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.
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.
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.
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.
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.
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.
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.