Design rules

The full, cited Rule Base the engine reasons with — building-code mandates (hard gates), weighted guidelines (the scored objectives), the program rules that pick a home’s rooms, and the room-by-room best practices. Every rule cites where it came from. The checkable mandates are toggled and tightened in the studio’s Rules panel.

35 mandates (10 enforced now)14 guidelines24 program rules202 room best practices10 site & exterior10 accessibility

Mandates — hard rules; a design that fails one is invalid

Habitable room — minimum horizontal dimensioncodeenforcedIRC 2021 R304.2
No habitable room may be narrower than 7 ft in any horizontal dimension.
Habitable room — minimum floor areacodeenforcedIRC 2021 R304.1
Every habitable room needs at least 70 sq ft of floor area.
Hallway — minimum clear widthcodeenforcedIRC 2021 R311.6
Hallways need a clear width of at least 36 in (3 ft).
Habitable room — daylight + egress exterior wallcodeenforcedIRC 2021 R303.1 / R310
A habitable room needs glazing for natural light (R303.1) and a sleeping room an emergency escape opening (R310); both require an exterior wall.
Minimum room dimension (program request)programenforcedProgram request
Each room must meet the minimum wall length the program asks for (≥ the code floor; the program may ask for more).
Required adjacencies satisfiedprogramenforcedFunctional / plumbing requirement
Connected rooms (kitchen↔living, hall↔bedrooms/bath) must actually share a wall so the plan is usable and plumbing can stack.
Every room is connected (no stranded wing)programenforcedFunctional requirement (usable plan / means of egress)
Every room must reach every other through SHARED WALLS, so the detailing can place doors and the whole house is walkable. A room or wing that shares no wall with the rest is stranded — physically unreachable — so the plan is rejected.
Realizes the requested program areasprogramenforcedProgram adherence
Each room's built area must land close to the requested target, or the design isn't the house that was asked for.
Primary suite is the largest bedroomprogramenforcedNAHB convention / market expectation
The primary (owner's) bedroom must be at least as large as every other bedroom — buyers expect the primary suite to be the biggest room of the sleeping wing, never a secondary bedroom dwarfing a cramped primary. Rejected if a secondary out-sizes it.
Living/family room is not a corridorprogramenforcedLivability best practice (room shape)
A primary social room (living / family / great room) must not be more elongated than 2.4:1. Past that it reads as a corridor: the sofa and the TV end up at opposite ends of the room, far too far apart for conversation or comfortable viewing, and traffic to the doors all along it leaves no clear facing walls. Tighter than the general 2.6:1 sliver line because a social room with a furniture group feels long sooner than, say, a service room.
Habitable room — minimum ceiling heightcodeat detailed designIRC 2021 R305.1
Habitable rooms need a finished ceiling of at least 7 ft — a height property, checked once the section/3-D is modeled.
Required egress door — minimum clear widthcodeat detailed designIRC 2021 R311.2
The required egress door needs at least 32 in clear width — a door property, checked when openings are placed.
Sleeping room — emergency escape openingcodeat detailed designIRC 2021 R310.2.1
Each sleeping room needs an openable escape opening (≥ 5.7 sq ft) — a window property, checked when openings are sized.
Habitable room — natural ventilationcodeat detailed designIRC 2021 R303.1
Openable area for ventilation must be ≥ 4% of floor area — a window property, checked when openings are sized.
Smoke alarm in each sleeping roomcodeat detailed designIRC 2021 R314
A smoke alarm is required in each sleeping room — a fixture, added at detailed design.
Carbon monoxide alarm near sleeping areascodeat detailed designIRC 2021 R315
A carbon monoxide alarm is required near the sleeping areas — a fixture, added at detailed design.
Stairway — width, headroom, landings, treads/riserscodeat detailed designIRC 2021 R311.7
A stair needs ≥ 36 in clear width, ≥ 6 ft 8 in headroom, treads ≥ 10 in / risers ≤ 7¾ in, and a landing top and bottom — and nothing (a door swing, a fixture) may block the run or the walkway off it. Applied when the stair + openings are placed (the two-story detailing reserves the run + landings and routes doors around them).
Two means of egress (fire safety)codeat detailed designIRC 2021 R311 + fire-safety best practice
Every dwelling needs at least one egress door (R311.2); long-standing fire-safety practice is a SECOND exterior door on a different wall so there are two ways out if one exit is blocked. Placed at detailed design (a back/side door in addition to the front entry).
Bathroom fixture clearancescodeat detailed designIRC 2021 R307.1
A bath needs 21 in of clear floor in front of the toilet/lavatory and 15 in from the toilet centerline to any wall or fixture — so a full/¾ bath must be ≥ ~5 ft wide and a half-bath ≥ 30 in. Checked when fixtures are placed.
Garage / dwelling fire separationcodeat detailed designIRC 2021 R302.5 / R302.6
The garage is separated from the living space by ≥ ½-in gypsum on the garage side (⅝-in Type X under habitable space), and the door into the house is a self-closing, 20-minute (or 1⅜-in solid) door — never into a sleeping room. A wall/door property, applied at detailed design.
Floor assembly fire protectioncodeat detailed designIRC 2021 R302.13
Floors over a basement/crawl need ½-in gypsum (or equivalent) membrane protection unless exempt — an assembly property, applied at detailed design.
Attic access openingcodeat detailed designIRC 2021 R807.1
An attic with ≥ 30 sq ft and ≥ 30-in vertical clearance needs a ≥ 22×30-in access opening — located at detailed design, kept out of a closet too small to drop a ladder.
Receptacle spacing + GFCI/AFCI protectioncodeat detailed designIRC 2021 E3901 / E3902
Wall receptacles within 6 ft of any point along a wall (≤ 12 ft apart); GFCI in baths/kitchens/garage/exterior/laundry; AFCI on most living-area circuits — an electrical layout property, at detailed design.
Plumbing traps + ventingcodeat detailed designIRC 2021 P3101 / P3201
Each fixture has a trap and is vented; back-to-back and stacked fixtures share a wet wall/stack — drives the wet-wall clustering the layout already favors, finalized at detailed design.
Clothes-dryer exhaustcodeat detailed designIRC 2021 M1502.4
The dryer vents to the outdoors through a ≤ 35-ft smooth 4-in duct (less per bend), not into an attic/crawl — a duct-routing property that favors siting the laundry on an exterior wall.
Guards + handrailscodeat detailed designIRC 2021 R311.7.8 / R312.1
A graspable handrail 34–38 in on stairs of 4+ risers, and a ≥ 36-in guard (no 4-in sphere passing) at open sides/landings > 30 in above grade — a railing property, at detailed design.
Thermal envelope (energy code)codeat detailed designIRC 2021 N1102 / IECC
Insulation (walls/ceiling/floor) + fenestration U-factor + air-sealing meet the climate-zone minimums — an assembly property the cost/energy model approximates and detailed design finalizes.
No room reached only through another habitable roomcodeat detailed designIRC 2021 R311 (means of egress) + functional-obsolescence best practice
Every room must be reachable from circulation (a hall, foyer, or the public core), never ONLY by passing through a bedroom or bath — a pass-through bedroom is a classic functional-obsolescence defect. Carried as data; to be made checkable on the 2-D footprint.
House footprint fits the lot after setbackscodeat detailed designLocal zoning ordinance (typical front 20–25 ft, side 5–10 ft, rear 15–25 ft)
The footprint plus required yard setbacks must fit inside the lot — subtract the setback band before fitting. Carried as data; to be made checkable.
Habitable basement — emergency escape openingcodeat detailed designIRC 2021 R310.1
A basement with habitable space, and every basement sleeping room, needs an emergency escape and rescue opening (window well ≥ 9 sq ft) — a window/areaway property at detailed design.
Exterior wall fire rating by setbackcodeat detailed designIRC 2021 R302.1 / Table R302.1
Walls less than 5 ft from a lot line need a 1-hr fire rating and limited openings — drives how close the footprint sits to a side line, finalized at detailed design.
Whole-house mechanical ventilationcodeat detailed designIRC 2021 M1507 / R303.4
A tight, energy-code dwelling needs mechanical whole-house ventilation sized to floor area + bedrooms — a systems property at detailed design.
Emergency-escape window well & covercodeat detailed designIRC 2021 R310.2.3
Below-grade escape openings need a window well ≥ 36 in projection, a ladder if deeper than 44 in, and an inside-openable cover — a window-well property at detailed design.
Landing at every exterior doorcodeat detailed designIRC 2021 R311.3
Each exterior door opens onto a landing not more than 1.5 in below the threshold, ≥ the door width and ≥ 36 in in the travel direction — a stoop property at detailed design.
Foundation & under-floor access / ventilationcodeat detailed designIRC 2021 R408 / R807
A crawl space gets a ≥ 18×24-in access + venting (or is sealed/conditioned); an attic > 30 sq ft gets a ≥ 22×30-in access — assembly properties at detailed design.

