US Building Codes: The IRC, State by State on Chippy Tools

Shower & Tub Wall Finish (IRC R307.2)

Thu, 30 Jul 2026 00:00:00 +0000

The requirement

The IRC doesn’t hand you a full waterproofing spec for a bathroom the way some other codes do. What it sets is narrower and more specific: a nonabsorbent surface, to a set height, wherever a tub or shower gets wet (IRC 2021, Section R307.2 “Bathtub and shower spaces”).

Where	What’s required (IRC R307.2)
Bathtub and shower floors	Nonabsorbent finish
Walls above a bathtub with an installed showerhead	Nonabsorbent finish, up to 72 in (1829 mm) above the floor
Walls in a shower compartment	Nonabsorbent finish, up to 72 in (1829 mm) above the floor

The 72-inch (1829 mm) height is measured up from the floor, or from the drain inlet in a shower without a curb. Below that line the code wants a surface — tile, solid surface, an integral fiberglass or acrylic tub-shower unit — that won’t absorb water the way bare drywall does.

IRC Stair & Guard Rules: Riser, Tread, Handrail, Guards

Thu, 30 Jul 2026 00:00:00 +0000

The requirement

The IRC sets a residential stair with a handful of numbers you can measure with a tape. The two that shape every step are the riser and the tread.

Riser — how tall each step is. The IRC caps it at 7¾ in (196 mm). Go taller and the step is too big to climb safely, so you add a step to bring each one down. Every riser in a flight must be near-equal, varying no more than 3/8 in top to bottom (R311.7.5.1).
Tread depth (the going) — how deep each step is, measured nosing to nosing (front edge of one step to the front edge of the next). The IRC minimum is 10 in (254 mm) (R311.7.5.2).

Then three more that keep the stair usable:

US Footing Sizes & Frost Depth (IRC R403)

Thu, 30 Jul 2026 00:00:00 +0000

The requirement

Before you pour, the code tells you two things about a footing: how big it has to be and how deep it has to sit. In the United States, houses are built to the International Residential Code (IRC), Section R403.1 “Footings.” That’s the model code. Your town or state adopts it — sometimes an older edition, sometimes with changes — so always confirm the numbers with your local building department.

US Minimum Ceiling Heights (IRC R305)

Thu, 30 Jul 2026 00:00:00 +0000

The requirement

The IRC sets a smallest floor-to-ceiling height for the rooms in a house. It is not one number for the whole house. How much headroom you need depends on what the room is used for (IRC 2021, Section R305).

Here’s the quick version:

Where	Minimum ceiling height (IRC R305)
Habitable rooms — bedroom, living, dining, kitchen	7 ft (2134 mm)
Hallways	7 ft (2134 mm)
Bathrooms, toilet rooms, laundry rooms	6 ft 8 in (2032 mm)
Over the showerhead — a 30 in × 30 in (762 mm) area	6 ft 8 in (2032 mm)
Basement with no habitable rooms or hallways	6 ft 8 in (2032 mm)
Beams, girders and ducts may drop to	6 ft 4 in (1931 mm)

A habitable room is one people live in — bedrooms, living rooms, dining rooms and the like. The IRC also counts the kitchen as habitable space, because it’s space for cooking, so the kitchen sits on the full 7 ft. Bathrooms, toilet rooms and laundry rooms are the ones that drop to 6 ft 8 in.

US Ramp Slopes (IRC R311.8)

Thu, 30 Jul 2026 00:00:00 +0000

The requirement

The IRC gives your house ramp a slope limit, and it depends on which ramp you’re building.

There are two lines to know:

The ramp	Steepest slope allowed
The ramp serving the required exit door	1:12 (8.3%)
Any other ramp at the house	1:8 (12.5%)

So the ramp at your front exit door is the strict one: 1 unit up for every 12 along. Every other ramp on the job can be steeper, up to 1 unit up for every 8 along.