Basement Apartment Ideas: Four Layouts, Drawn to Scale
Most basement apartment ideas fail on four things before anyone picks a paint colour: a separate entrance, an egress window in the bedroom, a 7 foot ceiling, and where the toilet can drain.
Free: draw, save in your browser, download a watermarked image. Paid: clean to-scale PDF and materials list.
| Unit | Finished area | Rooms |
|---|---|---|
| Studio | 350–500 sq ft | One room, bath, kitchenette along a wall |
| One-bedroom | 500–700 sq ft | Bedroom with egress, bath, kitchen, living |
| Two-bedroom | 750–950 sq ft | Two bedrooms each with egress, bath, kitchen, living |
| Guest suite | 400–600 sq ft | Bedroom, bath, sitting area; a kitchenette only where a full kitchen is not allowed |
Planning figures for a 30 × 25 ft basement. Many cities set a minimum unit size (often 220–400 sq ft) and a maximum share of the house; check the local accessory-unit rules.
Layouts
Pick a layout
Each one opens in the canvas below with its sizes already drawn; change anything.
One-bedroom apartment
Bedroom and bath on the window wall, a kitchen run and living room by the entrance. The standard rental unit; about 550 sq ft finished.
Two-bedroom apartment
Two bedrooms stacked along the west wall, each with an egress window, a bath and the kitchen in the middle, living room by the stairs. Needs two window wells.
Studio apartment
One open room with the bed at the window end, a kitchenette along the wall and a bath by the door. The least framing and the easiest to keep above 7 feet.
Guest suite with a kitchenette
A bedroom, bath and sitting room with a small kitchen run and storage left unfinished. For family and guests where a full rental is not allowed.
A one-bedroom basement apartment: bedroom with egress window, bath, kitchen run, living room and a separate entrance. Click it to resize the rooms.
About
The four layouts below put a one-bedroom, a two-bedroom, a studio and a guest suite into the same 33 by 25 foot basement with the stairs on the east wall and the utility room in the south-east corner, so you can compare them before you change the walls to your own sizes. Each room has a zone and a ceiling height, the plan flags rooms under the code minimum, and the bed, toilet and door clearances are checked as you move things. A drawing tool with a few checks, not an AI and not a permit set.
01
The four things to settle first
A separate entrance: a walkout door on a sloped lot, or a stairwell dug on the side of the house with a drain at the bottom. The entrance sets where the living room goes, because nobody wants to walk through the bedroom. An egress opening in every bedroom: under the 2021 IRC (R310) that is a window with 5.7 square feet of clear opening, at least 24 inches high and 20 inches wide, with the sill no more than 44 inches off the floor, usually in a window well with a ladder. A ceiling of 7 feet in the habitable rooms and 6 feet 8 inches in the bath (R305), measured under the lowest duct or beam, not between them. And the drain: a toilet near the house sewer line drains by gravity if the line is low enough; anywhere else needs an ejector pit under the slab, which is a line item of a few thousand dollars and decides where the bath can go.
02
Kitchen under the kitchen, bath under the bath
The cheapest plumbing runs straight down. Put the apartment bath under or beside the main floor bath and the kitchen run on the wall below the upstairs kitchen, and the supply, drain and vent lines are short. The one-bedroom and two-bedroom layouts above keep the bath against the utility room for that reason, with the kitchen on the next wall. If the sewer leaves the house on the other side, flip the plan on the canvas rather than fight it.
A kitchen also needs a range hood vented outside, a 20 amp circuit or two, and, in most cities, that is what turns a guest suite into a legal dwelling unit that needs its own permit. The guest-suite layout has a kitchenette with a sink and a fridge but no range for that reason.
03
Sound, light and the feeling of a basement
Floors carry sound better than walls. Insulate the joist bays over the bedroom and the living room, use resilient channel or a second drywall layer on the ceiling, and put the apartment bedroom under a quiet room upstairs. For light, make the window wells big; an egress well that is 36 inches wide and deep is the minimum, and a 5 or 6 foot well with a planted slope reads as a room with a garden. Keep the ceiling as high as the joists allow and run ducts along the walls, inside soffits, rather than across the middle of a room; the ceiling check on the plan tells you which rooms are at risk.
- Bedroom under a quiet room; insulated joists and a resilient ceiling.
- Window wells as large as the lot allows; a ladder in any egress well deeper than 44 in.
- A separate thermostat or a mini-split, so the tenant controls heat.
- Smoke and CO alarms interconnected with the house (IRC R314, R315).
04
Is a basement apartment legal where you are?
Say it plainly: in many US cities a rented basement unit is only legal if the zoning allows an accessory dwelling unit on your lot and the unit meets the building code for a separate dwelling, with its own entrance, egress, heat and, often, a parking space. Some cities ban them outright, some allow them by right since 2020 under state ADU laws, and many allow a family suite but not a rental. Call the planning department with your address before you spend on plumbing. The plan you draw here is a schematic for that conversation and for pricing, not a permit drawing.
05
What the plan checks and what it does not
On the canvas: bed clearances (24 inches at the sides and foot), the toilet (15 inches each side, 21 inches in front), the shower size, the kitchen aisle (42 inches), door swings, and the ceiling height per room against the IRC minimums. Finished rooms feed the materials list. Not checked, so measure them yourself: egress window size, stair width, the distance to the sewer line and anything structural. The PDF and the materials CSV are paid; drawing and the checks on screen are free.
06
Frequently asked questions
- How big should a basement apartment be?
- A studio works from about 350 sq ft, a one-bedroom from 500 to 700, a two-bedroom from 750 to 950. Most cities set a minimum of roughly 220 to 400 sq ft for a dwelling unit and a bedroom minimum of 70 sq ft (IRC R304).
- Does a basement apartment need a separate entrance?
- For a legal rental unit, almost always yes: a walkout door or an exterior stairwell. A guest suite for family can usually share the house stairs. Either way every bedroom needs its own egress window or door.
- What ceiling height does a basement apartment need?
- 7 feet in bedrooms, living rooms and kitchens, 6 feet 8 inches in bathrooms, with beams and ducts allowed down to 6 feet 4 inches under the 2021 IRC. Some cities require more for a rental unit.
- Where should the bathroom go in a basement apartment?
- Near the house sewer line if it is low enough to drain by gravity, ideally under or beside the upstairs bath. Anywhere else needs an ejector pump under the slab.
- Can I legally rent out my basement apartment?
- Only if zoning allows an accessory unit on your lot and the unit is permitted as a dwelling: entrance, egress, ceiling height, heat, alarms and often parking. Rules differ by city; ask the planning department before building.
- How do I turn one of these into a basement apartment floor plan for my house?
- Pick the card closest to your foundation shape, type the real wall lengths, then place the bathroom under or next to the existing stack and the kitchen on an outside wall for venting. Keep the egress window in the bedroom and the 7 ft ceiling; the canvas checks the ceiling and fixtures, your building department checks the rest.
Sources
Where the numbers come from
Local amendments apply; check your own jurisdiction.