Page 632 - 2018 National Home Improvement

2018 National Home Improvement Estimator, All Rights Reserved Page 505

Think about earthquake resistance when you add living space to a home. Removing any wall bracing will
increase the risk earthquake damage. Any increase in the living area, the roof area or the floor area will
add extra weight and thus increase earthquake loading.

Horizontal additions will require extra bracing around new wall penetrations - and possibly extra bracing
of interior walls. Check to be sure that bracing and anchors in the completed wall comply with the IRC.

Tie the addition to the existing house with steel straps. Ideally, the joint between old and new should be
as secure as though both sections were built at the same time. You can't join the old and new
foundations as though both were poured at the same time. But you can strap the new top plates and sill
plates securely to existing top plates and sill plates. If possible, connect structural sheathing panels
across the joint between old and new construction.

A vertical addition will more than double the gravity and lateral loads on walls of the floor below. That
usually means you'll have to bring the entire home into compliance with the current code. In theory, you
could probably meet IRC requirements when adding a second story. But it's usually more practical to
prepare a plan that meets design requirements of the International Building Code.