Occasionally, oriented strand board (OSB) panels may exhibit thickness swell after being exposed to jobsite moisture/water during project construction. The severity of the condition generally depends on the amount of water and the length of exposure. One visible result of this exposure is an increased panel thickness at the 4’ panel end (as those edges absorb moisture more easily). Oftentimes, adjacent panels may have expanded into each other creating a slight ridging effect along the 4’ joint.
As referenced in OSB-4004 and APA Subfloor Preparation Guide (V440), builders may find it advantageous to remove this slight ridging by sanding along the panel edges. Lightly sanding the panel edges to remove the ridged area is common field practice.
Sanding of the thickened area should be delayed until the panels have dried. In many cases, the swelling will decrease (or go away) as the panel dries. The best scenario for interior drying is established when the roof and windows are installed, and the HVAC system is properly operating.