Guidelines — soft, weighted; bending one costs points

Construction costcostscoredLine-item cost model (cost.ts)
Total estimated construction cost — shell, finishes, roof, walls, windows, and fixed fixtures. The load-bearing objective.
Natural lightdaylightscoredIRC R303.1 best practice; Alexander — Light on Two Sides (159)
Daylight reach: exterior-wall exposure per habitable room, a bonus for south-facing (back) glazing, AND light on two sides — the rooms people live in (living/family + the primary bedroom) read best lit from two directions, i.e. on a corner.
PrivacyprivacyscoredAlexander — Intimacy Gradient (127); split-bedroom + acoustic-buffer best practice
Bedrooms set back from the street and not opening onto the living room; a NOISE BUFFER (no bedroom sharing a wall with the kitchen/laundry/garage); and a SPLIT plan (the primary suite set apart from the secondary bedrooms).
Circulation efficiencycircscoredYoung Architect — net/gross areas; NKBA bedroom-to-bath convention
Efficient flow: required adjacencies realized, the hall RIGHT-SIZED to the rooms it serves — a slim band, not a full-width corridor that runs past the last door into a useless dead-end stub (a 2-bedroom home should not carry a 50-ft hall) — not over-exposed on the exterior, and a short trip from EVERY bedroom to a usable full bath (no bedroom stranded far from a bath).
Energy efficiencyenergyscoredPassive design: surface-to-volume + orientation (concept §14.4)
A compact envelope loses less heat (less exterior wall per sq ft); south-facing glazing adds passive solar gain in heating climates.
Room proportionsspacecarriedProportion / golden-ratio design guides (Homes&Gardens, Thos. Moser) — best ≈ 1.15–1.6:1
Rooms read best as a gentle rectangle, not a perfect square (static) or a corridor: a length-to-width ratio in the ~1.15–1.45 sweet spot (up to the golden ratio ~1.6) — a 2:1+ room feels like a hall with furniture. Folded into the 'usable space' objective so it influences the search.
Usable area + primary suitespacescoredYoung Architect — net/gross/usable areas; NAHB (primary is the largest bedroom); proportion guides
Floor area spent on usable rooms not corridor, the primary bedroom coming out as the largest bedroom (the convention buyers expect), AND rooms in good proportion (a gentle rectangle, not a square or a corridor).
Kitchen ↔ living/dining adjacencyfunctioncarriedNKBA; Alexander — Common Areas at the Heart (129)
The kitchen should open onto the living/dining social core — the most frequent daily trip.
Functional zoning (public / private / service)circcarriedAlexander — Intimacy Gradient (127); residential zoning convention
Rooms cluster into three zones — public (living/dining/kitchen), private (bedrooms/baths), service (laundry/garage/mudroom) — with the private zone deepest from the entry.
Entry sequence & sightlineprivacycarriedAlexander — Entrance Transition (112); Intimacy Gradient (127)
The front door should not open on a direct sightline into a bedroom, bath, or the kitchen sink — reward a foyer/transition buffer.
Compact massingcostcarriedConstruction-cost best practice (perimeter drives shell + roof cost)
A simpler perimeter costs less to frame, roof, and weatherproof — reward a footprint close to a rectangle (1.0 = a perfect square; lower = more articulated).
Indoor–outdoor connectionspacecarriedBest practice (indoor–outdoor living); Alexander — Outdoor Room (163)
Reward a main living/kitchen room on an exterior wall away from the street, able to open to a patio/deck/yard.
Street presence / curb appealsitecarriedBest practice (NAHB curb appeal); anti 'snout house' (Portland design guidance)
The garage door shouldn't dominate the street face — reward living space, a porch, or the entry holding the front plane; penalize a garage projecting forward of the front door.
Bedroom-zone acoustic separation from the garageprivacycarriedAcoustic best practice (impact + door noise)
Beyond the kitchen/laundry buffer, keep sleeping rooms off any wall shared with the garage (engine + impact noise, and a cold wall).

