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McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
What are the tie-down requirements for a mobile home?
Tuesday, October 2, 2018
Because manufactured/mobile homes are lighter than site-built homes and most are also elevated above the ground on piers, they need special protection when tropical storm or hurricane winds are blowing. Florida also experiences occasional violent summer thunderstorms that reach tropical storm force for brief periods. Storm winds can get under the house and lift it up, and press against the walls to push it off the foundation. Wind blowing over the roof also creates a wing-like lifting action.
All manufactured/mobile homes are required to be secured according to the manufacturer’s installation specifications. In the case of a used mobile home, or where the manufacturer’s specifications are not available, the home must be tied-down in accordance with the Florida Department of Highway Safety and Motor Vehicles specifications. Each AHJ (Authority Having Jurisdiction), typically a county or city building department, is responsible for enforcing the regulations through permitting and on-site inspection.
To download a copy of the Department of Highway Safety and Motor Vehicles requirements Rule 15C-1 & 2 as a pdf document, click the link below:
Also, here is a link to a summary of the key requirements in 15C-1 and 2:
Single and double-wide mobile homes both require diagonal tie-downs. Single-wide homes are more vulnerable to the lateral (sideways) wind forces due to their narrow width, so they also need vertical tie-downs. These over-the-top straps will be a visible wrap in older single-wides. The number of tie-downs required is dependent on two criteria:
1) The Wind Zone where the home is located. To determine which zone your home is designed to be located in, look on the home’s data plate. Here’s a link to our blog about how to find and interpret the data plate:
To make sure that your home is located in the wind zone that it was designed for, check our blog with a wind zone map at:
Only diagonal (frame) tie-downs are typically required for wind zone 1, but a vertical (wall) tie is also necessary at each frame anchor for wind zones 2 and 3, as shown below.
If your home is a “D-sticker,” meaning that it was designed to be installed within 1500 feet of the coastline in Wind Zone 3, there are additional installation requirements in Section 15C-1.01031. To learn more about D-sticker homes, go to our blog at What is a D-sticker mobile home?
2) The year the home was built. HUD tightened the spacing requirements in the mid-1990s, following the devastation caused by Hurricane Andrew in South Florida, where 97% of all manufactured homes in Homestead were destroyed. In our area, located in Wind Zone II, homes manufactured after the original HUD standards went into effect in July, 1976 and before the upgraded standards enforced beginning in July, 1994, had tie-downs spaced approximately eight feet apart on average. After 1994, tie-downs are placed approximately five feet apart. Additional stabilization bracing is also now required on double-wides. Florida Administrative Code 15C-1, upgraded in 1999, added further standards for wind-resistant mobile home installation. More recently, HUD standardized installation guidelines nationwide in 2009. If you unsure of when your home was built, see our blog post How do I find out how old a mobile home is and who manufactured it?
If you are purchasing an older mobile home, and the financial institution or insurance company requests a foundation inspection, it is because they want to verify that the home meets the newer installation standards. The inspection must be done by a licensed mobile home installer or engineer, but not a home inspector; except that some home inspectors are affiliated with an engineering firm, and act as their agent to take reference photos for the engineer’s report. FHA and VA financing accepts only an engineer’s report.
The installation of a mobile home, including the tie-downs, is required by Florida law to be done by a professional installer licensed by the Department of Highway Safety and Motor Vehicles, with a final inspection by the local building department. Besides the numerous code requirements that must be complied with to install a home correctly, another reason for not allowing a homeowner-installation is that that setting a mobile home on piers is dangerous work, even when done by experienced professionals.
Here are some of the defects we typically find in an inspection of a mobile home foundation:
- Corroded and loose anchor straps.
- Anchor straps that have been cut or removed.
- Anchor straps installed at more or less than the specified angle.
- Tilting piers, no longer in direct contract with steel frame.
- Site-built additions (including porches) that bear on the structure of the mobile home.
And by the way, if your tie-downs are metal cables instead of straps, like in the photo below, then you have a pre-HUD home produced before 1976 with the original foundation system.
Also, see our blog posts What are the HUD minimum requirements for foundation footings and piers under a mobile/manufactured home? and What are the most common defects in mobile/manufactured home foundation piers?
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