Overlooked Support Piers

I recently came across another situation where the “pier print” provided by the manufacturer was in error and resulted in a pretty significant problem along the marriage line of the home.

Those of you that I have worked with in the past know that I am not a fan of pier prints. This is primarily because they are not reviewed by the design approval agencies-DAPIA’s. As a result, they often miss some important marriage line and side wall supports for the home. One thing every pier print does contain is a little note telling the installer to always refer to the installation manual. That way, if a problem pops up, it is the installer who takes the blame.

Typical pier print-where is the DAPIA stamp of approval?

 

So, let’s look at a few problem areas that are often overlooked and should be checked against the specific DAPIA approved installation manual. Remember, while installation manuals look alike, there are variations that can lead to big problems if overlooked.

An excerpt from a typical installation manual. But, there are variations that you need to know!

 

Almost every manufacturer’s installation manual requires support piers (with footings) for manufactured homes with fireplaces installed along the side wall or marriage wall. Rarely are these shown on any pier print, and I have not seen them on any actual installations. However, every manual I have checked requires them. Installers would be wise to start including a support pier under the rim joist for homes with fireplaces at the marriage wall or side wall. Maybe an adjustable outrigger? While I have not seen this in the installation manuals, it would be worth asking the manufacturers to approve.

Watch for unusual window configurations!

Everyone knows that openings in the side wall or marriage wall wider than four feet require supports, but often overlooked are multiple windows that are ganged together with mullions. If there are not studs separating each window, it is likely that pier supports will be needed. Be alert for other unusual window configurations that may be 4’ wide, often over a kitchen sink.  These need support as well.

Kitchen window that needs support!

 

Certain manufacturers want you to provide “intermediate supports” at any marriage line span greater than 10’. I have seen these shown on a few pier prints, but not consistently. So double check the manual to see if you need to provide intermediate supports along the marriage line.

Speaking of marriage lines, when it comes to piers and footings under marriage line openings, a good number of manufacturer’s installation manuals have a little note that is overlooked by many installers. The note says that “if the support is shared by spans on both sections of the manufactured home, add the loads together”. In essence, the load shown in the chart is only for one of the two home sections. Therefore, you may need to double the load from the chart when the marriage line opening is on both the A & B sections. This is a manufacturer specific issue.

Another often overlooked area is where the “through-the-rim” crossover ducts penetrate the rim joist at the marriage line (except perimeter frame homes). Quite a few manufacturers call out for these supports in the installation manual, but rarely do they show up on any pier print or even marked under the home as a needed pier location.

Improperly installed G strap and pier.

 

G straps (shear wall straps), are not utilized by many manufacturers, but I see them enough to warrant mention. I don’t recall ever seeing them with the proper pier/footing. Even if you are using an alternative anchoring system, if the home is designed with these G straps, they must be provided with an anchor, strap and often a pier. These G straps have more to do with the transfer of wind load through the structure than anchoring the home to the ground.

Watch for G straps!

 

Ok, I know this can become a little confusing, but it is definitely worth a harder look. As always, refer to the specific installation instructions for the home you are installing. Read all of the notes, and if you are unsure, call the Quality Assurance Manager at the factory.

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Let’s Talk About Addendums to the Installation Manuals

I have had several professional installers reach out to me lately regarding some recently issued addendums (documents or designs) to the manufacturer’s installation manuals.  So, I thought we should talk about these addendums to help installers take advantage of these alternative approaches to the installation, and possibly sound a warning on some steps that might be overlooked.

Should you receive any designs or documents from the manufacturer (or any other source) that are not a part of the installation manual that was shipped with the home, I suggest you consider the following:

These addendums, designs, or documents MUST be stamped by the manufacturers DAPIA (design approval primary inspection agency), and the particular manufacturer must be identifiable on the documents. Without these elements, these documents should not be used. Remember, only use DAPIA approved designs!!!

Samples of DAPIA stamps of approval.

Even with the DAPIA stamps and the manufacturers identification on these addendums, it is important to be certain that they are current. DAPIA approvals are always changing to keep pace with changing construction structure methods and evolving building codes. If you are hanging onto details and designs that are more than a few years old, double check with the manufacturers Quality Assurance Manager to be determine if the documents that you are using are current.

Read the fine print! Take the time to read and re-read every note on any addendum you use and be prepared to defend every step you have taken. There are often limitations that may restrict the use of certain designs. For example, many foundation addendums require a minimum soil bearing capacity of 2,000 PFS, so be certain you haven’t overlooked such limits to these addendums.

Obtain all needed support documents! For example, if the addendum is limited for use on non-frost susceptible soils, you will need to have documents in your installation file to show the soil meets these requirements. Maybe you are using designs that require you to determine the “air-freeze index, so you’ll need to gather this information before construction begins!

Don’t forget the local building code official! Most addendums require acceptance by the local authority having jurisdiction (AKA code official), so discuss the addendum with him/her during the building permit application process. Get his approval in writing (if possible). Keep in mind, you are the primary source of information for the code official. Make certain that you are both on the same page before the construction starts!