Program rules — which rooms a home should have, and why

Front entrywhen: alwaysResidential design convention (NAHB)
The front door opens into a transition/social space — a foyer or entry hall, or the living/great room with a coat closet by it — never directly into a kitchen, bathroom or bedroom.
Laundrywhen: alwaysBest practice (NAHB — most-wanted features)
A dedicated laundry/utility room is standard in US single-family homes; omitting it is a major functional gap.
Primary bath (ensuite)when: bathrooms ≥ 2Best practice (NAHB — near-universal in new construction)
The primary bedroom should open onto its own bath, not share the hall bath with the rest of the house.
Powder roomwhen: bedrooms ≥ 3 (or on request)Best practice (NKBA)
Guests shouldn't have to use a private bedroom bath; a half-bath off the public zone is expected at this size.
Dining roomwhen: separate living style, or bedrooms ≥ 4Best practice (NAHB; RoomSketcher — a defined eating area adjacent to the kitchen)
A separate dining room when the homeowner asks for one, or for a larger family home (4+ beds) that's expected to seat guests. Smaller open-plan homes use an eat-in kitchen / great-room table instead — but a dining space, open to the kitchen, is always provided.
Mudroomwhen: on request (pairs with a garage/side entry)Best practice
A drop-zone at the secondary entry keeps coats, shoes and gear out of the living space.
Coat closetwhen: always (by the front entry)Best practice (RoomSketcher — entry storage)
A reach-in by the front door for coats and shoes — the single most-cited missing-storage complaint; placed at detailed design.
Linen closetwhen: always (by the bathrooms)Best practice
Shelved storage near the baths for towels and linens; placed at detailed design where a wall allows.
Primary walk-in closetwhen: the primary bedroomBest practice (NAHB — near-universal)
The primary suite gets a walk-in; secondary bedrooms a reach-in. Storage is woven through the home, not concentrated in one spot.
Family / TV roomwhen: on requestHomeowner program
A second, casual gathering room separates loud media from the formal living area.
Guest suitewhen: on requestHomeowner program
A guest bedroom with its own ¾ bath gives visitors privacy without tying up a family bath.
Home officewhen: on requestHomeowner program (post-2020 norm)
A quiet, daylit room for remote work, buffered from the public living zone.
Garagewhen: on request (0–3 cars)Homeowner program
Covered parking + storage; sized at ~220 sq ft per stall. Unconditioned — costed at a lower shell rate.
Foyer / entrywhen: alwaysAlexander — Entrance Transition (112); NAHB
A defined entry transition between the front door and the living core — a place to pause, greet, and drop keys, not a door opening straight onto the sofa.
Pantrywhen: kitchen, and bedrooms ≥ 3 or on requestBest practice (NAHB — most-wanted features)
A walk-in or reach-in pantry off the kitchen is one of the most-requested features in new construction; auto-added for family-sized homes.
Primary walk-in closetwhen: the primary bedroomBest practice (NAHB)
Promote the detail-design walk-in to a sized room between the primary bedroom and its bath, so the suite reads bedroom → closet → bath.
Front porch / covered entrywhen: always — default ON, excludable (a covered back porch is on request)Best practice (NAHB; Alexander — Private Terrace on the Street 140)
A covered front porch is included on every plan by default (the homeowner can omit it). Its size + whether it's inset (recessed) or extended (projecting) follow the home's style and the front-yard room; a full porch for traditional styles, a covered entry for modern.
Deck / patiowhen: on request, or default off the main living roomBest practice (indoor–outdoor living)
An outdoor living surface off the kitchen/living, on the private (non-street) side.
Basementwhen: on request (cold climates / sloped lots)Best practice; IRC R310 (egress)
A full or partial basement adds low-cost area for mechanicals, storage, and rec space; needs egress if finished.
Mechanical / utility closetwhen: alwaysIRC M1401 / best practice
A dedicated space for the air handler / furnace, water heater, and panel — sized for service clearances, not crammed into a closet corner.
Broom / general storage closetwhen: alwaysBest practice (RoomSketcher — missing storage)
A reach-in for vacuum, mop, and household gear near the kitchen/service zone — the second-most-cited missing storage after the coat closet.
Drop zone / pet feeding nookwhen: with a mudroom/garage entry, or on requestHomeowner program
A counter + charging + pet-bowl niche at the secondary entry; keeps the kitchen counter clear.
Workshop / hobby roomwhen: on requestHomeowner program
A bench-and-tools room, often in the basement or off the garage, buffered from quiet rooms.
Wine room / cellarwhen: on requestHomeowner program
A small insulated, cooled room (ideally below grade or on a north wall) for wine storage.

Room priority — which rooms come first, so a reading nook never crowds a bedroom

The engine places the essentials first and gives them the prime positions (the social core toward the street, the primary suite its own quiet end). The least-important rooms are pushed to the far end of the plan, and the smallest nice-to-haves are added only when the footprint has slack.

