Home Foundation Repair: The Basics

Image Gallery “Green Restorations” has practical suggestions for homeowners and contractors, and is unique in that it addresses both green building and preservation in chorus. COVER: NEW SOCIETY PUBLISHERS

The following is an excerpt from Green Restorations by Aaron Lubeck (New Society Publishers, 2010). Room by room and system by system, Lubeck discusses the steps for restoring historic buildings using sustainable practices and green building techniques, including the massive financial incentives of residential historic tax credits. This excerpt is from Chapter 9, “Structural.” 

Old homes were designed with structural logic much different from today’s. New homes are designed with strict adherence to the lumber sizing and spans listed in the building code. Old homes were built with common sense, logic and feel. Most homes built between 1880 and 1930 were built on inferior footing. These old footings offer foundation walls little support, which then may support often overspanned joists and girders. Historic home foundations were subject to improper load calculation, inferior footings and substandard mortar. Old framing systems can be vastly over- or under-built. Each is a potential point of failure. It is crucial to understand such risks during a rehabilitation.

Structural failure is a phrase that scares the average Joe. Unfortunately, most structures subject to a century of seasonal expansions, water, humans, animals, deferred maintenance, improper storage and poor footings are destined to have some structural issues that need to be addressed. Combine construction flaws, time and the dreadful soil of central North Carolina, and it’s rare that I see an old home that doesn’t have some sort of structural problem. Structural issues can all be addressed, however, and most are simple (but laborious) fixes.

The structure of a building is formed by foundation and framing. The foundation is a structure that transfers loads to earth. It keeps earth and wood apart. The concept is simple: A house is heavy, so a foundation spreads that load over an area suitable for the earth to handle. The average two-story Queen Anne Victorian weighs between 30 and 60 tons, enough for three 20-ton jacks to support the whole thing (theoretically, but don’t try it at home).

The framing forms the structure, defines separate rooms and carries the floor, wall and roof loads to the foundation.

I’ll discuss the most common foundation and framing techniques, common problems and how each is typically fixed. I’ll also discuss basic preservation and sustainability issues related to the structure.