Unfortunately, many mobile homeowners attach porches and additions onto their mobile homes incorrectly. Itโs not usually a detrimental issue, thankfully, but an incorrectly installed mobile home addition can pose problems. In this article, we are going to cover mobile home additions as thoroughly as possible. Weโll cover the advantages and disadvantages of adding to your mobile home and all the basics of building an addition or porch onto your mobile home, plus a few more important things you should know.
The Basics of Building a Mobile Home Addition
There are a few basics you should know before you decide to build an addition onto your mobile home.
The most important thing a homeowner should know before adding to a mobile home is that the addition should never be attached to the home at all meaning the addition has to be built completely separate from the home with its own footers so that the weight of the build is distributed directly into the ground and not the home.
Mobile Home Additions Must Have Their Own Foundation So It Can Shift Independently of the Home
A mobile home addition must move freely from the home itself. Porches, decks, and additions must have their own foundation or footers so the structure can shift independently of the home. The addition is simply โbutted upโ and attached to the mobile home, and โsealedโ so nothing impedes the separate movement.
In other words, an addition should have at least 4 footers, one at every corner to transfer its weight to the ground. If you only see two footers at the โendโ of the addition (the side opposite the home), then itโs probably wrong and should be checked by a licensed profesional.
To put it simply, you arenโt attaching the addition to the home at all, you are building extremely close to the home and then sealing the crack between the home and the addition to prevent air and moisture leaks.
Footings for Mobile Home Additions
An addition needs a completely separate foundation from the home. And, like any structure, the footers must be placed below the frost line to keep them from shifting when the moisture around the cracks in the ground freeze causing the footers to heave and bow.
There are poured footers, cinder blocks, slabs, and piles.ย Footings for a mobile home addition should be determined by the depth of the frost line of your area, even if your home does not have the frost line footers so that shifting is minimal.
Hereโs a map showing the frost line depths for the US:
Footers are installed below the frost line so that the addition doesnโt sink or shift.
Financing and Insurance Issues for Mobile Home Additions
Additions to manufactured homes are not often seen as an โimprovementโ โ meaning it probably wonโt increase the value of the home in most cases. It wonโt change the classification of a manufactured home from personal property to real estate unless the home is permanently installed.
A big disadvantage of building an addition on your mobile or manufactured home involves financing and insurance. It may be harder to obtain both if your home has been modified in any way. If you didnโt get the proper inspections and permits you may run into serious issues if you try to sell the home later down the road.
Permits and Inspections
Some state mandates override local and county regulations when it comes to manufactured homes. Research properly for your location before you begin planning a mobile home addition. With some locations, you could run into so much red tape that the project ends before it even begins.
With all that said, mobile home additions are perfect projects for families that need a larger home but you must get permits and inspections done before, during, and after the construction process. Read about one manufactured homeownerโs experience while building an addition onto his single wide. He failed to get permits and inspections done and paid a price when he sold the home.
Addition on 1985 Liberty Single Wide
Sarah and Justin Wartick built an addition onto their 1985 Liberty single wide. You can see how they created the footers right up against the home and then framed the floor of it out (they were test framing the top in the first image). The second image shows the walls and roof have been framed and the floor joists being laid.
These next two images are the interior of the addition. The image on the right showing the door with the two steps is where the mobile home and the addition are attached. Technically, this is the only place the two structures meet other than where the roof and the siding are โsealedโ together.
HUD Guide on Manufactured Home Foundations and Support Structures
There are some great online resources about mobile home foundations. This guide about manufactured home foundations and supports is invaluable.ย
For information about general construction footers, Front Porch Ideas and More has some nice illustrations that show the poured concrete and pier footings.
There are new products hitting the market to aid in DIY footings such as theseย square foot concrete forms.
Framing an Addition
You want the mobile home addition to having framing that is equal to or better than the framing that your home has. Of course, youโll need to follow your local code.
Below shows a mobile home addition being framed out by SM Construction.