Keep good records of every home you install!

Finally, as we have talked about in the past, you are required to maintain records of every home you install for at least 3 years. Be certain to keep copies of these addendums along with your other records.

Piers You’ve Probably Overlooked!

I know that most professional installers are very conscientious when it comes to proper pier placement. But with all the variations in the installation instructions, some piers are often missed. Even while the manufacturers are required to identify “point load support areas” many areas are still overlooked.

One example of identifying point load locations.

Let’s take a quick look at some of manufacturers installation instructions to see where they do or do not require “point load” support piers.  

  

I started with the new Clayton Installation Manual to see exactly where they require point load support. They want supports at each side of exterior doors in the side wall. No support is needed if the door is on the end wall supported by a “steel header”. So, do we need supports if the door is at the tail end of the home if it doesn’t have a header? They go further and say no support in needed for doors in the side wall if the chassis I-beam spacing is 112”.

A support pier may be needed at through-the-rim crossover locations.

Support is also required at locations where through-the-rim joist heat duct penetrate the floor rim-joist.  I have seen this requirement in a few installation manuals, but not much further direction. I don’t know exactly where to position this pier, and I have never seen these areas identified as point load support areas on the underside of any home. 

A support is needed at each side of a factory installed fireplace when located along the side wall or marriage wall, (again with the exception of fireplaces supported by the front chassis crossmember). 

Adjustable outrigger at patio door location. Note the white paint marking the location.

The Clayton Installation Manual does allow adjustable outriggers to replace piers at the fireplace locations and door locations (less than 48”) along the marriage wall or side wall. The Clayton Manual doesn’t mention the use of an adjustable outrigger at the “through-the-rim” heat duct location. (check out page 21 on the Clayton Installation Manual).

So, just for fun, I decided to compare a few other installation manuals, starting with Champion.  

Window configuration creates side wall opening greater than 4′.

When it comes to doors, Champion is pretty clear (page 16). They require a support at each point load including: both sides of doors in the side wall. If the door is less than 48”, adjustable outriggers may be used in place of door piers. “Blocking” is not required for doors in non-load bearing end-walls.  

Here is an interesting one: Champion requires support “Under heavy (400 lbs or greater) items, such as heavy furniture, waterbeds, fireplaces and large fish tanks”. I better have a few extra blocks ready for the next visit from my mother-in-law!

Typical porch support.

What about Commodore/Colony you say? Ok, turn to page 15 in their installation manual. They want support at both sides of exterior doors at the side wall, but not at doors in the end walls. Porch posts always require support. They also want a support at through-the-rim heat crossover ducts, and under heavy items like waterbeds, fireplaces, and mothers-in-laws.  

Here is the curve ball: “…where marriage line openings are greater than 10 feet, intermediate supports must be placed at maximum 10 feet on center”. Some other manufacturers have this same requirement. Others only want these intermediate supports if the home has perimeter supports (evenly spaced under the side walls).

T Brace (pier saver).

I think it’s only fair to say, that Commodore/Colony was the first manufacturer I was aware of to introduce “Pier Savers” for support of patio and other exterior doors! I am a big fan of pier savers.  Look up their “Alternate T Brace” addendum A-7.

Adjustable Outrigger

Skyline requires a support at exterior doors on side walls (not end walls), typical 4’ marriage line and side wall openings, through-the-rim crossover ducts, porch posts, heavy furniture, fireplaces, etc. BUT..Skyline utilizes the adjustable outriggers more liberally than most. Basically you can use an adjustable outrigger to replace a support with a load up to 1,700 lbs. Go to their charts on page 20 of their installation manual for span loads. Some Skyline plants provide the adjustable outriggers with the homes. Make sure you get a copy of the “Addendum to Installation Instructions for Installation of Adjustable Outriggers”   

Shear wall strap needs pier support.

Finally, I checked out Fleetwood, pretty similar to the others, except they want support at “labeled G-2 strap locations” (see page 20 in their installation manual)

At this point you might be thinking, “just follow the pier print”. Well, I checked out a handful of “pier prints”, and most of the locations mentioned above are NOT identified on the pier prints. None showed the piers at the through-the-rim crossovers, or at any fireplaces. Also, the “intermediate” supports at the marriage line is missed by most. One pier print I noticed shows piers that defied any reasoning!

OK, here are the take-aways:

There is no “One Size Fits All”. Make sure you take 30 seconds, and open the installation manual and look under the heading “Install Footings” where you “Determine Locations”. Make sure you know each particular manufacturer’s variations.

Don’t trust the pier prints! Never, Ever! Follow only DAPIA stamped (approved) designs and instructions.

Investigate pier savers and adjustable outriggers! Some manufacturers already approve their use. If yours doesn’t, start asking for approval! The squeaky wheel always gets the grease.

And lastly, don’t invite my mother-in-law to your house!