Manufacturers instructions and required anchoring

Manufactured Structures Bulletin 31

To:

Licensed Manufactured Home Manufacturers, Licensed Manufactured Home Dealers, Licensed Manufactured Home Installers, Certified Minnesota Building Officials, Licensed Limited Manufactured Home Dealers, NCSBCS/HBT, and H.U.D.

From:

Elroy Berdahl
Supervisor, Manufactured Structures

Date:

June 27, 2000

Subject:

Manufactured home manufacturers instructions and required anchoring

The Office of Housing and Urban Development, (H.U.D.), Manufactured Home Construction and Safety Standards, Code of Federal Regulations, (C.F.R.), part 3280 are the standards required to be complied with for the design and construction of manufactured homes. The National Standards have been in effect since June 15, 1976. Minnesota Building Code Chapter 1350 requires that each manufactured home shall have its stabilizing system installed in accordance with the manufactured home manufacturer installation instructions, (see 1350.2600).

"Stabilizing System", means a combination of the anchoring system and the support system when properly installed, (1350.0100 supb. 53). "Installation" of a manufactured home means assembly, at the site of occupancy, of all portions of the manufactured home, connection of the manufactured home to existing utility connections, and installation of support or anchoring systems, (see 1350.0100 subp. 27). "Support system" means any foundation system or other structural method used for the purpose of supporting a manufactured home at the site of occupancy (see 1350.0100 subp. 55).

As per H.U.D., C.F.R. 3280.306, each manufactured home shall have provisions for support/anchoring or foundation systems that, when properly designed and installed will resist overturning and lateral movement (sliding) of the manufactured home as imposed by respective design loads. For Wind Zone I, (Minnesota), the design wind loads to be used for calculating resistance to overturning and lateral movement shall be the simultaneous application of the wind loads indicated in 3280.305(c)(1)(I), (Minnesota, horizontal wind load not less than 15 p.s.f. and net uplift load of not less than 9 p.s.f.), increased by a factor of 1.5. H.U.D., C.R.F. 3280.306(a)(2), the 1.5 factor of safety for Wind Zone I, (Minnesota) to be applied simultaneously to both the vertical building projection, as horizontal wind load, and across the surface of the full roof structure, as uplift loading.

H.U.D., C.F.R. 3280.306(a)(2), requires the manufacturer of each manufactured home to make provision for the support and anchoring systems but does not require them to provide the anchoring equipment or stabilizing devices. Pursuant to H.U.D., C.F.R. 3280.306(b)(1) requires the manufacturer to detail at least one acceptable system of anchoring needed to transfer the wind loads from the manufactured home to an anchoring or foundation system. Additionally, MSBC 1350.0100 subp. 23, defines a "foundation system" as a permanent foundation constructed in conformance with the State Building Code. As per H.U.D., C.F.R. 3280.306 (d), Manufactured Homes in Wind Zone I, (Minnesota), require only diagonal ties. These ties shall be placed along the main frame and below the outer sidewalls.

In accordance with H.U.D. Federal Standards for required manufactured home design for installation and Minnesota Laws and Rules for Manufactured Home Installation, the following items are required as of July 1, 2000.

1.	All H.U.D. labeled manufactured homes constructed after June 15, 1976, are required to be anchored in accordance with the manufacturers instructions.
	A.	This applies to new H.U.D. labeled manufactured homes sited/installed and all H.U.D. labeled used manufactured homes relocated/re-installed in manufactured home parks or on private property in Minnesota.
2.	Licensed Installers or private owners (own and reside in the manufactured home after installation) installing a new or used H.U.D. labeled manufactured home shall follow the manufactures instructions for anchoring, number one (#1) above, and if the manufacturers installation instructions state shall or must for the following, they are to be completed in accordance with the installation instructions;
	A.	Slope grade away from under the home for required drainage.
	B.	Vapor retarder, (i.e. polythene sheeting) required to be installed on the ground under the home to keep ground moisture out of the home.
	C.	Footing depths for support piers are required to be below design frost depth for the zone in which the home is installed, (reference MSBC 1300.5500).

When the manufacturers instructions state shall or must, (unless specifically stated otherwise in the manufacturers instructions or a specific letter of exemption from the manufacturer is submitted), items #2A, #2B, and #2C would be required for compliance to the Federal Standards and State Rules in manufactured home parks and throughout the state of Minnesota (including areas that have not adopted zoning or the State Building Code for private property foundation construction). Note MSBC Chapter 1350 is applicable throughout the state of Minnesota. If you have any questions concerning the required anchoring of manufactured homes or other items in this bulletin, please contact Building Codes and Standards, Manufactured Structures.