A 20 foot steel beam has no fixed price, because length is only one of two things that set the steel in it. The other is the beam size, and the size depends on how far the beam spans and what it carries. A 20 ft W8x18 contains 360 lb of steel; a 20 ft W12x26 contains 520 lb. Since longer spans usually need heavier sections, the cost of a beam tends to grow faster than its length. Fabrication, delivery and installation are then added on top.
Below, we show how much common beams weigh at 10, 20, 30 and 40 feet, explain why span drives size, and list the costs that change with length. We don't publish prices, but once you know the size and length, you can see exactly what a supplier is pricing.
Beam weight by length
Wide-flange beams are priced from their weight, and the weight per foot is part of the name. In imperial, the second number in W8x18 is pounds per foot. In metric, the second number in W200x27 is kilograms per metre. Our guide to reading steel beam sizes explains the naming.
Here is the steel in some common sizes at the lengths people ask about most:
| Beam | 10 ft (3.05 m) | 20 ft (6.10 m) | 30 ft (9.14 m) | 40 ft (12.19 m) |
|---|---|---|---|---|
| W200x27 (W8x18) | 180 lb (81 kg) | 360 lb (162 kg) | 540 lb (243 kg) | 720 lb (324 kg) |
| W250x33 (W10x22) | 220 lb (100 kg) | 440 lb (201 kg) | 660 lb (301 kg) | 880 lb (401 kg) |
| W310x39 (W12x26) | 260 lb (118 kg) | 520 lb (237 kg) | 780 lb (355 kg) | 1,040 lb (473 kg) |
| W360x45 (W14x30) | 300 lb (137 kg) | 600 lb (273 kg) | 900 lb (410 kg) | 1,200 lb (546 kg) |
| W410x54 (W16x36) | 360 lb (164 kg) | 720 lb (327 kg) | 1,080 lb (491 kg) | 1,440 lb (655 kg) |
Pounds use the nominal weight per foot; kilograms use the actual mass per metre from the CISC section tables, so the two columns differ slightly. Plates, connection material and paint add a little to the shipped weight.
For metric lengths, the arithmetic is the same: a 3 m W200x27 is about 80 kg, and a 6 m one is about 160 kg. A 6 m beam is just under 20 ft (about 19 ft 8 in), so it can be cut from a 20 ft stock length with little left over.
Why a longer beam is usually a bigger beam
The table holds the size constant, but real beams don't work that way. For a beam carrying a uniform load, basic beam theory gives two rules of thumb:
- Bending grows with the square of the span. Double the span with the same load per metre and the bending moment the beam must resist goes up four times.
- Deflection grows with the fourth power of the span. Double the span and, for the same beam and load per metre, the sag goes up sixteen times.
In houses, deflection often controls: floors that bounce and ceilings that crack are what the design is trying to prevent. So a beam that spans 30 ft is rarely the same section as one that spans 10 ft. It is deeper, heavier, or both, which means it has more steel per foot as well as more feet. That is why a 30 ft beam usually costs more than three 10 ft beams.
The fix designers use is posts. Adding a post in the middle of a 30 ft run turns one long span into two 15 ft spans, and the beam can drop to a much lighter section. Whether that saves money depends on the cost of the post and its footing, and whether the room can live with a column. Our steel beam span tables article explains how spans are set for Ontario houses, and the beam itself must be sized by an engineer or qualified designer.
10, 20 and 30 foot beams: what each job usually looks like
Every project is different, but beam length tends to bring a predictable set of issues:
Around 10 ft (3 m). Short beams over a single opening, a short basement span between posts, or a header in a wall. The steel is light enough to carry by hand with a few people. Because fixed costs (detailing, cutting, plates, handling) are spread over few feet, short beams cost more per foot than long ones.
Around 20 ft (6 m). A common length for opening up a main floor or carrying a basement floor between foundation walls, often with a post or two. A 20 ft beam lines up with a common stock length, which helps keep waste down. It is heavy enough that moving it into a basement takes planning, equipment or a team.
Around 30 ft (9 m) and longer. Long open spaces, garages and additions. The section is usually heavier, delivery may need a longer truck, and getting the beam into position may take a machine. If one piece can't get into the building, the engineer may design a splice so it comes in sections.
Costs that change with length
Beyond the steel itself, several parts of a beam price respond directly to length:
- Stock lengths and drops. Beams are commonly stocked in imperial lengths such as 20 ft and 40 ft. A 21 ft beam may have to come out of a 40 ft length, leaving a 19 ft drop. Our guide to standard steel beam lengths and delivery limits covers stock lengths in detail.
- Delivery. Short beams ride with other material. Long beams need a trailer that fits the load and a site the truck can reach.
- Handling and installation. A crew can carry a short light beam. A long heavy one may need a lift, a boom truck or temporary supports, plus more people on the day.
- Splices. A designed splice adds plates, bolts or welds, and engineering time, but it can be cheaper than fighting access with a single long piece.
- Camber. Long beams are sometimes cambered so they settle flat under load. It is a fabrication step and is specified by the engineer.
- Posts, plates and footings. A long run broken up with posts adds posts, base plates and footings, which are part of the comparison.
How to work out the cost of a beam yourself
The "40 ft steel beam cost calculator" people search for is the same arithmetic estimators use:
- Get the size from the design. Without it, any number is a guess.
- Find the weight. Weight per foot times length, or kg per metre times metres.
- Apply a current material price from a supplier quote. Steel prices move with the market, so old figures are unreliable.
- Add the fabrication: cutting, holes, end plates, cap plates and any camber.
- Add finish, delivery and installation, plus posts, footings and permits if they are part of the job.
Our guide to steel beam prices in Canada explains each of these parts and how to compare quotes. If you already know your section, W-beam prices by size covers the common W8, W10 and W12 beams.
Get a price for your beam
The quickest route to a real number is to send the beam size and length, or the drawings if the beam has been designed, along with the site address and how the beam gets from the truck to its position. We supply wide-flange beams cut to length or fully fabricated with plates, holes and connections, with in-house shop drawings and delivery across the GTA and Ontario. We also supply and install basement beams and posts. Request a quote or browse our steel products.
Frequently asked questions
How much does a 20 foot steel beam cost?
It depends mostly on the beam size, which is set by the span and the load, and then on fabrication, finish, delivery and installation. A 20 ft W8x18 has 360 lb of steel, while a 20 ft W12x26 has 520 lb, so the size changes the material cost far more than the length. Send the size or your drawings for a price.
Is a 30 foot beam three times the cost of a 10 foot beam?
Usually more. A beam that spans 30 ft generally has to be a heavier section than one spanning 10 ft, so it has more steel per foot as well as more feet. Delivery, handling and installation also get harder with length.
How much does a 20 foot steel I-beam weigh?
Multiply the weight per foot by 20. The imperial name gives the weight per foot, so a W8x18 is 18 lb/ft and weighs 360 lb at 20 ft. In metric, a W200x27 is about 27 kg/m, so a 6 m length is about 160 kg.
Can a 30 foot steel beam span without a post?
Some can, but it takes a deep or heavy section, and the size depends on the loads the beam carries. Many 30 ft runs in houses use one or more posts to allow a smaller beam. An engineer or qualified designer has to size it.
