A Guide To Understanding Wind Zones For Mobile Homes

by | Oct 12, 2018 | Blog, FAQ, Safety




We’re all too familiar with the sight of mobile home debris of wiped out communities spread over miles on the news. This has falsely led many to believe that manufactured homes aren’t up to it when it comes to resisting high winds. However, this is an aspect of manufactured home construction and safety that’s tightly regulated. In fact, mobile homes have made leaps and bounds in safety and quality over the last few decades.

Featured image for "A Guide To Understanding Wind Zones For Mobile Homes" blog post

In many cases, the homes that end up on the news were either too old or not located within the appropriate wind zones for mobile homes. One way to not become a statistic is to ensure that you understand mobile home wind zones as well as the standards and regulations behind them.




What does the HUD code have to say about it?

Hopefully, you know by now that the Manufactured Home Construction and Safety Standards at CFR 3280 (or, the HUD Code) needs to be the first thing you refer to when dealing with your home’s construction safety. In this document, almost two entire sections are dedicated to the requirements for mobile homes when it comes to wind.

The HUD Code was brought into effect in 1976. Homes built before that date cannot be made HUD-compliant. This also means that older mobile homes cannot meet current zoning standards.

§ 3280.305 Structural design requirements:

The goal of this section can be summarized in the first sentence:

“Each manufactured home shall be designed and constructed as a completely integrated structure capable of sustaining the design load requirements of this standard, and shall be capable of transmitting these loads to stabilizing devices without exceeding the allowable stresses or deflections.”

In § 3280.305(c) it goes into further detail of what the requirements are for each zone. Homes built for Zone 1 should be able to resist horizontal wind loads of no less than 15 psf and upward roof lifting loads of no less than 9 psf. This translates to about 70mph in basic wind speeds.

Things get a bit more complicated for Wind Zones 2 and 3. Homes built for Wind Zone 2 should be able to withstand winds up to 100 mph. Zone 3 homes should be able to resist winds of up to 110 mph.

In § 3280.305(c)(1)(ii)(B), there is a comprehensive table listing all the requirements.

Zone 2 and Zone 3 homes should be able to resist a horizontal drag load of 39 and 47 psf and an uplift load of 27 and 32 psf, respectively. However, there are many other requirements for different parts or fixtures of the home, such as eaves.

The document makes clear that homes built for lower zones cannot reside in higher zones. However, Zone 3 homes can be placed in Zone 1 and 2 areas and Zone 2 homes can go in Zone 1 areas.

Lastly, as not all areas have exactly the same conditions, the HUD Code makes provision for local departments to set even more stringent standards or requirements. It targets explicitly mountainous regions for snowfall and wind. If you live in any extreme conditions, you should check with your local housing authorities whether you will be subject to any additional requirements.

§ 3280.306 Windstorm protection

In general, this section is less informative than the former, but is still important:

“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 the respective design loads.”

Strong wind, cyclone

This section deals with the anchoring systems and foundations of mobile homes. These systems are meant to protect your home from being flipped or overturned in adverse weather. Be aware that your home might come with instructions on how to properly install and use these anchoring systems. This means that, depending on what mobile home you have, you may have to prepare and set it up yourself.

It also provides guidelines and information on how these systems should function, for example:

  • Ground anchors should be embedded below the frost line.
  • Anchors and stabilizers should be certified per the testing procedures in ASTM D3953-97 by a registered engineer.
  • Ties should be weather resistant according to the local conditions.

Stronger than average winds or storms for a specific zone are compensated for by taking the wind load limits in § 3280.305 and multiplying them by a constant factor. For example, the anchors and stabilizing systems for a Zone I home should be able to resist 1.5 times the wind load as the structure of the home.




What are wind zones?

As you probably know, the U.S. is a sizeable country with a diverse range of climates and weather patterns. That means that the local weather conditions differ from place to place, including how high the wind speeds can reach. To make sure that homes stand up to the local conditions, wind zones were established.

To this effect, the U.S. is split into three different zones: Zone I, Zone II, and Zone III with Zone I being the least extreme and Zone III being the most extreme. Wind zones refer to the maximum wind speeds that can be reached in that area, measured in mph, as well as the resulting force it applies to structures, measured in psf (pounds per square foot).

We call the amount of force a home should be able to resist in order to be suitable for a certain zone the “wind load.”

However, the actual wind is just one of the factors taken into account when zoning a mobile home. Officials also take the local weather conditions into account as well as the other possible effects of higher winds, such as snow, rain, and extreme weather.

Where are wind zones located in the U.S.?

Whether you need to worry about your home’s wind zone classification depends mainly on where it’s located. Zones don’t encompass entire states. Different parts of the same state can be subject to different zoning requirements. You can find a complete map of wind zones in the U.S. here at the Manufactured Housing Institute.

