Mobile Home Foundations
Tuesday Mar 21st, 2023
Mobile Home Foundations
--------My Video is at the end---------
Let's end some Mobile homes Ignorance, shall we?
It is a known fact that Manufactured homes are set on Blocks. This fact gives many people the idea that they are not really permanent.
But, did you know that nearly all housing was set on blocks until about the 1950's? Ah, yes. Today, most houses built are site built using
a poured concrete footer system to distribute weight over a larger area of the ground (To prevent sinking) and to attach the home using rebar or a more direct connection method. When I worked as a draftsman for an architect in the late 1990's I drew up many foundation plans for custom homes and understand them fairly well. Home builders used my plans to build homes. I appreciate these systems. But they are not the only way to set a home on site.
Prior to the 1950s, homes were built using many different foundation methods. The misconception is that ALL site built homes are on a "Permanent Foundation". I argue that they are not.
Many of the homes you see are set on dry or wet stack blocks. This means that concrete blocks have been set directly on the ground and the wood beams of a home set atop them. Most Craftsman homes that we have come to love and admire are built over these types of foundations. How are they attached, you may ask. They are not. That is right. Do not freak out. They made it through Hugo. There are no actual holding connections on many homes made prior to the 1950s. Some have various attachments because of the builder or home owner who had their own personal concerns. But, it was not common to consider such things. The weight of a home was more than enough to hold it down. Certainly no wind could shove it off and we do not have many earthquakes in South Carolina. I have seen homes built around 1900 that actually sit atop river rocks. Yep, the round ones. Still sitting still after all this time. It seems these people took the proverb given by Jesus quite literally.
What do Mobile homes use today?
First, "Mobile Home" actually refers to a home built prior to 1977. This is when the new HUD standard became the law for building and setting up "Mobile homes". And this is very important to what we are talking about here. Prior to 1976 these light weight single wide, thin built homes were literally made to "Move". I am not referring to moving them from the manufacturer to a piece of land. No, they were designed to move around from place to place. They were built light, thin and cheap on purpose. Campers were made to move every day. Mobile homes were built to essentially move every year for various reasons. They filled a niche and need in the market. But, as they gained popularity, many started using them as permanent living structures. Homes of this era gave us the commonly used slang term "Trailer Home". They begun building them larger and heavier. Pretty soon, a problem arose. While there were state and local building codes for site built homes, mobile homes/trailer homes were built the way the manufacturer decided, and then the homes were shipped to their resting place. Often, in states far from where they were made, Manufactures were sidestepping local building codes. This meant many homes were built with no quality control standard.
Enter the Manufactured Home Construction and Safety Standards (MHCSS) .
1976 : This new HUD Code became the standard for all Manufactured homes. These new standards were a drastic improvement to the "build like you want" methods of the previous Mobile homes. These standards were an agreement with all states to build these new "Manufactured Homes" to a code that everyone agreed was acceptable in quality and stability for a permanent residence. All states accepted and allowed this new Code. With a few exceptions. Wind zones. There are certain areas of the country that receive more wind than others. This includes hurricanes and tornadoes. These higher wind zones require stronger builds. The area I live requires a Zone 2 structure. More inland can accept a Zone 1. Zone 2 homes are built to withstand stronger winds than zone 1. Insurance companies will always ask for the Zone type of a home when writing a policy. It matters. These standards were put in place to consider a home a permanent structure, instead of a "Mobile" one.
With these new standards in place, a New term was created to refer to a Post-HUD CODE structure. "Manufactured Home". This term replaced "Mobile Home" according to the the Housing and Development Department of the United States.
- Mobile Home= Pre-1977
- Manufactured home= Post-1977
This is also the time permanent foundations become standard.
The above picture is a modern strapping and foundation system.
In the past, mobile homes/trailer homes were simply jacked up and blocks were set underneath to stabilize it. The wheels, axles, and transportation tongues were left on them. To move them, all you had to do was pull the bocks out and pull it away. However, Manufactured homes are built with one to two moves in mind. Yes, they are designed to not only withstand the area zoning winds, but also 60 MPH while they are transported down the highways to their final resting location. Quite impressive for a home most people believe to be too flimsy to survive a wind storm. The new standard set in place codes for making a home "Permanent". The old way used blocks tossed under in any old fashion. The new standard included a solid Block at bottom to distribute weight over the ground, a series of blocks turn strength side up for elevation, a solid block to cap, and then a wood block of a specific size to distribute weight over the cap and cushion the frame to concrete connection. The standard also included how many of these piers were needed for each home, depending on it's size.
