Mobile Home Roof Over Manual
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Many mobile homeowners attach porches and additions onto their mobile homes incorrectly. It’s 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. We’ll 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.
There are a few basics you should know before you decide to build an addition onto your mobile home.
The top priority for any homeowner considering an extension to a mobile home is to understand that the extension must not be connected to the existing structure. This implies that the extension should be constructed independently with its own footers. This ensures that the load of the new construction is evenly distributed into the ground rather than onto the original 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 ‘butted up’ and attached to the mobile home, and ‘sealed’ 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 ‘end’ of the addition (the side opposite the home), then it’s probably wrong and should be checked by a licensed profesional.
To put it simply, you aren’t 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.
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. 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.
Here’s a map showing the frost line depths for the US:
Footers are installed below the frost line so that the addition doesn’t sink or shift.
Additions to manufactured homes are not often seen as an ‘improvement’ – meaning it probably won’t increase the value of the home in most cases. It won’t 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 didn’t get the proper inspections and permits you may run into serious issues if you try to sell the home later down the road.
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 homeowner’s 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.
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 ‘sealed’ together.
There are some great online resources about mobile home foundations. This guide about manufactured home foundations and supports is invaluable.
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 these square foot concrete forms.
You want the mobile home addition to having framing that is equal to or better than the framing that your home has. Of course, you’ll 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. It’s 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.
Here’s the interior of the home:
You’ll 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. That’s 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 it’s easier to seal around the home and to keep from needing to support the perimeter wall with a beam.
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 1×6 board to the home vertically so the addition will butt up against the middle of that board. You’ll 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 – this brings the addition toward the home and helps seal it without overly damaging the home.
These questions were asked in the comment section of our very informative article about building mobile home additions found here.
Flashing and vinyl siding will cover it all up.
To connect the addition to the mobile 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’s meeting points.
For a metal roof, you would tuck a single length of 18″ 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 2″ 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 don’t want it too long. If the flashing is too long, it can cause cracks.
If the addition’s 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 – the best method to prevent shifting of a manufactured home.
If the 2 roofs are at the same height, you just use flashing. Screw and seal.
When planning structural modifications or additions to a mobile home, especially those involving metal frames or support structures, understanding welding techniques becomes crucial. Mastering welding positions—such as flat, horizontal, vertical, and overhead—ensures that welds are strong, secure, and compliant with building codes. Whether you’re installing a steel foundation, reinforcing skirting, or crafting custom frames for extensions, proper welding enhances the durability and safety of your addition. A complete guide to welding positions empowers DIYers and professionals alike to work more efficiently and confidently on mobile home projects.
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 18″ 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.
Here’s a park model manufactured home getting an addition built onto it. Notice how they’ve 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:
We’ve featured a few mobile and manufactured homes with additions:
The Directory of Mobile Home Manuals may help you find more information about your specific builder’s suggestions about mobile home additions here.
Here is a great resource from HUD about manufactured home foundations that explains everything.
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 I’ll try my best to find you an answer. As always, thank you for reading Mobile Home Living!
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View Comments
Our current double wide has standard 8 ft ceilings and we’d like to build an additional room with 9 ft ceilings. Do you see a problem with this?
Hi Kim,
An addition's ceiling height will not be affected by the home's ceiling height because it's 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 wouldn't 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 - apologies for the confusion. So, an addition is technically attached to the home at the roof, the siding, and the floor. The addition's roof will be attached to the home's roof via framing and then shingles will go over that so that it all looks like it's 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 you're 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 addition's subfloor right against the home's 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 - 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 don't feel stupid. These things aren't common knowledge and it's not easy to find information online when you're looking up things. And don't fret yet, the garage may just look attached. As long as it sits on its own foundation and isn't 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 'attached' and it not be an issue - its all about where the addition is getting its structural integrity from.
The L and I insurance is total malarkey and it's overly complicated. In some states, a person hired directly by you for 1 project is just considered a subcontractor unless it's 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 don't have the needed coverage) they can sue the homeowner. In some states, they'd 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 homeowner's insurance may not cover any claims on any part of the home for any reason (and I've heard about the insurance company using the lack of worker's comp as an excuse even though the contractor had the error and commissions policy. It's 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. Don't fret anything but when you call your insurance and your county offices don't tell them anything about a past project - just act like you're getting information about a project you're thinking of doing. Only after you gather all the information should you lay it all on the line and say 'here's the issue, what inspections or paperwork do I need to remedy the problems' and then go from there. I've 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 32x80 double wide on a permanent foundation and it has been detitled. Can i attach a addition or do i have ti keep it seperate
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 didn’t 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 home… have a bless day.
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!
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,
There's only a handful of companies that will insure pre-HUD homes. American Modern or maybe it's 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 can't understand the theory of a free floating addition, I have a single wide, shortly it's 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, it's 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 don't 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 it....
I so appreciate all the articles and pics! Thank you! We are remodeling (again...) an 85 16x64 (I think, maybe longer) 2br 2ba 7'' 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 10'. Just not sure that is wise the REAL issue is the roofline and I haven't really seen it addressed anywhere. This house doesn't 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 you're all finished. It's 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 can't 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 - 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 it's under 1", 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 doesn't really matter how the home is installed or what it's skirted with.
Thanks!