They are also manufactured by different methods. Plywood is made from thin veneer layers of wood that are peeled from a spinning log and laminated together. There is always an odd number of layers and each layer is glued with the grain at right angles to the one underneath it, for strength and stability of the material. OSB starts with rectangular wood strand pieces that are arranged in cross-oriented layers which are pressed and heat-cured.



   Here’s the pros and cons of each material:

PLYWOOD

Pro

  1. Both off-gas formaldehyde, but plywood produces less because not as much glue is used to manufacture it. While formaldehyde is primarily an irritant, that can cause eye and throat irritation, coughing, and allergic reactions, the EPA states that “long-term exposure to high levels has been associated with cancer in humans.” See our blog post How can formaldehyde gas in the house be a problem?” for more information on this issue.

  2. Plywood is slightly stiffer, by about 10%, than comparable OSB.

  3. Better at holding nails and screws.

Con

  1. Plywood tends to delaminate as it ages in exterior applications, especially at the base of siding in the high humidity of Florida.

  2. More expensive than OSB.

OSB

Pro

  1. OSB is considered a “greener” material, because it can be made from small, younger and farmed trees.

  2. OSB is more structurally uniform, without the soft spots at gaps in the veneer layers of plywood.

  3. Can be manufactured in larger sheets.

Con

  1. Swells more when wet, especially at the edges of the panel. Stays somewhat swollen after drying.

  2. About 15% heavier than plywood.


While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here. ©2015 - McGarry and Madsen Inspection.

 
 

How to Look

at a House


A blog with answers
to your questions about
HOME INSPECTION
and HOME MAINTENANCE


More blog posts about roofing:

  1. I’m buying a ‘50s house with a “gravel” roof. Is the roof going to be a problem.

  2. Are roof trusses better than roof rafters (stick framing)?

  3. Why is the attic painted silver?

  4. Should I buy a house that needs a new roof?

  5. What is the cost difference between asphalt shingle and metal roofing?

  6. What is the minimum pitch of an asphalt shingle roof?

  7. What’s the difference between a gable roof and a hip roof?

  8. What do you look for when you inspect a roof?

  9. What is roof pitch?

  10. What’s the difference between a roof inspection and a roofing estimate?

  11. What are the most common problems with older houses?

  12. I saw some staining on the ceiling. Do you think the roof is okay?

  13. What is a “cool roof”?

  14. Can metal roofing be used on a slow slope/pitch roof?

  15. How many layers of roofing are allowed on a home?

  16. How can I be sure my roofing contractor got a permit?

  17. What is the difference between galvanized and galvalume metal roofing?

  18. What is an H-clip?

  19. Why is a popped nail in a shingle roof a problem? How do I fix it?


More blog posts on related subjects:

  1. How can I tell if a house has insulation?

  2. What are the warning signs of a dangerous deck?

  3. Does it make sense to buy an older mobile home and remodel it?

  4. How do you determine when the house was built?

  5. Should I buy a fixer-upper?

  6. How do I remove cigarette odor in a house?

  7. The house has asbestos siding. What should I do?

  8. How do I get insurance if my home can’t pass a 4-point inspection?

  9. There’s an old fuel oil tank underground in the yard. Is it a problem?

  10. What is “knob and tube” wiring?

  11. Why do the floors slope in this old house?

  12. The garage has been converted to a family room. Is that alright?

  13. What is the minimum pitch for a metal roof?

  14. What does “lack of tab adhesion” in an asphalt shingle roof mean?

  15. What is a TPO roof?

  16. When is a railing required for the edge of a deck or porch?

  17. What is the average lifespan of plywood siding?

  18. What is Z-flashing?

  19. What is the difference between a clip, single wrap, and double wrap for the wind mitigation form?

  20. What is a “continuous load path”?

  21. What are the pros and cons of aluminum siding?

Plywood

OSB

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