Question 1

What thickness of plywood do I need?

Accepted Answer

For subfloors: 3/4" (with joists 16" OC) or 5/8" (joists 12" OC). For wall sheathing: 1/2" or 7/16" OSB. For roof decking: 1/2" to 5/8". For cabinet backs and underlayment: 1/4" to 3/8". For furniture and shelving: 3/4".

Question 2

How heavy is a sheet of plywood?

Accepted Answer

A standard 4x8 sheet of 3/4" plywood weighs approximately 60-70 pounds. A 1/2" sheet weighs about 40-48 pounds. A 1/4" sheet weighs about 22-25 pounds. OSB is slightly lighter than plywood of the same thickness.

Question 3

What is the difference between plywood and OSB?

Accepted Answer

Plywood is made of thin wood veneers glued in alternating grain directions. OSB (Oriented Strand Board) is made of compressed wood strands and resin. Plywood is stronger and more water-resistant but more expensive. OSB is suitable for most structural sheathing applications.

Question 4

What plywood grade should I use?

Accepted Answer

CDX is the most common construction plywood for sheathing and subfloors (C and D faces, exterior glue). ACX has one good face for exposed applications. Marine-grade plywood is for boat building and extreme moisture. BC sanded plywood is good for visible surfaces like shelving.

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