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TOPIC: Screws

screw size in 7/16" OSB

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Some manufacturers recommend a #14 screw for exposed screws fastening metal to 7/16" OSB. Is there any national building code that addresses this topic? thanks in advance...
Guest User

4/21/2005
Not to my knowledge. Generally they rely on testings and product approvals. A broad base answer is difficult as there are many types of roof assemblies possible, many differant occupancies and certain parts of the country like Florida and Texas require wind uplift properties in the code. In residential you must ventilate and use an underlayment as example. We have had our systems tested by our screw supplier and recommend a minimum of a #10 screw in plywood and a #12 screw in OSB board. If the screw is overdriven and spun then it does not matter what size it is but definitely a standard #9 washered screw is not big enough.
Allan Reid
Dura-Loc Roofing Systems, Inc.

4/21/2005
I have been told by contractors who learned the hard way that OSB will not hold screws that fasten vertical panels. Are there manufacturers who specify OSB as suitable for fastening to?
Guest User

4/21/2005
This is too complex an answer as there are too many factors. Basically the best way to determine is to ask to see the manufacturers product approval report which in the US today is generally issued by The International Code Council which will state that the product has been tested and approved to the building code which includes wind uplift requirements and will dictate how to install the product with what fasteners. Our products as example went through the UL580 and 1897 wind uplift tests for the severe weather areas of Florida and Texas and require a minimum #10 screw but it was tested with strapping fastened into the rafters as we can not generally trust that the sheathing is of proper quality and attachment to ensure long term performance. A sheathing grade plywood will hold screws better than an OSB board of similar thickness, probably 2-3 times. Further if one was to use improper screws that were too long or undersized, then it will have a bearing on the life of the attachment. This is why those manufacturers that do approve of application to OSB recommend a minimum #12 or #14 screw.
Allan Reid
Dura-Loc Roofing Systems, Inc.

4/22/2005
To answer my own question, I just talked to the manufacturer's dealer/installer about the installation. The key to the method lies in the screw's design, which he says was developed for application of the product (Fabral) to plywood and OSB. Problems associated with fastening he has seen derive from the use of too fine a thread screw thread.
Guest User

4/22/2005
Asking the manufacturer or their dealers is always a good idea.
Allan Reid
Dura-Loc Roofing Systems, Inc.

4/25/2005