For Arizona homebuyers considering a manufactured home, selecting the right foundation is one of the most important long-term decisions you’ll make. While every manufactured home is built to the rigid national HUD Code, foundation types vary across Arizona’s diverse regions based on soil, climate, installation standards, and whether the home is placed on private land or in a community.
Across the state, from Phoenix and Tucson to Prescott, Yuma, and Flagstaff, you’ll encounter four primary foundation types: piers, slabs, crawlspaces, and pit-set foundations. Each option offers benefits depending on your location, budget, and goals for the home.
1. Pier Foundations – Pier-and-beam foundations are widely used throughout Arizona, especially in manufactured home communities and on private land in lower desert areas.
What They Are
- Concrete or steel piers support the home along the steel beams.
- Ground anchors secure the home against wind and shifting soil.
- Skirting or block (non load-bearing) is installed around the perimeter.
Why They Work Well in Arizona
- Affordable and suitable for a wide variety of soil types.
- Fast installation, ideal for desert lots that need minimal grading.
- Easy access for plumbing and utilities, which is important in Arizona’s settling-prone soils.
Where They’re Most Common
- Phoenix metro
- Tucson
- Yuma
- Mohave County (Kingman, Bullhead City, Lake Havasu)
- Most MH communities statewide
2. Slab Foundations (Concrete Slab-on-Grade) – Slab foundations are increasingly popular in Arizona because they offer stability, durability, and a residential appearance.
What They Are
- A reinforced concrete slab poured level with the ground.
- The home is installed directly on the slab using HUD-approved methods.
Why They’re Great for Arizona
- Excellent for desert climates with no frost-depth requirements.
- Provide a solid, stable base for areas with expansive clay soils.
- Favored by many lenders for permanent installation and long-term financing.
Where They’re Common
- New manufactured home subdivisions in Phoenix, Tucson, Casa Grande, Buckeye, Maricopa, and Surprise
- Infill redevelopment lots
- Land–home packages throughout the state
3. Crawlspace Foundations – Crawlspaces elevate the home slightly above the ground and are used strategically across different Arizona regions.
What They Are
- A short perimeter wall (non load-bearing block or poured concrete) with an enclosed space beneath the home.
- Piers inside the crawlspace support the home.
Why They’re Used in Arizona
- Important for colder regions such as Prescott, Flagstaff, Show Low, and Payson, where frost impacts installations.
- Provide an intermediate appearance, less elevated than standard pier systems.
- Better protection for plumbing and utilities in colder climates.
Where They’re Found
- Northern and high-elevation Arizona
- Upscale MH subdivisions seeking a residential look
- Sloped or rocky sites where leveling is needed
4. Pit-Set Foundations (Low-Profile Crawlspace or Set-In-Ground Installation) – Pit-set installations have grown in popularity in Arizona, especially in areas seeking a site-built appearance.
What They Are
- A portion of the ground is excavated so the home can sit lower than a traditional crawlspace, often just 12–18 inches above grade.
- Piers or supports are installed inside the pit, and the perimeter is finished with block, concrete, or stucco.
- When complete, the home looks almost flush to the ground, similar to a site-built house.
Why Pit-Sets Appeal to Arizona Buyers
- Most site-built appearance of any manufactured home foundation option.
- Helps meet residential subdivision standards in growing markets like Phoenix, Mesa, Buckeye, and Maricopa.
- Offers better energy efficiency due to reduced airflow under the home.
- Provides a low-profile installation without fully embedding plumbing in a slab.
Where They’re Common
- New MH subdivisions
- Infill sites in metro Phoenix and Tucson
- Northern Arizona developments wanting both frost protection and a low-profile look
- High-end manufactured home neighborhoods and ADU installations
Considerations for Pit-Set Installations
- More expensive than standard pier foundations.
- Requires careful engineering for drainage and groundwater management, especially during Arizona monsoon season.
- May require permits specific to excavation depth and retaining walls.
What Determines Which Foundation Is Used in Arizona?
1. Soil and Climate – Arizona’s soil types vary dramatically:
- Caliche and hard desert soils; Piers and slabs work well.
- Expansive clays in areas like Chandler or Queen Creek; Slabs or engineered pit-sets may be preferred.
- Northern Arizona with frost cycles; Crawlspace or pit-set foundations often required.
2. Local Building Codes and Engineering – Cities and counties may require:
- Soil tests
- Engineered anchoring systems
- Drainage and grading plans
- Frost-depth compliance in northern regions
3. Financing Requirements – To qualify as real property, lenders may require:
- A permanent slab
- A permanent pit-set or crawlspace foundation
- Or an engineered permanent pier system meeting HUD standards
4. Budget and Appearance
- Lowest cost: Standard pier foundation
- Mid-range but highly stable: Slab-on-grade
- Most residential look: Pit-set
- Best for cold climates: Crawlspace
5. Community vs. Private Land
- Manufactured home communities typically use pier foundations.
- Private land installations—especially those intended to resemble site-built homes—favor slabs, pit-sets, or crawlspaces.
Which Foundation Is Best for Arizona Buyers?
If cost and speed matter most, a pier foundation is the practical choice. For long-term durability in desert climates, slab foundations offer excellent performance. In colder or elevated regions, crawlspace foundations provide needed frost protection. And for homebuyers who want their manufactured home to blend seamlessly into a site-built neighborhood, pit-set installations deliver the lowest profile and most residential look.
With Arizona’s diverse geography, from desert basins to mountain towns, the best foundation depends on your site conditions, goals, budget, and financing plans.