Introduction
The same 12-foot span can be crossed by a $60 built-up lumber beam, a $300 LVL, or a $600 steel beam — and each is the right answer in different circumstances. Beam materials differ in strength, stiffness, consistency, cost, and exposure tolerance, and choosing well means matching the material to the span, the load, the environment, and the budget rather than defaulting to whatever is familiar.
Size the load first with the Beam Calculator — the required moment and stiffness are material-independent — then use this guide to pick the material that delivers those numbers most economically for your situation. For what each option costs installed, see the cost guide.
Sawn Lumber: The Default
Dimensional lumber — 2×8, 2×10, 2×12 in single or multi-ply built-up beams — is the cheapest option and available everywhere. A 3-ply 2×12 of #2 Southern Pine carries the 7,200 lb-ft (9.76 kN·m) deck-beam load from the complete guide with margin, at a fraction of the engineered-lumber price.
The trade-offs are variability and span limits. Every board has knots, grain deviations, and a unique stiffness — published design values (E ≈ 1.4–1.6×10⁶ psi / 9.7–11.0 GPa for common #2 grades) already account for this statistically, but an individual board can be the weak one. Practical span ceiling for built-up sawn lumber is roughly 3.6–4.9 m (12–16 ft) depending on load; beyond that, depth requirements get impractical and engineered lumber takes over. Use pressure-treated lumber (or naturally durable species) for any exterior or ground-contact application, and seal all cut ends.
LVL: The Workhorse Upgrade
Laminated veneer lumber bonds thin wood veneers with all grain running lengthwise, producing a member that’s stronger, stiffer (E ≈ 1.9–2.0×10⁶ psi / 13.1–13.8 GPa typical), and far more consistent than sawn lumber. It comes in long lengths — up to 18 m (60 ft) — so splices disappear, and in depths to 600 mm (24 in) for serious spans.
LVL is sold in 45 mm (1¾ in) plies that are face-fastened into multi-ply beams on site. It’s the default choice for flush headers, long floor girders, and any span where sawn lumber fails deflection but the budget won’t stretch to PSL or steel. Limitations: it’s not rated for permanent exterior exposure unless specifically treated or protected — keep LVL dry and inside the building envelope — and it’s roughly 2–3× the cost of equivalent sawn lumber per linear foot.
PSL: Maximum Wood Capacity
Parallel strand lumber bonds long strands of veneer into a dense billet, yielding the highest bending strength of the common engineered wood products (Fb up to ~2,900 psi / 20 MPa for top grades, E ≈ 2.0×10⁶ psi / 13.8 GPa). PSL shines as heavily loaded girders, long headers carrying multiple floors, and columns — anywhere the load overwhelms LVL.
Expect to pay a premium over LVL (roughly 1.5–2×), and note that PSL is heavy — a 3½ × 11⅞ in beam weighs noticeably more than its LVL equivalent, which matters for handling. Like LVL, standard PSL is an interior product; verify exposure ratings with the manufacturer for any outdoor use.
Glulam: Strength Plus Appearance
Glued-laminated timber stacks dimension lumber laminations into large sections, available in widths to 260 mm (10+ in) and depths to 1 m+. Strength is comparable to LVL at similar sizes, but glulam’s real advantage is exposed applications: ridge beams, great-room girders, and porches where the beam is architecture, not just structure. Appearance grades come sanded and finished.
Glulam handles exterior exposure better than LVL/PSL when specified with exterior-rated adhesives, making it a candidate for covered outdoor structures. Cost runs above LVL; availability of odd sizes may require ordering through a specialty dealer rather than a big-box store.
Steel: Maximum Capacity Per Inch
A wide-flange (W-shape) steel beam carries several times the load of a wood beam at the same depth — the answer when headroom is fixed and the span is long, or when loads are simply too large for wood. A W8×18 (200 mm deep, 27 kg/m) spanning 6 m can carry loads that would demand a 400+ mm deep wood girder.
The costs beyond the material price are real: corrosion protection (paint or galvanizing), fire protection to satisfy code, heavy handling (a 6-m W10 can weigh 200+ kg / 440+ lb), bolted or welded connections, and usually professional installation with rigging. Installed cost typically runs several times the wood equivalent. Any structural steel beam should be sized by an engineer — the DIY vs pro guide puts steel firmly in pro territory.
Flitch Beams: The Hybrid
A flitch beam sandwiches a steel plate between two wood plies, bolted together. It delivers more capacity than wood alone at wood-like depth, and it can be an elegant fix when an existing wood beam proves undersized but headroom won’t allow a deeper member. Downsides: the steel plate must be protected from corrosion (a concern in exterior or damp locations), the assembly is heavy, and the composite action depends on proper bolting. Treat flitch design as engineered work.
Head-to-Head Comparison
| Material | Typical E | Span sweet spot | Exterior use | Relative cost |
|---|---|---|---|---|
| Sawn lumber (multi-ply) | 1.4–1.6×10⁶ psi (9.7–11.0 GPa) | To ~4.9 m (16 ft) | Yes, if pressure-treated | $ |
| LVL | 1.9–2.0×10⁶ psi (13.1–13.8 GPa) | 3.6–9 m (12–30 ft) | Only if rated/protected | $$ |
| PSL | ~2.0×10⁶ psi (13.8 GPa) | Heavy loads, long headers | Only if rated/protected | $$$ |
| Glulam | 1.6–1.8×10⁶ psi (11.0–12.4 GPa) | Long spans, exposed | Yes, exterior adhesive | $$$ |
| Steel W-shape | 29×10⁶ psi (200 GPa) | Longest spans, tight depth | Yes, with protection | $$$$ installed |
E values above are typical published values for common grades — always use the manufacturer’s published values for the specific product you buy, since they vary by grade and producer. Deeper background on the E and I terms is in the formula-explained guide.
How to Choose
- Start with exposure. Exterior or ground contact narrows the field immediately: pressure-treated sawn lumber, exterior-rated glulam, or protected steel.
- Check the span against the sweet spot. Under ~4.9 m (16 ft) with ordinary loads, sawn lumber usually wins on cost. Past that, or when deflection controls, step up to LVL.
- Let deflection decide. Run the numbers — if the wood option needs absurd depth to meet L/360, that’s the material telling you to upgrade, not to keep adding plies. The common mistakes guide covers the “just add plies” trap.
- Consider appearance. Exposed beams earn their keep visually — glulam or a well-finished sawn beam beats a hidden LVL.
- Get manufacturer tables. Engineered lumber producers publish span tables and sizing software for their exact products — use them; they supersede generic guidance.
Related Guides
- Complete Beam Sizing Guide — the sizing method with a worked example.
- Cost Guide — installed price ranges for every material here.
- Pro Tips — handling, storage, and installation by material.
- Estimating Guide — measuring the inputs the material choice depends on.
- Beam Calculator FAQ — quick answers on LVL vs PSL, steel, and notching.
Get Your Number
Material choice is an optimization problem: meet the required moment and stiffness from the Beam Calculator at the lowest total cost that suits the exposure and the architecture. For most residential spans that means pressure-treated lumber outdoors and LVL indoors past 12 feet; PSL, glulam, and steel each earn their premium in specific situations. Pick the material, verify with the manufacturer’s span tables, and confirm structural selections with your local code or an engineer.
Disclaimer: Material properties and span capabilities described here are typical planning values. Always use the manufacturer’s published design values for the specific product and grade you purchase. Verify selections with span tables or a structural engineer, and check your local building code before building.
