How close a building sits to a lot line or another building drives how fire-resistant its exterior walls must be, and how much glass they can have. IBC 705 ties everything to the fire separation distance — the distance from the exterior wall to the lot line, centerline of a street, or an imaginary line between buildings. Shorter distances require higher wall ratings and sharply limit allowable openings (windows and doors) per Table 705.8. Projections like eaves and balconies, and parapets, have their own rules.
The common mistake is a wall with too much glazing for its fire separation distance, or unprotected openings where the distance requires protection — often discovered when the site plan and the elevations are checked together.
Reviewers cross-reference the fire separation distance from the site plan against the wall rating and the allowable-opening percentage in the elevations. It's a classic coordination gap, because the architect sizing the windows and the one setting the building on the site aren't always looking at the same constraint.
This guide describes the model code for general understanding and is not a substitute for the adopted code and amendments enforced by your local authority having jurisdiction. Verify all figures against your jurisdiction's codes of record.