I design every basement by twelve rules, in order: fix water first, test for radon, respect the mechanical room, put wet rooms on the drain, put bedrooms on the egress wall, turn the beam into a boundary, land the stairs at the edge, finish what you'll use, light in layers, run one floor everywhere, size the TV wall to the seats, and spend on what you touch.
The first three protect the house, the next five are layout decisions you can't undo, and the last four make a basement feel like part of the home.
On this page
Why I design by principles
Every basement I design is different, but the decisions that make one great are the same ones every time. These are the rules I apply before I draw a single wall, in the order I apply them. Each links to the article where I go deep on it. If you remember nothing else from this journal, remember these.
Before design: the house comes first
1. Fix water before anything else
A finished basement is only as good as the slab and walls behind it. Grading, gutters, cracks, the sump pump and its backup come before framing; humidity should stay below 60 percent, ideally 30 to 50. No finish fixes a water problem. See moisture and mold and sump pumps.
2. Test for radon before and after
The Minnesota Department of Health says more than two in five Minnesota homes have radon at levels that pose a significant health risk. Finishing turns a basement into space you breathe in for hours, so test before you finish and again after. See radon.
3. Respect the mechanical room
The furnace, water heater and panel need room to be serviced and replaced: a 30 by 30-inch level working space in front of appliances and 30 by 36 inches in front of the panel. I design the mechanical room first and the finished rooms around it, never the reverse. See the mechanical room.
Layout: decisions you can't undo
4. Put wet rooms on the drain
Bathrooms, bars and laundry go near the existing rough-in and stack. Every foot of drain line trenched through the slab is money that buys nothing you can see. See bathrooms.
5. Put bedrooms on the egress wall
A legal bedroom needs an egress opening of at least 5.7 sq ft with a sill no higher than 44 inches, and a window well outside it. That decides which walls can hold bedrooms. The egress window also brings the best daylight in the basement. See egress bedrooms.
6. Turn the beam into a boundary
The beam and posts down the middle are the basement's spine. I use them as the line between two zones, not an obstacle inside one. See beams, posts and soffits.
7. Land the stairs at the edge of the living space
The stairs are the entrance. They should arrive at the side of the family room, never behind the sofa or inside a bedroom's path. See layout and zoning.
8. Finish what you'll use, organize the rest
The low corner by the mechanicals is usually more useful as storage than as finished space. Open floor area is the cheapest part of a basement, so I don't shrink rooms to save money; I leave unused space unfinished and organized. See storage.
Finish: what makes it feel like the house
9. Light in layers, in warm white
General light, task light and accent light, on dimmers, at about 2,700 to 3,000 K, which ENERGY STAR calls warm white. Lighting is the single upgrade that changes a basement most for its cost. See lighting.
10. One floor, everywhere
A waterproof floor that tolerates a damp slab, run continuously through every room, bathroom included. No thresholds, no patchwork. See flooring.
11. Size the TV wall to the seats
Seating distance of about 1.36 to 1.86 times the screen width, the TV away from window-well glare, blocking and a cable chase built into the wall before drywall. See entertainment walls.
12. Spend on what you touch
The faucet, the door levers, the light switches, the floor. Save on what you notice once. Every product has a budget inside BuildFlow's price, and going under one pays for going over another. See where to spend.
How these show up in an Emma design
When you talk to me about your basement, I'm applying these in order: I ask about water and the mechanicals first, place the wet rooms and bedrooms where the house allows, then design the finish. The renderings show your own space; the products are real and priced; and the price range comes from BuildFlow's pricing engine, the same engine that produces every number in this journal. Read more about how Emma works.
How BuildFlow does it
BuildFlow Basements designs and prices your finished basement, and licensed, insured local contractors build it — one fixed price, agreed before work starts.
It starts with me, Emma, BuildFlow’s free AI designer. In about five minutes I design your own basement: renderings of your space, real products you pick, and a real price range for your project. The design is yours to keep, even if you never hire BuildFlow.
Design my basement with EmmaQuestions people ask
What should you do first when finishing a basement?
Fix any water problem and test for radon. Grading, gutters, cracks, the sump pump and humidity come before framing; MDH says more than two in five Minnesota homes have significant radon levels.
Where should bedrooms go in a basement?
On an outside wall where an egress window of at least 5.7 sq ft with a sill no higher than 44 inches can be cut, away from the mechanical room.
How much space does the mechanical room need?
Enough to service and replace the equipment: a 30 by 30-inch level working space in front of appliances and 30 by 36 inches in front of the electrical panel, plus a door or opening large enough to remove the largest appliance.
What is the most important design choice in a basement?
Where the bathrooms and bedrooms go. They're set by the drain and the egress walls, and they're the most expensive decisions to change once built.
What lighting color is best for a basement?
Warm white, about 2,700 to 3,000 K, in layers of general, task and accent light on dimmers.
Sources (9)
- University of Minnesota Extension, Moisture in basements: causes and solutions — Fix grading, gutters and water sources before finishing
- US EPA, A Brief Guide to Mold, Moisture and Your Home — Keep indoor humidity below 60 percent, ideally 30 to 50 percent
- Minnesota Department of Health: Radon in Homes — More than 2 in 5 Minnesota homes have radon at levels that pose a significant health risk
- The Building Code Forum: IRC M1305.1 quoted — Appliances accessible for service and replacement; 30 x 30 in level working space in front
- InterNACHI forum: IRC M1305.1.2 appliances in rooms (quoted text) — Basement appliance access: an opening or door large enough to remove the largest appliance
- Anne Arundel County, Finished Basement Code Requirements — Electrical panel working space 30 in wide by 36 in deep
- City of Saint Paul, Emergency Escape and Rescue Openings handout (2020 MN Residential Code) — Egress opening 5.7 sq ft (5.0 at grade), 24 in high, 20 in wide, sill no more than 44 in; window well 9 sq ft
- ENERGY STAR: Color and Mood — Kelvin ranges for warm, neutral and daylight white
- Sound & Vision, What Size Screen?...How Far Away? — Viewing distance of about 1.36 to 1.86 times the screen width
More in Design & layout
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