What Size Plywood Do You Need for a Subfloor?
There are many reasons you might need to replace your mobile home’s subfloor. If your home was built before the 1990s, the original subfloor is likely particle board, which softens and crumbles when exposed to moisture. Pest damage, water leaks, and years of wear can also cause sagging or squeaking. Some homeowners replace their subfloor even before significant damage occurs, to improve strength or prepare for heavier flooring, such as tile or hardwood.
Whatever the reason, one of the most important details to get right is plywood size. Using the wrong thickness can lead to sagging, wasted materials, or long-term structural problems.
So, what size plywood for a subfloor should you use? Most site-built homes feature standard 5/8- to 3/4-inch plywood. Meanwhile, manufactured or mobile homes typically perform best with 5/8-inch panels, which strike a balance between strength and weight. The right choice depends on how your home is built and the type of flooring that will be installed on top.
Best Materials for Mobile Home Subfloors
Before choosing a thickness, it helps to know what types of plywood and other alternatives are suitable for subfloors so you can select the best material that fits your budget and environment.
CDX Plywood
CDX plywood is an exterior-grade panel made from multiple wood layers bonded with weather-resistant glue. It’s strong, reliable, and widely used in both new construction and mobile home repairs. Because of its layered structure, it provides solid support and holds screws securely, making it a dependable option for most subfloors.
| Pros of CDX Plywood for a Subfloor | Cons of CDX Plywood for a Subfloor |
| Durable and structurally strongHandles moderate moisture exposureEasy to install and widely availableHolds fasteners securely, minimizing squeaks | Can warp or swell if exposed to standing water for long periodsA rough surface usually requires an underlayment for smooth flooring installation |
CDX subfloor plywood performs well in most dry to moderately humid environments. It’s best used in living areas and bedrooms where moisture exposure is limited, or where you plan to install a vapor barrier for added protection.
Pressure-Treated Plywood
Pressure-treated plywood is chemically treated to improve its durability and increase its lifespan. It’s designed for areas where moisture and humidity are consistent issues. In fact, pressure-treated plywood is even used in outdoor applications.
In mobile homes built close to the ground, subfloors made of this material help prevent decay and damage caused by limited ventilation or damp air.
| Pros of Pressure-Treated Subfloor Plywood | Cons of Pressure-Treated Subfloor Plywood |
| Excellent resistance to moisture, rot, and insectsLong-lasting even in humid conditionsIdeal for bathrooms, kitchens, and laundry roomsReduces the risk of mold growth and wood deterioration | Higher cost compared to standard plywoodMay release mild odors after installationNot necessary for dry areas |
Pressure-treated plywood is best reserved for sections prone to leaks or consistent humidity. Installing it only where needed allows you to protect the flooring in damp areas without the expense of using it as a subfloor for the entire home.
Oriented Strand Board
Oriented Strand Board (OSB) is a popular alternative to plywood for subfloor projects. Unlike plywood, which is made from thin sheets of wood veneer layered in alternating grain directions, OSB is manufactured from wood strands arranged in cross-oriented layers and bonded with resin under heat and pressure. OSB panels are available in large, standardized sizes that make installation simple.
| Pros of OSB Panels | Cons of OSB Panels |
| Cost-effective and widely availableConsistent strength across the panelSmooth surface suitable for most flooring typesStrong fastener-holding ability, reducing movement between panels | Absorbs moisture faster than plywoodCan swell or weaken along edges if left wetRequires sealing of seams and edges to prevent water damage |
OSB performs better than particle board and provides reliable structural support when kept dry. For mobile homes in humid climates, sealing all edges and using vapor barriers will extend the life of OSB subfloors.
Standard Subfloor Plywood Thickness: Why It’s Different From Manufactured Homes
Subfloor plywood thickness determines how sturdy your floor feels and how well it supports weight. In most site-built homes, panels range between 5/8 inch and 3/4 inch, depending on joist spacing and the type of flooring installed above. Thicker panels are sometimes used in open or high-traffic areas to reduce flexing and noise.
Manufactured and mobile homes have different requirements. Their lighter framing and closer proximity to the ground mean the subfloor must provide enough strength without adding unnecessary weight. The underside of these homes is also more exposed to humidity and temperature changes, which can lead to condensation and moisture buildup if not properly protected.
Because of these conditions, the material type and fastening method are just as important as mobile home subfloor thickness. Each component contributes to preventing water damage and wear and tear.
Signs Your Mobile Home Subfloor Needs Replacing
If you’re considering repairing or replacing your subfloor and find yourself asking, “What size plywood for a subfloor should I get?”, you’re asking the right question.
Choosing the right thickness of plywood and recognizing early signs of damage helps ensure longevity and prevent bigger structural issues. Watch for these common indicators:
- Soft or Spongy Spots: Floors feel uneven or bouncy when walked on.
