Wind Storm Protection Basics

Watching the news today and seeing the devastation caused by Hurricane Harvey, I thought it would be a good time to talk about some of the basic considerations that are critically important to making sure our homes can withstand the wind forces as intended.

1.       Do NOT attach car-ports, awnings, patio covers, and similar items, directly to the manufactured home. All manufacturers clearly state that all accessory structures be free standing and independently supported. Check out this short video from the Today Show:  Click Here        This video not only illustrates what can happen when a carport is attached to a home, but it also shows how you can still offer your customers these type of features without creating a hazardous situation.

2.       Make sure you have properly installed anchor strapping so it can be counted on to hold the home in place.

Purchased Strap Protectors

a.       Every place the anchor strap touches the main chassis beam or attaches to a bracket, the strap must be protected so that the sharp edges of the steel doesn’t shear off the strap. Strap protectors can be made from left over pieces of strap material or purchased. Just make sure you install them!

Angle Finder

b.       Strap angle is critical! Buy yourself an inexpensive angle finder and make sure your strap angle is less than 60°! If it is too steep, the home can slide off the piers!

3.       While we have recently written two posts on ground anchors (July 3 and July 13), there is still a lot more to discuss.

a.       Make sure the anchor is the right length (below frost the line), and installed in the ground by the skirting line! Not in a concrete footing.   

Rock Anchor

b.       Don’t use rock anchors or other types of anchors that aren’t intended to stabilize a manufactured home. Rock anchors are to be used in solid rock!

Stabilizing  Plate

c.       Stabilizing plates are critical to keep the anchor from slicing through the dirt when it is called upon to hold the home in place. Remember that a poorly graded site can undermine a great anchor installation!

4.       Consider using the newer anchoring systems. I am a big fan, primarily because then are considerably easier to successfully to install.  Also, they can satisfy end-wall anchoring requirements. In freezing climates, make sure you attach the system to frost protected concrete footings and take a few minutes to review the installation instructions.  I have found that the big three anchor suppliers (Minute Man, Oliver Technologies and Tie Down Engineering) are super helpful and are eager to provide technical assistance. Here are links to their websites where you can find a ton of helpful information:

http://minutemanproducts.com/minute-man-products/

http://www.olivertechnologies.com/

http://www.tiedown.com/

Now is the time to re-examine your anchoring techniques. You might want to consider calling on some older homes and see if the residents might be agreeable to upgrading their anchoring system! Give it some thought, it might not seem as crazy as you think!

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Introduction to Alternative Anchoring Systems

All Steel Foundation-OTI with longitudinal bracing

Over the past few weeks we have been talking about conventional ground anchors as the tie down system for manufactured homes. But let’s look at some alternative anchoring systems that might be able to simplify the process for you.

As always, make sure that the manufacturer has approved whatever system you choose and that it is also approved by their Design Approval Primary Inspection Agency (DAPIA). If you are in a state that has oversight authority, make sure they approve it as well. To the best of my knowledge, the three systems that we are going to look at today are approved by most manufacturers. But, never take my word, you need to get copies of the approvals for your installation files. 

Xi2-Tie Down Engineering

 

Let’s take a quick look at the:

All Steel Foundation from Oliver Technologies Click Here for Oliver Technologies

L & L Bracing System (LLBS)  from Minute Man Click here for Minute Man

Xi2 from Tie Down Engineering Click Here for Tie Down Engineering

LLBS-Minute Man

I am a big fan of all three systems. They are much easier to install than conventional ground anchors, and they will save you significant time as they install quickly. While the systems are similar in many regards, they do have differences, so make sure you follow the instructions particular to the system you choose. We will limit this discussion to manufactured homes installed in Wind Zone 1.

Here are the some of the similarities of the three systems:

Only 2 devices (opposite corners of the home) are needed to anchor a typical 2 section manufactured home. 5/12 roof pitch and greater would require three or more systems.

