Wood I-joist (representative) - Design Values
Wood I-joist (representative) is a engineered wood (lvl / psl / i-joist) grade with reference design values to Representative - see manufacturer ICC-ES report. Its reference bending value Fb is 2,000 psi, compression parallel Fc is 2,000 psi, and modulus of elasticity E is 1,800,000 psi (NDS). Values are shown before adjustment factors; apply the relevant NDS C-factors or EC5 k_mod and γ_M for your load case.
Representative values. Wood I-joists are specified by RATED CAPACITIES (allowable moment M_r, shear V_r, and stiffness EI) per depth and series, not by member stresses. Use the manufacturer's span/load tables and ICC-ES report for design.
| Fb | Bending | 2,000 psi |
| Ft | Tension parallel | 1,500 psi |
| Fv | Shear parallel | 200 psi |
| Fc⊥ | Compression perpendicular | 500 psi |
| Fc | Compression parallel | 2,000 psi |
| E | Modulus of elasticity | 1,800,000 psi |
| Emin | Modulus for stability | 900,000 psi |
Source: Representative - see manufacturer ICC-ES report. Reference values are shown before adjustment factors (NDS C-factors / EC5 k_mod, γ_M) - apply these per your load case in design.
Understanding these values
For a beam in Wood I-joist (representative), bending at Fb 2,000 psi normally sets the size, but the check that actually governs depends on the span. Short heavily loaded members are often limited by shear at Fv 200 psi, and bearing at a support is limited by compression perpendicular to grain at Fc perp 500 psi, which is the lowest of the strength values and the one most often overlooked. Used as a post or stud, the governing value is compression parallel at Fc 2,000 psi.
Stiffness for Wood I-joist (representative) is E 1,800,000 psi, with the reduced modulus Emin 900,000 psi used for stability calculations such as the beam stability factor CL and the column stability factor CP. On typical floor spans, deflection rather than strength decides the section, so compare E before Fb when the member is a joist.
Within the engineered wood (lvl / psl / i-joist) entries in this catalogue, Wood I-joist (representative) ranks 4 of 4 on bending at 2,000 psi; the strongest listed is LVL 2.0E (representative) at 2,900 psi. Grade choice is usually a trade of cost against section depth, so it is worth checking whether a lower grade in a deeper section is cheaper than a higher grade at the depth you started with.
The closest alternative in the same family is LVL 1.9E (representative) at 2,600 psi in bending, 23% above this grade. If availability drives the choice rather than capacity, that is the substitution to price first - but re-run the deflection check as well, because stiffness and strength do not always move together.
The Wood I-joist (representative) figures above are representative of engineered wood (LVL, PSL and I-joists) rather than of any one manufacturer's product. engineered wood (LVL, PSL and I-joists) is proprietary: published design values differ between suppliers, and for engineered products they depend on the grade stamp and the depth supplied. Use this page for scheme design and take the specific product's evaluation report for the final check.