Building mobile home additions is a popular home improvement project. In fact, additions are the #1 choice for remodeling and improvement projects for homeowners. Adding mobile home additions are a great way to add additional square footage without incurring much debt. It’s much more affordable to ‘grow as you go’ than it is to buy a whole new home!
Surprisingly enough, mobile home additions aren’t that complicated. Yes, you will have to deal with permits, codes, and inspections, but with the right know-how, you can do it yourself. Of course, you can always hire contractors to build the addition, but if frugal living is your goal, and money is tight, you can be your own contractor and save a lot of money. Building mobile home additions is a great DIY project for those that are comfortable with basic construction and building methods.
My husband and I are planning an addition for our own home that will extend the living room and our daughters bedroom by 8 feet. The total length of the addition will be 22 feet long – adding a total of 176 square feet to our home. That’s more than 25% of our current living space. It will be like a whole new home when we get it finished and I can’t wait! I figured since I get quite a few questions about additions and I’ve been doing the research for our own build, that I would write this article. It should answer all the most basic questions and get you started in the right direction.
Home Addition Advice from Professionals
First and foremost, mobile home construction professionals say that if your home is simply on cinder-blocks, without poured footings that are below the frost line (called frost line footings)- an addition should not be attached to the home at all. In that case, you would have to build the addition as a completely separate unit that is simply butted up to the home and sealed. However, from what I’ve read, some don’t even recommend that – several professionals actively try to talk you out of all additions for mobile homes, but I think with some common sense, and the right knowledge anything is possible. If there’s a will, there’s a way!
Additions to manufactured homes are not often seen as an ‘improvement’ – meaning it won’t increase the value of the home in most cases. It won’t change the classification of a manufactured home into a regular home for financing or insurance. It won’t help you in any way, other than having more room. Financing and insurance may be harder to obtain if your home has been modified in any way – including additions.
With all that said, mobile home additions are perfect projects for those of us that know what we are getting into and believe the advantages far out weight the disadvantages. If your home is paid for, and you don’t plan on refinancing or trying to obtain a home equity loan, they can be turned into a true dream home with additions and modifications – just know what you are getting into before you start.
Permits and Inspections
Some states have mandates that override local and county regulations when it comes to manufactured homes. Research properly for your location before you begin planning anything. You could run into so much red tape that the project ends before it even begins.
You will be dealing with one of 2 scenarios – first, you live outside of city limits so you can build an addition with no inspections needed. No permits, codes, inspections or added expenses will be incurred. However, you are on your own and the safety of your home and your family is in your hands. Handle them with care!
The second scenario is the one most of us will face – we live in a town or park that requires permits, inspections and fees. I’ll not get into the political aspects of this – but I will say permits and regulations have all gotten out of hand in the last few years. Completely out of hand.
It took me 8 phone calls, a trip to the city hall, and a trip to the county courthouse before I was able to start the permit process for our addition. The fact that we would have no electricity or plumbing added to the addition stumped them, and they couldn’t figure out how to make more money off of us if we didn’t need the plumbing or electrical inspections at $150 each. The 1% permit fee calculated from the estimated total cost of the addition ($1600 in our case), seemed to low for them, I guess. I’m still waiting on the final word – and the permit.
Footings for Mobile Home Additions
Essentially, you want your manufactured home addition to be a completely separate structure from your home if the homes foundation does not meet the permanent foundation regulations for frost line specifications for your area. If your home is situated on a permanent foundation that meets the frost line specs, your build will be more like a regular stick-built addition. For the sake of space, I’m going to be speaking about additions for a home that is not on a permanent foundation because that describes my home and most others that I know. The only ‘attachment’ for the later will be at the floor, roof and wall – you aren’t exactly attaching the addition, you are simply sealing around it to prevent leaks. You can design the addition to be equal in height with your home, lower (which is often an easier method of building an addition), or higher than the home. Building lower or higher can allow an easier roof attachment or sealing, but it will require steps or ramp. Decisions, decisions!
Regardless of the height that you will be using, you will need footings. There’s poured footers, cinder blocks, 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:
Footings or padding simply needs to do 2 things- insure the addition doesn’t sink or shift, and make sure it’s even to the height of the home as possible, unless of course you are going with a lower addition that will have a step going down into the added room. If you live in a frost free area, you can use footing pads – they will suffice.
There’s some great online resources about foundations. Front Porch Ideas and More (.com), has some nice illustrations that show the poured concrete and pier footings.
There’s lots of new products hitting the market to aid in DIY footings – I like the concept behind square foot concrete forms.
Framing an Addition
Standard framing techniques apply for additions. You want the additions framing to be equal to, or better, than the framing your home has. When it comes to insulation, spend the money. Below shows a mobile home addition being framed out by SM Construction.
A great blog called Dovetail Blog shares their 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 roof line down to the addition, keeping the pitch. The addition looks to be used as a entry way 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:
Sealing the Walls of a Mobile Home Addition
As stated previously, a basic mobile home addition is not completely attached to the home, per se. It is simply butted up to the home and the sealed all around. Of course, you’ll have to determine if your opening from the home to the addition will be a simple doorway or a complete opening. Doorways are easier to close up should the home ever need to be moved or the addition removed. Wide openings allow for a true room addition though. Either way, you want the addition and the home to shift independently and only have a minimal connection that doesn’t impede the separate movement.
To seal the gaps between the home and the addition you will need to use weatherstripping, flashing, backer rod, caulking, and regular ole boarding. Backer rod is just a fancy name for round foaming that can be used as a membrane between the 2 structures.
You will want to attach a wide board (1×6 should do it) to the home on the vertical – so that the addition will butt up against the middle of the board. You’ll attach another board to the side of the addition, along with a lip. Predrill some holes in the board on the side of the home, add the weatherstripping and then screw the lip on the addition to the board on the house – this brings the addition toward the home and helps seal it. You will then use flashing and vinyl siding to cover it all up and make it look good.
Roofing Your Mobile Home Addition
The roofing on a mobile home addition depends if the additions roof is lower, higher or equal to the homes roof.
To connect the additions roof to home if the addition is lower then the roof on your home, you will need to use flashing to seal the gap between the home and the addition. There’s also rubber roofing that could work well though I’ve been unable to find anything on the use of it for mobile home additions. For the metal roof and flashing, 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 the 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 to 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. There’s a rubber roofing that would work well and there’s also a rubber membrane that’s 24″ wide that professionals recommend for this situation.
If the addition roof is higher than the roof on your home, you add the flashing under the lip of the additions roof and over the homes roof (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.
Below is a graphic I found on Mobile Home Repair that shows a concept for sealing a mobile home addition. The top drawing shows a a cap built onto 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 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.
This concept is smart but there’s no way to seal the corners of the addition. I think some good ole American ingenuity could be used and as long as the material you use to seal is fire retardant and safe, you could come up with a way to do it. Think about chinking a log cabin and you should be able to figure out a way that works and passes inspections.
Examples of Mobile Home Additions
Look at the home below, without judging its appearance (because it could look just fine with some new siding). You are seeing a mobile home addition that did pass inspection and can be found on The Inspector Blues blog. It is independently supported, has wired smoke detectors, an exit, sits on a 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:
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:
There’s a couple of featured homes with additions here on MMHL:
The basic concept to 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. Make sure you understand the rules and can get your home addition to pass inspection. You want a safe, long lasting addition that will make your home work better for you and your family.
If you have any questions, please feel free to add them in the comments and I’ll try my best to find you an answer. As always, thank you for reading Mobile and Manufactured Home Living!
Top Image: ILLUSTRATION BY JAMES STEINBERG