walls being installed over flooring in manufactured home construction factory 2

How to Replace a Subfloor in a Mobile Home: Step-by-Step Guide

Chances are you’ll need to replace a subfloor in a mobile home eventually. This is especially true if your mobile home is older and you have a bathroom

A mobile home’s bathroom subfloor is usually the first space that needs replaced. The kitchen second.

In this in-depth article explains how to replace a subfloor in a mobile home and share some great photos and videos that show you the entire process from start to finish.

First things first…..

What is a Mobile Home Subfloor?

Mobile and manufactured homes have the same construction elements as a site-built home. They’re just built differently.

In order, ground up, a mobile home has a chassis, floor joists, a subfloor, and then the floor covering on top.

What’s the difference between a subfloor and a floor?

The subfloor sits between the floor covering and the floor joists. It’s the meat of the flooring sandwich for lack of a better description.

The images above are good depictions of a mobile home subfloor. The only issue is that the image shows the subfloor as boards instead of the 4′ x 8′ sheets that they are.

Mobile homes were constructed with particle board subfloors for many years. Manufactured homes typically have plywood subfloors. Particle board is made from sawdust and glue and became popular after WWII. It’s a great product as far as strength goes but has one fatal flaw: water can destroy it a bit quicker.

Soft Spots and Warping

Water and fire are the two scariest enemies for any home, whether it be manufactured or site-built. Fire is sudden and obvious, water not so much.

A small amount of water can cause particle board to start bowing, warping, and developing soft spots. Rot quickly follows.

If you have a soft spot or bowing in your subfloor it needs to be addressed as soon as possible. You’ll need to find and fix the cause of the problem first. Once that’s done, you’ll want to replace the damaged area so there’s no further damage.

Most newer homes now use a higher-grade plywood or OSB because it can withstand water better.

Read about mobile home MDF cabinets here.

Is a Mobile Home Subfloor Replacement a DIY Project?

Replacing a mobile home subfloor isn’t easy but it’s doable if you have a fair amount of construction experience. I give it a difficulty score of 7 out of 10.

For bathroom and kitchen subfloor replacements you will be dealing with major components like plumbing and wiring so it’s smart to have a professional involved. However, since this is the real world and most of us can’t afford a professional, we just have to do the best we can with what we have and that’s just fine. You’ve already proven yourself capable than most by researching first.

The most difficult parts of the job are removing the old flooring, building out the perimeter joists, and keeping everything level. We’ll deal with each part below.

Tools and Materials to Replace Subflooring a Mobile Home

Thankfully, the material list to replace a mobile homne subfloor is fairly short.

  1. Plywood (3/4″ OR 5/8″). We recommend marine grade plywood for kitchens and baths.
  • 2 X 6 and 2 X 4 Lumber (scrap lumber will work in many situations)
  • Galvanized Screws
  • Liquid Nail Adhesive
  • Underlayment or waterproofing depends on the floor covering

Tool List

  • Circular Saw (this is vital)
  • Hammer
  • Pry Bar
  • Knife, Blade, Scraper
  • Standard DIY toolbox should be close cause you just never know what you’re gonna see

Step-by-Step Process to Replace Subflooring in a Mobile Home

This is a ‘quick and dirty’ list of the basic steps needed to replace flooring in a mobile home.

Step 1: Remove the Trim and Floor Covering

The first step to replace subflooing in a mobile home is to remove the trim and floor covering.

If it’s carpet you will need to remove the nail strips carefully.

Vinyl floor (that is one solid sheet) will usually need to be cut around the perimeter of the room.

Tile will need to be ripped up.

Learn more about floor covering for mobile homes here.

Water Leaks Need to Be Found and Fixed

If a leak caused rotting or flooring warping and bowing, you must find it and repair it before moving on to the next step. Plumbing, doors and windows, and roofs are the most common places for leaks.

With the floor covering removed you will be able to trace the leak better. Follow the damage. Most of the time it will be a window or roofing issue and the water is running down the wall.

