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Defines exceptions for various additions and accessory structures by size and location, specifying overexcavation or foundation letter requirements. Provides alternate construction methods for slab-on-grade and raised foundations, including specified excavation, reinforcement, vapor retarder, damp proofing, concrete strength, and compaction/inspection documentation, with a noted limit for projects requiring grading plans and permits.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":40,"@type":76,"position":81},"https://docshare.wps.com/document/research-report/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/foundation-requirements-for-residential-projects-and-accessory-structures-policy-exceptions-and-foundation-construction-requirements/648255/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/foundation-requirements-for-residential-projects-and-accessory-structures-policy-exceptions-and-foundation-construction-requirements/648255.png","ImageObject",300,407,{"name":92,"@type":93},"Valentina","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-30","2026-10-23",true,{"@type":102,"interactionType":103,"userInteractionCount":81},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"When is a geotechnical investigation report required under the 2019 CRC and CBC?","Question",{"text":112,"@type":113},"A geotechnical investigation report is required for all residential and accessory structure projects except the listed exceptions. The document ties requirements to CRC Section R401.4 and CBC Section 1803.5.11, including seismic category and potential expansive soil conditions.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"What are the exception criteria for one-story room additions to single family dwellings?",{"text":117,"@type":113},"Exceptions depend on whether the addition is located in a liquefaction area and its individual area size limits (up to 1,200 square feet in non-liquefaction areas; up to 500 square feet in liquefaction areas). Larger additions within liquefaction areas require specified overexcavation.",{"name":119,"@type":110,"acceptedAnswer":120},"What alternate foundation methods are required when geotechnical investigation is not provided?",{"text":121,"@type":113},"For slab-on-grade, the policy specifies excavation/recompaction, compaction reporting, damp proofing and base/pre-saturation, a reinforced slab with vapor retarder, and tying into continuous footings. For raised foundation construction, it requires a continuous perimeter foundation with defined reinforcement and minimum embedment for interior piers, plus concrete strength and documentation conditions.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},648255,1792792858,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":39,"category_name":40,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":81,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":81,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":129,"read_time":39},13056703020460,"https://ap-avatar.wpscdn.com/avatar/be000253dac470eee5d?_k=1778207105932848923","EFFECTIVE DATE:June 22,2020  \n# BACKGROUND:\n\n1.Section R401.4 of 2019 California Residential Code(CRC)requires a soils test to determine the soil'scharacteristics if expansive soils are likely to be present.  \n2.Section 1803.5.11 of 2019 California Building Code(CBC)requires a“geotechnical investigation”for anystructure determined to be in Seismic Design Category C,D,Eor Fin accordance with Section 1613.  \n3.Exception to Section 1803.2 states,\"The building official shallbe permitted to waive the requirement for ageotechnical investigation where satisfactory data from adjacent areas is available that demonstrates aninvestigation is not necessary for any of the conditions in Sections 1803.5.1 through 1803.5.6 and Sections1803.5.10 and 1803.5.11.”  \n# POLICY:\n\nSince majority of the County of Orange is located in Seismic Design Category Dand due to the presence of expansivesoil in some county areas,we have developed the following policy to comply with the 2019 CRC and CBC.  \nGeotechnical investigation report is required for all projects except as prescribed below.  \n# Exception:\n\n1.One storv room addition(s)to a single family dwelling up to 1,200 sauare feet of individual areas if it isNOT located in liquefaction area.  \n2.One story room addition(s)to a single family dwelling up to 500 sauare feet of individual areas if it ISlocated in liquefaction area.  \n3.(a)Room addition(s)to a single family dwelling larger than 500 square feet of individual areas but notmore than 1,200 square feet located in liquefaction area shall require 4'ofoverexcavation.  \n(b)Detached accessory structure or single family dwelling larger than 500 square feet but not more than  \n1,200 square feet located in liquefaction area shall require 4'overexcavation.  \n4.One story detached accessory structure up to 1,200 square feet located in non-liquefaction area.One story detached accessory structure up to 500 square feet located in liquefaction area.  \n5.Second story addition above existing first floor within the footprint of existing dwelling.  \nExcepted projects as described in item 5 above shall provide a letter from a California Licensed GeotechnicalEngineer or Civil Engineer practicing soil engineering stating the condition of existing foundation and supporting  \nPublicWorks  \n# Foundation Requirements for Residential Projectsand Accessory Structures\n\nsubgrade soils and providing foundation recommendations due to the added vertical and lateral loads from theproposed second story addition.Excepted projects as described above item 1 through 4 shallfollow thealternate method as outlined below in lieu of geotechnical investigation report provided minimum foundationclearance from slope is maintained based on Section 1808.7 or R403.1.7 or County of Orange Grading Code,whichever is more restrictive:  \n# For slab on grade construction\n\n●  Scarify top 12”or recompact 4'overexcavation prior to trenching for the utilityand/or foundation.90%compaction report is required at the time of foundationinspection.Damp proofing,base course and pre-saturation are required.  \n·  Provide 5”slab on grade reinforced with \\#4 at 18”on centers each way over 4”base of Y”or larger clean aggregate with 10 mil vapor retarder in direct contactwith concrete.Slab shall be tied-in to continuous 12“wide X 24”(minimumembedment into firm soil)foundation.  \n·  Continuous foundation must be reinforced with 2\\#5(or 3\\#4)top and bottom.See attached slab on grade foundation detail'A'for additional information.  \n## B.     For raised foundation construction:\n\n·     Provide continuous foundation with 12”wide X24”(minimum embedment intofirm soll)around the perimeter of the addition.  \n·    Continuous foundation must be reinforced with 2\\#5(or 3\\#4)top and bottom.  \n·     Provide 18”(minimum embedment)for all interior pier footing.  \nSee attached raised floor foundation detail‘B'for additional information.  \nNote:All concrete shallbe fc'=4,500 psi(minimum)with type V cement maximum water cement ratio of  ","cbCaihPWcT5R2sOU","https://ap.wps.com/l/cbCaihPWcT5R2sOU","pdf",648144,"English","# BACKGROUND\n# POLICY\n# Exception\n## For slab on grade construction\n## For raised foundation construction\n# Approved by\n# Foundation Details","[{\"question\":\"When is a geotechnical investigation report required under the 2019 CRC and CBC?\",\"answer\":\"A geotechnical investigation report is required for all residential and accessory structure projects except the listed exceptions. The document ties requirements to CRC Section R401.4 and CBC Section 1803.5.11, including seismic category and potential expansive soil conditions.\"},{\"question\":\"What are the exception criteria for one-story room additions to single family dwellings?\",\"answer\":\"Exceptions depend on whether the addition is located in a liquefaction area and its individual area size limits (up to 1,200 square feet in non-liquefaction areas; up to 500 square feet in liquefaction areas). Larger additions within liquefaction areas require specified overexcavation.\"},{\"question\":\"What alternate foundation methods are required when geotechnical investigation is not provided?\",\"answer\":\"For slab-on-grade, the policy specifies excavation/recompaction, compaction reporting, damp proofing and base/pre-saturation, a reinforced slab with vapor retarder, and tying into continuous footings. For raised foundation construction, it requires a continuous perimeter foundation with defined reinforcement and minimum embedment for interior piers, plus concrete strength and documentation conditions.\"}]","Foundation Requirements for Residential Projects and Accessory Structures - Policy Exceptions and Foundation Construction Requirements | PDF"]