Manufactured (mobile) homes require that they be permanently attached to the ground. Modular homes (also manufactured) are placed on a permanent foundation, which anchors them to the ground. The construction of a mobile home is controlled by HUD (Department of Housing and Urban Development), and is not inspected by local authorities, but each county within each state will have its own requirements as to how the homes must be set up so that they are safely attached to the ground. When weather conditions include storms and high winds, the manufactured home is not a safe place to be unless the home is sufficiently anchored to the ground. This is done with anchors and tie downs.
Why Use Tiedowns?
When mobile homes are built, they are placed on a steel chassis that has axels and wheels attached for mobility. Since they are not required to be placed on a permanent foundation (as a site built home is) they are much lighter in weight than a site built home would be. When these homes are set up, they are normally positioned on concrete piers (which are cemented into the ground), elevating them so they have a crawl space underneath. No matter where the home will be located, storms with high winds can develop, and wind can flow underneath the home, lifting it upward. Additionally, the home is built in a rectangular shape, and wind passing over the top can create uplift activity It is for these reasons that the homes must be anchored to the ground
Requirements for the number of tie downs needed to anchor the home will depend on the length of the home, and its location. More tie downs are needed in coastal areas where there is more storm activity, and more damaging storm history. To combat the force of winds, two types of tie downs are used. A vertical tie is used over the roof of a single-wide home to combat wind damage. A diagonal tie down is used to tie the frame down to the ground. This combats winds from lifting up the home. Single-wide homes require both types of tie downs. Due to weight factors, a double-wide mobile home only requires the diagonal tie down to anchor the home and frame to the ground.
Use of Tiedowns
The number of diagonal tie downs range from three to five per side in less storm danger areas. In coastal areas, four to seven per side are used to serve the greater need. For single-wide homes, vertical ties (on the roof area) required are two to four, depending on the length of the home. More can be used for greater insurance against storm and wind ravages. If the home has attachments or other site considerations, an engineer from your county should be consulted to gain knowlege of how to sufficiently tie down the home. Some loans require an engineer to inspect the ties and give certification that the home is sufficiently anchored and area safe.
Diagonal tie downs are attached to the homes' steel frame, which is secured by frame anchors. The type of frame anchor used depends on the type of soil in the area. In the case where a concrete base is being poured, a concrete anchor should be installed. Other types of anchors are used that are designed to hold tight in various soils from rock and hard clay to soft and sandy soils. These anchors are engineered and time tested.
Consult the Experts
When investigating proper setup of a home, leave it to the experts. Professional mobile home delivery and set up crews are trained for correct and safe setup and installation of ties and anchors best suited for the area. If an inexperienced person is considering tackling the job, they should do so under the guidance of a building inspector or trained mobile home installer. They would instruct you to be sure the home is leveled before anchoring. Check to see if you are in a zone that is considered high risk, and additional ties are needed. Find out the soil type in the area to be certain the correct anchors are used. Locate where cables, wires, gas, sewer and water lines are before placement of anchors. Make sure all anchoring supplies meet specifications and are resistent to corrosion and weather. Follow explicit direction given with all supplies. When in doubt, call your county engineers office for advise.