MaterialCalc — Floor Truss vs I-Joist Cost Calculator

Estimate prepared 10/31/2026. Estimates only; verify against your plans before ordering.

Floor Truss vs I-Joist Cost Calculator

Enter your measurements and get both numbers: how much material the job takes, and what it costs in your state.

60Calculators

09/01/2026Prices checked

2assumptions shown

Live estimate—

01 / 03Measurements

How big is it?

Measure to the outside. Round to the nearest half foot — nothing on a job site is exact.

Clear span

Floor length

Floor trusses, I-joists and sawn lumber are not interchangeable at every span, and where two of them work the cheaper one is not always the cheaper job. Trusses cost more per foot and save a day of drilling for mechanicals. This prices all three against your span and tells you where sawn lumber stops being an option at all.

Assumptions used

These are the numbers behind the result. Where one of them is soft, the cost range widens rather than pretending to a precision the data does not have.

Lumber waste allowance: 0.1
Floor joist span table: 360 L/360 deflection limit

Prices verified 09/01/2026 (US national average, big-box retail shelf price and regional ready-mix quotes). Regional adjustment: Blended from RSMeans city cost index bands and BLS construction wage differentials.

The formula

Members = (floor length ÷ spacing) + 1. Total linear feet = members × span. Trusses and I-joists are priced per linear foot; sawn lumber is priced by the board, so the span is rounded up to stock lengths. Sawn feasibility comes from the span table for 2x12 at your spacing.

Worked examples

20 ft span at 19.2 in o.c.

Clear span 20
Floor length 32
Spacing 19.2
Waste 3

Beyond the reach of sawn 2x12, so the real choice is trusses against I-joists. Twenty-one members, 420 linear feet.

14 ft span at 16 in o.c.

Clear span 14
Floor length 28
Spacing 16
Waste 3

All three work at this span, and sawn lumber is usually cheapest on material. Whether it is cheapest overall depends on how much drilling the mechanicals need.

26 ft span at 24 in o.c.

Clear span 26
Floor length 40
Spacing 24
Waste 3

Well past sawn lumber and pushing I-joists. Floor trusses handle long spans at wide spacing better than anything else in wood.

Choosing materials

Open-web floor trusses let ducts, drains and wiring pass through without a single hole drilled. On a floor carrying HVAC, that saves more labor than the trusses cost extra.
I-joists have knockouts for small penetrations, but the flanges must never be cut and the web can only be opened where the manufacturer permits. A plumber who does not know that can ruin a floor in an afternoon.
Sawn lumber can be drilled, but only within limits: holes no larger than a third of the depth, at least 2 in from the edges, and never in the middle third of the span in the tension zone.
Both engineered options arrive straight and stay straight. Sawn 2x12 crowns, twists and shrinks, and a floor built from it needs sorting and crowning as you go.
Engineered members are made to order, so they carry lead time. Sawn lumber is on the shelf. If the schedule is tight, that difference can outweigh the price.

Common questions

Are floor trusses better than I-joists?

For running mechanicals, yes — open webs take full-size ducts without any cutting. I-joists are usually cheaper per foot and are lighter to handle. Trusses also span further at a given depth, which matters on long open floors.

How far can a floor truss span?

Commonly 20 to 30 ft depending on depth, and further with deeper trusses. Because they are engineered to order, the practical limit is what the manufacturer will design and what you can get delivered rather than a table figure.

When do I have to stop using sawn lumber?

Around 18 ft with 2x12 in southern pine at 16 in on center, and less in weaker species or at wider spacing. Past that no sawn dimension lumber reaches, and engineered framing is the only wood option.

Can I drill through I-joists?

Only through the web, only where the manufacturer allows it, and never through the flanges. Each maker publishes a hole chart showing permitted sizes and locations. Cutting a flange destroys the joist and it must be replaced.

Do floor trusses cost more than I-joists?

Usually yes per linear foot, often 30 to 50% more. The comparison above prices both for your actual quantity. The saving comes back in mechanical rough-in labor, which does not show up in a material quote.

Which option is quietest underfoot?

Deeper members at tighter spacing, whichever type. Both engineered options are stiffer than sawn lumber at the same depth, and both are far more consistent — squeaks usually come from fastening and subfloor detail rather than from the joist type.

In this topic

Floor Framing Calculators — 2 calculators

Floor Joist Span CalculatorThe smallest joist that clears your span, and what it costs.

Related guides

How Far Can a Floor Joist Span?Rough spans for 2x6 through 2x12, what changes them — species, grade, spacing, load — and why the span table is the only answer that counts.