A great blog called Dovetail Blog shares its mobile home addition process in detail. Itโs a small addition but the end results are beautiful:
As you can see, they used poured concrete footings and extended the roofline down to the addition, keeping the pitch. The addition looks to be used as an entryway that houses the stove and is a few inches lower than the home, except for a platform that the stove sits on.
Hereโs the interior of the home:
ย Opening Between the Home and the Addition
Youโll have to determine the size of your opening from the home to the addition. Doorways are easier to close up should the home ever need to be moved or the addition removed.
If you do opt for a wider opening between the home and the addition you will need to consider support issues for the opening. Wider openings, where studs would need to be removed, will likely require support beams. Thatโs not the smartest move for mobile home perimeter walls because those are your load-bearing walls. In other words, keep the opening small so that itโs easier to seal around the home and to keep from needing to support the perimeter wall with a beam.
Sealing Around the Mobile Home and the Addition
As stated previously, basic mobile home additions are not completely attached to the home. They are simply butted up to the home and then sealed all around to prevent leaks.
There are a variety of ways to seal the connection between the home and the addition. To seal the gaps between the home and the addition you can use weatherstripping, flashing, backer rod, caulking, and lumber. A backer rod is just a fancy name for round foaming that can be used as a membrane between the 2 structures.
There is a popular way to attach the siding of the home to the addition. Attach a 1ร6 board to the home vertically so the addition will butt up against the middle of that board. Youโll attach another board with a lip to the side of the addition. Then, add weatherstripping and screw the lip of the addition to the board on the house โ this brings the addition toward the home and helps seal it without overly damaging the home.
Flashing and vinyl siding will cover it all up.
Sealing the Addition Roof to the Mobile Home Roof
To connect the additionโs roof to the home if the addition is lower than the roof on your home, you will need to use flashing to seal the gap between the home and the addition.
For a metal roof, you would tuck a single length of 18โณ flashing, that has been bent to the needed angle, place the flashing under the homes roof edge and over the addition roof. Attach to both with screws. Using 2โณ neoprene flashing tape is always a good idea, and always seal the screws with weatherproof caulking (neoprene based). One note about the flashing, you want as long a piece as possible, but you donโt want it too long. If the flashing is too long it can cause cracks.
If the 2 roofs are at the same height, you just use flashing. Screw and seal.
Thereโs a rubber roofing that would work well. There is also a rubber membrane thatโs 24โณ wide that professionals recommend for this situation.
If the additionโs roof is higher than the roof on your home, you add the flashing under the lip of the roof of the addition and over the roof of the home (the opposite of above). This creates what roofing professionals call valleys and are problematic areas on any home. Special care should be made to keep water from sitting in the valley that is created.
The graphic below is based on a graphic found on Mobile Home Repair that shows a concept for sealing a mobile home addition. The top drawing shows a cap built on the home (labeled Alum Cap) and a piece of wide weatherstripping folded over to make a bulb shape and screwed into a board on the top edge of the addition.
The bottom drawing in the image above is showing the home and addition from the top, looking down. A flexible vinyl with fiberglass insulation is used to seal the sides of the addition to the home. It allows the needed movement required if your home is not set on a permanent foundation that is set below the frost line โ the best method to prevent shifting of a manufactured home.
Examples of Mobile Home Additions
Below you can see a mobile home addition that passed inspection and can be found on The Inspector Blues blog.
It is independently supported, has wired smoke detectors, an exit, sits on an 18โณ grade, and is built with pressure-treated wood. It may not be great looking but it had what it needed to pass its inspections and current codes are not lax at all.
Hereโs a park model manufactured home getting an addition built onto it. Notice how theyโve done the roof:
Another park model manufactured home addition and carport built by HorseFly Construction:
The next photo shows a huge addition built onto a double wide manufactured home by Addon Rooms:
Weโve featured a few homes with additions:
- Gorgeous Single Wide Mobile Home with Unique Addition
- Like A-Frames? You Have to See this Unique Mobile Home Addition!