Tier 1EssentialLiving, Kitchen, primary bedroom + ensuite bath, a full bath, the hallIRC R304 (habitable rooms) / NAHB (most-wanted)
The rooms a dwelling cannot be without — always generated, and given the prime positions (the social core toward the street, the primary suite its own quiet end).
Tier 2StandardSecondary bedrooms, dining, laundry, powder room, pantry, foyer, mechanical/utility, entry + linen storageBest practice (NAHB / NKBA)
Expected in a normal family home; generated whenever the brief implies them, placed after the essentials.
Tier 3Flex (opt-in)Family room, guest suite, home office, study, mudroom, garage, bonus, sunroom, media, gymHomeowner program
Added on the homeowner's request; placed after the essentials, toward the far end of the plan from the bedrooms + entry.
Tier 4Nice-to-haveSitting room, reading nook, breakfast nook, game room, butler's pantry, wine room, workshop, drop zoneHomeowner program (space permitting)
Small bonuses placed LAST, and only when the footprint has slack after every more-important room is satisfied.

Room-by-room best practices — the governed-by rules, shown when you click a room

Bathroom

Bath sizing follows a hierarchy: the PRIMARY (ensuite) bath is the largest, a full hall bath next, a half-bath (powder) the smallest — a powder is never bigger than a full bath Bath-program convention (NAHB / NKBA)
A right-sized full bath is ≈ 40–100 sq ft; it should not balloon to a habitable-room footprint at the expense of the bedrooms it serves Bath-program convention
Clear floor in front of every fixture: 21 in minimum (code), 30 in recommended IRC R307.1 / NKBA
Toilet centerline ≥ 15 in to any wall/fixture (18 in recommended); a 30–36 in stall IRC R307.1 / NKBA
Lavatory/sink centerline ≥ 15 in to any side wall or fixture (20 in recommended) — elbow room each side, the same side-clearance standard as the toilet NKBA
The toilet FACES open floor — ≥ 21 in clear in front to stand/sit — never set looking straight into the tub/shower or a vanity a foot away; if its wall would force that, the toilet rotates to a wall that looks into the room IRC R307.1 / NKBA (clear floor space)
≥ 5 ft wide to seat a 5-ft tub or a 3×3 shower with a clear approach Best practice (NKBA)
Shower interior 30×30 in min (36×36 in comfortable); a hinged door swings OUT IRC / NKBA
Standard alcove tub 60×30 in; keep ≥ 1 tub in the home for resale Best practice (resale/bathing)
Two sinks: 30 in centerline-to-centerline min (36 in rec.); double vanity ≥ 60 in NKBA
Vanity 32 in standard / 36 in comfort height; sink on the mirror wall, not a window NKBA / convention
Fixtures ordered from the door inward by use + privacy: SINK/vanity nearest (used most), TOILET tucked deeper (privacy), TUB/SHOWER deepest — on the wall opposite the door Best practice (NKBA)
The sink and toilet share ONE wet wall where the bath's shape allows — a single plumbing run is cheaper to build, and the walk to the back of the bath stays straight instead of weaving between fixtures on opposite walls; the tub/shower takes the opposite or end wall Best practice (plumbing economy / circulation)
The tub/shower is the DEEPEST fixture, never between the door and the toilet/sink — so its bulk doesn't obstruct the walk in; the entry path stays clear Best practice (NKBA)
Toilet + vanity line the wall OFF the walking path from the door to the tub — a fixture that would stand in that walk shifts to the OPPOSITE wall so the route to the tub runs straight Best practice (clear circulation)
The door swings IN when its arc clears the fixtures — so it never blocks or hits into the hall; it swings OUT only when the bath is too tight to swing in. It hinges toward the NEARER wall so the open leaf lies flat against it, not across the room Best practice (door swing) / IRC R311.2
Walk-in shower in compact/secondary baths; the vanity keeps clear wall for a mirror — off the window, or beside it (the window re-centers to the open span) when a fixture is pushed to the far wall to clear the path Best practice
Exhaust fan ≥ 50 CFM (~1 CFM/sq ft) ducted outside, or an openable window IRC R303.3 / NKBA
GFCI receptacles; a switched light at the entry; wet/damp-rated fixtures over the tub/shower IRC E3902 / NEC
Block the walls for future grab bars (300 lb, 33–36 in AFF) — aging in place NKBA / NAHB CAPS
A water-closet compartment or privacy wall for the toilet in a shared/primary bath Best practice (NKBA)
A recessed niche in the shower/tub wall for bottles; a curbless entry where aging-in-place is a goal Best practice / NAHB CAPS
Slip-resistant floor finish; a heat source (fan/heater) so the room warms quickly Best practice
Vanity light at face height on both sides of the mirror (not just overhead) to kill shadows Best practice (lighting)
Drain the shower floor away from the door; a 2 in curb or linear drain on a curbless layout IRC P2709 / best practice

