CLT Grade E1 (PRG 320) - Design Values
CLT Grade E1 (PRG 320) is a cross-laminated timber (clt) grade with reference design values to ANSI/APA PRG 320. Its reference bending value Fb is 1,950 psi, compression parallel Fc is 1,800 psi, and modulus of elasticity E is 1,700,000 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. E1 major-direction laminations are 1950f-1.7E MSR Spruce-Pine-Fir. Panel bending/shear capacity depends on the layup (thickness, layers) - use PRG 320 panel tables or the shear-analogy method for design.
| Fb | Bending | 1,950 psi |
| Ft | Tension parallel | 1,375 psi |
| Fv | Shear parallel | 135 psi |
| Fc⊥ | Compression perpendicular | 425 psi |
| Fc | Compression parallel | 1,800 psi |
| E | Modulus of elasticity | 1,700,000 psi |
| Emin | Modulus for stability | 620,000 psi |
Source: ANSI/APA PRG 320. 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 CLT Grade E1 (PRG 320), bending at Fb 1,950 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 135 psi, and bearing at a support is limited by compression perpendicular to grain at Fc perp 425 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 1,800 psi.
Stiffness for CLT Grade E1 (PRG 320) is E 1,700,000 psi, with the reduced modulus Emin 620,000 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 cross-laminated timber (clt) entries in this catalogue, CLT Grade E1 (PRG 320) is the strongest in bending at 1,950 psi, against 900 psi for CLT Grade V1 (PRG 320) at the other end of the range.
The closest alternative in the same family is CLT Grade E2 (PRG 320) at 1,650 psi in bending, 18% below 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 CLT Grade E1 (PRG 320) figures above are representative of cross-laminated timber rather than of any one manufacturer's product. cross-laminated timber is proprietary: published design values differ between suppliers, and for CLT they also depend on the layup and the panel thickness you actually specify. Use this page for scheme design and take the specific product's evaluation report for the final check.