- Debt-Free And Dreamy 1985 Liberty Single Wide Mobile Home Remodel
- Building A Two-Story Addition Onto A Manufactured Home
Questions and Answers about Mobile Home Additions
Itโs not hard to grow out of a home. We had two adults, a child, and 3 fur babies living in a 1978 single wide with 696 square feet of living space. I often dreamed of building an addition onto the home!ย
The following questions about mobile home additions cover topics such as adding a garage, living in a home while the addition is being built, and the cost of an addition.
4 Common Questions about Mobile Home Additions
These questions were asked in the comment section of our very informative article aboutย building mobile home additions found here.
Can I Add a Garage Beside My Manufactured Home?ย
I have a 1300 sq ft home on a permanent foundation in rural Colorado. Last year I had cedar log siding put on the outside (big improvement).
Is it possible to add to the end of the place an attached double car garage with a small apartment above? My building department told me if I add 33% SQ footage to the home, it changes from mobile to standard construction. I am thinking of a 20 x25 addition. An apartment could be rental income.
You should have no issues building a separate garage with a second story beside your manufactured home assuming it meets your local codes.
Additions arenโt truly attached to manufactured homes. They must be built as a completely separate structure with its own foundational support. Typically, an addition to a manufactured home will be close to the home and then sealed together at the roof and sides. Siding is then wrapped around to create the illusion of a single home. Structurally, the manufactured home will move, settle separately from the addition of any size.
Structurally, the manufactured home will move and settle separately from the addition.
Make sure to research insurance and tax increases if your home changes to real property. Manufactured homes usually have low taxes so if you transition the home into real property your tax liability may increase significantly.
The Directory of Mobile Home Manuals may help you find more information about your specific builderโs suggestions here.
Related: How to Make Your Manufactured Home Look More Like a Site-Built Home
How Much Does a Mobile Home Addition Cost?ย
Iโm looking to add a bedroom to my mobile home. Can it be done at $2000 or under? Iโm thinking of either a nursery or the master. Thinking if Iโm going to add might as well get a bigger bedroom. Iโm assuming I have footings because I donโt have blocks.
Iโm thinking of either a nursery or a master bedroom. Thinking if Iโm going to add might as well get a bigger bedroom. Iโm assuming I have footings because I donโt have blocks.
The simple answer to your question is no. There is little chance that you can legally build a complete bedroom addition for less than $2000. Materials alone will cost at least $2000 and then you have labor and inspections to pay for.
The foundation of your manufactured home will not matter because the addition must be built as a completely separate structure. New footers or slab foundation (depending on code) will be required for the addition.
Here is a great resource from HUD about manufactured home foundations that explains everything.ย
Can you Live in the Home While Building a Mobile Home Addition?ย
Is it possible to live in the main home while the addition is being built and sealed or is there a certain point when you have to move out for a bit? Even if hiring contractors and builders.
Yes, you should be able to live in your home while building a mobile home addition. Since the addition is a completely separate structure you can absolutely live in the home during construction. Only when you are cutting through to โattachโ the two together will there be any activity done to the home itself.
Can I Move a Mobile Home Addition?ย
Can the addition be moved together with the mobile home when we have to move? Or will the addition have to stay?
If the addition is properly built it can typically be moved. It will be transported via a flatbed truck (assuming itโs not too large). Then it will be installed beside the home once the foundation or footers have been laid for each.
Transportation companies will charge extra for that service so make sure to factor it into the overall cost.
Summary
The basic concept of mobile home additions is to keep the addition separate from the home, while still allowing a connection that is weatherproof and leak proof.
Inspectors and building consultants are available at your local and state agencies, use them to your advantage. You want a safe, long-lasting addition that will make your homework better for you and your family.
If you have any questions, please comment below and Iโll try my best to find you an answer. As always, thank you for reading Mobile Home Living!
We are starting the process to add a stick built new master bedroom to our existing manufactured home. We were hoping to break through the back of the foyer closet to make the entrance to our new bedroom but our local county permit office will not approve this plan unless we show proof that HUD building codes will allow this. Where can we find any specific HUD building codes related to adding on a stick built addition? I have contacted multiple manufactured housing companies in our area and all I get in response is fishing emails to start the process to buy from their companies. I have also left a voicemail with HUDโs Office of Manufactured Housing. And I have attempted to read through the codes myself but the wording is pure legalese and is really hard to find the specific codes I need.
