A shingle offset is a method used by roofing contractors to prevent butting joints between shingles and is required by many shingle manufacturers to ensure a properly installed roofing system.
Instead of placing shingles evenly one on top of the other, the singles are offset by a couple of inches.
Each shingle manufacturer has a different requirement to what degree offset, but every manufacturer has it.
Installing shingles without an offset is jeopardous because the connected joints form closely intersecting channels for wind and rain to travel.
Instead of rain evenly running down the face of your roof, these channels will act as funnels for water to run down, accelerating erosion of the asphalt granules that serve to protect your home from external elements.
Also, the shingles’ channels caused by butting joints will be more susceptible to lifting during strong wind events, leading to shingle loss, broken seals, and rippled surfaces.
6" shingle Offset
How to know if your contractor is offsetting your shingles:
Offset shingles will be applied diagonally across each facet of your roof.
If you notice your contractor applying shingles vertically upward, they are racking your shingles; although this is a quicker way to install shingles without the hassle of frequent relocation of the application area, it puts your home at risk and only serves to benefit the contractors time.
Don’t rob yourself of knowledge! Here are some more helpful articles to improve your basic knowledge of your roof.