I recently had the opportunity to inspect 20 new manufactured home installations, and I thought it might be helpful to share my observations.
The individual installers were invited to participate in the inspections and for the most part, they all did. Having the installers present to answer questions and being able to show their processes and procedures proved very beneficial. Several installers brought along their installation files which were very helpful. These documents helped to illustrate how they determined footing size and spacing, anchoring, and their self-inspection of the job through their use of the installation check list.
The most common finding (as usual) were problems with site grading. Many of the homes would have benefitted from a few lifts of fill dirt to elevate the home site. Keep in mind, the area under the home must be higher than the surrounding lot.
One installer had some issues with the installation of the alternative anchoring system, which they will need to correct. The first problem was that the long transverse arm (from the footing to the opposite side frame), was attached to the bottom of the frame (I-beam). These alternative anchoring systems are designed and tested with the transverse arm attached to the top of the frame. The top of the frame is lagged to every floor joist and as a result is stiffer and more able to handle the forces generated in a wind storm.
Also, when anchoring single section homes, the required ground anchor straps at each corner of the home were installed vertically. The straps were straight up from the footing to the frame as opposed to diagonally from the skirting line to the frame as generally required. Note: Xi2 will allow for vertical anchor straps if the footings are of sufficient size to support the loads, see the specific instructions for the system you are using for more details.
A few of the anchor straps were not wrapped sufficiently around the slotted bolt at the anchor head. In general, you need 4 to 5 wraps around the slotted bolt. None of the anchor straps had protection from the edges of the frame as needed. Check the anchoring and manufacturer’s instructions, and make sure you are properly installing whatever system you are using.
Another concern at a few of the homes were undersized footings. The piers were placed on 18” diameter footings spaced 8’ apart. Since no determination of soil bearing capacity was made and/or documented, there was no choice but to default to a 1,500 PSF soil which would require a 24” diameter footing for 8’ pier spacing per the manufacturer’s instructions. Be certain that you can justify your foundation decisions based on soil conditions and the manufacturer’s installation instructions.
Since we are talking about foundations, I ran across a few marriage line support piers that were incorrectly positioned as they were parallel with the marriage line. These piers should be perpendicular to the marriage line.
I saw one home with a gas fired water heater that was drawing combustion air from the crawl space under the home. In general, all combustion air intake ducts must be extended to draw air from outside of the skirted crawl space.
The vinyl siding on the end walls of a few two section homes were installed in a manner that could restrict the movement of the siding. The siding seams were overlapped over 3”, when the instructions only allow 1/2” to 1 ½” overlap.
Finally, one installer was having trouble with the flash rings installed in the exterior light fixtures. It is important to remember that any combustible material exposed to the canopy of the light fixture must be protected with the non-combustible flash ring provided by the manufacturer. This is important for “jelly jar”, “carriage” or other fancy light fixtures installed on vinyl, wood or other combustible siding materials. Generally, unless the light fixture canopy is the same shape and size as the junction box to which it is being installed, a flash ring is required.
Ultimately, I am thankful for opportunity to work with some great professional manufactured home installers. I was impressed with their level of knowledge and pride in their work, and hope to work with them again in the future.
As always, be sure to follow the manufacturer’s approved installation instructions for all of your installations!