This is what I found, โIf the property has an addition attached after the home was sited, the attachment is not regulated by HUD Standards or Regulations; therefore the property does not need an AC Alternate Construction (AC) letter. If an addition has been added to a manufactured home, it may take the home out of conformance with the Standards.โ https://www.hud.gov/program_offices/housing/rmra/mhs/faqs#:~:text=If%20the%20property%20has%20an,of%20conformance%20with%20the%20Standards.
Can I add an addition to a mobile home in Massachusetts>
Check with the area the home is in to make sure there are no restrictions, otherwise, there is no reason you couldnโt add an addition.
I bought a 1972 double wide mobile home in California. The home has a room addition (bump out) that was built when house was built. My question is: what size are the roof rafters and spacing? Thanks
Charles Bowley.
I am looking to improve the look of the add on, which is the metal interior roof of the add on. I wish to improve the ascetics of the interior ceiling.
Looking for a contractor to do large extensive additions and remodel to a double wide in the Campbell county Lynchburg va area
Right now we donโt have a directory of contractors (but we are working on one). You might be able to call a mobile home dealer and ask for a recommendation or just start calling places from the yellow pages. Just make sure you ask for references, and that you donโt pay them all their money upfront.
Hi this is Teresa. Hope you are doing well! I have found one of really nice homes for sale, it is a single-wide home that is for sale out in a rural setting. Can I put an additions to the home like family room, office and a bigger closet? The home that is currently for sale, it does not say about den or family room so I really would need that for installing a stove and also for an office. I live in the state of Virginia in Spotsylvania county. Please let me know by send me an email at tkilby2009@hotmail.com all lower cases. Have a great goodnight!! Teresa
Is it cheaper to add on a bedroom and bathroom and porch room, to existing singlewide or better to replace with a double wide?
Hello,
i live to los angeles
I would like to add a living space of about 430sq to the mobile home I live in.
If not, I would like to make a perio with a covered roof.
I would like to know roughly the estimated unit price
thanks
I want to extend our 14 foot hallway out by 12 inches. Like a long bay window but without windows. We want to add cabinets along the hallway large enough for small storage like board games, books, magazines, moves and music discโs and any other items small enough to fit in them. The hallway it self is already 33 inches wide and we have a 6 inch shelf system there now with all our DVDโs, CDโs and small paperback books. But we are thinking if we can extend the hallway out we can add even more storage.
___________ The outside would look like this. Can this be done?
_____/ _ _ _ _ _ _ _ _\____________________________________________
Can you safely attach one-half of a double wide mobile home to a single wide mobile home? The double wide section is 40ร12 and the single wide is 16ร80. Thanks
Our current double wide has standard 8 ft ceilings and weโd like to build an additional room with 9 ft ceilings. Do you see a problem with this?
Hi Kim,
An additionโs ceiling height will not be affected by the homeโs ceiling height because itโs a completely separate structure and just sealed around at the roof, sides, and floors. You would need to figure out how to transition from the home to the addition considering the height difference but it wouldnโt be too complicated.
I live in PA our town requires a $25 permit to build an unattached add on to my mobile home. No inspection on my diy project is required from them. I explained to them that I wanted to build as close as I could to my mobile home so any debre from my trees and snow would not cause a problem. There reply was as long as it was not attached it would not need a different permit requiring inspections. I told them could I attach the roofs together as to keep anything from being trapped between them. Why is this not attaching them together? I read a lot of the articles on your web site to keep myself from getting in trouble. And how is a doorway not a problem from the trailer into the addition? Thank you for your inputs of knowledge
Hi Larry,
I have a hard time explaining additions โ apologies for the confusion. So, an addition is technically attached to the home at the roof, the siding, and the floor. The additionโs roof will be attached to the homeโs roof via framing and then shingles will go over that so that it all looks like itโs part of the home but the weight of the addition is not being transferred to the home in any way. The weight of the addition is only held by its own footers.
