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.

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Embedment Factors? Cohesive Soils? Let’s talk about it!

Looking over a recently revised manufactured home installation manual, (DAPIA approved in Feb. 2018),  I ran across something that I thought was worth a closer look.

In the section of the manual that talks about footings, I found a chart titled “Foundation Embedment Factors for Cohesive Soils” (there is also a chart for Non-Cohesive Soils).

In case you are wondering, cohesive soils are described as clay, or soil with a high clay content, which has cohesive strength. Cohesive soil does not crumble, can be excavated with vertical sides, and is like plastic when wet. Cohesive soil is hard to break up when dry and sticks together when submerged. Cohesive soils include clayey silt, sandy clay, silty clay, clay. 

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Cohesive Soil

 

On the other hand, non-cohesive soils are loose soils like sand, or sandy soils.

Ultimately, by using these charts and directions, you can increase the maximum load per footing based on the depth that the footing is embedded in the soil.

Let’s try to work through the process.  This manufacturer tells me that a 14’ wide home, in the south (20 psf) roof load zone, with piers spaced 8’ apart, has a pier load of 5640 pounds (per pier).

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Since I like to auger round footings, the chart for circular shape footings says that I need a 28” round footing at a soil bearing capacity of 1,500 PSF. But my auger is only 24” diameter! Well, this is where the “Foundation Embedment Factors for Cohesive Soils” chart might come in handy!


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Since I can only dig 24″ round footings, I need to start there. The chart for circular footings tells me that a 24” round footing can carry 4710 pounds (again 1,500 Soil bearing capacity). I know my 24” round footing will be 36” deep (for example, to get below the frost line) in a clay (cohesive) soil, so I can multiply the 24” footing capacity by the 1.56 as indicated in the cohesive soils chart and my 24” footing works! (4710 pounds x 1.56=7347 pounds, well beyond the 5640 pound load needed to support the home).

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It is not as confusing as it seems. You just need to know if your soil is cohesive (clay) or non-cohesive and know the footing size and depth. Use the chart to determine the embedment factor and multiply the footing capacity by the factor from the chart.

A few important things to consider before you start reducing footing sizes. Currently, this is specific to only a few manufacturers. You need to check with the Quality Control Manager at your factories to see if they allow you to utilize embedment factors. One manufacturer told me that they provide these designs only upon request.

Next, you need to have a very thorough understanding of the soil at the job site. You need to have all of your documents in order and make certain that the building code official (and possibly the purchaser) understand how you are calculating these footings sizes/loads. As always, keep good records for your installation files, including copies of these charts.

While I am not an engineer, I do think that the embedment factor is to be applied only to poured in place concrete footings. But you can verify that with the factory. 

Finally, on the one manual I reviewed, there is a big typographical error, labeling the chart for non-cohesive soils, so be cautious. Stay in touch with Quality Control folks and watch for further changes to the manuals. 

A Tool to Improve the Building Permit Application Process

Having just wrapped up a week of talking to building code officials in three different states, I was reminded of the importance of the building permit application process and how professional installers need to improve the flow of information between themselves and the building code officials. 

Far too many installers continue to pretend that the entire installation process for a manufactured home can be boiled down to a one-page pier print. Then complain if the code official doesn’t uniformly enforce installation requirements on other installers. The problem is that it is very difficult to organize the documents needed into a manageable sized packet of information. The typical installation manual is far too cumbersome and code officials are not going to spend time flipping through these 100+ page manuals for each permit application. Nor should they!

I thought if we could create a tool to help assemble a packet of designs, extracted from the manufacturer’s  installation instructions, it could streamline the process, focus on the important issues of support and stabilization and help eliminate bad actors from the business of manufactured home installation. This post is intended to help installers assemble just such an informational packet through the use of a cover-sheet to pull everything together! 

I know you don’t think you have the time to organize all the documents needed for a complete building permit application, or that the code official doesn’t want anymore then the one page pier print. But if we are ever going to move the manufactured housing industry and careers as professional installers forward, we need to look at the bigger picture when it comes to working with building code officials. 

Here are a few things to consider:

 Manufactured homes have gotten significantly more sophisticated over the years, yet our approach to working with the building code officials remains unchanged! If we want to improve the image of manufactured housing and attract a larger segment of the home buying public, we need to earn the confidence of the code officials.    

Getting familiar with charts like this is step #1 to a more professional installation

 As a trained and licensed professional installer, you should take charge of your installations by being in control of all of the documents needed to properly install the home. The way we have always done things in the past is probably wrong, out dated, and a waste of money and time. Housing designs have changed rapidly over the years, both installers and code officials must be on top of these changes. The only way to keep up with the changes is to make sure we are submitting and following current and pertinent installation documents with every permit application. We just lacked a tool to help installers organize the designs they need for a building permit. 

 Are there unlicensed installers stealing work from you? Once building code officials start seeing exactly what is to be expected for every building permit and subsequent installation, unlicensed installers will not be able to keep the pace.