Bad toilet rings and damaged water supply lines are other common source of leaks in mobile homes.

You can learn more about mobile home plumbing repair here.

Understanding How Home Mobile Homes are Constructed

You may need to use a Dremel tool or knife to get the sub-flooring out from underneath the walls if the sub-flooring is damaged or rotted. If it’s healthy, you’ll likely want to leave the subflooring under the walls alone.

knowing how a home is constructed is important when replace subflooring in a mobile home
The subfloor and floor covering are installed before the walls when a manufactured home is built.

Manufactured home builders construct homes in layers. All the flooring is laid before the walls are installed so chances are your flooring and floor covering will be under the entire wall.

https://www.youtube.com/embed/duJE9EuFsMM

Measure Your Subfloor Thickness

Next, you will need to measure your subfloor. Most subfloors are either 3/4″ or 5/8″ thick.

You will use the measurement to set your circular saw to the proper height. One of the most tedious parts of replacing subflooring in mobile homes is the removal of the original sub-flooring.

After you set your saw, you will carefully cut only the subfloor. Use caution so you don’t cut a joist. Here’s a video showing how to use a circular saw to cut out subflooring in a mobile home:

Cutting Out the Subfloor

If your flooring is 3/4″  set your circular saw to that and follow the perimeter along the edge of the room. You do not want to touch the joists below.

This is one of those tedious jobs no one likes to do!

Cut the Subflooring Between the Joists

Now that you’ve cut the subflooring around the edges, you will need to cut them down so you can remove them easier.

The smaller the pieces, the easier it is to get them out of your way. If you have ensured there are no pipes or wires between the joists you can simply saw between the joists and remove each piece.

Remember to keep the saw set to the same thickness of the flooring to keep so you do not damage the joists.

If you can cut out an inch or so under the wall without damaging the wall you can slide the new sub-floor under the wall.

This is the ideal method in the subflooring is rotted or weakened in any way.

new plywood to replace subflooring in a mobile home

Inspect and Repair Joists

At this point, all the sub-flooring has been removed and you have a perfect opportunity to inspect the joists for any damage. If you do see damage,  you can reinforce it by adding an additional 2 x 6 to the original or removing and replacing.

If there’s not much damage, reinforcing is probably easier. Measure the space between the joists so you can cut the lumber (2×6) to the right length so they fit in between the joists.

Adding New Insulation is Crucial When You Replace Subflooring in a Mobile Home

This should be a top priority. Spending an extra $30 can save you a lot more in energy costs in the future. Remember, wiring and piping should be above the insulation so that the heat from the home can get to it.

Laying the New Sub-Flooring Down

Around the perimeter of the room, you will need to attach an additional 2 x 4 to the original so that you have a shelf or lip to lay the new sub-floor down, then nail and glue.

At each seam, where one piece of plywood ends and another begins, you will need to reinforce under it.

This means you will need to add a 2 x 4 between the original joists so you have a place to nail and glue down the plywood.

You can see this happening in the photo above, where the small boards have been added between the long joists.

https://www.youtube.com/embed/6Opo8ADrf_k

Sub-flooring should be laid in the same direction as the original, usually opposite the direction of the joists.

replacing subflooring in a mobile home 640x430 1
New subflooring in a mobile home.

Install the New Floor Covering

Luckily, your choices are endless when it comes to floor covering for mobile homes.

If it’s in a bathroom, it’s probably best you go with a thick vinyl that has some protection against water will help protect your floor.

updated single wide-flooring during 3
New floor covering installed in a single wide.

 

Enjoy Your New Floor

Congratulations, you have a great looking floor that will last for many years!

updated single wide-flooring after
New flooring in a mobile home.

It is complex to replace subflooring in a mobile home but it’s a common project for homeowners of older mobile homes.

New subflooring, along with new insulation, will help your home last longer and save heating and cooling costs.

As always, thank you for reading Mobile Home Living!

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