Subfloor and Finish Floor Replacement in Water Damaged RVs
Written by Structural Repair Lead, Structural and Frame Lead, OCRV Center. Reviewed by Claims Coordinator
In shortA soft floor is almost never a flooring problem. It is rotted decking under it. Real repair cuts back to sound framing, $750 to $9,500+ at $210 per hour.
What does subfloor and finish floor repair involve on an RV?
Subfloor and finish floor repair removes rotted decking down to sound framing, sisters or replaces damaged floor trusses, bonds in exterior grade plywood, reseals the underbelly, then lays new finish flooring. Rancho Santa Margarita owners bring soft floors to our Yorba Linda bays for this work regularly.
- OSB decking fails faster and further than plywood does
- The rot is always wider than the soft spot you can feel
- Cabinets and sometimes a slide room must come out for access
- Underbelly coroplast and insulation get replaced, not just taped
- Price range
- $750 to $9,500+6 to 40 labor hours at $210 per hour
- Labor rate
- $210 per hourBody and paint department
- Typical turnaround
- 3 to 12 shop daysDrying time to a measured target is part of the schedule
- Common sources
- Shower pan, toilet flange, slide seal, entry threshold, water heater bay
- Written estimate
- $150Credited in full against an authorized repair
Last verified
The call almost always starts the same way. There is a spongy patch in front of the shower, or near the entry step, or along the edge where the slide comes in, and the owner would like new flooring. New flooring is the last twenty percent of that job. The other eighty percent is the deck underneath, which has been absorbing water for somewhere between one and ten years and has lost most of its strength.
An RV floor is a structural deck. Plywood or OSB spans steel or aluminum floor trusses, bolted and bonded to the frame, with insulation and a coroplast underbelly beneath it. When that deck softens it is not a cosmetic issue, it is a load path issue, and laying luxury vinyl over it produces a beautiful floor that flexes exactly as much as it did before.
The floor is structure, and that changes everything
An RV deck spans steel or aluminum floor trusses and is fastened and bonded to the frame. It carries you, your furniture, your water and everything you loaded into the coach. It also ties the sidewalls together at their base. So when a section softens, the consequence is not just an unpleasant feeling underfoot, it is a section of the vehicle no longer doing its job.
Owners frequently ask whether they can just cover it. The honest answer is that covering a soft deck is spending flooring money to hide a structural defect, and the defect keeps progressing underneath the new material where nobody can see it. By the time it becomes undeniable, the repair includes the flooring that was just paid for.
Why OSB decks fail worse than plywood decks
Both materials rot. They do not rot the same way. Plywood is cross laminated veneers, so water tends to produce a defined soft zone that stops reasonably close to where the water was. OSB is compressed strands with adhesive, and once moisture gets into it the strands swell, the bond fails, and the failure travels along the panel much further than the wetting did.
In practice that means an OSB deck with a toilet flange leak often needs an entire bay replaced where a plywood deck with the same leak needs a couple of square feet. It also means a probe feels different: plywood goes soft, OSB crumbles. We always replace in exterior grade plywood regardless of what came out, because putting the weaker material back into a location that has already proven it gets wet is not a repair strategy.
- Plywood: defined soft zone, repair stays local
- OSB: strand swelling travels well past the wet area
- Probe feel differs, soft against crumbling
- Replacement is always exterior grade plywood
The five places the water usually comes from
Shower pan flange separation is first. The pan holds water fine, but the joint where its flange laps behind the wall surround opens, and every shower sends a little water down behind the pan instead of into the drain. Toilet flanges are second, and they are easy to check because a toilet that rocks has already lost its bearing surface.
Third is the slide floor seal, which lets rain track along the leading edge of an extended room. Fourth is the entry threshold, where sealant has failed at the most flexed and most trafficked part of the floor. Fifth is the plumbing bay, where a weeping fitting drips into a cavity that a coroplast underbelly then holds shut.
We check all five before ordering material, because a deck replaced under an unresolved source will fail again on the same timescale. We simply do not start the deck until the water is dealt with.
What has to come out to reach the deck
Access is where the hours live. Factory sheet vinyl runs underneath cabinetry, so the deck under a vanity or a galley base is genuinely inaccessible until those boxes move. Fixtures come out, and on damage at a slide threshold the room itself sometimes has to be pulled to get a clean cut and a proper new bearing surface.
That last item is the single biggest step change in cost on this page, and it is why the range runs as wide as it does. We establish at estimate whether a slide has to come out, and we say so plainly, because an owner comparing quotes deserves to know whether the cheaper one simply planned to work around the room.
