Five Common Footing Types Used in Altadena Residential Construction

Why Footing Choice Matters More Than You Think

A home's foundation is a major investment, often accounting for roughly 18% of the total construction cost, according to industry analysis. This single component dictates the structural integrity and longevity of the entire building, making the initial choice one of the most consequential decisions in any project.

The right footing is not determined by regional trends but by the specific conditions of your property. As technical guidance from material experts confirms, the selection depends primarily on soil strength and the building's load. This is why a one-size-fits-all approach is bound to fail.

While national data from the National Association of Home Builders shows that 89.9% of new homes in the Pacific division use slab foundations, this statistic is only a starting point. Altadena's unique combination of hillside lots and seismic activity demands a more rigorous, site-specific evaluation.

Across technical and engineering resources, five primary footing types are consistently identified for residential construction. Understanding these options is the first step toward a sound structural design.

• Spread Footings: Individual pads of concrete that distribute a column's load over a wide area of soil.
• Continuous Strip Footings: Long strips of concrete that run under load-bearing walls to distribute weight evenly.
• Mat or Raft Footings: A single, large slab that covers the entire footprint of the building, used when soil is weak.
• Pier Footings: Deep, vertical supports that transfer loads to stronger soil or rock far below the surface.
• Stepped or Sloped Footings: Designed for sloped lots, these footings change elevation to match the natural grade of the land.

Choosing correctly requires a deep understanding of geotechnical data and structural engineering principles. At JMB Builders, we treat footing selection as a non-negotiable part of pre-construction planning, ensuring every custom home is founded on a solution engineered for its specific Altadena location.

What the Pacific Region Data Tells Us — And What It Doesn't

The headline number grabs attention: 89.9% of new single-family homes in the Pacific division used slab foundations in 2024, according to NAHB data. That statistic is a starting point for conversation, not a blueprint for every lot in Altadena. Regional trends reflect broad climate patterns where warmer areas favor slabs for affordability and efficiency, but they don’t capture the site-specific engineering required on individual properties.

Altadena’s reality often diverges from the regional average due to its unique topography and soil conditions. Many lots feature significant slopes, expansive clay soils, or sit within hillside overlay zones where local ordinances demand specialized solutions. In these cases, standard slab-on-grade may not meet structural or code requirements, prompting consideration of alternatives that address differential settlement or lateral forces.

This gap between national categorization and actual design decisions highlights a key limitation in how foundation types are commonly reported. One source classifies residential foundations as slab, crawl space, basement, hillside, and pier systems, while another lists slab, raft/mat, spread footing, pier, and basement/crawl space as the primary types. These overlapping but distinct frameworks show why generic labels like “slab” can obscure the specific footing systems — such as spread, stepped, or mat — that engineers actually specify based on geotechnical reports and structural loads.

For JMB Builders, this distinction shapes every pre-construction conversation. During the Discovery & Feasibility and Pre-Construction Planning stages, soil testing and geotechnical review are non-negotiable first steps, especially when building on Altadena’s variable terrain. The builder works with structural engineers to evaluate whether conditions call for conventional spread footings under a slab, a stepped system to follow the grade, a pier foundation to reach stable strata, or a mat system to distribute loads across weak soil. Each decision roots in the same principle: the right footing depends mainly on soil strength and building load, not regional averages. Pacific division data informs the discussion, but site conditions determine the specification.

The Five Footing Types JMB Builders Evaluates During Pre-Construction

Every Altadena lot tells a different story once you start digging. JMB Builders evaluates five footing types during pre-construction planning, matching each to the specific soil conditions and structural demands of the site.

Spread footings remain the baseline choice for stable soils. They're generally the most cost-effective option and suitable for most soil types, and they're typically the easiest footing to repair or replace according to structural engineering analysis. A column carrying 60,000 pounds on soil rated at 2,000 psf requires roughly 30 square feet of bearing area — a 5.5-by-5.5-foot pad. Typical residential spread footings range from 3-by-3 feet for light loads to 12-by-12 feet or larger on weaker soils.

Continuous strip footings run under load-bearing walls rather than isolated columns. Standard single-story residential strips measure 16 to 24 inches wide and 8 to 12 inches deep, sized upward based on actual soil bearing capacity. They're commonly used in homes where walls carry most of the weight.