For single section homes, typically you will need two devices and a ground anchor installed at each corner of the home.

The systems are limited to a home with a maximum pier height of 48”.

The systems can be bolted or “wet set” into frost protected concrete footings.

All Steel Foundation-OTI-replaces a pier and anchors end walls.

They are easily adapted to address longitudinal anchoring. 

 

Xi2-Minute Man- Beam Clamp

LLBS from Tie Down-Beam Clamp

When using these systems, it is important to make sure you don’t mix parts. If you are using the Xi2, don’t use parts from Minute Man or OTI, if installing the OTI, don’t use Tie Down or Minute Man parts. I also believe that for multi-section homes it is important that your fastening at the marriage line be consistent with the installation instructions for the home being installed. Watch for gaps between the sections that may impede the transfer of wind load across the marriage line (this is true of all manufactured home installations).

If you are not using these systems, I encourage you to reconsider. All three producers provide exceptional customer support. They have comprehensive information on their websites including videos, and are very helpful on the phone and in person! 

From my perspective, it is a rare occasion when a manufactured home installed using conventional ground anchors is anchored properly; site grading, rocky soils, underground utilities, and frost depths make conventional ground anchors a challenge for many installers. However, installers using these alternative systems have had great success with these products.

 

 

Anchoring With “J” Hooks

Typical “J” concrete anchor

Recently I have been asked questions about anchoring manufactured homes using “J” Hooks (or “J” concrete anchors) that are wet set in the concrete footings. While I am not an engineer, let me share with you a few practical things that I learned over the years about anchoring and what you should consider if you want to use “J” type concrete anchors.

Incorrect vertical strap from “J” anchor to beam

A quick look at an installation manual shows that in Wind Zone 1, we need to anchor the home with diagonal straps attached from the chassis beam to  ground anchors placed just inside the skirting line of the home.  In Wind Zone 2 and 3 we need both diagonal and vertical straps. In every case, diagonal straps are needed. Diagonal straps secure the home from sliding and up-lift in the event of windstorm. If the home is anchored only with vertical straps from the footing to the main beam, they might prevent up-lift, but not sliding of the home.

 

Angle finder showing 75°-Too steep!

Most installation manuals require a maximum strap angle of 60° from horizontal. Installing “J” anchors in the footing generally result in a strap angle of around 90° .  An inexpensive ($5 to $10)  angle finder is a valuable tool to make sure you have the proper strap angle. Snap a picture for your installer file.

 When I look over the actual instructions for proper use of the “J” anchor, it is obvious that these anchors are designed for concrete slab design, not to be placed in individual footings. This is based on the fact that each “J” anchor must withstand 4725 lbs. of tension without lifting. Assuming one cubic yard of concrete weighs about 4,000 lbs., you can see that you would need close to 1 ¼ yards of concrete per footing to properly hold the “J” anchor. A typical 24” diameter x 36” deep footing takes roughly 1/3 of a yard of concrete. Not even close to the amount needed to reach the required holding capacity of 4725.   

Slab design with “J” anchor at side wall

So, where does this leave us? If we are placing a manufactured home on a frost protected concrete slab, the “J” concrete anchor might be the answer. Place them a minimum of 4” to a maximum of 10” from the edge of the slab, and keep an eye on the strap angle! The thickness of slab should be 2” greater than the “J” length where it is embedded in the concrete. So, a 6” “J” anchor should be embedded in 8” of concrete.  But as always, you need to do your homework and make certain you are anchoring every home consistent with the home manufacturers installation manual and using the anchor components as they were designed!

My advice is to look at the newer anchoring systems that are available on the market today. Most of the home manufacturers have reviewed and approved them to properly anchor their homes. While they may be a little more expensive, they are certainly less labor intensive than other anchoring techniques, especially when you factor in end wall anchors. As always, talk to the home manufacturer. The anchor producers all have a lot of good information on their web sites and they all have some great technical folks on staff who are always available to answer any questions. So, give them a call before you start your next job!