’, sprinklers, and alarms. As you consider a new unit, you’ll want to incorporate, at minimum, containment and detection systems. Small multi-unit residences and Two-Flats are not required to have sprinkler systems.

Containment consists of dividing the building into different zones and building walls or partitions to slow the spread of fire. The partitions are classified by their fire resistance, recorded in ‘burn-time’ or the duration it takes for materials to fail in a fire. In principle, the one or two-hour rated partitions—required between units, ceilings, and surrounding egress corridors—allow time for occupants to hear fire alarms and safely exit.

Fire detection takes the form of smoke detectors. These must be incorporated in your new unit and basement utility areas. While detector placement is fairly simple, alarms should be wired into the building electrical system and connected—if one sounds, they all sound—with placement near the ceiling. If absent, detectors should be added to the existing apartments and stairwells and connected together.

Carbon monoxide alarms should be added near fossil-fuel appliances, such as furnaces, water heaters, and gas stoves. Inefficient or blocked exhaust can put your family at risk for carbon monoxide (CO) poisoning. Carbon monoxide detectors are either stand-alone units or incorporated with smoke detectors and should be installed at ceiling or upper wall height.

Is your new unit designed to detect and contain fire:

Does your new unit contain integrated smoke alarms at specified distances from/in bedrooms, bathrooms, and shared stairways (Fire Partitions & Smoke Detectors) ? (14B-9-907.2.10.2)

Note the three types of smoke detectors—heat, smoke, optical—and req. distances from kitchen areas. Does your unit plan accommodate this? (14B-9-907.2.10.3)

Does your new unit contain integrated alarms near fuel-burning appliances (Fire Partitions & Smoke Detectors) ? (14B-9-915, 916)

• This includes carbon-monoxide alarms for gas ovens, furnaces, and water heaters.

Are all the doors and walls along your egress route adequately sized - 5-6” thick for one or two-hour fire partitions? Have you incorporated partition sizing into the calculation of the unit’s exterior walls and ceiling, esp. regarding unit height (Partition Fire Resistance) ? (14B-7-708 partitions, 721 - prescriptive assemblies)

• See prescriptive fire assemblies at 14B-7-721, table 721.1(2)