Choosing between LVT, sheet vinyl and marine carpet
Luxury vinyl tile is what most owners want and it works well, provided it is installed with an understanding that a coach flexes and gets hot. Click lock floating installs need expansion room at every perimeter and at slide thresholds. Glue down handles flex better and is our default in high traffic and high heat areas, particularly on south facing units that sit in Orange County sun all summer.
Sheet vinyl is what the factory used, and it has real advantages: one continuous piece with no seams for water to find, and it runs under cabinetry so nothing telegraphs. Marine grade carpet remains the sensible choice inside slide out floors, where a hard surface fights the seal every time the room moves. Most coaches end up with a mix, and the transitions between them are worth doing properly.
| Material | Best location | Main limitation |
|---|---|---|
| Glue down luxury vinyl tile | Main living areas and galley | Requires a flat, sound deck |
| Click lock luxury vinyl tile | Bedrooms and low traffic areas | Needs expansion room at every edge |
| Roll sheet vinyl | Wet bath and full floor OEM style | Cabinets must be off to install correctly |
| Marine grade carpet | Slide out room floors | Wears at the seal contact line |
Drying is part of the schedule, not a delay in it
Once a deck is opened and the wet insulation is out, the surrounding structure still holds moisture. Framing, the bottom of a wall, the edge of a panel that was never going to be replaced. Bonding new plywood against material that is still wet puts the repair in a damp sealed cavity, which is precisely the condition that created the original problem.
So the coach sits with air moving through the opened area until readings match a dry baseline taken elsewhere in the same unit. How long that takes depends on how much water was in there and on the weather that week. It is measured rather than guessed, and it is written into the schedule at estimate so nobody is surprised by a coach that appears to be sitting still while something important is happening to it.
Note
If a quote for a soft floor has no drying time in the schedule, ask where it went. Sealing new decking over damp framing is the fastest way to buy the same repair twice.
Floors, claims and the gradual damage exclusion
This is the page where owners most often discover the difference between sudden and gradual. A pipe that burst last Tuesday is usually a covered loss. A shower flange that has been weeping since 2019 generally is not, because most policies exclude damage that develops over time from a maintenance condition. That is not a carrier being difficult, it is what the policy says.
Where it gets worth documenting carefully is a floor damaged by a covered event: a storm that drove water past a seal, a collision that opened a seam, a slide that failed and let rain in. In those cases the moisture map, the photographs of the open deck and the truss condition are what support the claim. We capture all of it as a matter of course, whether or not a carrier is currently involved.
On the claim
Photograph the deck while it is open. Once new plywood is bonded down, the evidence for what was under there exists only in whatever pictures somebody remembered to take.
What is included
- Moisture mapping with meter readings
- Readings are taken in a grid and recorded with a baseline from a dry area of the same coach, so the cut line is a measurement rather than a guess.
- Cabinet, fixture and slide access
- Whatever sits on top of the affected deck comes off. On some units that includes pulling a slide room, which is disclosed at estimate rather than discovered.
- Water source identification and correction
- Deck work does not begin until the source is found and fixed. Replacing decking under a live leak is a repair with a countdown attached.
- Deck removal back to sound framing
- Cuts land on a truss centre with solid material on both sides, and blocking is added where a cut falls between supports.
- Truss inspection and repair
- Steel and aluminum floor trusses are checked for corrosion and deformation where the water sat, and sistered or sectioned where needed.
- Underbelly and insulation renewal
- Wet insulation is removed and coroplast is replaced or properly resealed, because a sealed underbelly holds water against the deck if it is not repaired.
- Finish flooring installationwhere applicable
- LVT, sheet vinyl or marine carpet is installed with correct transitions and expansion allowance for a vehicle that moves and heats.
How the work runs
Map the wet area properly
1 to 2 hours
A meter grid across the affected area, compared against a dry baseline elsewhere in the coach, establishes the real boundary. The soft spot you can feel is the middle of the damage, never the edge of it, and cutting to the feel is how repairs get done twice.
Find and fix the water
1 to 6 hours
Shower pan flange, toilet flange, slide seal, threshold, tank fittings. Each gets checked and the source is corrected before any decking is ordered. This step is short when the source is obvious and long when it is not, and it is never skipped.
Clear access and open the floor
3 to 14 hours
Fixtures, cabinetry and sometimes a slide room come out. The deck is cut on truss centres past sound material, wet insulation is pulled from below, and the cavity is opened up so the structure can dry rather than trapping moisture in.