For your siding you will build the addition as close as possible to the home and then once youโre finished building it you will seal the space between the home and the addition and then install the siding so that it looks like it is part of the home. For the entryway, you can butt the additionโs subfloor right against the homeโs subfloor, and then floor covering will go over that making it all look cohesive.
So, the addition will be attached and sealed along the roof, siding, and flooring. But the weight of the addition is not transferred to the home via these attachments.
Best of luck!
How do you seal the two portions together at the roof, siding and floor?
To seal the gaps between the home and the addition you can use weatherstripping, flashing, backer rod, caulking, and lumber. A backer rod is just a fancy name for round foaming that can be used as a membrane between the 2 structures. (All the information about the options can be found in the article.)
Where can we find help to go backward and get plans for a garage that has already been to attached to a manufactured home back in 2017? We are selling the home now and though we had permit; we had no idea we needed to work with L&I โ or any knowledge of the non-attach Rules until now! Yes we feel stupid. Yet, how to fix as quickly as possible yet correctly??
Hi Joe,
Please donโt feel stupid. These things arenโt common knowledge and itโs not easy to find information online when youโre looking up things. And donโt fret yet, the garage may just look attached. As long as it sits on its own foundation and isnโt using the home for support it could be perfectly fine. You can still have a doorway straight into the home (or even a large opening) and you can still have it โattachedโ and it not be an issue โ its all about where the addition is getting its structural integrity from.
The L and I insurance is total malarkey and itโs overly complicated. In some states, a person hired directly by you for 1 project is just considered a subcontractor unless itโs a construction job. Then they can be considered a contractor and if they hire their own subcontractors or employee for just that one job (but donโt have the needed coverage) they can sue the homeowner. In some states, theyโd laugh the worker out of the courtroom (as they all should). In some states, you have to prove that the remodel or construction was covered by a fully licensed and insured crew or the homeownerโs insurance may not cover any claims on any part of the home for any reason (and Iโve heard about the insurance company using the lack of workerโs comp as an excuse even though the contractor had the error and commissions policy. Itโs all very confusing and unfair and a regular homeowner would have no idea about any of it nor would they know to even ask about it which I think is exactly how they want us all (ignorant and confused). I hope it all works out. Donโt fret anything but when you call your insurance and your county offices donโt tell them anything about a past project โ just act like youโre getting information about a project youโre thinking of doing. Only after you gather all the information should you lay it all on the line and say โhereโs the issue, what inspections or paperwork do I need to remedy the problemsโ and then go from there. Iโve found that when it comes to insurance and the government its usually best to tell them the bare minimum.
Best of luck!
I have a 32ร80 double wide on a permanent foundation and it has been detitled. Can i attach a addition or do i have ti keep it seperate
Hi Larry,
Additions have to be build separately due to structural issues, not titling or foundation. If you build onto a mobile home like you would house (attaching it completely) stress can cause structural damage.
Best of luck!
I live in a 1997 Southridge mobile home that is setting right at 3000sq now we have remodeled 5 times and every time we knocked out a wall, window, door something and im fixing to do it again. Im on a permanent foundation and we have NEVER built anything separate and in 25 years had one problem with structural problems. We didnโt take down load bearing walls but built within the structure and enforce the structure. I so wish i could add photos to this if you want to see just email me and ill send you photos of my homeโฆ have a bless day.
Some guidance from a real estate appraiser. Do not modify/cut the manufactured home without consulting an engineer. When the project is complete have the engineer sign off on the modification. If you ever have to refinance or sell, the mortgage company is required to have an engineers report for any modifications or an inspection by state agency if there is one. Also never remove the Hud tags from the outside and never remove the Compliance Certificate in side aka The sticker with a map on it. If you do, you will need to obtain letters from IBTS for any one of these missing.
Crystal,
How does one insure a pre hud single wide mobile home(1972) with stick built addition that is larger than the singlewide? I plan on building soon.
Thank you, Sheri
Hi Sheri,
Thereโs only a handful of companies that will insure pre-HUD homes. American Modern or maybe itโs Modern America is one of the most popular but Foremost, Geico, and a couple of others may cover you. Best of Luck!