Kitchen

Open-concept: a WIDE opening (≈ 6–8 ft, not a 5-ft doorway) into the living/great room so the kitchen flows into the main living space — the most-wanted layout in new homes; a peninsula or island defines the edge where the wall is removed Best practice (NAHB most-wanted — open kitchen/living)
That opening stays UNOBSTRUCTED — no pantry, tall cabinet, or appliance is forced into the cased passage to the living/dining; a full-height box in the gap kills the pass-through. If the kitchen is too tight to seat the pantry clear of the opening, it shrinks or moves walls rather than blocking the walk-through Best practice (clear circulation between rooms)
Sink + counter on a plumbed wet wall Plumbing (concept §9 requires)
Work flow: wash → prep → cook — sink between the fridge and the cooktop NKBA; Cook Smarts
Work triangle (sink↔range↔fridge): each leg 4–9 ft, total ≤ 26 ft, no traffic through it NKBA Guideline 3
Sink landing counter: 24 in one side + 18 in the other NKBA Guideline 11
A 36 in+ uninterrupted prep counter beside/between the sink and cooktop NKBA Guideline 12
Landing counter ≥ 15 in beside the range/oven/microwave and the fridge handle side NKBA Guidelines 16–23
Range/cooktop not under an operable window NKBA Guideline 18
Full-height appliances + cabinets (the FRIDGE, a pantry) never stand in front of a window — they block the glass and the daylight; the window sits in the open run of wall, not behind a tall box Best practice (kitchen daylight) / IRC R303.1
Sink under a window where the layout allows — the classic light + view over the sink Best practice (near-universal)
Dishwasher within 36 in of the sink, with 21 in standing room beside it NKBA Guideline 13
Work aisle ≥ 42 in (one cook) / 48 in (two cooks); a no-work walkway ≥ 36 in NKBA Guidelines 6–7
Island/peninsula: ≥ 42 in clear all around; 24 in width + 15 in knee overhang per seat NKBA Guideline 9; This Old House
Total countertop frontage ≥ ~13 ft (158 in), 24 in deep NKBA Guideline 25
Large/multi-cook kitchens: layer the 5-zone model (store/prep/cook/clean/non-cook) over the triangle Best practice (Kingswood, Fabuwood)
A reach-in or walk-in pantry within a step or two of the prep zone Best practice (NKBA most-wanted)
An eat-in table sits in the OPEN part of the kitchen — never in the work zone (counters / appliances / island) or the aisle in front of the range/fridge/sink. The hard-working kitchen and its work aisles are reserved; the table centers in the floor that's left Best practice (eat-in kitchen / NKBA work aisles)
Trash/recycling pull-out beside the sink/prep, not across the room NKBA Guideline 24
Microwave at a safe height — drawer or counter-level for households with kids/short cooks, not over a 30 in range Best practice (safety)
A landing ≥ 15 in beside or above the cooktop for hot pans; range hood vented outside ≥ 100 CFM NKBA Guideline 21 / IRC M1503
≥ 24 in clearance between a cooktop and any combustible above it (or per hood listing) IRC M1901 / NKBA Guideline 19
GFCI on all counter-serving receptacles; a receptacle every 4 ft of counter and at any island IRC E3902 / E3901

Bedroom

Emergency escape + rescue opening: egress window ≥ 5.7 sq ft, sill ≤ 44 in AFF IRC R310
Natural light ≥ 8% of floor area IRC R303.1
Minimum 70 sq ft, ≥ 7 ft in any dimension; secondary ~10×12 ft, primary ~14×16 ft IRC R304 / convention
Headboard centered on a solid wall (not under a window); bed reachable from both sides Best practice (interior design)
Orient the bed so it extends into the room's LONGER dimension — the walk-around path in front of the bed stays usable (≥ 36 in) in a narrow room; on the short wall a deep bed leaves almost no floor Best practice (NKBA bedroom clearance)
Bed sees the door but isn't in line with it (the 'command position') Best practice (interior design)
24–36 in clear on each usable side of the bed; ~36 in at the foot Best practice (NKBA / interior design)
Door near a corner — the leaf opens flat, leaving one long wall unbroken for the bed/dresser Best practice (interior design)
~36 in clear in front of a dresser (drawer pull); 24–30 in in front of a closet Best practice (interior design)
Closet on a solid wall, never across the window (it would block the daylight) Best practice (interior design)
A closet's swing door is HINGED toward its own side of the opening, so the leaf opens flat against the nearer wall and a small opening clears the entry — you don't have to swing the door wide to reach the rest of the closet Best practice (door swing)
Sited a short walk from a usable full bath — no bedroom stranded far from one Best practice (NKBA bedroom-to-bath)
Not sharing a wall with a noisy room (kitchen/laundry/garage) — buffer with a closet/hall/bath Acoustic best practice
Reached from a hall, never THROUGH another bedroom (no pass-through bedroom) Best practice (functional obsolescence)
Primary suite set apart from the secondary bedrooms (a split-bedroom plan); its door not off the living room Best practice (split-bedroom)
A gentle rectangle (~1.15–1.45 : 1), not a square or a corridor Proportion / golden-ratio guides
A wall opposite or diagonal to the bed for a dresser/TV, kept off the window wall Best practice (interior design)
Primary suite: a wall-mounted TV on the foot wall (the wall the bed faces), centered on the bed and clear of the window — mounted high, above the dresser/closet doors Best practice (interior design)
When a closet lines the same wall as the TV, its door is shifted to the SIDE so the screen (centered on the bed) doesn't sit over the closet entrance — you still walk into the closet beside the TV Best practice (interior design)
Blocking + a junction box for a ceiling fan/light centered over the bed area IRC E3905 / best practice
Two flanking nightstand zones (~24 in each) when the bed is a queen+ on its long wall Best practice

Living / family

Natural light ≥ 8% of floor area IRC R303.1
Direct access to circulation concept §9 adjacent-to
Door near a corner so a long wall stays unbroken for the sofa/media Best practice (interior design)
Seating faces a focal point (fireplace/TV); facing seats 3.5–10 ft apart Best practice (Emily Henderson, Apartment Therapy)
The TV/media sits DIRECTLY IN FRONT OF the sofa — centered on the wall the couch faces, squared up on the sit-to-screen axis — never behind it or off to one side; in an open plan the sofa faces the most solid wall and slides to line up with the screen Best practice (TV setup / interior design)
TV viewing distance ≈ 1.5–2.5× the screen diagonal; screen center ~30–42 in AFF Best practice (TV setup guides)
Coffee table 14–18 in from the sofa, ~½ the sofa length Best practice (interior design)
≥ 36 in walkways through the seating; leave ~40% of the floor open (60/40) Best practice (interior design)
On a corner for light on two sides — the room people use most reads best lit from two directions Alexander — Light on Two Sides (159)
Direct access to a yard/patio/deck from the main living space Best practice (indoor–outdoor)
Rug at least under the front legs of the sofa + chairs Best practice (interior design)
A primary furniture wall ≥ 11 ft unbroken for a sofa + flanking pieces Best practice (interior design)
If a fireplace, it anchors one wall and the TV shares or stacks — avoid two competing focal walls Best practice
Switched receptacle(s) for lamps; the room not used as the only path to another room IRC E3903 / circulation best practice