 Most importantly, a properly applied for building permit eliminates variables and unknowns from the process and goes a long way in increasing profits and reducing liability.

Ok…here is a breakdown on what should be included at permit application as a minimum:

Identify the licensed installer! Show the code official your license so that they come to expect a licensed installer for every new manufactured home installation.

Identify the home by manufacturer as well as home width, side wall height, roof pitch, foundation type and for a few manufacturers, the size of the eaves along the sidewall.

A copy of the manufacturer’s DAPIA approved installation instructions that highlight the appropriate charts and tables needed to construct the foundation. If not submitting the entire installation manual and only the table of contents page shows the DAPIA stamp, provide a copy of that page as well.

Provide DAPIA approved documents from the manufacturer that show approval for any alternate installation methods you might be using (such as alternative anchoring system or shallow frost protected foundation).

Include the Complete Installation Checklist from the installation manual or a Expanded Installation Checklist (from October 16, 2017 post) to better address the installation.

Provide notes on the soil bearing capacity, frost depth and other site-specific considerations that are needed to assure a proper installation.

Typical Pier Print-an installation tool, but must be used with several other design details.

 

And finally, prepare a plan of the home where you can layout the proper location of piers. CAUTION! Pier prints from the manufacturer are not to be trusted. Every pier print refers the installer to the actual installation instructions.  You may want to use the pier print as a tool to help you determine pier locations, but never trust these pier prints without first reviewing it yourself! 

A sample of the permit application cover sheet.

The link below will take you to my attempt at developing a tool to help professional installers organize the documents needed for the building permit application. Feel free to modify it for your particular use.  Click Here for Manufactured Home Building Permit Application Cover Sheet

You will likely need to add some additional documents for the code official (plot plan, sewer tap permits, etc.), but the cover sheet in the above link, will help you get the home specific details in order. Consider making this a part of your typical building permit procedure. I promise, if you try it one time you will quickly see the benefit! 

    

Alternative Foundations

This concrete slab on grade is one example of an alternate foundation.

I know that through the years a lot of community owners have hired professional engineers to design foundations for homes installed in their parks. Many times, these foundations are elaborate, well designed, and constructed beyond the minimum requirements of the installation standards.

 In some places, these foundation designs were also reviewed and approved by the state, county or local code official.  With approval from engineers and building code enforcers, what could be the problem???

 Well grab your “Model Manufactured Home Installation Standard” and open to section 3285.2(c)(1). It says that BEFORE an installer provides support or anchorage that are different then the installation instructions, or if the installer encounters site conditions that prevent the use of the installation instructions, the installer MUST:

  •  Try to get DAPIA approved designs or instructions from the manufacturer; or
  •  If the designs are not available, have designs prepared and stamped by a professional engineer (or architect), and submit these designs to the manufacturer for their approval, and approval by the DAPIA!

After a few modifications, this foundation was manufacturer and DAPIA approved!

 Basically, any foundation system that is not addressed in the manufacturer’s installation instructions would be considered an “Alternative Foundation System”. It would need to be approved by the manufacturer and their DAPIA before you can use it to support/stabilize a new manufactured home. Ultimately, the manufacturer needs to agree that any alternate foundation will properly support and stabilize their homes.   

 So, if you are placing new manufactured homes on anything other than a typical concrete block pier with individual footings that extend below the frost line, and a ground anchor tie down system, you have a little paper work to do.

 First off, do you follow an actual design plan for the foundation you are constructing? I know far too many installers follow  the “way we have always done it” plan. If it is a concrete slab or a purchased system from a supplier, or something entirely different, make sure there is a design to be followed and make sure you follow that design.

 Next, check through the manufacturer’s installation manual for the home. Some installation manuals provide the installer supplements that address a wide verity of alternative foundations. For example, certain manufacturers provide DAPIA approved designs on placing their homes on steel crossbeams in masonry crawl spaces and basements, and others have DAPIA approved designs for concrete slabs. Most have DAPIA approvals for alternative anchoring systems. Grab the most current manual from the manufacturer and see if your foundation is addressed. If it is, make sure you read all of the little notes and disclaimers so that you are in full compliance.

 If you can’t find any designs for the alternative foundation you utilize, call the factory’s Quality Assurance Manager and ask him to help. It is possible that the manufacturer already has designs that can help you.  Don’t ask the sales department, service department or supplier about design or code related issues. The Quality Assurance Department is your best bet.

 A word of caution, I have seen foundation products from supply houses that appear to be approved by a DAPIA, but the specific manufacturers approval is needed as well.

 So, before you get too deep into your busy season, take some time and make sure you:

1.       Have a manufacturer and DAPIA approved design that clearly addresses the foundations you construct for new manufactured home installations.

2.       Make sure you read all of the fine print, notes, instructions, and limitations of the designs you are using.

3.       Make sure you follow the designs!

4.       Make sure you have copies of these designs for your records.

5.       Take a few pictures through the process.

Bottom line, make sure you have a design from the manufacturer that has a stamp showing it is DAPIA approved for every foundation type you construct!