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Glossary

Common Earthquake and Seismic Retrofitting Glossary Terms

The following are commonly used earthquake and seismic retrofitting terms.

For more about the science of earthquakes and earthquake terms visit USGS Glossary.

Adequately braced - Wood framed cripple walls are considered to be adequately braced if they have been strengthened in accordance with the provisions of Appendix Chapter A3 of the California Existing Building Code.

Adhesive anchor - Adhesive anchors consist of a steel threaded rod or rebar and a chemical adhesive that are inserted into a hole that has been drilled into the concrete or masonry substrate. Adhesive anchors generally use epoxy adhesives.

Anchor bolt - Steel rod threaded on one end that is fixed in concrete (or masonry) to attach a structure to its foundation. (Anchor bolts in new construction are placed in concrete before it cures or hardens. Anchor bolts in existing construction are typically adhesive or expansion anchors).

Applicant - Someone who has applied to become a Participating Homeowner in a CRMP retrofit program. Learn more about our seismic retrofit programs.

Application - The information provided by seismic retrofit grant applicants to the California Residential Mitigation Program (CRMP). Providing this information is a requirement in order for a homeowner to be considered for participation in a CRMP grant program.

Bearing wall - A partition (wall) that supports any vertical load in addition to its own weight.

CEA Brace + Bolt Program - A seismic retrofit grant program of the California Earthquake Authority (CEA), only available to qualifying policyholders invited to participate. Learn more about the CEA Brace + Bolt program.

Cement - A fine gray powder that produces a bonding paste when mixed with water.

Chapter A3 - Prescriptive provisions for seismic strengthening of cripple walls and sill plate anchorage of light, wood-frame residential buildings.

Concrete - A combination of cement, sand, crushed rock, or gravel. It is used for foundations, slabs and sidewalks.

Continuous perimeter foundation - A foundation, typically constructed of concrete or masonry, that is continuous under the exterior walls of a dwelling.

Crawl space - A shallow, unfinished space beneath the first floor of a house without a basement. The crawl space allows ventilation of floor framing and access to pipes and ducts.

Cripple stud - A short stud that is used in a framed timber wall.

Cripple wall - A less than full height wood stud wall extending from the top of the foundation to the underside of the lowest floor framing.

CRMP - California Residential Mitigation Program (CRMP) is a joint-exercise-of-powers entity formed by its members, the California Earthquake Authority, a public instrumentality of the State of California (CEA), and the California Governor’s Office of Emergency Services (Cal OES). CRMP is a legally separate entity from its members.

CRMP-funded EBB program - The original Earthquake Brace + Bolt program funded primarily with funds from the CEA Earthquake Loss Mitigation Fund.

Drywall - Also known as wallboard, gypsum board, plasterboard, and by the trade name Sheetrock (TM), a wall-surfacing material composed of sheets of gypsum plaster sandwiched between a low-grade backing paper and a smooth-finish front surface paper that can be painted.

Earthquake Brace + Bolt Program - The California Residential Mitigation Program (CRMP) offers earthquake retrofit grants to qualified California homeowners in high-risk areas with vulnerable types of houses. CRMP has two retrofit grant programs: Earthquake Brace + Bolt (EBB) and Earthquake Soft-Story (ESS). The EBB program offers grants to qualified homeowners to complete a residential seismic retrofit of houses with a raised foundation. Learn more about EBB retrofits.

Engineered solution - Under California Building Code Chapter A3, an engineered solution is required for cripple walls between 4-feet and 7-feet. An engineered solution is unique to each house.

Expansion anchor (wedge anchor) - A type of anchor that is designed to expand inside the drilled hole in which it is placed; thereby securing itself by the resulting pressure and friction against the sides of the hole.

FEMA-funded EBB program - The Earthquake Brace + Bolt program funded by grants from the Federal Emergency Management Agency.

Foundation - The part of a building or wall that supports the superstructure. Typically made of concrete or masonry in residential construction.

Foundation plate - Used when there is not adequate vertical clearance under a house to properly anchor the mudsill to the foundation with conventional anchor bolts.

Framing clip - A device used to connect wood framing members. Typically used to connect bearing walls to floors and to the roof in residential construction.

General contractor - The contractor who has main responsibility for the construction, improvement, or renovation project under contract, and who is the party signing the prime construction contract for the project.

House - A single-family residential building (one to four dwelling units) meeting the requirements of Section 4.1 of the Program Rules.

House Retrofit Expense - Expenses that a Participating Homeowner incurs in performing seismic retrofit work on a house.

Joist - A framing member that supports a floor or ceiling load in a series of parallel members. Typically a 2x8 (2" by 8") or 2x10 (2" by 10") in residential construction. Lumber sizes are "nominal;" the actual finished lumber size will be less than the size indicated.

LA City Standard Plan No. 1 - A standard plan set available to homeowners and contractors for use as the construction document for the seismic retrofit of a wood frame dwelling. LA City Standard Plan #1, is in accordance with Chapter A3 of the CEBC and is available for download on the Los Angeles Department of Building and Safety website. Check with your local building department to see if they have adopted LA City Standard Plan #1.

Lateral-force resisting system that relies on poles or columns embedded in the ground - Some dwellings are supported on poles or columns embedded in the ground or supported on concrete piers and do not have any perimeter bearing walls. Without walls below the exterior walls of the dwelling, these supporting poles and columns will be required to act as lateral-force-resisting elements during an earthquake. Dwellings supported solely on poles and columns do not qualify for inclusion in the Earthquake Brace + Bolt program. (Poles or columns supporting decks or porches are not part of the lateral-force-resisting system provided there are walls or foundations below the exterior walls of the building.)

Low-slope site - A building site with a natural slope of 10 percent or less.

LSOG - Living space over garage.

