Originally Posted By: dvalley
This post was automatically imported from our archived forum.
H clips are not required by code. The purpose of H-clips is to reduce the effective spacing of the roof rafters and stiffen the roof deck, and they are an alternative to utilizing solid blocking.
The clips are slipped over the edges of the plywood and OSB sheathing between the rafters to keep the edge of each sheet aligned with its neighbor, which reduces the likelihood of warping. When you place the H-clip at the halfway point (12") between the rafters, the plywood stiffens. As a result the roof shingles nail easier and the roof will remain straighter over time (no sags with accumulated load). H-clips can also strengthen any horizontal seams between rows.
H clips are an option for Carpenters. Some utilize these at all seams to leave room for the sheathing to expand and contract with the change in moisture/temperature and others utilize these to replace any blocking at the edge supports.
Here is a table for the spacing requirements of supports on the underside of sheathing as you described...
Massachusetts Certified Home Inspections
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