Piers- Part 4-It’s All About Location!

So far, we have talked about pier construction from top to bottom, but as you know, it’s all about location! And not quite as simple as you might think!

Typical Pier Print, missing piers at windows.

 One big problem when it comes to pier location is when installers only follow a “pier print” as opposed to actually digging into the Manufacturer’s Installation Instructions. While pier prints may be helpful, they are often in error and rarely show all of the piers required. Make sure to read all the notes on the pier print, they all refer you to the installation instructions. Remember, simple pier prints generally have not been reviewed and stamped as approved. So, if a pier is missed at either side of the picture windows, or under marriage line columns, or any other location, is the sole responsibility of the professional installer. 

Since the manufacturer’s installation instructions require the installer to prepare a sketch to determine pier locations, the pier print may be helpful when starting your sketch. But we need to crack open the instructions to find all of the piers required that might be missing from the pier print. 

If you have been installing manufactured homes for a long time, you know that piers are needed at openings in the side wall or marriage wall that are 4’ or larger. But some locations that are often missed.

6′ side wall opening, needs support piers

 Multiple windows that are installed in openings in the side wall over 4’, even if the individual windows are under 4′, often need support. When you see two or more windows together, determine if the header above the window is spanning the entire opening, or are there support studs dividing the opening.  If there is siding between multiple windows, the opening is divided. If the windows are joined with a mullion or “H” bar, consider it one big opening and not divided.  Some manufacturers require piers in all cases where windows are ganged together. As always, check the installation instructions! 

6 piers needed along this side wall.

When it comes to doors, there is little variation between manufacturers. Most manufacturers require support at both sides of doors located along the side wall. No supports are needed if the door is located at the end wall of the home.  

One style of pier saver under a patio door.

We are seeing many manufacturers reinforcing the floor to eliminate piers under patio doors. I hope to see this trend continue and expanded to eliminate piers at all doors and windows.  Truth be told, when pier savers were first introduced several years ago, I was a skeptic. But I was proven wrong and now I highly recommend them! If your manufacturer does not offer pier savers, you need to ask for them!

Adjustable outriggers support patio door opening.

 It is also worth mentioning that several manufacturers have approved the use of “adjustable outriggers” as an alternative to piers at certain door and window openings. There are differing design limits depending on the home manufacturer. Some limit the use of an adjustable outrigger to side wall openings not greater than 4′. Still others allow adjustable outriggers to support each side of a 6’ patio door in the south roof load zones. Some manufacturers approve the use of adjustable outriggers in the middle roof load zone as well.  Check the approved manufacturer instructions before you proceed. I suggest giving a call to the plant Quality Control Manager and ask him to send you their approved design on adjustable outriggers.

 Did you know that most manufacturers require “intermediate supports” to support marriage wall openings greater than 10’? Piers spaced 10’ on center maximum are required. See the third bullet on the chart below. 

 Also, supports are required where heat duct crossovers go through the rim joist (unless the home has a perimeter frame system). See bullet #4.

There is the troubling requirement (see the last bullet) that installers are to provide a support “Under heavy (400 Lbs. or more) items such as heavy furniture, waterbeds, fireplaces or fish tanks”.  Troubling for two reasons:

1.       The installer will never know where the homeowner is going to place heavy furniture, a fish tank or waterbed!

2.       The direction is too vague. Where is the support to be located? Under the frame (chassis)? Under the perimeter joist or marriage line? And if the manufacturer installs the fireplace, why don’t they beef up the floor in that area?

I think we have covered this topic pretty thoroughly,  but here are a few final points:

Perimeter Pier Location

The manufacturers are required to identify the point load support areas of the home with tags, paint, or in some other way so that the identification is visible after the pier is installed. I have seen too many tags or markings misplaced. So, make sure you know where supports are needed. If in doubt, call the QC manager.

Over spaced first pier!

 There is some variation when it comes to the first and last support piers at the ends of the home. Some manufacturers indicate that the pier must be located within 12” of the end of the I-beam. Others want the first support pier to be 24” from the end of the floor to the center of the pier, and yet another within 24″ of the end of I-beam! So, double check that you doing this correctly.

 Also, watch for shear wall straps (sometimes called G-2 strap) that may require piers, and other manufacturer specific requirements. We will explore the topic of shear walls at a later date.

 Ok, that is a lot to consider. Make sure you aren’t overlooking some odd window configurations that may need support and work with your manufacturer to have them add floor reinforcement at every possible location.  Watch out for marriage line spans that may require intermediate supports. If you haven’t been preparing sketches of the pier layout, make sure you start, and keep a copy in your home file! 


2 thoughts on “Piers- Part 4-It’s All About Location!

  1. Mark,
    Great topic. I would like to add, knowing the process very well from the retail ordering side of things…I am disappointed that manufacturers tend to not “hear” retailers and installers when we call upon them to give serial # specific loading designs when the home is ordered , before the footings are installed, and before the home is delivered. If the installer does not have a hand in the retail sale or constructions of footings, then there are large gaps for error. Finding out a perimeter pier is needed in a special location, after the home is delivered is not very productive. It seems like the industry sometimes “asks” for additional regulation by not stepping up and providing a reliable plan that shows ALL the load points. Most plants will give this information if the retailer insists on obtaining it, but I feel the design should be presented for every home, serial # specific, without asking for it. We all want high quality installations, and I think this will help.


  2. Thank you for continuing to share this important information. I just “shared it” on the Massachusetts Association website http://www.MassMHA.org for additional outreach. Very helpful, useful information with photos and diagrams. Appreciate your sharing, its timely and filled with photos and diagrams.


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