Enclosed storage under a staircase \u2014 anything with a door or access panel, not open shelving \u2014 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.<\/p>\n\n\n\n
Before framing anything, work out how much usable volume you actually have with the under-stair storage calculator<\/a> \u2014 the raw triangular volume and the realistically usable volume are two different numbers.<\/p>\n\n\n\n The space under a straight staircase is a right-triangle prism. Volume = 0.5 \u00d7 run length \u00d7 total rise \u00d7 usable width.<\/p>\n\n\n\n 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 \u00d7 11.67 \u00d7 8.75 \u00d7 3 \u2248 153 cubic ft (4.34 m\u00b3).<\/p>\n\n\n\n That’s the raw number \u2014 not the usable one. The lowest 12\u201318 in (300\u2013450 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\u201375% of the raw volume for actual storage once you account for that dead zone and for framing thickness.<\/p>\n\n\n\n Pull-out drawers on casters work best in the tallest 4\u20135 ft (1.2\u20131.5 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 \u2014 shoe racks, flattened boxes, or a fitted bench seat with a lift-up lid.<\/p>\n\n\n\n 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.<\/p>\n\n\n\n Skipping the gypsum board lining because the space “is basically a closet” \u2014 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.<\/p>\n\n\n\n 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.<\/p>\n\n\n\n Screwing drywall or shelving hardware directly into the stringers without checking their layout first, which can split a stringer or miss solid backing entirely \u2014 box out the stringers with furring strips before finishing.<\/p>\n\n\n\n Sealing the space completely with no ventilation path when it’s used to store anything with moisture risk (shoes, sports gear, cleaning supplies) \u2014 not a code requirement, but a common cause of musty odor in enclosed under-stair closets.<\/p>\n\n\n\n Storage layout depends on a few other stair dimensions. The stair headroom calculator<\/a> confirms clearance if you’re adding a door into the storage space. The riser height calculator<\/a> and tread depth calculator<\/a> 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<\/a> sizes that opening correctly.<\/p>\n\n\n\n Is under stair storage a good use of space? <\/strong>Yes, for most homes \u2014 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.<\/p>\n\n\n\n Do you need drywall under stairs for storage? <\/strong>If the space is enclosed and accessible through a door or panel, yes \u2014 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.<\/p>\n\n\n\nCalculating usable volume<\/h2>\n\n\n\n
Stair scenario<\/strong><\/td> Total rise<\/strong><\/td> Run length<\/strong><\/td> Raw triangular volume<\/strong><\/td><\/tr> 10-step stair, 7.75 in riser, 10 in tread, 3 ft wide<\/td> 6.5 ft (2.0 m)<\/td> 8.3 ft (2.5 m)<\/td> 81 cu ft (2.3 m\u00b3)<\/td><\/tr> 14-step stair, 7.5 in riser, 10 in tread, 3 ft wide<\/td> 8.75 ft (2.7 m)<\/td> 11.7 ft (3.6 m)<\/td> 153 cu ft (4.3 m\u00b3)<\/td><\/tr> 16-step stair, 7.25 in riser, 11 in tread, 3.5 ft wide<\/td> 9.7 ft (2.9 m)<\/td> 14.7 ft (4.5 m)<\/td> 250 cu ft (7.1 m\u00b3)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Design layouts that work with the taper, not against it<\/h2>\n\n\n\n
Common mistakes<\/h2>\n\n\n\n
Related calculators you might need<\/h2>\n\n\n\n
Frequently asked questions<\/h2>\n\n\n\n