Why mobile home floors go soft
Water is the usual cause: a slow leak, a burst pipe or poor ventilation. Bob Vila's cost guide says particleboard softens faster than other subfloor materials and often needs full replacement. FEMA describes a typical floor as wood composite panels or plywood over joists at 16-inch centers, on a steel chassis. So when the decking fails, you feel it give between the joists. About 77% of occupied mobile homes in Polk were built before 2000, which means a lot of older decking is still in service.
Where soft spots show up
- Around the tub, shower and toilet.
- Under and around the water heater. Today's HUD standard requires a drain pan under tank water heaters (24 CFR 3280.709). An older home's pan may be missing or rusted through.
- At the washing machine and kitchen sink.
- Just inside exterior doors, where rain can get in.
- Along a wall under a roof leak.
Find the water first
Patching a floor over a live leak only buys time. Check supply lines, drains and the toilet seal, look under sinks for stains, and look at the belly from outside for sagging or wet insulation. A HUD-backed study found homes with floor moisture problems often have bottom board damage, so check the underbelly too. If the water comes from above, start with the roof. See Minimizing Moisture Problems in Manufactured Homes.
How the repair is done
- The flooring comes up, and the soft area is cut back to solid material.
- Damaged joists are reinforced or replaced.
- New decking goes in, fastened to the joists. Florida's repair rule calls for material and design equivalent to the original, and that covers the floor system. See Rule 15C-2.0081.
- Any opening in the bottom board is closed and sealed afterward. HUD says missing insulation goes back before the board is closed (24 CFR 3285.804).
- The finished flooring goes back down.
Plywood, OSB or particleboard?
Bob Vila's guide puts plywood at about $1.50 to $3.50 per square foot installed and OSB at about $1.40 to $3. Particleboard is the cheapest and the least durable, and OSB costs less than plywood but doesn't last as long. In bathrooms and laundry areas, ask what the crew plans to use and why.
What floor repair costs
- A damaged subfloor section: about $500 to $700.
- A full subfloor: about $1,800 to $3,000.
- Reinforcing a joist: about $100 to $300 each.
- Floor repair jobs overall: about $300 to $5,000, with an average near $2,650.
- These figures come from Bob Vila's guide. The price depends on the area, the material and what's hidden underneath, so get a quote that says how extra rot will be priced.
Permits and who does the work
Unincorporated Polk lists repairs to mobile homes among the work that needs a permit, so ask whether your job qualifies: Building Division, 863-534-6080. Florida's handyman exemption ends at $2,500 for labor and materials combined, and it doesn't apply to anyone who advertises as a contractor. Plumbing leaks should go to a licensed plumber. Ask any floor crew how much mobile home work they've done, because the floor framing and belly differ from a site-built house.
Buying or moving a used home?
Polk's used-home standard says floor, wall and roof systems must be structurally sound. If estimated repairs exceed the home's market value, the county won't issue a set-up permit. See Polk's used home standards and our guide to moving and setup.
Questions to ask before you sign
- Where did the water come from, and is that fixed?
- How far will you cut back, and what will you replace it with?
- Are any joists damaged?
- How do you open and reseal the belly?
- How will extra rot be priced?
- Does this job need a permit?