The structural characteristics of both are equivalent, and it’s true that they can be used interchangeably.
However, there are differences that roofers and homeowner’s should be aware of when constructing a
new roof or starting a roof repair.
The biggest difference between the two is how they react when exposed to large amounts of moisture
over extended time periods. With the exception of projects in very arid regions like the Southwest,
roofing panels are routinely covered with rain, snow, and ice during construction delays. It’s here that
CDX has the edge.
- When CDX gets wet, it tends to swell consistently across the sheet. It returns to its normal
dimensions and dries out relatively quickly, and the swelling is usually not enough to affect roof
finishes.
- In comparison, OSB performs like a sponge & takes longer to dry out. When used for roofing,
this tendency to hold moisture means it can degrade faster than CDX when exposed to chronic
leaks or on soffits. - OSB also tends to swell along the edges when wet. Those edges stay swollen even after the
material has dried out, sometimes causing the roof sheathing to show through the roofing
materials.
Aside from moisture protection, CDX is approximately 15% to 19% lighter than OSB. While the
additional weight of OSB does not mean increased strength, it does mean that it is heavier to handle on
the job. In addition, OSB’s higher weight means higher thermal conductivity than CDX.
- The biggest feature for CDX might actually be the homeowners’ perception of higher quality.
Unlike OSB, CDX actually looks like wood, and is familiar to customers.
At Integrity Roofing & Construction, we only use CDX for all of our roofing projects. Our customers
can be assured that they are getting top of the line products and service.