Anchoring and tie-downs

Anchors and straps

Anchoring and foundation systems must handle the design loads shown on the home's data plate.

HUD defines an anchoring system as anchoring equipment plus anchor assemblies that resist uplift, overturning and lateral forces.

In frost-susceptible soil, ground anchor augers go below the frost line unless the foundation is frost protected.

Missouri's PSC guidance sets tie-down straps at a 40 to 50 degree angle and requires longitudinal anchoring.

Arkansas rules bar reusing anchors, straps or clips, which matters when a used home is moved.

Sources: Anchor after leveling; What an anchoring system is; Frost; Strap angle (Missouri example); Reused anchors (Arkansas example)

What the instructions must cover

Anchor instructions and designs must be prepared by a registered professional engineer or architect.

They must give the maximum spacing of diagonal ties, the allowed tie angles, how ties attach to the chassis, mate wall tie downs, strap connections and protection at sharp corners.

Source: 24 CFR 3285.401

Wind zone and anchoring

A home placed in a less demanding wind or roof load zone may use an anchoring system built for those lower loads only if the instructions or an engineer provide that design.

Source: 24 CFR 3285.401

Ground anchors

Ground anchor makers must have their anchors tested and listed by a nationally recognized laboratory, or tested and certified by an independent professional engineer.

Anchors listed before November 10, 2014 had to reach a working load of 3,150 pounds and an ultimate load of 4,725 pounds in the weakest soil they were certified for.

An anchor may not be used in a weaker soil class than the one it was tested in, which is why installers classify the soil first.

Any sidewall, over the roof, mate line or shear wall straps on the home must be connected to an anchoring assembly.

Sources: 24 CFR 3285.402; 24 CFR 3285.403

Alternatives to anchors

Foundations other than piers and anchors are allowed when designed and certified by a registered engineer or architect, or listed by a national testing agency.

Source: 24 CFR 3285.301