Dry to a target and repair framing
2 to 10 hours
The area is dried until readings match the coach baseline, not until it looks dry. Corroded or deformed truss sections are sistered or replaced while everything is open, which is the only sensible moment to do it.
Deck, seal and reinstate
4 to 16 hours
Exterior grade plywood is bedded in adhesive and fastened to the trusses, the underbelly is closed with new coroplast and insulation, and fixtures and cabinetry go back with fresh seals at every penetration.
Lay the finish floor
3 to 12 hours
LVT, sheet vinyl or carpet goes down last with proper transitions at doorways and at slide thresholds. On coaches where the original vinyl ran under cabinetry, we discuss whether to reproduce that or to floor to the boxes.
What this costs
$750 to $9,500+
6 to 40 labor hours at $210 per hour, body and paint.
- Body supplies at $5 per body hour.
- Parts at $100 or less carry 100 percent markup. Parts over $100 carry 35 percent. Special order parts require a full non refundable deposit at order.
- Sales tax of 7.75 percent applies to parts and materials. Labor is not taxed.
- A 50 percent deposit is taken at authorization on any job over $2,000, with an additional 25 percent when parts arrive on any job over $10,000. Final balance is due at pickup.
- A single bay of deck at a toilet flange with a small finish floor patch sits at the bottom of this range.
- A rotted deck spanning the wet bath, hallway and slide opening with cabinetry removal sits at the top and can exceed it.
- Pulling a slide room for access is the single largest step change in cost on this work.
How estimating is billed
- Written repair estimate: $150, credited in full against an authorized repair.
- In depth diagnostic, scan and programming: $285 per hour, one hour minimum, credited in full against an authorized repair.
- In shop pre purchase inspection: $400 to $1,200 depending on unit size and systems count.
- Insurance walk ins are accepted during posted hours. All inspection and estimating work is performed in shop at the Yorba Linda facility.
What you will notice first
- A spot that gives underfoot in front of the shower or the toilet
- Flooring that has lifted or curled along a seam at a doorway
- A dark stain spreading out from the base of the toilet
- Screws or staples backing out through the finish floor in one area
- A musty smell in the coach that gets stronger near the floor
- Deflection at the leading edge of a slide room opening as you step across it
- Coroplast underbelly sagging or torn with wet insulation visible
- Vinyl that has stayed flat everywhere except a two foot circle by the entry
How this fails, and what we do about it
| Failure mode | How we diagnose it | The fix |
|---|---|---|
| Localised rot at a toilet flange | Rock the toilet gently. Any movement means the flange has lost its bearing surface. Probe the deck around it with an awl and take moisture readings outward until they drop to the baseline for that coach. | Remove the fixture, cut the deck back past sound material, bond and fasten a new section with blocking to the trusses, then reset the flange with a new seal and fresh closet bolts. |
| Progressive rot from a shower pan flange | Soft flooring in front of the pan with the pan itself still holding water. Pull the surround trim and look for a separated flange. Water has been running behind the pan, not through it. | Pull the pan, replace the deck under and in front of it, reset the pan with a properly lapped flange to surround joint, and reseal. Replacing the deck without correcting the flange lap simply restarts the clock. |
| OSB decking that has delaminated across a wide area | Probing produces crumbling rather than a clean soft spot, and the affected area extends well past where the floor feels spongy. OSB wicks along its layers and loses integrity over a much larger footprint than plywood. | Cut back to a truss centre with sound material on both sides and replace in exterior grade plywood. Patching OSB against OSB in the same bay usually means returning to the same coach. |
| Deflection at a slide opening | The floor moves as you step across the slide threshold and the leading edge shows staining. The truss under the opening often has corrosion where water tracked along it. | Support the room, replace the deck at the opening, sister or replace the affected truss section, then address the slide floor seal before the room goes back to service. |
Why it happened
- Shower pan flange separation, where the pan and the wall surround stop sealing and water runs down behind the pan into the deck rather than into the drain
- Toilet flange leaks at Thetford and Dometic fixtures, which wet the deck immediately around the flange and are frequently mistaken for condensation
- Slide floor seal wear, which lets water track along the leading edge of the opening every time it rains on an extended room
- Entry door threshold sealant failure, which puts water into the deck at the busiest and most flexed part of the floor
- Fresh tank and water heater bay fittings weeping into the cavity, where the coroplast underbelly holds the water against the deck instead of letting it drain
- OSB decking as originally specified on entry level units, which loses strength faster and further from a given amount of water than plywood does
Parts and brands we work with
- Exterior grade plywood in five eighths and three quarter inch for deck replacement
- Structural construction adhesive and stainless fasteners into steel and aluminum floor trusses
- Coroplast underbelly sheet, closed cell insulation and underbelly repair tape
- Luxury vinyl tile in click lock and glue down formats, plus roll sheet vinyl for OEM style installs
- Marine grade carpet for slide out floors and transition mouldings for doorways
- Thetford and Dometic toilet flange kits, closet bolts and seals replaced during floor work
What not to try yourself
- Laying new luxury vinyl over a soft deck. The finish will look correct and the floor will still flex, and every seam over the weak area will fail within a season.
