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!

 

Mobile Home Additions - illustration

 

Home Addition Advice from Professionals

First and foremost, additions should not be attached to a manufactured home at all. You have to build the addition as a completely separate unit that is simply butted up to the home and sealed.

 

mobile home addition- proper footings for additions

 

mobile home additions - additions are not attached to manufactured homes

Financing and Insurance Issues for Mobile Home Additions

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.

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 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. 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. The 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. 

 

 

Footings for Mobile Home Additions

You need your manufactured home addition to be a completely separate structure from your home. The only ‘attachment’ for the later will be at the floor so the addition will need a completely separate foundation from the home.

You aren’t technically attaching the addition, you are simply sealing around it to prevent leaks.

 

There’s 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:

 

frostline depth - building mobile home additions - footers

 

Footers are installed below the frost line so that the addition doesn’t sink or shift.

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. 

For information about general construction footers, Front Porch Ideas and More (.com), has some nice illustrations that show the poured concrete and pier footings.

Mobile Home Additions - correct frost line footings and pier

Mobile Home Additions - correct frost line footings and pier graphic

 

pouring a pier foundation - Mobile Home Additions - correct frost line footings and pier

 

There are new products hitting the market to aid in DIY footings such as these square foot concrete forms.

Mobile Home Additions - correct frost line footings and pier - proprietary systems

Framing an Addition

Standard framing techniques apply for additions.

You want the mobile home addition to having framing that is equal to or better than the framing your home has. You’ll need to follow your local code.

Below shows a mobile home addition being framed out by SM Construction.

framing of mobile home additions

 

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:

mobile home before addition

 

mobile home additions - foundation poured

 

mobile home addition being built

 

mobile home additions - after

 

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:

 

mobile home additions - interior with stove

 

mobile home additions - interior of kitchen after

Sealing the Walls of a Mobile Home Addition

As stated previously, a basic mobile home addition is not completely attached to the home. It is simply butted up to the home and the sealed all around.

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.

Wide openings create the popular open space designs. 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. If you do opt for a wide opening between the home and the addition you will need to consider support issues for the opening. Wider openings, where studs are removed, will likely require support beams.

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. Pre-drill some holes in the board on the side of the home. Then, 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.

 

Roofing Your Mobile Home Addition

The roofing on a mobile home addition depends if the addition’s roof is lower, higher, or equal to the home’s roof.

Addition’s Roof is Lower than the Mobile Home’s Roof

To connect the addition’s 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 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 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.

 

Addition’s Roof is Same Height as Home

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. There is also a rubber membrane that’s 24″ wide that professionals recommend for this situation.

Addition’s Roof is Higher than Home’s Roof

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.

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 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.

 

mobile home additions - how to handle the roofing transition

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.

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.

mobile home additions - not the prettiest but it passed inspection

 

 

Here’s a park model manufactured home getting an addition built onto it. Notice how they’ve done the roof:

mobile home additions - park model with addition being built

 

 

Another park model manufactured home addition and carport built by HorseFly Construction:

single wide park model - building mobile home addition

 

 

The next photo shows a huge addition built onto a double wide manufactured home by Addon Rooms:

double wide - building mobile home additions

 

 

There are a couple of featured homes with additions here on MMHL:

 

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 home work 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!

Top Image: ILLUSTRATION BY JAMES STEINBERG