Dining

Open to the kitchen concept §9 adjacent-to
≥ 36 in (42–48 in ideal) from the table edge to a wall/furniture to seat + pass Best practice (Emily Henderson, Lamon Luther)
~24 in of table width per place setting Best practice (interior design)
Chandelier ~30–36 in above the table, ~½–¾ the table width Best practice (interior design)
Rug extends ~24–36 in past the table so chairs stay on it Best practice (interior design)
Seats the household + 2 guests minimum: ~10×12 ft for a 6-seat table with chair pull-out Best practice
On the path between kitchen and living, not a dead-end a server has to backtrack from Best practice (flow)

Laundry

Dryer needs an exterior vent run (≤ 35 ft, less per bend; 4 in duct) IRC M1502.4
Washer on a plumbed wall with a drain pan / floor drain IRC P2706 / best practice
≥ 36 in clear in front (42–48 in for front-loaders); a side-by-side pair ~54–60 in wide Best practice (appliance guides)
In a PASS-THROUGH laundry (two doors), the washer + dryer line the wall OFF the walking path between the doors — if the near wall would block that route, the pair shifts to the opposite wall so you can still walk straight through Best practice (clear circulation)
A folding counter ~18–24 in deep at 36 in height Best practice
Sited near the bedrooms or off the kitchen/mudroom; not against a bedroom wall (noise) Best practice
Upper cabinets or open shelving above the machines for supplies; a hanging rod for line-dry Best practice
A utility sink where space allows — pre-treating, hand-wash, mop fill Best practice
Upper-floor laundry near bedrooms gets a pan + drain and ideally a leak sensor IRC P2706 / best practice

Powder room

Half-bath: toilet + sink only (no tub/shower) Definition
Compact — a half-bath is the SMALLEST bath (≈ 18–30 sq ft, a ~3–5 ft × 6–7 ft niche); it should never be larger than a full bath or the primary bath Bath-program convention (NAHB / NKBA)
≥ 30 in wide; 21–24 in clear floor in front of fixtures; 15 in from the toilet centerline to any wall OR fixture — the sink and toilet never pressed together IRC R307.1 / NKBA
Sink is the focal point (faced on entry) for a quick hand-wash; the toilet is tucked to a side wall toward the door end, out of sightline and clear of the sink Best practice (interior design)
Door near a corner; a pocket or out-swing door where the footprint is tight, so the swing doesn't hit the fixtures Best practice (interior design)
Mechanical ventilation or an openable window IRC R303.3
Off circulation near the public/entry zone, not a bedroom Best practice

Office

Natural light ≥ 8% of floor area; desk by a window but the screen not facing it (glare) IRC R303.1 / best practice
Egress window + a closet so it can convert to a bedroom later (flex/resale) IRC R310 / best practice
Buffered from the public living zone (and the laundry/kitchen) for quiet Best practice (acoustic)
A door for privacy + acoustic separation on video calls Best practice

Mudroom

At a secondary entry (garage / side / back door) as the car-to-house drop zone Best practice
~18–24 in of locker/cubby width per person; hooks at ~60–66 in (a child row at ~40 in) Best practice (cabinet guides)
Bench ~14–18 in deep at 17–19 in high; durable, washable floor Best practice

Garage

2-car ≥ 20×20 ft (22–24 ft wide comfortable); 1-car ~12×20 ft; ~20–24 ft deep Best practice (garage builders)
~2.5–3 ft clear on each side of a car; ~2 ft between two parked cars Best practice
Overhead door: single 8–9 ft, double 16 ft wide; 7–8 ft tall Best practice
Enter the house through a mudroom/service door, not directly into a bedroom Best practice
Unconditioned — a thermal buffer on the cold/hot side of the house Passive design
A 3-ft clear service door to the yard in addition to the overhead door Best practice
Slab pitched ~1–2% to a door or floor drain; a 3–4 in curb step up to the house for fire/fumes IRC R309 / best practice
Water heater/furnace on an 18 in platform or sealed-combustion if in the garage (ignition source) IRC M1307.3

Media room

Can be windowless (blackout) — not a sleeping room IRC R303 (habitable exemption)
Buffered from quiet rooms (bedrooms) for sound isolation; no main traffic path through it Best practice (acoustic)
Seating ~1.5–2.5× the screen diagonal from the screen wall; dedicated AV wall Best practice (home theater)
Mechanical ventilation (a sealed/blackout room still needs fresh air) IRC R303.4

Gym

Durable, resilient floor (rubber); ventilation + natural light preferred Best practice
≥ 8 ft clear ceiling for standing presses/jumps; a mirror wall Best practice
Buffered from bedrooms/quiet rooms (impact noise) Best practice (acoustic)

Sunroom

Generous glazing on the sunny (south/east) exposure Passive solar (concept §14.4)
Opens off the main living area / kitchen Best practice
Insulated/low-e glazing + shading so it isn't an oven in summer / icebox in winter Passive solar

