Two common enhanced surface panels are medium density overlay (MDO) and high-density overlay (HDO), made from high-grade hardwood or fully repaired fir faces. Available in ½" or ¾" thicknesses (with custom options), they come in two grades: concrete form and general purpose. General purpose panels suit signage, painting projects like garage cabinets, and murals.
For general use, MDO and HDO can be produced via one-step or two-step processes. One-step panels apply the overlay in a single press cycle, while two-step panels first sand the plywood substrate to a glassy smooth finish before a second press, resulting in a refined surface with minimal telegraphing risk.
Concrete form grade MDO/HDO outperforms BBOES, with embedded release agents allowing 10-15 pours when cleaned properly, versus BBOES requiring respraying after each use.
Proper fastening and spacing are critical for plywood installation as sheathing or underlayment. Follow nailing patterns from the APA or approved agencies, covering fastener specifics (length, diameter, corrosion resistance) and spacing at perimeters and in the field.
A common mistake is skipping panel spacing, which can cause buckling in outdoor exposure. Leave gaps to allow expansion/contraction from moisture.
For panel orientation, install perpendicular to roof trusses or joists. When using tongue-and-groove underlayment, choose between scant-face (47.5" face from 48" panels) and full-face (48" face from 49" panels), influenced by regional availability (e.g., Seattle offers both, Southern California uses scant-face only).
