What Are The Grades Of Plywood? | Clear Quick Guide

Walking into a lumber aisle, the stamps and letters on plywood can feel cryptic.
Once you know how the system works, picking the right sheet gets straightforward fast,
saves rework, and delivers the look or strength you expect. This guide breaks down
the letters on faces and backs, the panel grade pairs, and the weather exposure lines,
then shows how to match a grade to real jobs.

Plywood Grades At A Glance

Two grade systems sit on a sheet. First are veneer grades for the face and back: A, B, C, or D.
Then comes the panel grade, which is a pair such as AC, BC, or CDX. The letters tell you about the
surface quality you’ll see and the repairs that are allowed. The panel grade ties that look to the intended use. Always check stamps on every sheet in any bunk carefully too.

Veneer Grades And Where They Fit

Veneer Grade	Appearance & Repairs	Typical Uses
A	Sanded smooth, clean face, tight grain; minor repairs blended; ready for clear finish or paint.	Cabinets, built-ins, furniture, visible panels.
B	Sound face with patches and filled splits; paintable and uniform.	Paint-grade casework, shelving, soffits, fascia.
C	More knots and repairs; open splits may be filled; not fully sanded.	Substrates, utility furniture backs, underlayment when paired with better face.
D	Knots and open defects allowed; no fancy surfacing.	Backs, structural sheathing when paired as CD or CDX.

Understanding The Grades Of Plywood For Projects

The letter pair on the stamp tells you the face quality on each side.
AC means an A face with a C back. BC means a B face with a C back.
CDX is a common sheathing with a C face, a D back, and a bond suited for short weather exposure during construction.
You’ll also see named panel grades like Rated Sheathing, Sturd-I-Floor, or Underlayment for structural tasks.

If you’re decoding a stamp on site, the fastest reference is the
APA panel trademark guide,
which maps each line on the stamp to what it means. A longer chart, with every field numbered, sits in the
APA grade stamp anatomy handout.

Softwood Veneer Grades: A, B, C, And D

Softwood plywood relies on those A–D letters.
Higher letters look better and cost more; lower letters are fine when the face won’t show.
Most building panels pair an improved face with a leaner back to balance looks and budget.

Panel Grade Combinations: From AA To CDX

AA is top appearance on both sides for two-sided work.
AB gives a show face with a solid back.
AC lands in a sweet spot for paint-grade casework.
BC handles built-ins where the back is hidden.
CDX is a workhorse sheathing; the “X” points to a moisture-resistant bond line suited to brief rain during buildout.

Exposure Ratings And Glue Bonds

Exterior Or Exposure 1

Exterior panels use bonds tested for long-term wetting and drying.
Exposure 1 panels use bonds that ride out normal rain during construction but aren’t meant to live uncovered.
Pick Exterior for permanent wet settings like siding or boat parts. Use Exposure 1 for sheathing and subfloor that gets covered.

Decorative hardwood plywood follows a different rulebook.
The letter on the face pairs with a number on the back, such as A-1 or B-2, and the limits for patches, splits, and figure match come from the
ANSI/HPVA HP-1 standard.

Grades Of Plywood Explained For Builders

Hardwood Plywood: Letters And Numbers

What A-1, B-2, C-3 Mean

Cabinet and furniture panels use hardwood faces over veneer, MDF, or combination cores.
The letter is the face. The number is the back.
A-1 means a top face with a sound back suited for interiors that show both sides.
B-2 is a popular paint-grade pick for built-ins.
C-3 lands in utility territory for hidden backs or shop jigs.

Face grades set color match and defect repair limits.
Back numbers set how many repairs and small knots you may find.
Core type shapes how screws hold and how edges route:
veneer core is light and strong across the grain, MDF core machines clean for paint, and combination core blends both traits.

Marine And Exterior Panels

Marine-grade plywood uses high-quality face and back veneers and tight core construction with an exterior bond.
It’s built for harsh, wet service where hidden gaps would fail fast.
It also sands to a clean face for brightwork when the species suits finish.
For exterior trim or soffits that see sun and splash, look for Exterior on the stamp and pick a face grade that matches the finish plan.

How To Read A Plywood Grade Stamp

Every APA trademark packs key facts in a tight block.
Once you can scan the lines, you’ll buy faster and install with fewer surprises.
Here’s a quick field sheet you can keep on your phone.

Grade Stamp Cheat Sheet

Stamp Line	What It Tells You	Why It Matters
Panel Grade	AC, BC, CDX, Rated Sheathing, Sturd-I-Floor, Underlayment.	Signals the face/back mix or the assigned use.
Span Rating	Two numbers like 32/16.	Max roof span over rafters / floor span over joists.
Performance Category	Thickness label such as 15/32, 19/32, 23/32.	Pairs with fastening schedules and code tables.
Exposure	Exterior or Exposure 1.	Glue line durability for weather or build phase wetting.
Standard	PS 1 or PS 2.	Manufacturing and performance compliance path.
Agency & Mill	APA logo and plant number.	Traceability and quality program.

Pick The Right Grade For The Job

Match the grade to the task and finish plan.
These picks keep costs in line while hitting the mark for strength and appearance.

