Lots of plywood at Home Depot have the letters RTD in the title, with no further detail. Many of these have multiple user questions of the form "What does RTD mean?" Answers seem to be split 50/50 between what it actually means though. On the one hand are those who think RTD stands for the manufacturing process. Almost all of these answers (and others on the internet) seem suspiciously close to this wording on theplywood.com which makes me suspect that a single source from 2017 has been repeated over and over on the internet enough times that it's being accepted as infallible.
Example:
RTD refers to the method used to manufacture the plywood. This is, essentially, next generation CDX plywood which is manufactured with a quality control system using RTDs (Resistance Temperature Detectors) to maintain correct temperature during the bonding process. This process helps ensure complete bonding of the layers to minimize delamination.
On the other hand are those who think RTD just means it's "rated," here's an example:
RTD is an abbreviation for RaTeD. Yes in the manufacture of plywood the use of Resistance Temperature Detectors is normal to ensure delamination does not occur later on. But this generally applies to all plywood manufacturing, not just to those listed as RTD.
So which is it?
Best Answer
The “RTD” in RTD plywood stands for Resistance Temperature Detector.
You have your normal CDX plywood for exterior sheathing. This plywood is made to function better outdoors - deals with temp changes and moisture better than other forms of plywood. The main difference between this and your normal plywood is that you will have less delamination.
Now RTD takes the CDX a step further and has controls for the amount of glue used, types of glue, and most importantly making sure the bonding temperature is highly accurate for each layer of veneer.
This will result in less delamination for CDX and makes it superior for outdoor use.
The grading difference between the two most common types of plywood can be summed up in that CDX is Exposure 1 rated (which means that water hitting it won't hurt it) and RDT is purely Exterior rated (yes I know CDX is still used as exterior sheathing in some places). Being exterior rated means it will withstand constant exposure to temp changes and moisture.
Depending on the price difference we may buy CDX for subfloors but RDT is used for everything on exterior, including walls and roof.