Re-Decking 101: When Do You Need New Roof Decking in Minnesota?
Asphalt shingles are installed using pneumatic nail guns that shoot coil roofing nails through the shingle and into the sheathing or deck boards underneath. If you have sheathing, OSB or plywood, you more than likely will not have to install any new sheathing unless the OSB or plywood is in bad condition.
The need to “Re-Deck” usually comes into play when deck boards are what make up your roof deck. The problem lies in the “gapping” between those boards, as seen below:
If one shingled a roof that had deck boards with large gaps in between them the likelihood of shingle “blow-off” substantially increases! If the nails meant to attach the shingles to the decking lands within these gaps then there is nothing attaching your shingle to the deck except for the tar strip that exists on the back or top of every shingle made. Unfortunately, this tar strip is not intended to hold off large wind gusts and if the shingled isn’t properly affixed to the decking it will eventually blow off.
This fact became very evident and as a result the MN Building Code made it a requirement that any gaps over ½” wide be either filled in or re-decked. Fast forward a few years and the Code deferred to manufactures installation instructions which then evolved, to protect their warranty, into requiring that any gaps over ¼” gaps be filled in or re-decked. Unfortunately, this has become a costly addition to most roofing projects for the consumer.
On a positive note, in the event one is replacing their roof due to an insurance claim, it is commonly written into policies that “Code Upgrades” are a “coverable” cost that they will pay for. Make sure to check your policy for this type of language.
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