Lumber - The product of the sawmill and planing mill by sawing, planing, cutting to length, and grading. 1" stock is sawed to 1" thickness then finished (planed) to final size of 3/4", 5/4" stock finishes out to 1" thickness, and 2" stock finishes out to 1 1/2". Lumber sizes are "nominal;" the actual finished lumber size will be less than the size indicated.

Masonry - Building elements constructed of stone, brick, hollow clay tile, concrete blocks, gypsum blocks, or similar materials, or a combination of them.

Mudsill - The lowest sill of a structure. Typically supported by the foundation in residential construction.

Napa Brace + Bolt program - The FEMA-funded incentive program in Napa.

Nominal dimension - The stated size of lumber, such as 2x4 (2" by 4"). Lumber sizes are "nominal;" the actual finished lumber size will be less than the size indicated.

Participating Contractor - A contractor who has successfully completed the education module and requirements on the website.

Participating Policyholder - A homeowner and CEA policyholder who is participating in the CEA Brace + Bolt program.

Plan Set A - A standard plan set, developed by the Association of Bay Area Government (ABAG), available to homeowners and contractors for use as the construction document for the seismic retrofit of a wood frame dwelling. "Plan Set A" is in accordance with Chapter A3 of the CEBC and is available for download on the Association of Bay Area Government (ABAG) website. Check with your local building department to see if they have adopted Plan Set A.

Planing - The removal of the rough, or excess surface of a wood board.

Post - A timber member set on end to support a wall, beam, or other structural member. Typically a 4x4 (4" by 4") or 6x6 (6" by 6") in residential construction. Lumber sizes are "nominal;" the actual finished lumber size will be less than the size indicated.

Prescriptive standards - This prescriptive provision or plan set is a "blueprint" version of a prescriptive ("cookbook") standard for strengthening homes to better withstand earthquake shaking. When approved by the local building official, the plan set may be used to strengthen older homes without the need for costly site-specific plans and design calculations. This plan set provides a low-cost method to help improve an older home's chances of surviving an earthquake.

Qualifying Building - A building that meets the specifications detailed in the International Building Code ('IEBC”) Appendix Chapter A3, “Prescriptive Provisions for Seismic Strengthening of Cripple Walls and Sill Plate Anchorage of Light Wood-Framed Residential Buildings, as adopted (by reference) into the California Existing Building Code (CEBC) Chapter A3, 2010 Edition.

Raised floor - A wood-framed floor that is supported or raised up off the ground by either wood-framing (such as a cripple wall) or a concrete foundation.

Raised foundation - A house with a raised foundation has an open area between the ground and the first floor (may be referred to as a crawl space). The raised foundation is created by there being short (less than full-story height), wood-framed walls and/or a concrete stem wall between the foundation and the wood-framed first floor.

Rules - Each CRMP seismic retrofit program has unique Program Rules. Learn more about CRMP's Program Rules.

Shear wall - A wall that has been designed and detailed to resist lateral (horizontal) loads on buildings. Often used in buildings to resist earthquake and wind loads.

Sheathing - The wooden covering on the exterior of walls and the roof. Typically made of 1/2" construction-grade plywood; older homes may have shiplap boards or planks.

Siding - The finish covering of the outside wall of a frame building. It may be made of horizontal weatherboards, vertical boards and battens, shingles, or other material.

Sill - Strong, horizontal wood member at the base of a stud wall. Typically a 2x4 (2" by 4") or 2x6 (2" by 6") in residential construction.*

Sill plate - A horizontal member, or board, laid directly on top of the foundation, to which the cripple wall, or first floor of the building, is connected.

Single-family detached dwelling - A free standing residential dwelling that is not structurally attached to a large, multi-family building. For the purposes of this program the dwelling may have one to four family living units.

Soft Story - A structure where the first floor is substantially weaker and more flexible than the stories above it due to large openings in the walls or very tall stories. This type of house typically requires an engineered solution due to cripple walls that are over 4 feet and/or wide garage door openings.

Standard Plan - A plan set that includes specifications, details, and instructions for the installation of foundation anchors and cripple wall bracing (for walls shorter than 4'-0" tall). These plan sets are intended for use without the services of a design professional (architect or engineer). Check with your local building department to see if they have adopted a standard plan for seismic retrofits.

Story - A story is a level part of a building usable by people for living or work, or both. A roof (or a patio roof) is not considered a story. An attic or attic space is considered a story if it has been remodeled for use as a room that can be used by people for living or work, or both. A basement is defined as being beneath the main floor of a house, either completely or partially below ground. A full basement is considered a story. All bi-level and tri-level houses are considered greater than one story.

Stud - Vertical member of a framed wall. Typically a 2x4 (2" by 4") or 2x6 (2" by 6") in residential construction. Lumber sizes are "nominal;" the actual finished lumber size will be less than the size indicated.

Subfloor - Boards or sheet material laid on joists and over which a finish floor is laid.

Supplemental Grant - Funding for income-eligible homeowners that is in addition to the EBB $3,000 retrofit grant is available for qualified homeowners. The EBB grant plus the Supplemental Grant will, in most cases, cover up to 100% of the cost of completing a seismic retrofit for low-income families and will help neighborhoods be more resilient after an earthquake.

Unreinforced masonry - A masonry structure that has no steel reinforcing bars embedded in it. The masonry blocks or bricks are connected by mortar.

Washer (Plate washer) - Square metal plates placed between the nut (head) of an anchor bolt and the wood mudsill. The washer acts to clamp the mudsill securely to the foundation. Note: It is now mandatory to use hot-dipped galvanized 3"x3"x1/4" square plate washers under the anchor bolt nut. Lumber sizes are "nominal;" the actual finished lumber size will be less than the size indicated.