Estimate usable attic storage area and the decking to cover it. Enter the attic size and roof type, and mind the load warnings.
Usable Storage Area
— sq ft
Area with usable headroom.Usage Tip
Store light, bulky items (holiday decor, luggage) in the attic and keep heavy things like books and tools low in the house. Lay decking perpendicular across the joists and screw it down.
THE MATH
Usable area = floor area × usable fraction (by roof shape)
Decking = round up (usable area ÷ 32 sq ft per 4×8 sheet)
Headroom, not floor size, usually limits attic storage
Decking = round up (usable area ÷ 32 sq ft per 4×8 sheet)
Headroom, not floor size, usually limits attic storage
Only the part of an attic with standing or crouching headroom is usable — a steep roof gives more usable width than a shallow one. The fraction here is a rough guide.
Decking is 4 × 8 ft plywood or OSB (32 sq ft per sheet) laid over the joists.
Decking is 4 × 8 ft plywood or OSB (32 sq ft per sheet) laid over the joists.
Attic (ceiling) joists are often sized only to support the ceiling and light loads, not heavy storage. Check the joist size and span, or consult a pro, before loading an attic.
Keep weight light, spread out, and over load-bearing walls — not in the middle of a long joist span.
Leave airflow gaps, do not crush or cover insulation, and never block soffit vents; it causes moisture and roof problems.
Keep weight light, spread out, and over load-bearing walls — not in the middle of a long joist span.
Leave airflow gaps, do not crush or cover insulation, and never block soffit vents; it causes moisture and roof problems.