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HUD/FHA Manufactured Home Permanent Foundation Certification

A Manufactured Home is a structure built on a permanent chassis, transportable in one or more sections that are no more than 8 feet wide and 40 feet long, or 320 square feet when erected on the site. It is designed to be used as a dwelling and contain plumbing, heating, air-conditioning and electrical systems. The category does not include recreational vehicles (RVs), structures designed for temporary living, or modular homes.

Mortgages are available for the purchase of new or existing manufactured homes. Most mortgages written by a lender are almost certain to be insured by the Federal Housing Administration (FHA), a division of the U.S. Department of Housing and Urban Development (HUD).

As a condition of providing insurance, the FHA requires that the foundation for new homes be designed by, and the design sealed by a licensed Professional Engineer. The design must comply with FHA guidelines. For existing homes, a Professional Engineer is required to certify that the foundation meets the FHA requirements.

A permanent foundation is one that is “constructed of durable materials (concrete, mortared masonry, treated wood) and be site built. It shall have attachment points to anchor and stabilize the manufactured home to transfer all loads to underlying soil or rock. The permanent foundations shall be structurally developed in accordance with this document or be structurally designed by a licensed professional engineer.” Although the design must comply with the manufacturer’s instructions, doing so does not guarantee that it complies with the HUD Guide.

The design must provide vertical stability.

  • Anchorage capacity to prevent uplift and overturning due to winds or seismic forces, whichever controls. Screw-in soil anchors are not considered permanent anchorage.

  • Footing size to prevent overloading the soil-bearing capacity and avoids soil settlement. Footings shall be reinforced concrete to be considered permanent.

  • Base of footing below maximum frost-penetration depth.

  • Enclose a basement or crawl space with a continuous wall (whether bearing or non-bearing) that separates the basement of the crawlspace from the backfill, and keeps out vermin and water.

The design must provide lateral stability with anchorage capacity to prevent sliding due to wind or seismic forces, whichever controls, in the transverse or longitudinal direction.

There are two methods to prepare acceptable design solutions. The first is to offer an engineered solution using the Guide criteria. The second is to use the appendices in the guide and the worksheets offered to select and document a design of an approved type.

Criterium-Hardy Engineers provides design and certification services that meet the criteria.

Requirements

The following improvements beyond the minimum manufactured home installation regulations are necessary to meet the more stringent requirements of the Permanent Foundations Guide for Manufactured Housing, HUD Publication HUD-7584, which must be met for a home to qualify for FHA financing.

  • The foundation piers must bear upon reinforced poured concrete footings that are constructed below the frost line.
  • Foundation piers must be constructed of “solid materials”, such as reinforced concrete, masonry, steel, or treated wood. Dry-stacked block piers, which are commonly used in manufactured home foundations, can be upgraded to meet this requirement by applying an adequate coating of fiber-reinforced surface bonding cement.
  • A permanent well supported perimeter wall (skirting) must enclose the foundation to keep out vermin and water. This wall must be self-supporting and must rest on a concrete footing. An access opening must be constructed in this skirting wall. Most often these walls are constructed of block or brick masonry. However, treated wood walls can qualify if properly constructed.
  • The home must have adequate tie downs anchored to the footings to resist horizontal overturning, transverse and longitudinal loads. HUD-7584 specifically prohibits dependence on screw-in tie-down anchors commonly used in manufactured home anchorage systems. There are several anchorage systems that can be installed to satisfy this requirement. Two examples are illustrated below:
  • The tongue, axles, and wheels must be removed.
  • An adequate number of screened vents must be installed around the entire perimeter of the building to provide air circulation in the crawl space (1 sq. ft. of net free area per 150 sq. ft crawl space floor area).
  • The perimeter walls must extend at least 8 inches above grade.
  • The exterior grade must taper away from the home for drainage.
  • The dirt floor of the crawl space must be covered with 6-mil polyethylene plastic vapor barrier.
  • Utilities must be permanently installed.

This information is provided as a courtesy to help illustrate some of the HUD Permanent Foundation requirements that apply in our local area. This is not a comprehensive list of requirements or a complete manual of accepted good practice. Additional building code and engineering considerations may apply to various situations. Therefore, meeting the requirements listed above does not ensure that the installation can be certified.

 

Download this Requirements Document in PDF format.