Under-Stair Storage Ideas That Actually Work

Enclosed storage under a staircase — anything with a door or access panel, not open shelving — must be lined on the enclosed side with 1/2 in (12.7 mm) gypsum board, per IRC R302.7 (2021 edition, unchanged from the 2018 edition). It’s a fire-separation rule most DIYers miss until an inspector flags it, because open shelving under an open stringer isn’t “enclosed accessible space” and doesn’t trigger the same requirement.

Before framing anything, work out how much usable volume you actually have with the under-stair storage calculator — the raw triangular volume and the realistically usable volume are two different numbers.

Calculating usable volume

The space under a straight staircase is a right-triangle prism. Volume = 0.5 × run length × total rise × usable width.

Worked example: 14 risers at 7.5 in (190 mm) each give a total rise of 105 in, or 8.75 ft (2.67 m). 14 treads at 10 in (254 mm) give an 11.67 ft (3.56 m) run. At a 3 ft (0.91 m) width, raw volume is 0.5 × 11.67 × 8.75 × 3 ≈ 153 cubic ft (4.34 m³).

That’s the raw number — not the usable one. The lowest 12–18 in (300–450 mm) of the triangle, nearest the bottom of the stair, is too shallow to shelve or box anything taller than a picture frame. In practice, expect to use 65–75% of the raw volume for actual storage once you account for that dead zone and for framing thickness.

Stair scenario	Total rise	Run length	Raw triangular volume
10-step stair, 7.75 in riser, 10 in tread, 3 ft wide	6.5 ft (2.0 m)	8.3 ft (2.5 m)	81 cu ft (2.3 m³)
14-step stair, 7.5 in riser, 10 in tread, 3 ft wide	8.75 ft (2.7 m)	11.7 ft (3.6 m)	153 cu ft (4.3 m³)
16-step stair, 7.25 in riser, 11 in tread, 3.5 ft wide	9.7 ft (2.9 m)	14.7 ft (4.5 m)	250 cu ft (7.1 m³)

Design layouts that work with the taper, not against it

Pull-out drawers on casters work best in the tallest 4–5 ft (1.2–1.5 m) section near the top of the stair, where there’s enough height to reach in and lift items out. The shallow end near the bottom of the flight suits flat storage only — shoe racks, flattened boxes, or a fitted bench seat with a lift-up lid.

A single walk-in closet along the full run wastes the tapering headroom at the far end; stepped shelving that follows the stringer angle uses the same footprint more completely, though it costs more in framing labor than a flat back wall.

Common mistakes

Skipping the gypsum board lining because the space “is basically a closet” — under IRC R302.7, any enclosed, accessible space under stairs needs 1/2 in gypsum board on the enclosed side; local jurisdictions can adopt amended versions of the IRC, so confirm the exact requirement with your local building department before finishing the space.

Building shelving that ignores the sloped ceiling and treats the whole cavity as one flat-topped closet, which wastes the tallest section near the top of the stair where the most usable volume actually is.

Screwing drywall or shelving hardware directly into the stringers without checking their layout first, which can split a stringer or miss solid backing entirely — box out the stringers with furring strips before finishing.

Sealing the space completely with no ventilation path when it’s used to store anything with moisture risk (shoes, sports gear, cleaning supplies) — not a code requirement, but a common cause of musty odor in enclosed under-stair closets.

Related calculators you might need

Storage layout depends on a few other stair dimensions. The stair headroom calculator confirms clearance if you’re adding a door into the storage space. The riser height calculator and tread depth calculator let you plug in your actual dimensions if they differ from the example above. If you’re cutting a new access opening into the stringer side, the stair opening/floor cutout calculator sizes that opening correctly.

Frequently asked questions

Is under stair storage a good use of space? Yes, for most homes — a typical 14-step staircase yields well over 100 cubic feet of enclosed volume that otherwise sits empty. The tradeoff is that roughly a quarter to a third of the raw triangular volume isn’t practically usable due to the low taper near the bottom.

Do you need drywall under stairs for storage? If the space is enclosed and accessible through a door or panel, yes — US building codes based on the IRC require 1/2 in gypsum board on the enclosed side under Section R302.7. Fully open shelving without an enclosing door generally isn’t subject to the same requirement, but confirm locally.

How much storage space is under a typical staircase? It varies with rise, run, and width — a 14-step, 3 ft-wide stair yields roughly 150 cubic feet raw, but the exact figure depends on your specific dimensions. Use the under-stair storage calculator with your own measurements for an accurate number.

What can you build in the shallow end of under-stair storage? Flat storage only, generally: shoe racks, drawer units under 8–10 in tall, or a bench with a lift-lid seat. Anything requiring you to stand or reach in vertically needs to go in the taller section near the top of the flight.