• Cabinets and built-ins: A-1 or B-2 hardwood plywood with a core that fits your tooling. Seal edges before finish.
• Paint-grade shelves and casework: AC or BC softwood plywood, sanded face out. Prime knots and patches.
• Wall sheathing: Rated Sheathing (often CDX) with Exposure 1. Follow the span rating on the stamp.
• Roof decks: Rated Sheathing with Exposure 1, clipped at the panel edges where the span rating calls for it.
• Subfloor: Sturd-I-Floor with Exposure 1; glue and fasten per the span rating and your adhesive maker.
• Wet trim and fascia: Exterior-rated panels with an A or B face under a solid coating system.

One more tip: read the rack labels at the yard.
The same face grade can sit over different cores, and changes weight, screw hold, and how clean edges route.
If the project needs tight reveals or heavy fasteners, pick the core that supports the plan before you load cart.

Common Myths And Tricky Terms

“CDX is exterior plywood.” Not exactly.
CDX points to a C/D face-back with an Exposure 1 bond.
It can sit in rain during the build, then it needs a roof, siding, or membrane.
For long-term weather, you need Exterior on the stamp.

“A face means flawless.” An A face is clean and sanded, yet you may still see tight patches or light color swing.
Pick the species and cut that match your finish and layout your parts to showcase the best areas.

“A-1 and AC are the same thing.” A-1 is a hardwood plywood label from HP-1 with a number back grade.
AC is a softwood pair that follows the PS standards for structural panels.
Different rules, different use cases.

Care, Storage, And Cutting Tips

Store flat on level stickers to keep sheets straight.
Bring panels inside a day before cutting so the faces relax to the room.
Use a sharp 40–80T blade for clean crosscuts on hardwood faces, score the cut line with a utility knife, and use a backer to cut down tear-out.
For edges that will show, ease with a block plane and seal end grain before primer or clear coat.

On exterior work, seal cut edges and fastener heads the same day.
Follow the paint maker’s instructions for primers over knot repairs and patch fills.
Leave the required panel gaps noted on the stamp or in the installation sheets so seasonal movement has room.

Quick Buying Checklist

1. Read the panel grade: letters or named use.
2. Check the exposure line: Exterior or Exposure 1.
3. Match the span rating to your framing layout.
4. Confirm performance category for fastener length.
5. Scan the face for layout-friendly figure and patches.
6. Plan edge sealing and the finish system before checkout.

Thickness, Span, And Fasteners

Span ratings keep framing and panel stiffness in step.
A stamp like 32/16 reads as roof span over rafters and floor span over joists.
Match your layout, use panel clips where the stamp calls for them, and leave the required gaps.
Nails should seat flush without crushing the top veneer.
On subfloors, a quality subfloor adhesive plus nails or screws makes a tight, quiet deck.

Species, Face Cuts, And Finish

Species and slicing style shape how a face looks under stain or paint.
Softwood faces are often rotary cut, which yields bold cathedrals.
Hardwood faces may be rotary, plain-sliced, rift, or quartered.
Plain-sliced shows arching grain; rift and quartered run straight.
If you’re staining, buy from one lot and lay out parts so neighboring fronts track the grain.
For paint, B faces cover well once you spot prime patches and sand light between coats.

Named Panel Grades You’ll See

MDO And HDO

Sanded plywood has a smooth face ready for paint or clear coat.
Rated Sheathing targets walls and roofs and pairs strength with an economical face.
Sturd-I-Floor is subfloor stock with a span rating line geared to floor loads.
Underlayment gives a tight, smooth face for resilient flooring and tile backers.
MDO and HDO are plywood with resin-treated fiber faces.
MDO paints to a slick sign-board finish; HDO is built for concrete forms and demanding surfaces.

Troubleshooting Panels In The Shop

Edge chip-out on hardwood faces calls for a fresh blade, a zero-clearance throat plate, and a light scoring pass.
On arcs and cutouts, a down-cut spiral bit keeps the face clean.
Face checking shows up when dry panels take on moisture fast or when faces run across a heater or strong sun.
Seal both sides of parts that will live in variable moisture and keep finish build even.

Jobsite Handling That Pays Off

Lift sheets flat to the saw; dragging a corner scuffs the face.
Carry pairs back-to-back so the faces protect each other.
Mark the A or B face so it stays out during assembly.
On sheathing day, stage stacks near the work and strap the bundle between lifts.
Keep the stack under a cover with air flow on all sides.

Finishing By Grade

A faces: Sand to 180–220, raise the grain with a damp wipe, sand again, then stain or clear coat.
Poplar and birch faces can blotch under pigment stains; a washcoat fixes that.
B faces: Fill light patch witness lines, spot prime repairs, then shoot a bonding primer.
C and D faces: Save these for paint behind built-ins, backer panels, and structural layers.
A stain on a C or D face brings knots and repairs to the front, which is rarely the goal.

PS Standards In Plain Terms

North American structural plywood follows PS 1 and PS 2.
PS 1 sets rules for plywood layups and veneer grades.
PS 2 is a performance path that verifies strength and stiffness.
Both feed the span ratings and stamp lines you see at the yard under the APA mark.

Cost Savers Without Regrets

Pick the cheapest face that still fits the finish.
If a cabinet side sits against a wall, a BC panel often makes sense.
Reserve AA or A-1 for doors, drawer fronts, and panels that sit at eye level.
On a roof or wall, the span rating limits are the same across face grades, so an upgraded face won’t make the deck stronger.
Put your budget into the right thickness, spacing, fasteners, and a solid weather barrier.