But Wait, There's More!!!
Depending on soil type, a 36"-48" series of anchors are screwed into the ground and fastened to steel strapping that attaches to the structure. While we already learned that older homes simply sat on blocks, these homes have to be strapped to the ground. Each zone, soil type, and area might require a different number of these straps. The fewest I have ever seen on a home was 4 on each side and 2 on the ends. The most was 10 on each side. These straps are then ratcheted, holding the home tight to the piers. The wheels in many cases were required to be removed, along with the transportation tongues. Making it very difficult to move them again.
While these new permanent foundations were a drastic improvement, there was still a need to make them better. In 1992 Hurricane Andrew, which hit Florida, taught us all that the standard needed improvement. Studies were conducted, and in 2000 the Manufactured Home Improvement Act of 2000 was put in place. One of the problems that Hurricane Andrew taught us was that if a home received more wind on one side than the other, the home could be twisted and pull away from its hurricane strapping. So new strapping systems were designed. Including the Oliver System. I can only assume the name is a play on Oliver Twist. These systems were designed to prevent Lateral movement. (Twisting)
So, not only do Manufactured homes now have better blocking foundations, but they also have vertical strapping and other systems in place to prevent lateral movement.
This is important to you if you are buying a pre-2000 manufactured home using an FHA or VA loan. They will require an engineer to certify the home meets the new HUD code.
Do not worry. I know people that can install various systems and bring your home up to modern code, should it not meet the current standard. (Oliver is just one of many systems available)
If you read my last Blog, you know that brick skirts cause problems. But, some sort of skirting must be installed to prevent wind from getting under a home and causing the home to be lifted up. New codes do require homes to have some sort of skirting to be framed in using brick, wood, Hardie board, or some sort of material that is not so easily removed during windstorms. Even fiberglass can be used and is used often. But the HUD code for FHA and VA will require those types to be attached by wood framing to increase strength.
All of these systems working together help create a stable and strong attachment to the ground.
Back to Site built homes. Pre-1950 homes may not have many wind prevention attachments to the ground at all. This is something you will have to crawl under to check for yourself. Here is a picture of a 1920 Craftsman crawlspace. 102 years old. It has seen many storms and still stands strong. Look at those Gorgeous hand cut beams! Yet, there is no strapping. The home is simply sitting atop stacked bricks.
The point of this blog is not to scare you from buying an older home. I wish to remove some ignorance of what is and is not a "permanent foundation".
Many believe Manufactured housing to be an inferior building product. And while this case can be made concerning some building methods, I wish to (for the time being) answer the argument that the foundation is not sufficient in comparison to "Site built" homes. In most modern cases, Manufactured homes are set in place using debatably better methods than many Site built homes of the past. So, instead of assuming that a manufactured home is not using a stable foundation, ask WHEN it was installed and if it has an updated foundation system in place. If it does not, that is correctable. The blanket statement "Mobile homes will just fly away in a storm" is simply not true. Many people are unaware that there has been a change in building codes for these Factory pre-built homes. These unaware people still call every rectangular shaped home a "Trailer Home". Some might even argue that a steel chassis remains underneath and so it remains a "trailer". Well, that is a hard one to argue out of haha. All I can say to that is: "Yes, there is a strong steel Chassis under the house that termites and wood rot cannot eat away. There are also floor joists and a subfloor, like in your site built home. But, there is an extra steel structure under there supporting it and strengthening a Manufactured home." If that bothers you, move along.
There is quite a stigma on Manufactured homes that I aim to help remove by doing a series of blogs about the ignorance spanning a few decades.
I'll be covering building standards and even why some of the thoughts of "cheap" building materials are in fact true. But, not always.
Click here for- Manufactured Home Install Video
I am a Licensed Realtor in South Carolina with much experience in buying and selling Manufactured housing.
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