- Warping or Bulging: Raised or uneven areas point to water damage.
- Persistent Squeaks: Loose fasteners or deteriorated panels cause creaking.
- Discoloration or Mold: Dark stains or musty odors signal moisture intrusion.
- Structural Weakness: Joists beneath the subfloor may be unstable or rotted.
If you notice any of these signs, replace the affected panels promptly. Inspect joists, repair damage, and install new panels with adhesive and screws to ensure lasting stability.
Factors That Affect Subfloor Plywood Thickness in Mobile Homes
The correct mobile home subfloor thickness depends on several conditions unique to its design. Because manufactured homes use lighter framing and often have wider joist spacing, slight variations in material, spacing, or moisture can noticeably affect the feel and stability of the floor.
Understanding these factors helps you choose a subfloor that stays strong, quiet, and moisture-resistant for years.
Joist Spacing
Joists provide the main structural support for a subfloor. In mobile homes, joists may be spaced wider apart than in traditional houses, which changes the amount of load the subfloor must carry.
- 16 Inches on Center: 5/8-inch plywood or OSB is generally sufficient for most living areas.
- 24 Inches on Center: 3/4-inch or thicker panels offer better support and reduce bounce or flexing underfoot.
Floor Type
Hard flooring, such as tile and hardwood, needs a stiffer base to prevent cracks and gaps. Meanwhile, softer flooring materials, such as carpet and vinyl, can tolerate more flexibility.
- Tile or Hardwood: Use 3/4-inch plywood or thicker for a rigid surface.
- Vinyl, Laminate, or Carpet: 5/8-inch plywood is typically adequate if the panels are securely fastened and properly supported.
Moisture and Humidity
Because mobile homes sit closer to the ground, their subfloors are more vulnerable to humidity and ground moisture. Without adequate protection, condensation can form beneath the home, weakening the wood over time.
Moisture-resistant materials, such as exterior-grade plywood and pressure-treated panels, help prevent this. Adding a vapor barrier or sealing seams with adhesives and caulks offers an added layer of protection.
Basic Components supplies adhesives, caulks, flooring, ventilation products, and underlayment materials designed to seal and protect subfloors in manufactured housing, helping homeowners avoid costly future repairs.
How To Install or Replace Subfloor Plywood in a Mobile Home
Before you begin, gather your subfloor materials, construction adhesive, screws, and safety gear. Make sure that joists are level and undamaged before laying new panels. Then, follow the steps below:
- Apply construction adhesive along joists to prevent squeaks.
- Lay panels perpendicular to the joists and stagger the seams for added strength.
- Secure with screws every 6 to 8 inches along edges and 12 inches across centers.
- Leave 1/8-inch gaps between panels for expansion.
Afterward, seal plumbing penetrations and install a vapor barrier beneath the home to prevent humidity from damaging the new subfloor.
Cost Considerations for Mobile Home Subfloors
Subfloor repair costs depend on material type, thickness, and extent of damage. Because mobile homes face more moisture exposure, projects may include underbelly or joist repairs.
The following are the general price ranges of each type of subfloor material. Keep in mind that costs will vary based on your location, the size of the project, and whether you’re completing the work yourself or hiring a professional. Material thickness, quality, and moisture treatment will also affect the final price.
| Material Type | Retail Price (per 4×8 sheet) | Contractor / Wholesale Range |
| 5/8″ CDX Plywood | $35 to $45 | $28 to $38 |
| 3/4″ CDX Plywood | $45 to $60 | $35 to $48 |
| 5/8″ OSB | $30 to $40 | $25 to $35 |
| 3/4″ OSB | $35 to $45 | $28 to $38 |
| Pressure-Treated Plywood | $55 to $75 | $45 to $60 |
Labor typically ranges from $1.50 to $2.50 per square foot. Costs may be higher if the contractor needs to address older damage or work on older homes that require structural repairs.
FAQs About Mobile Home Subfloors
Can you use 1/2-inch plywood?
No. It’s too thin to support daily use and will flex between joists. Ideally, mobile home subfloor thickness should be 5/8-inch CDX plywood, pressure-treated plywood, or OSD.
Is OSB stronger than plywood?
They have similar strength, but plywood handles humidity better.
What’s the minimum mobile home subfloor thickness required for tile flooring?
Use at least 3/4-inch plywood with a cement backer board.
What if joists are 24 inches apart?
Use panels that are 3/4 inch or thicker to prevent sagging.
How long should a subfloor last?
A properly installed and sealed subfloor can last 20 to 30 years with regular inspections.
Shop High-Quality Materials for Your Subfloor Replacement Project
Basic Components, Inc. has supplied high-quality materials for the manufactured housing and modular industries for over 30 years. Our nationwide warehouse network provides fast and reliable service to contractors, builders, and homeowners.
Browse our catalogs online or contact our team for help selecting the right supplies for your subfloor replacement project.