Zone 1

Luckily for most mobile homeowners, and U.S. citizens in general, by far the largest portion of the U.S. is Zone 1 wind zones. Every state on the West Coast, Rocky Mountains, and Midwest are completely within the bounds of Zone 1. In the Southwest, Arizona, New Mexico, and Oklahoma are completely safe as well as the interior states of the North and Southeast. Alaska is also mostly a Zone 1. About 40 US states fall completely within Zone 1, while only one falls completely out of it.

Zone 2

These areas are already far less common than Zone 1 but still larger in total than Zone 3. Zone 2 is mostly a thin strip just of the coast that runs from the southeast of Texas along the Gulf Coast and up along most of the east coast (although it skips a few states, such as Maryland, New Jersey, and New Hampshire). However, the entire southern half of Louisiana and most of Florida falls in Zone 2.

Storm approaching Florida land

Zone 3

Once again, we’re lucky as Zone 3 is by far the smallest of the three wind zones. There are only 6 states with even a foot in Zone 3, and even then it’s a tiny area. In the continental U.S., a large part of the southern coast of Louisiana and Florida, as well as the complete length of the Alaskan coast, falls within Zone 3. Hawaii also falls entirely within Zone 3.

How to find your home’s wind zone rating?

First of all, if you don’t know your home’s wind rating don’t worry because we won’t judge. However, it’s probably for the best that you find out as soon as possible. It shouldn’t be an issue in most cases as most people and parks usually follow the zoning requirements. If you have bought or are moving into an older mobile home, it doesn’t hurt to make sure. And don’t worry, it’s not hard to find out.

The HUD code itself stipulates that every manufactured home must have a data plate which provides this information. The data plate may be in different locations based on the manufacturer or model. However, a few standard locations include one of the kitchen cabinets, close to the furnace or main electrical panel, or in a bedroom closet.

Below is an example of what this plate looks like:

data plate sample

As you can see, it handily comes with a wind zone, roof load, and temperature map so that you can confirm whether your home is in a suitable location. It also provides info on the home itself. Additionally, the data plate confirms that the home has been built in accordance with the HUD Code.




What if my data plate is missing?

If you can’t find your data plate anywhere, don’t throw in the towel just yet. You can apply for a replacement data plate from the Institute for Business Technology and Safety. They contract with the HUD Department and maintain a database of manufactured home models going all the way back to the beginning of the HUD Code in 1976.

All you need to do is find your model’s serial number or HUD certification number. The number will be on the HUD label/tag which is usually an embossed, red tag located near one of the exterior corners of the home. This is another piece of proof that your home is in compliance with HUD standards.

Home Certificate (HUD plate / certification label with manufactured home serial number)

Although they can’t issue you a new data plate, the manufacturer will be able to tell you the wind zone rating of your mobile home if you can provide them with this info. As a last resort, a certified HUD inspector or inspection agency should be able to tell you whether your home is still HUD-compliant according to its wind zones.

Can I upgrade my home’s wind zone load?

The short answer is a resounding no. Once a home is built, it can never be officially upgraded for a higher wind zone. Theoretically, you could upgrade a home to be wind or load resistant up to a higher zoning standard. However, you will never be able to label a Zone 1 home as a Zone 2 home, etc.

Understandably, the HUD is very concerned with the safety of manufactured home inhabitants, especially considering older mobile homes’ less than stellar record. Because of this, homes have to pass a number of tests and inspections by several agencies before being approved for a certain wind zone.

When a new manufactured home is built, various HUD-authorized agencies participate in the various processes involved. This includes:

  • an agency for the design of the load-bearing components,
  • an in-plant inspection of the manufacturing process and home,
  • the manufacturer itself,
  • and a state supervisor.

All must approve and sign-off on the home.

Furthermore, when it comes to Zone 2 or 3 homes, the HUD Code explicitly mentions these parts of a home:

Wind resisting parts:

  • Shear walls
  • Diaphragms
  • Ridge beams (including fastening and anchoring systems)

Components and cladding materials:

  • Roof trusses
  • Wall studs
  • Exterior sheathing
  • Roofing and siding as well as exterior glazing (including connections and fasteners)

A professional engineer or architect must design these parts to meet the load-bearing requirements for the specified zone. The HUD code also states how the weight should be distributed through all parts of the home from the roof to the framework to the chassis. Most if not all of these components cannot be reached or altered without significantly affecting the structure of the home.

Roof plates

Simply put, it would almost be easier to take apart and put together or build an entirely new home than to just upgrade its wind load capacity.

That’s all you need to know about wind zones for mobile homes!

By now, you should have a working knowledge of:

  • Wind zones 
  • What the HUD requirements are for different zones 
  • Which areas of the U.S. fall under which zones
  • And how to find out what wind zone your home falls under

Today, mobile homes are much closer than ever to stick-built homes when it comes to their safety in storms or natural disasters. However, this is only the case if your house is built according to HUD standards and located within the appropriately zoned area. That’s why it’s so important not to take chances with you or your families’ safety and make sure your home is zoned correctly.

Wind zoning is only one safety concern when you own a mobile home. Another crucial area of concern is fire safety which we walk you through in our article Mobile Home Fire Safety | What To Do In An Emergency.



 

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