Pressure Treated
Ground Contact (UC4A)
Pressure treated for direct ground contact — fence posts, structural posts, retaining walls
Standard: AWPARelative price: Mid-RangeRank: 1
What this grade means
UC4A (Use Category 4A) ground contact treated lumber is pressure-treated with preservatives to a higher retention level than above-ground treated wood. Required for any lumber that will be in direct contact with the ground or embedded in concrete.
Defects allowed
Same structural defects as base grade, plus treatment chemical appearance (green/brown tint)
Typical uses
Fence posts, deck posts, sill plates on concrete, landscape timbers, retaining walls, raised beds
Grade rules vary by species, region and grading agency. For structural work, use the grade stamp and governing code or an engineer’s specification—not appearance alone.
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