RTD on a plywood stamp means the panel is rated sheathing manufactured under tightly controlled temperature to ensure strong, weather‑resistant bonds.
Walk down the lumber aisle and you will spot stamps full of letters and numbers. Among them, “RTD” often raises eyebrows. Is it a special grade? Does it signal water resistance? This guide clears the fog in plain language, equipping you to pick the right sheet the next time you load a cart.
Decoding The RTD Stamp
Rated Sheathing In Plain Terms
According to the Engineered Wood Association, “RTD” is shorthand for Rated Sheathing. The full phrase “RTD Sheathing” simply tells buyers the panel meets published structural and span requirements for roofs, walls, or sub‑floors. The letters are not a standalone performance grade such as “CDX” or “Marine.”
Temperature‑Controlled Bonding
Many mills also use resistance temperature detectors during pressing to keep adhesive heat inside a tight range. By holding the core at the sweet spot, veneers fuse with fewer voids, lowering the odds of delamination once the panel faces rain or high humidity.
| Property | RTD Plywood | CDX Plywood / OSB |
|---|---|---|
| Meaning Of Letters | Rated Sheathing; temp‑controlled assembly | CDX = C & D veneer faces, Exterior glue; OSB = Oriented Strand Board |
| Typical Use | Roof & wall panels in stick‑frame builds | Roof, wall, sub‑floor when code allows |
| Surface Smoothness | Often pre‑sand for quicker finishing | Rougher; sanding added on site if needed |
Key Performance Specs Of RTD Panels
Strength And Load Ratings
Every bundle leaves the mill with an APA stamp showing the maximum on‑center spacing for rafters or studs. A common 15/32 inch RTD sheet carries a 32/16 span mark, safe up to 32 inches on a roof or 16 inches on a floor.
Moisture And Delamination Resistance
Plywood sold as RTD uses waterproof phenolic glue — the same adhesive found in Exposure 1 or “exterior” panels. When installed promptly and covered within the build schedule, it tolerates wet/dry cycles that often wreck interior‑grade boards.
Fire Safety Traits
Standard softwood faces char at a predictable rate, buying evacuation time during a blaze. Where stricter ratings are required, designers add fire‑retardant treatments or double layers rather than switch to a unique RTD variant.
Taking A Closer Look: RTD Vs CDX Sheathing
On store shelves, CDX and RTD often sit side by side. The label is not the only difference, so here are the real deciding factors:
- Bond line control. RTD presses rely on electronic sensors, whereas CDX lines may depend on manual checks.
- Surface prep. Many RTD mills sand faces to save finishing time. CDX sheets usually need an orbital sander before paint or stain.
- Cost. RTD fetches a slight premium — a 23/32 inch southern‑yellow‑pine RTD panel recently ran about five dollars above the same thickness CDX at a big‑box store.
Choosing RTD Plywood For Your Project
Walls And Roofs On Stick‑Frame Homes
When local building code asks for Rated Sheathing or lists specific span tables, RTD hits the mark without extra engineering paperwork. Framers appreciate the smoother faces when they plan to roll on liquid house‑wrap or attach peel‑and‑stick membranes.
Cabins, Sheds, And Tiny Homes
Small‑footprint structures see large swings in humidity. The tighter glue‑line control of RTD reduces edge swelling over the seasons, helping exterior paint hold up longer.
Jobsite Schedules Fighting The Weather
If forecasts threaten rain before underlayment goes down, RTD earns its keep. Panels stay flatter after a downpour compared with bargain OSB, shortening the time spent sanding roof edges flush before shingles.
Budget Reality Check
Pricing trends move weekly. Always compare the square‑foot cost of RTD, CDX, and exterior OSB at the same thickness. A small difference can wash out if you account for reduced prep and fewer callbacks.
| Thickness (in.) | Common Span Rating | APA Bond Class |
|---|---|---|
| 15/32 | 32/16 roof / floor | Exposure 1 |
| 19/32 | 40/20 roof / floor | Exposure 1 |
| 23/32 | 48/24 roof / floor | Exposure 1 |
Handling, Cutting, And Installing RTD Boards
Storage And Conditioning
Keep bundles off bare soil with stickers under the skid. Slip a tarp over the stack but leave the sides open for airflow. Let panels acclimate on site for at least 24 hours so they match ambient moisture before nailing.
Fastener Choice And Spacing
Galvanized nails or exterior screws spaced 6 inches on panel edges and 12 inches in the field keep RTD sheets tight to framing. Follow the layout printed on the face if provided, and back off the driver clutch to avoid crushing surface fibers.
Expansion Gaps
Leave a 1/8‑inch gap at all panel edges. A roof‑sheathing spacer or a 10‑penny nail shank works as a quick gauge.
Keeping RTD Plywood In Top Shape & Looking At Alternatives
Sealants And Finishes
Exterior acrylic primer and paint lock out sunlight and moisture. For deck sub‑floors that will receive a waterproof membrane, roll on a coat of liquid rubber or asphalt emulsion to the underside before install.
Competing Panel Choices
- CDX: Widely stocked, slightly cheaper, but can swell more along edges.
- Exposure‑rated OSB: Consistent thickness and spans but slower to dry after soaking.
- Marine‑grade: Uses defect‑free hardwood veneers and gap‑free cores for prolonged water exposure.
Reading The Full APA Trademark
An RTD panel carries more than three letters. It also lists wood species group, panel thickness, mill number, and the “PS 1‑09” or “PS 2‑18” manufacturing standard. APA explains the rating system clearly for first‑time buyers.
Quick Reference Takeaways
- RTD stands for Rated Sheathing and signals compliance with APA structural charts.
- Mills monitor glue‑line temperature with sensors, aiming for stronger bonds.
- When budgets allow, RTD offers smoother faces and tighter moisture control than basic CDX.
- Always look beyond the letters; thickness, span rating, and bond class drive performance in real builds.