Depending on the soil stability of your land and total load of your home, manufactured homes have several foundation systems that help make it a durable and permanent home. It can be on a pier and beams to keep the home economical and portable, or have a basement foundation to gain extra square footage.
Basically there are four kinds of foundations that manufactured homes typically use:
- Pier and Beam
- Slab
- Crawl Space
- Basement
Choosing which system to use will depend on your soil type, how much load it needs to carry from your home, your site and weather conditions as well as budget.
Pier and Beam Foundation
Pier and beam foundations are the most simple, economical and therefore most common foundation system for manufactured homes. This foundation holds the home down, to secure it from strong winds. Here’s a step by step installation below by Clayton:(1)
- Cement anchors are driven into the ground or screwed onto a concrete pad (below frost line approximately 42” deep)
- Steel straps are attached to ground anchors to connect to beams of your home
- Anchors connect by wrapping straps around the steel I-beams of the home’s frame
- I-beams are connected with cross-members for added stability.
- Outriggers are welded to steel I-beams for added strength and support
Simply put, these concrete piers serve as a tether to secure the house down to the ground from strong uplift winds. They raise the house enough to give room for the home’s main beams that run across the structural frame.(2)
Having less materials makes installation time quicker relative to other foundation systems. Less materials and labor also adds attraction to its lower cost.
Despite being affordable, it is still resilient against weather conditions having good wind zone resistance. It can be used in seismic and flooded areas or those that experience heavy frost. (1)
If your site has softer soil or is subject to heavy storms and snow, more anchors and tie-down straps may be specified to safely fasten the home to its foundation.This is typically specified by your building professionals and local codes.
Being elevated off the ground works well for places with high humidity but is difficult for underfloor repairs and may generate some dampness. (3)
Do note that if you plan to use this foundation system, you can fund your manufactured home with almost any type of loan except with an FHA loan. (2)
Single and double wide homes can make use of this pier and beam foundation. Often homeowners opt to cover the exposed piers (like the image below) with a vinyl skirting. (4)
Slab Foundation
A large concrete slab is placed on the ground with ground anchors (embedded in concrete) and supports your entire home’s footprint. The slab is often insulated at the perimeter to maintain the ground’s warmth underneath and to comply with FHA requirements. (1)
Compared to other foundation systems, it is still considered quicker and cheaper than most. It will cost more than a pier and beam system, but if you’re availing your home through an FHA loan, it meets the FHA requirements and criteria of the tax office tax for property as real estate. (2)
It is equally resistant to seismicity and weather conditions. In the snow, it does not do well if the slab is “floating” but can be efficient when insulated. It is not advisable to be used in sloping lots or those with an uneven terrain.(1,3)
This foundation consists of a 4” to 6” inches deep concrete pad with drain tiles, keeping the ground dry, clean and warmer underneath. This is in order to prevent any pad movement or “float” (which will not meet FHA requirements). Insulating the pad from water drainage also ensures stability. (2)
Slab foundations typically have a layer of 4 to 6 inches of gravel and sand beneath as drainage. The slab serves not only as the home’s floor but also as its structural support. The electrical wiring and plumbing lines need to be coordinated early if they’ll be embedded in the flooring or unlike other manufactured homes, within some walls. Both single and double wides can make use of this foundation. (3,4)
“In areas where the ground freezes during the winter – like West Michigan – slab foundations are often poured over piers to add stability through freezes and thaws. If a slab foundation is poured without piers, it is called a floating slab. However, not all homes can be placed on a slab foundation without piers; in 2017, the Department of Housing and Urban Development (HUD) put a new code into effect that now requires an engineering study of the soil to see if a home can be safely placed without piers.” (4)
If elevated enough, it can be paired with a concrete block skirting to provide a bit of storage and utility space underneath the home. This can also protect the home from weather damage and pests, but can be harder to do repairs and requires a longer installation. Know that this tactic is mainly for the illusion of a stick-built home and does not provide structural support. (4)
If you really want to utilize your underhome space, check the last foundation systems below:
Crawl Spaces
Specially catered to manufactured homes, the floor is excavated around 48 inches deep and built with cast in place concrete walls and footers to give weight and fasten the home to the ground. This has the frame sitting on the perimeter wall while the perimeter beam combines the idea of using steel straps to connect ground anchors. Depending on your home, pier locations and quantities are placed for additional support. (1, 2, 4)
This foundation system is ranked to cost more in price and time than the previous ones. It is not ideal for hurricane or flood prone areas, but still performs well against strong uplift winds, seismic activity and heavy frost. (1)
It has resistance to termites, humidity, frost and winds but can be susceptible to flooding and the extra under space is not habitable. (3)
It is considered the top choice in securing an FHA loan and converting a manufactured home into a “real property.” It naturally provides a more stick-built home appearance and this time the block piers beneath really serve as your structural support. Having no solid slab, it has no problems with drainage. (2)
This type of foundation is more commonly found in modular homes than manufactured homes (4)
Basement Foundation
Basements here act as a great structural support system, while giving extra living space!
More on manufactured home basements in our article. For an overall comparison of all systems, basement foundations are the most costly, take the longest to build and do not perform well against flooding. They do however have the biggest financial returns, in FHA loans, resale value and real property conversion. It drastically increases square footage and is resistant to frost and earthquakes. It even acts as a bunker for strong winds.(1)
They take the most time even at the conceptual planning stage, being another structural element to design, it must specifically cater to your local codes. This gives them the flexibility to be placed in sloping lots of various levels. (3)
Which Foundation is Best?
There are several factors to go over with your home consultant in choosing the best foundation for your home. Besides the site conditions and overall budget, your intentions for your manufactured home play a big role. (4)
Do you want to keep its transportability? Or apply for conversion into “real property”? Note this needs a lot of careful consideration from the Federal Housing Administration (FHA), Housing and Urban Development (HUD) and/or the Veteran Affairs Department (VA) guidelines. (3)
Permanent foundations like your basement and crawl space provide better financial returns, qualify for more real estate loans and offer extra square footage. Non-permanent foundations are those you can detach from the home like your slab or pier and beam, making them quicker to install and cheaper upfront.
Rest assured all manufactured home foundations are certified by the Department of Housing and Urban Development and are rendered safe since requiring a building permit. (4)
References:
- R, A. (2020, April 24). What to know about manufactured home foundation types. Types of Manufactured Home Foundations | Clayton Studio. Retrieved May 2022, from https://www.claytonhomes.com/studio/building-on-strong-manufactured-home-foundations/
- Campbell, J. (n.d.). Manufactured homes: Pier vs. Slab Foundation. Hunker. Retrieved May 2022, from https://www.hunker.com/13414638/manufactured-homes-pier-vs-slab-foundation
- Worthy Inspection Services, LCC. (2018, June 7). A Quick Guide to Manufactured Home Foundations. A quick guide to manufactured home foundations. Retrieved May 2022, from https://www.worthyinspections.com/blog/a-quick-guide-to-manufactured-home-foundations
- Preferred Homes. (2022, January 18). Modular & Manufactured Foundation Types & requirements to know. Preferred Homes. Retrieved May 2022, from https://preferredhomesmi.com/manufactured/foundation-types-and-requirements/