When soil bearing drops below approximately 1,000 psf or differential settlement must be minimized, mat or raft foundations distribute the entire structure's weight across a single large slab. This approach becomes necessary on compressible soils where isolated footings would settle unevenly.

Pier foundations reach past weak surface layers to competent bearing strata. They elevate structures significantly above grade — often 8 feet or more — making them essential for flood-prone areas and hillside transitions where a level building platform is needed on sloping ground.

Stepped and sloped footings adapt to grade changes without excessive cut-and-fill. Stepped footings follow terraced elevations; sloped footings match the natural land gradient. Both reduce excavation costs and preserve site drainage patterns.

• Spread footings — cost-effective, easiest to repair, ideal for stable soils above 1,500 psf
• Continuous strip footings — 16–24" wide standard under load-bearing walls
• Mat/raft foundations — triggered when bearing drops below ~1,000 psf
• Pier foundations — deep support for weak surface soils or flood elevation
• Stepped/sloped footings — adapt to grade changes without over-excavation

Soil testing before construction can save major repair costs later, and the Pacific division's 89.9% slab adoption rate in 2024 reflects how often stable soils allow simpler solutions.

How Pre-Construction Planning Turns Soil Data Into Footing Decisions

Soil data doesn't just inform a footing choice — it dictates the entire structural logic of a home. In Altadena's hillside terrain, where a single lot can span multiple soil strata, the pre-construction sequence at JMB Builders begins with a geotechnical investigation, moves to structural engineering review, and only then lands on a footing system that satisfies IBC, IRC, ACI 318, and the city's hillside ordinance.

Industry guidance is direct: "The right footing depends mainly on your soil strength and building load." Skipping this step invites the kind of foundation repairs that run from $200 to $7,000+ — and that's before temporary shoring enters the picture.

The math is unforgiving. A column carrying 60,000 pounds on soil rated at 2,000 psf demands at least 30 square feet of bearing area — roughly a 5.5-by-5.5-foot spread footing. Code-referenced sizing data shows strip footings typically starting at 16 to 24 inches wide and 8 to 12 inches deep for single-story loads, then scaling upward from there. Mat foundations enter the conversation only when allowable soil pressure drops below approximately 1,000 psf or when differential settlement must be minimized.

• Geotechnical borings first — no exceptions
• Structural loads calculated per ASCE 7 and ACI 318
• Footing type and dimensions derived from actual bearing capacity, not regional defaults
• Hillside ordinance requirements folded in before permit set

This is where generic advice ends and site-specific engineering begins. The Pacific division may run 89.9% slab adoption, but an Altadena hillside lot with expansive clay or shallow bedrock plays by its own rules. JMB Builders coordinates the geotechnical engineer, structural engineer, and plan check consultant in the same room — virtually or physically — so the footing specification reflects the ground it sits on, not the trend it follows.

Next Steps: From Footing Questions to a Project Conversation

Understanding which footing type belongs under your Altadena home isn't something you decide over coffee — it's a conclusion reached through soil data, structural calculations, and code review. National trends show slab foundations dominate 89.9% of new Pacific division starts, but regional prevalence only frames the conversation; your lot writes the specification.

At JMB Builders, footing selection happens in two deliberate stages. During Discovery & Feasibility (Stage 2), we review existing conditions, any geotechnical reports you already have, and the realities of your site — slope, soil bearing capacity, drainage patterns. Then in Pre-Construction Planning (Stage 3), the structural engineer sizes and details the system: spread footings for stable ground, mat foundations where bearing pressure drops below roughly 1,000 psf, piers or hillside systems where topography demands it. The research is clear: "The right footing depends mainly on your soil strength and building load," and soil testing before construction can save major repair costs later.

• Stage 1 — Initial Conversation: We walk your lot, listen to your goals, and review any existing soils reports
• Stage 2 — Discovery & Feasibility: Site conditions, constraints, and early engineering input
• Stage 3 — Pre-Construction Planning: Final footing specification, budget alignment, and design-team coordination

Every project starts with a no-obligation consultation — no pressure, no commitment, just an honest look at whether we're the right fit for your Altadena build. Call Isaac Rebollo at (310) 491-6878 (CSLB #1103479) to schedule yours.