I have seen additions and most look like crap, having thirty years in the contractor world I canโt understand the theory of a free floating addition, I have a single wide, shortly itโs getting overhauled, my plan is welding steel square tubing to the frame, yes I will add cross members same as a truck frame to stop buckling, the point of contact is where the axles were, itโs about twelve inches there, this will allow to have the same floor height, on the addition outer wall I will build the same footing that is under the existing mobile, why donโt people weld frame members, I have welded a whole new hitch on the front to get it home, same as the roof, you can add more meat on the original outrigger angle brackets to carry a heavier wall , if your contemplating an addition, go see a local welding shop with a knowledgeable person, buttrace to cantilever you can do anything you want with a mobile if you got steel under itโฆ.
I so appreciate all the articles and pics! Thank you! We are remodeling (againโฆ) an 85 16ร64 (I think, maybe longer) 2br 2ba 7โ ceiling at the walls We are planning an addition along the back half I think we are going to have to open it up at the double windows in the current livingroom to maintain structural integrity, although we are really wanting a wider opening closer to 10โฒ. Just not sure that is wise the REAL issue is the roofline and I havenโt really seen it addressed anywhere. This house doesnโt have a pitched roof, just the slight arch. If we go perpendicular, I think we are going to have to add on a pitched and hip into the addition. Is there absolutely any other way? The back of the house currently is at about the highest point on the grade and is going to be a challenging addition without doing a stepdown anyway addition is planned to add to the living area, a craft room and a new master. And trust me! I WILL have tons of process pics! Very motivated to resolve this sticking point and get my 3 grandkids on my old place in the country.
Hi Jenn,
I would love to get my hands on your photos when youโre all finished. Itโs so hard to find photos to help explain things! There is a formula that architects use to determine if a door/hole needs to be supported with beams. It involves the weight of the roof and the span width to help determine whether you need a support beam. I canโt tell you if that formula would work for your home but you could get a contractor to come in and give you an estimate and see if they think a post and beam support is needed.
Best of luck! Please keep me in mind when you are finished and please take a ton of photos โ I would be so grateful.
The reason the gap is there, is bc the block wall is not supporting the mobile home in any way and merely used as an underpinning. Depending on the gap size, you can either use backer rod and caulk it if itโs under 1โณ, or use the same material that the siding is and just add to the bottom to cover the gap.
CRYSTAL
Hi I have been reading some of the posts. I have a manufactured home from 1979 that was set on a block foundation. It was a rental. Now we are wanting to make it a Dog training space and are wanting to add on an addition. Can we tie into the trailer since it is on block? or does it still need to float? Live in northern Illinois. Would love to share some pics with you.
Hi Jacob,
You would still need to build the addition separate from the home. It doesnโt really matter how the home is installed or what itโs skirted with.
Thanks!
Hi Crystal,
We added on to our mobile home several years ago and the addition must have settled down because the mobile home is higher than the additionโฆโฆthe floor is slantedโฆ.I know i probably make no sense because I donโt understand it myself but do you think we could maybe lower the mobile home to even it out? What kind of company would I call to fix something like this? I sure do love my home and have hope of fixing it. I hope you can help me.
Hi Samantha!
You make perfect sense! It does sound like the addition has settled or the home has become unlevel in some way or another.
Iโm pretty sure it will be easier to raise the addition rather than to lower the home (but Iโm no expert and an inspection would be needed). If the footers didnโt go below the frost line the ground heave can make a structure uneven so this is kind of a common issue in the northern states (especially the old coal camp house where Iโm from in WV because they were built so cheaply).
In the most simple cases, youโd just use hydraulic jacks and cement blocks to give the addition the proper height. I donโt think it would be that expensive if itโs just a basic sinking issue. Of course, there are always two ways of doing things when it comes to stuff like this: the right way and a way that gets it done good enough. The pro would probably tell you that the footers need to be redone completely and that would be expensive. You may be able to get buy with just jacking it up and adding new pier material to raise the structure. While I think anyone with basic construction experience could do this job you may want to try a manufactured home installer first since they are so experienced (and they deal with additions a lot).
Best of luck! Let me know how it goes.