Structural Support and Your Home
Structural support in a home transfers the weight of the roof, floors and walls safely through beams, bearing walls, columns and footings to the foundation and supporting soil. Any changes or modifications to your homes structure will typically require a design and building permit.
How Structural Support Works in a Home
A home is designed so that structural loads are transferred safely from the roof and upper floors down to the foundation and supporting soil. This continuous path is often referred to as the load path. Roof loads, floor loads and the weight of the building itself must all be carried by properly designed structural components.
Depending on the construction of the home, these loads may be carried by load-bearing walls, beams, columns, floor joists and roof framing. Beams can transfer loads to columns or supporting walls, while columns carry concentrated loads downward to properly sized footings. The foundation then distributes these loads to the soil beneath the building.
Removing or Modifying Load-Bearing Walls
Open-concept renovations often involve removing or modifying interior walls, but a wall should never be removed until it has been determined whether it forms part of the home's structural support system. A load-bearing wall may support floor joists, roof framing, another wall above, or a combination of these loads.
When a load-bearing wall is removed, the load it was carrying does not disappear. It must be transferred to another properly designed structural component, commonly a beam supported by walls or columns. Those concentrated loads must then continue downward through the building to suitable footings and ultimately the supporting soil.
Looking at the framing direction of floor joists, the location of beams and columns in the basement, and the construction of the roof can provide useful clues about whether a wall may be load-bearing. However, renovations, additions and engineered framing systems can make the load path less obvious than it appears.
Structural alterations may require a building permit and, depending on the work, drawings or specifications prepared by a qualified designer or professional engineer. Before removing or substantially modifying a wall that may be structural, the proposed changes should be properly evaluated and designed for the loads involved.
Beams, Columns, Footings & Foundations
Beams and columns are important parts of a home's structural support system. A beam carries loads from floor joists, walls or other structural components and transfers those loads to supporting walls or columns. Columns then carry concentrated loads downward toward the foundation.
In many basements, the main beam is supported by steel columns. Each column should transfer its load to a properly sized footing beneath the basement floor. The concrete floor itself is generally not intended to support a concentrated structural load unless it was specifically designed for that purpose.
Foundations and footings perform another critical job: they distribute the weight of the building over an area of soil capable of supporting it. The required size and design depend on the loads being carried and the conditions of the supporting soil. Poor soil conditions, inadequate footings or improper alterations to the support system can contribute to settlement and movement.
Structural support is therefore more than simply installing a beam or post. There must be a continuous load path from the supported structure above, through the beam and columns, to adequate footings and ultimately the soil below.
Roof Trusses, Headers & Other Structural Components
The roof is another major part of a home's structural support system. Roof loads include the weight of the roofing materials and framing as well as temporary loads such as snow. These loads must be transferred through the roof structure to supporting walls and ultimately down to the foundation.
Many newer homes use engineered roof trusses rather than conventional rafters. Trusses are designed as complete structural units, with the individual top chords, bottom chords, web members and connection plates working together. In many truss-roof homes, much of the roof load is transferred to the exterior walls, although the actual design of the truss system determines where support is required.
A common concern during renovations is cutting, drilling or removing portions of a roof truss to make room for ductwork, plumbing, attic access or additional living space. Because each component forms part of the engineered system, a truss should not be altered without an appropriate engineered repair or design.
Conventional roof framing can also rely on structural support from ridge beams, bearing walls, posts and other framing members. Headers over large openings must be capable of transferring loads around doors, windows and other openings to suitable supports below.
During a home inspection, altered or damaged roof framing deserves particular attention. Cut trusses, missing members, inadequate supports and poorly executed renovations can change the intended load path and may require further evaluation.
Structural Problems Found During Home Inspections
Structural problems are sometimes obvious, but many are discovered only by following the load path through the home. During a home inspection, I look for signs that structural components have been altered, damaged or installed in a way that may prevent loads from being properly transferred to the foundation.
Common concerns can include cut or damaged floor joists, altered roof trusses, improperly supported beams, missing or inadequate columns, undersized headers, movement in foundation walls and renovations where load-bearing walls have been removed or modified. Previous renovations are particularly important because structural changes may be concealed behind finished walls and ceilings.
Cracks and movement do not automatically mean that a home has a serious structural problem. Buildings can move and materials can crack for many reasons. The location, direction and extent of movement, along with the surrounding construction, must be considered before determining whether further investigation is warranted.
A professional home inspection can identify visible conditions that may indicate a structural concern. When a condition requires calculations, structural design or a determination of load-carrying capacity, further evaluation by a qualified designer or professional engineer may be recommended.
With more than 20 years of experience and over 9,000 professional home inspections, I have inspected a wide variety of residential construction and structural conditions. Understanding how the components