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Construction glossary · Units of measure

What is PSFin construction?

PSF (pounds per square foot) is the unit US construction uses for loads spread over an area: a floor designed for a 100 psf live load must safely support 100 lb of people and movable contents on each square foot, on top of the structure's own weight. Psf values appear in the structural general notes (dead, live, roof, snow, and wind loads) and in the geotech report as allowable soil bearing pressure. To get total load, multiply psf by area in sf: the result is in lb, and dividing by 1,000 converts lb to kips.

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Updated June 2026 · Reviewed by the Ruh construction team

PSF = lb per sq ftOffice live load ~50 psfMeasures area / pressure load

Typical PSF loads on the scale

20 psf snow40 psf live (res)50 psf office live100 psf storage250 psf heavy40 psf typical floor live load
The definition

PSF (pounds per square foot), explained.

In US commercial work, psf shows up in two places that mean very different things, and estimators live in both. On the structural side it is a load: the general notes on the S-series sheets tabulate dead, live, roof, snow, and wind loads in psf, and the geotech report gives allowable soil bearing pressure in psf. Engineers set those values; estimators read them because they explain why the slab is 8 in thick instead of 5 in, why the steel tonnage grew, and what a deck can hold during construction. On the commercial side, PSF often stands in for dollars per square foot in conceptual budgets, bid leveling, and owner conversations. Two mistakes new estimators make: reading a load value where the conversation is about price (or the reverse), and trying to price the load itself. You do not price 100 psf; you price the concrete, rebar, and steel the engineer sized to carry it, so a load change reaches your estimate through the structural details, not as its own line item.

How it is measured

Psf is pounds of force per square foot of area, the US customary unit for uniformly distributed loads (metric drawings use kilopascals; 1 kPa is about 20.9 psf). Look for it in the design load table on the structural general notes, in the geotech report as allowable bearing pressure (an illustrative 2,000 psf to 4,000 psf for ordinary spread footings), and in roofing and flooring specs as material weight. To apply it, multiply the psf value by the area it acts on: load in lb = psf x sf, then divide by 1,000 to convert lb to kips. For pricing, the math runs the other way: divide total cost by gross floor area to get dollars per sf, and always say which area basis you used.

Worked example

A worked PSF (pounds per square foot) example.

Worked example

The structural notes show a design live load of 100 psf on a 5,000 sf elevated floor. Total live load: 100 psf x 5,000 sf = 500,000 lb. Engineers talk in kips (1 kip = 1,000 lb), so 500,000 lb / 1,000 = 500 kips, which is also 250 tons (500,000 lb / 2,000 lb per ton). Now use it the way a field team would. You want to stage 40 pallets of brick on that deck at 3,000 lb per pallet: 40 x 3,000 lb = 120,000 lb. Parked in a 1,000 sf corner, that is 120,000 lb / 1,000 sf = 120 psf, over the 100 psf limit before you count workers and equipment. Spread across 1,500 sf, it drops to 120,000 lb / 1,500 sf = 80 psf and you are back inside the number. Same pallets, different area, different answer: psf is always load divided by the area carrying it.

How Ruh handles it

How Ruh handles PSF (pounds per square foot).

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PSF (pounds per square foot): frequently asked questions

What is the difference between psf and psi?+

Psi is pounds per square inch and psf is pounds per square foot; since a square foot contains 144 square inches, 1 psi = 144 psf. Psi describes material strength and pressure (4,000 psi concrete, pipe test pressure), while psf describes area loads and soil bearing. Mixing them up is a factor-of-144 error, so check the unit every time you pull a number off a drawing.

What are typical design live loads in psf for commercial buildings?+

US code minimums under ASCE 7 commonly run 50 psf for offices, 80 psf for corridors above the first floor, 100 psf for lobbies and assembly areas, 125 psf for light storage, and 250 psf for heavy storage, with ordinary roofs around 20 psf. The structural general notes govern on any given job because engineers can design above code minimums. Read the notes on every project instead of assuming the last job's numbers carry over.

Does PSF also mean price per square foot?+

Yes. With a dollar sign attached, PSF reads as per square foot: an illustrative $300 per sf shell-and-core budget for a US mid-rise office, or an illustrative $10 per sf slab on grade. Conceptual estimates divide total cost by gross floor area so projects can be compared on one number. Always state the area basis (gross, rentable, or net), because changing the denominator changes the price without changing the building.

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Related terms

PSI (pounds per square inch)GaugeRoof pitchMBF (thousand board feet)EA (each)LS (lump sum)

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Figures on this page are illustrative. Construction estimates depend on project-specific conditions, source documents, market pricing, and professional judgment. Ruh's AI assists the estimator and does not replace professional review: your team reviews, validates, and approves every estimate, bid, and pricing decision.

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