Bonus room

Flexible space (rec/play/hobby/game room) off the circulation, away from bedrooms Homeowner program
If over the garage: egress window + conditioned air + insulated floor to be habitable IRC R310 / best practice

sitting

A quiet second living room / lounge — a place to read or talk away from the TV/great room Best practice (NAHB — formal vs. casual living)
Off the public circulation; seating faces a focal point (a window, fireplace), not a screen Best practice

reading

A small nook — an armchair + a bookcase, ideally by a window for daylight (a window seat where it fits) Alexander — Reading Nook (147) / best practice
Tucked off the circulation, not on a main traffic path; the smallest, lowest-priority space — added only when the plan has slack Best practice (space permitting)

butler

A pass-through service pantry BETWEEN the kitchen and dining — a prep/staging counter with upper + lower cabinets, out of sight of guests Best practice (NKBA — butler's pantry)
A bar/prep sink + counter run; ≥ 42 in aisle if it's a galley pass-through; landing counter for serving dishes NKBA
Doors/openings to BOTH the kitchen and the dining room so a server flows straight through Best practice (service circulation)

mechanical

A dedicated closet for the water heater + furnace / air handler (and panel) — with code service clearances, not crammed into a corner of the laundry IRC M1305 / M1401
≥ 30 in of service clearance in front of the furnace; combustion air + a condensate/drain for gas; near the plumbing stack IRC M1305 / M1411
Off the hall / service zone; can be windowless (non-habitable) Best practice

Hallway

Clear width ≥ 36 in (42–48 in comfortable / two-person) IRC R311.6 / best practice
Lit (a window or borrowed light) at the ends so it isn't a dark dead-end Best practice
Keep circulation lean (~8–12% of floor area) — halls are unusable area Best practice (Young Architect)
No hall stub running past the last door — terminate at a room, window, or built-in Best practice (Young Architect)
A linen or utility closet absorbed into the hall wall where the run is long Best practice (storage)

Stairs

Clear width ≥ 36 in above the handrail IRC R311.7.1
Headroom ≥ 6 ft 8 in over the whole run IRC R311.7.2
Risers ≤ 7¾ in; treads ≥ 10 in (a uniform run) IRC R311.7.5
A landing ≥ 36 in deep at the top and bottom of the run IRC R311.7.6
Handrail 34–38 in on at least one side IRC R311.7.8
No door swings over the stair; keep a walkway past it to reach every room on the floor IRC R311.7 / best practice
The run stacks above the floor below so it lands in usable space Structural (concept §12)
Max vertical rise 12 ft 7 in between landings (a long run needs an intermediate landing) IRC R311.7.3
Winder treads ≥ 10 in at the walk line, ≥ 6 in at the narrow end (no pie slivers) IRC R311.7.5.2.1
Usable storage or a powder room/closet captured under the run where headroom allows Best practice
Open the stair to a window/landing light so it isn't a dark shaft; switch at top and bottom IRC E3903 / best practice

Pantry

Opens directly off the kitchen, on or near the wet/cook wall — a few steps from where groceries land Best practice (NKBA)
Walk-in ≥ 5 ft wide for a 24-in shelf run + a 30 in+ aisle; a reach-in ≥ 24 in deep Best practice (cabinet guides)
Shelves 12–16 in deep (cans single-file, nothing lost at the back); a 16–18 in deep counter run for small appliances Best practice
A switched light and, for a 'working' pantry, a receptacle or two for charging/appliances IRC E3901 / best practice
No window needed (a non-habitable closet); keep it off an exterior wall to save daylight perimeter for rooms Best practice

Foyer / entry

A clear landing ≥ 5×5 ft inside the door so it can swing fully and two people can pass Best practice (interior design)
A coat closet within a step of the door; a bench or console for sitting/keys where width allows Best practice (NAHB)
No direct sightline from the front door into a bedroom, bath, or the kitchen sink Alexander — Intimacy Gradient (127)
Borrowed or sidelight/transom daylight so the entry isn't a dark box Best practice
A durable, washable floor (tile/LVP) for the wet/dirty transition zone Best practice

Walk-in closet

Walk-in ≥ 6×6 ft for single-side hanging + a 30 in aisle; ≥ 7 ft wide for facing hang rods Best practice (NKBA)
Double-hang rods at ~40 in and ~80 in (shirts/pants); a single rod at ~66 in for dresses/coats Best practice (closet guides)
24 in of hanging depth; a 14-in reach-in shelf clears the door swing Best practice
Between the primary bedroom and bath where it can act as an acoustic + light-lock buffer Best practice (split-suite)
A ceiling or switched light at the door; not on a daylight-needing exterior wall IRC E3903 / best practice
Reach-in closets for secondary bedrooms ≥ 24 in deep × 48 in wide with a shelf + rod Best practice

Basement

Finished/habitable areas and any sleeping room need an egress window well (≥ 5.7 sq ft opening, well ≥ 9 sq ft) IRC R310.1 / R310.2.3
Ceiling ≥ 7 ft for habitable space (beams/ducts may drop to 6 ft 4 in at spots) IRC R305.1
Cluster mechanicals (furnace/water heater/panel) with code service clearances, near the stack IRC M1305 / best practice
Stairs land in usable space, not a corner; a second egress door at a walkout/grade where the lot slopes IRC R311.7 / best practice
Manage moisture: perimeter drain, vapor barrier, and a sump where the water table warrants IRC R405 / best practice

Front porch

A covered front porch is standard on US homes — INCLUDED BY DEFAULT on every plan; the homeowner can omit it Market convention (NAHB most-wanted)
EXTENDED (projects OUTWARD with its own porch roof) adds the most outdoor living + suits a traditional roofline; INSET (RECESSED under the main roof, the building wrapping it) keeps a clean/simple roofline and a tight footprint Best practice (porch design)
Size is the homeowner's choice — SMALL (a covered entry/portico centered on the front door), MEDIUM (full-width at a standard depth), or LARGE (a deep full-width porch you can furnish with chairs/a swing). 'Auto' follows the style: a large porch for farmhouse/traditional/craftsman/coastal, a small covered entry for modern/minimalist/midcentury/industrial Best practice (style convention)
An extended porch must fit inside the front-yard setback; if it can't, recess it under the main roof instead Local zoning (front setback) / best practice
Covered entry ≥ 5×5 ft so the door swings clear and a person shelters out of the rain Best practice
A full porch ≥ 6–8 ft deep to seat chairs and still pass; floor pitched ~¼ in/ft to drain Best practice (NAHB)
Aligns with and signals the front door — the entry should be obvious from the street Alexander — Main Entrance (110)
Guard ≥ 36 in and a graspable rail where the walking surface is > 30 in above grade IRC R312 / R311.7.8
A covered BACK porch is a homeowner request (a back patio is the usual default); placed off the living/kitchen on the private side Best practice (regional / indoor-outdoor)

