Staircase makeover: from carpet to wood treads without breaking the riser rule
Pulling up stair carpet is the easy part. Getting wood treads to meet the code's 3/8 inch tolerance at the top and bottom of the flight is the part to plan.
To replace stair carpet with wood or wood-look treads, measure first. California's code measures stairs without the carpet, allows risers of at most 7 3/4 inches and treads of at least 10 inches, and lets the tallest and shortest riser in a flight differ by only 3/8 inch. New treads add thickness to every step, so the bottom and top risers change unless the floors at each end change with them.
That last point is the one to plan for, so it comes first below, with the arithmetic. Then the nosing, handrail and guard rules from the 2025 California Residential Code, how vinyl and wood treads are fastened, and the lead-paint rule that applies to older painted stairs.
Measure first: new treads move two risers
The code is explicit that carpet does not count: "For the purposes of this section, dimensions and dimensioned surfaces shall be exclusive of carpets, rugs or runners." A riser is "measured vertically between leading edges of the adjacent treads", and "The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm)."
Now add treads. If every step gains the same thickness, the risers in the middle of the flight do not change, because each tread and the one above it rise together. The two ends do, as long as the floors there stay where they are. The first riser, from the floor to the first tread, grows by the added thickness. The last riser, from the top tread to the landing, shrinks by it.
Two ways out: new flooring at the bottom and on the landing that rises by about the same amount, or full replacement treads chosen to keep the old height instead of caps laid over the old treads. Measure every riser before buying anything.
The code makes one allowance for old stairs: "Alterations to existing stairs shall not be required to comply with the requirements of this code where the existing space and construction does not allow a reduction in pitch or slope." It is about pitch and slope, not about leaving one riser taller than the rest.
The numbers a new tread has to meet
| Rule | 2025 California Residential Code |
|---|---|
| Riser height | "The riser height shall be not more than 7 3/4 inches (196 mm)." |
| Tread depth | "The tread depth shall be not less than 10 inches (254 mm)." |
| Riser and tread uniformity | 3/8 inch between the largest and smallest riser in a flight, and the same for treads. |
| Nosing | "A nosing projection not less than 3/4 inch (19 mm) and not more than 1 1/4 inches (32 mm) shall be provided on stairways." |
| When nosing is not needed | "A nosing projection is not required where the tread depth is not less than 11 inches (279 mm)." |
| Headroom | "The headroom in stairways shall be not less than 6 feet 8 inches (2032 mm)" |
| Width | 36 inches clear above the handrail height. |
A new tread with a thicker or rounder nosing can push the nosing projection out of range, so check the profile of the tread you choose against the 3/4 to 1 1/4 inch rule.
Handrails, guards and balusters
- A handrail on at least one side: "Handrails shall be provided on not less than one side of each flight of stairs with four or more risers."
- Its height: measured from the line of the tread nosings, "not less than 34 inches (864 mm) and not more than 38 inches (965 mm)." New treads raise that line, so measure the rail again after they go in.
- Continuous: "Handrails shall be continuous for the full length of the flight".
- Guards where the side is open and the drop is more than 30 inches. California sets them at "not less than 42 inches (1067 mm) in height" at open walking surfaces such as landings, and 34 inches along the open side of the stair itself.
- Balusters close enough: on the open side of stairs, no opening may "allow passage of a sphere 4 3/8 inches (111 mm) in diameter", and the triangle under the bottom rail may not pass a 6-inch sphere.
The 42-inch guard is a California amendment: the national model code, the 2024 International Residential Code, requires guards "not less than 36 inches (914 mm) in height", so guards copied from a national plan can come up short here.
How vinyl and wood treads are fastened
Floating is for floors, not steps. For its vinyl plank on stairs, Shaw is direct: "Shaw requires fully adhering installations on steps for safety and structural stability reasons." and "Planks must be full spread glued to the existing stair tread and riser". COREtec, a floating product, "may only be glued down underneath cabinets and at flush mount stairnosing."
For engineered wood, Shaw's stair nosing is to be secured "by gluing and nailing/ screwing down into place." Whichever material you choose, the stair is glued and fastened; only the flat floors on either side float. Our comparison of vinyl or wood covers the rest of that choice.
Older painted stairs: the lead rule
Pulling carpet can mean sanding or replacing painted risers, stringers and balusters. In homes built before 1978, EPA's rule applies: "anyone who is paid to perform work that disturbs paint in housing and child-occupied facilities built before 1978 must be certified. This includes all firms, even sole proprietorships."
Small jobs are carved out only below "six square feet or less of paint per room inside", and before the work the firm must hand the owner EPA's Renovate Right pamphlet. California has no state program of its own, so the federal rule is the one that applies.
Who builds it
Stairs are carpentry, which is what our framing and carpentry page covers. Where the treads meet new floors at the top and bottom, see the flooring that meets the stairs.
Quick answers
Can I put wood treads over my existing stair treads?
Often, but measure first. Covering every tread adds the same thickness to each step, which makes the first riser taller and the last riser shorter by that amount. The California code allows only 3/8 inch between the tallest and shortest riser in a flight.
What is the maximum stair riser height in California?
7 3/4 inches, with treads at least 10 inches deep, under the 2025 California Residential Code. Measurements exclude carpet, rugs and runners.
Do new stair treads need a nosing?
Yes, a projection of 3/4 to 1 1/4 inches, unless the tread is at least 11 inches deep. The nosings in one flight may differ by no more than 3/8 inch.
How high should a stair handrail be?
Between 34 and 38 inches, measured vertically from the line of the tread nosings, on at least one side of any flight with four or more risers. New treads raise that line, so check the rail afterward.
How far apart can stair balusters be?
On the open side of a stair, the openings may not pass a sphere 4 3/8 inches in diameter; elsewhere on guards the limit is 4 inches, and the triangle under the bottom rail may not pass a 6-inch sphere.
Can vinyl plank be used on stairs?
Yes, glued rather than floated. Shaw requires full-spread adhesive on the existing tread and riser for its vinyl on steps, and COREtec allows its floating plank to be glued down at flush-mount stair nosing.
Does lead paint matter on an old staircase?
In a home built before 1978, yes: paid work that disturbs more than six square feet of painted surface per room inside must be done by an EPA-certified firm, which also has to give you EPA's Renovate Right pamphlet first.
Sources
- 2025 California Residential Code, Chapter 3 Building Planning (with January 2026 errata) (International Code Council (publisher of Title 24 Part 2.5))
- 2024 International Residential Code, Chapter 3 (the national model code) (International Code Council)
- Resilient Step and Riser Directions (Shaw Floors)
- COREtec Scratchless Installation (COREtec (a Shaw / USFloors brand))
- Engineered Hardwood Flooring Installation Guidelines (Shaw Floors)
- Lead Renovation, Repair and Painting Program: contractors (U.S. Environmental Protection Agency)
- Renovate Right: Important Lead Hazard Information for Families, Child Care Providers and Schools (U.S. Environmental Protection Agency)
Read on 2026-10-16.