- Screwing a plywood patch over rotted decking. The fasteners land in material that has no holding strength and the rot underneath continues in a sealed, damp cavity.
- Cutting the deck to the boundary of what feels soft. Rot extends past detectable softness in every case we have opened, and in OSB it extends a long way past.
- Taping the underbelly closed over wet insulation. Coroplast holds water in rather than out, so a sealed underbelly over wet material keeps the deck damp indefinitely.
Which vehicles we do this on
Vehicles we perform Flooring on
Travel TrailerTravel trailer repair covers A frame tongue welds, the front cap that takes road debris, the roof front radius seam, sidewall delamination starting at a window corner, and equalizer and axle wearStandardStandard fifth wheel repair concentrates on the pin box and upper deck welds, the floor at the step up transition, the front cap above the pin and the roof front radius seamBunkhouseBunkhouse fifth wheel repair deals with the second entry door cutout weakening the rear sidewall, bunk room floors over the rear overhang, and a half bath crammed into a rear cornerClass CClass C motorhome repair centers on the cabover bunk, the joint where the coach body meets the factory van cab, and the stick built or laminated house behind itClass A GasClass A gas motorhome repair covers the molded front and rear caps, the vacuum bonded laminated sidewalls, the EPDM roof and the F53 chassis underneathToy Hauler TrailerA toy hauler travel trailer carries its garage behind the axles on a straight frame, so rear loading removes tongue weight and makes the rig sway sensitivePark ModelPark model repair treats the unit as a sited structure: frame corrosion and sag from years on blocks, pitched roof and flashing detail, residential window sealing, and moisture trapped behind skirtingI have never once cut open a floor and found the damage was as small as the soft spot suggested. Not once. You feel a patch about the size of a dinner plate, you take the vinyl up, and the stain runs two feet further in every direction. That is why I meter first and cut second, and why I always cut to a truss centre with good wood on both sides. If somebody tells you they can do a soft floor without pulling the toilet and the vanity, what they are really telling you is that they plan to work around the damage instead of removing it.
Appendix: questions and answers
- Can you lay new flooring over the soft area instead of replacing the deck?
- We will not. A soft deck is structure that has lost strength, and covering it means the flex stays, the seams over the weak area fail, and the rot keeps progressing where nobody can see it. The eventual repair then includes tearing out flooring that was just paid for.
- How much bigger is the damage than the soft spot I can feel?
- Consistently larger, and in OSB decking much larger. Softness you can detect by foot is the middle of the wet zone. We map with a moisture meter in a grid against a dry baseline elsewhere in the coach, then cut to a truss centre with sound material on both sides.
- My trailer has OSB decking. Do you put OSB back?
- No, we replace in exterior grade plywood every time. OSB strands swell and lose their bond once wet, so the failure travels far beyond the wetted area. Putting the weaker material back into a spot that has already proven it gets wet is not a repair, it is a delay.
- Does the slide room have to come out to fix the floor at the threshold?
- Sometimes, and it is the biggest single cost step on this work. Damage at a slide opening usually involves the truss under the threshold, and a clean cut with a proper new bearing surface is not achievable with the room in place. We establish this at estimate rather than mid job.
- Do you need to open the underbelly as well?
- Yes, whenever water has reached the cavity. Coroplast underbelly holds water in as effectively as it keeps road spray out, so wet insulation left in place keeps the deck damp indefinitely. We pull the wet material, dry to a measured target, then close with new sheet and insulation.
- Will insurance pay for a rotted RV floor?
- Usually not if the water arrived gradually from a maintenance condition, which most policies exclude. It often will when the floor was damaged by a covered event such as a storm, a collision or a failed slide letting rain in. Documentation taken while the deck is open is what supports the claim.
Open a file on this repair
Tell us the vehicle, what happened and whether a claim is open. We will tell you what the scope looks like and what it takes to get you back on the road.
Or call (949) 799-3387