Deck / patio

Off the kitchen/living on the private (non-street) side; flush threshold for indoor–outdoor flow Best practice (indoor–outdoor)
Size to the use: ~12×12 ft seats a table + chairs; ~16×16 ft adds a lounge zone Best practice
A guard ≥ 36 in (no 4-in sphere) on any deck surface > 30 in above grade; ledger flashed to the wall IRC R312.1 / R507
Orient for sun + a roof/pergola/awning where afternoon heat or rain would otherwise drive people inside Passive design / best practice

Wine room

A small, insulated, sealed room held ~55 °F / 60–70% RH by a dedicated cooling unit Best practice (cellar guides)
Below grade or on a north/interior wall away from solar gain; no direct sunlight Passive / best practice
Racking ~12 in deep per bottle row; a 30 in+ aisle to pull and read labels Best practice

Workshop

Off the garage or in the basement, buffered from bedrooms/quiet rooms (impact + tool noise) Best practice (acoustic)
A durable sealed-concrete or LVP floor, strong task + general lighting, and 20-amp + 240 V circuits for tools IRC E3901 / best practice
Bench depth ~24–30 in with ~36 in clear behind; dust collection / ventilation to the outside Best practice

Drop zone / pet

At the secondary (garage/side) entry: a counter for keys/mail + receptacles for device charging Best practice
A recessed pet-bowl niche out of the walk path; a nearby cabinet for food/leashes Best practice
Durable washable floor and wall finish — the muddiest spot in the house Best practice

Site & exterior — decisions that precede the floor plan: lot, setbacks, massing, roof, grade

Setbacks define the buildable envelopeLocal zoning ordinance (typical front 20–25 ft, side 5–10 ft, rear 15–25 ft)
Subtract front/side/rear setbacks from the lot before fitting the footprint; show the buildable rectangle. Also carried as the mandate `zoning-setback-fit` (to be made checkable).
Lot coverage / FAR capLocal zoning (typical 30–50% coverage)
Footprint + garage + covered porch shouldn't exceed the allowed share of lot area.
Orient the long axis and main glazing toward the equatorPassive solar (concept §14.4)
In heating-dominated climates, run the long axis east–west and put living glazing south; shade it for summer — the whole-house version of the energy guideline's south-glazing term (already scored).
Garage shouldn't dominate the street faceBest practice; anti 'snout house'
Hold the front plane with living space or a porch; recess or side-load the garage where the lot allows. Scored via the `street-presence` guideline (G5).
Driveway + parking apronBest practice (NAHB)
A driveway ≥ 10 ft wide (≥ 18 ft at a side-load apron for the turn); a 20 ft setback so a parked car clears the sidewalk.
Roof pitch + overhang to climateBest practice / IRC R903
Steeper pitch sheds snow/rain (cold/wet climates); 16–24 in overhangs shade summer sun and protect walls; low pitch for arid/modern.
Grade falls away from the houseIRC R401.3
Finished grade drops ≥ 6 in within the first 10 ft around the foundation so water runs away; downspouts discharge clear of the wall.
Service items off the street faceBest practice
Meters, the AC condenser, trash storage, and the dryer vent on a side/rear wall, not the curb elevation.
Window-to-wall ratio in bandEnergy + cost best practice (IECC)
Glazing ~15–25% of exterior wall — enough daylight without an energy/cost penalty; more on the shaded/view side, less on west.
Tree & view preservation / solar accessBest practice (site planning)
Site the house to keep mature trees and primary views, and to avoid shading a future south-facing array or a neighbor's solar access.

Accessibility & universal design — aging-in-place / visitability (mostly above-code best practice)

One no-step entryNAHB CAPS / visitability
At least one entrance (often through the garage or a side door) with no step — a flush or ramped threshold ≤ ½ in.
32-in clear at all passage doorsICC/ANSI A117.1 404; IRC R311.2
Interior passage doors give ≥ 32 in clear (a 34-in leaf) so a wheelchair/walker passes; pocket doors where swing space is tight. (Code-adjacent — IRC R311.2 sets the egress door.)
36-in halls, 42 in at turnsICC/ANSI A117.1 403
Already 36 in by code; widen to 42 in where the route turns or a door opens into it, for a wheelchair turn.
A 60-in turning circle in a key bath + the kitchenICC/ANSI A117.1 304
Reserve a 5-ft clear circle (or T-turn) in at least one full bath and the kitchen so a chair can rotate.
A bedroom + full bath on the entry levelNAHB CAPS / visitability
At least one sleeping room and one full bath on the main floor so the house works without stairs.
Lever handles + rocker switchesICC/ANSI A117.1 309 / best practice
Lever door/faucet handles (no tight grasp) and rocker switches; switches at 42–48 in, outlets at 15–18 in (reach range).
Reinforced walls for future grab barsICC/ANSI A117.1 / NAHB CAPS
Block toilet and tub/shower walls for 250–300 lb grab bars at 33–36 in — cheap now, costly to retrofit (extends the bath rule house-wide).
Curbless / roll-in shower optionICC/ANSI A117.1 608
A curbless 36×60 in shower with a fold seat and offset controls in the aging-in-place bath.
Stair design eases later lift/railNAHB CAPS
A straight (or one-landing) run ≥ 36 in wide with continuous handrails both sides allows a future stair lift; avoid winders as the only stair.
Kitchen reach + knee clearanceICC/ANSI A117.1 804
A section of counter at 34 in with knee clearance (a roll-under sink/prep), a wall oven, and a cooktop with front controls in the universal-design kitchen.

Rules are editable data, not hard-coded — domain knowledge with citations, surfaced so nothing about the design is a black box. Outputs are preliminary and advisory.