Full RV Roof Replacement in Rancho Santa Margarita: Membrane and Decking
Written by Structural Repair Lead, Structural and Frame Lead, OCRV Center. Reviewed by Claims Coordinator
In shortEverything comes off: air conditioners, vents, racks, trim and the sheet itself. Decking is inspected rafter by rafter, then a new membrane goes down in one piece. $3,500 to $18,000+.
What happens during a full RV roof replacement?
Full roof replacement strips every rooftop component, removes the old membrane, renews rotted lauan or OSB decking over the rafters, lays a new EPDM or TPO sheet, and rebeds every penetration. Rancho Santa Margarita owners get this done indoors at our Yorba Linda shop where adhesive conditions are controlled.
- Air conditioners, vents, racks and edge trim all come off first
- Decking is replaced in full sheets landing on rafters, not patched
- New decking thickness changes the air conditioner gasket requirement
- Twenty to eighty labor hours depending on length and substrate condition
- Price range
- $3,500 to $18,000+20 to 80 labor hours at $210 per hour
- Labor rate
- $210 per hourPlus body supplies at $5 per body hour
- Typical turnaround
- 6 to 15 shop daysAdhesive cure and full decking replacement drive the calendar
- Estimate
- $150 written$150 buys the written scope. It is credited back at authorization
- Rafter spacing
- Usually 16 inch centresSome older builds run 24 inch, which changes decking thickness
- Deposits
- 50 percent over $2,000, further 25 percent over $10,000Taken when parts and materials arrive on larger jobs
Last verified
There comes a point where patching a roof is throwing labor at a surface that has run out of service life. Usually it arrives one of three ways: the decking has rotted across too much area to cut out sensibly, the membrane has embrittled everywhere rather than in one place, or somebody adds up the cost of eleven patches and realises a single new sheet is cheaper and better.
A full replacement is a strip to the structure. Air conditioners come off, vents come out, the antenna, the racks, the solar and the edge trim all come away, and then the membrane is peeled and the substrate underneath is finally visible for the first time since the unit was built. Most owners are surprised by what that reveals. We photograph all of it, because that photograph is what explains the final invoice.
The point where replacement beats repair
There is no single trigger, but there are three that account for nearly every full replacement we do. The first is decking condition. Once soft areas appear in more than two separate zones, cutting each out leaves a deck that is more joint than sheet, and joints are where fasteners loosen and where the membrane above eventually telegraphs.
The second is the membrane itself. A sheet that tears rather than stretches under a probe has lost its elongation across the whole roof, not just where the damage shows. Patching it moves the weak point to the patch perimeter, and that is exactly why those repairs fail so predictably about a year later.
The third is simple arithmetic. When somebody brings us a roof with nine areas needing attention, we price the patches and we price the reskin, and the two numbers are often much closer than expected. Given a close call, one continuous sheet with one perimeter beats nine patches with nine perimeters every time.
What is actually under the membrane on an RV roof
Peel the sheet and you find decking, usually lauan in an eighth, quarter or three eighths inch thickness, sometimes OSB on entry level trailers. Under that are the rafters, typically aluminum tube on modern builds or wooden members on older ones, most often at sixteen inch centres although twenty four inch spacing shows up on some older units and on a few lightweight designs.
Rafter spacing is not trivia. It determines what decking thickness is appropriate, whether the roof is safe to walk, and how a replacement sheet has to be laid out so its joints land on structure. It also explains why hail fractures and foot damage always appear between trusses rather than over them: the bay is the unsupported span and it is where the load has nowhere to go.
The other thing that shows up at this stage is truss condition. Aluminum tube corrodes at the sidewall junction where water has been collecting, and wooden rafters rot at their ends for the same reason. Neither is visible until the decking is off, which is why we photograph every bay before new material covers it.
- Lauan at 1/8 to 3/8 inch, or OSB on some entry level builds
- Rafters usually at 16 inch centres, sometimes 24 on older units
- Trusses fail at the sidewall junction where water pooled
- Decking joints must land on a rafter, staggered between rows
Choosing the new membrane and whether to change families
Most replacements go back with the same family the coach left the factory with, because the edge trim, the adhesive system and the installer's technique all line up. EPDM at 45 mil is the traditional choice and it is forgiving to install. TPO and Alpha Systems SuperFlex are heat welded, which produces a genuinely continuous seam at any joint and does not chalk, so the sidewalls stay cleaner.
Changing families is possible and it is a real decision rather than a formality. Going from EPDM to TPO means a different adhesive system, a welding setup rather than a bonding setup, and occasionally different edge trim to suit the sheet thickness. Owners who are tired of black streaks on white sidewalls sometimes make this change deliberately, and it is a reasonable reason to do it.
| Option | Install method | Streaking | Notes |
|---|---|---|---|
| EPDM 45 mil | Bonded with matched adhesive | Chalks and streaks by design | Traditional, forgiving, widely stocked |
| TPO | Heat welded seams | No chalk | Continuous welded joints, cleaner sidewalls |
| Alpha SuperFlex | Heat welded with matched primer | No chalk | Common on late model towables |
The details that decide whether a new roof lasts
The membrane is the easy part. What separates a roof that goes twenty years from one that leaks in three is what happens at the edges and the holes. Every flange has to come down onto fresh butyl. The edge rail has to be bedded and then sealed with a non sag product, because self leveling sealant on a vertical face just runs off and leaves the fastener line exposed.
The air conditioner gasket deserves its own paragraph because it catches people out constantly. Changing decking thickness changes the gap the gasket has to fill. Refit the original three eighths gasket where the roof is now thicker and you crush it. Refit it where the roof is thinner and it never seals. We measure finished roof thickness and fit the gasket that matches, then torque the mounts to the compression the manufacturer specifies rather than to feel.
Note
We do this work indoors. Adhesive flash times, humidity and wind all change the result, and a marine layer morning in June is not a condition you want a roof bonding in.
Cost, deposits and how many days to plan for
Full replacements bill at $210 per hour from the body and paint department with body supplies at $5 per body hour. Twenty hours is a short trailer with sound decking and two vents. Eighty hours is a forty five foot fifth wheel needing complete decking, two air conditioners reset and a solar array removed, catalogued and refitted. Parts carry standard markup, tax applies to parts and materials, labor does not.
Plan on six to fifteen shop days. Deposits are 50 percent above $2,000 with a further 25 percent when parts and materials arrive on jobs over $10,000, and most full roofs clear the first threshold comfortably. $150 buys the written scope. It is credited back at authorization.
On cost
Rafter damage found after the decking comes off is a real scope change, not a surprise charge. It is quoted separately, with the photographs of the bay it was found in attached.
Insurance on a full roof replacement
A roof that aged out is not a claim. A roof written off by hail, a fallen tree, a collision or a storm event usually is, and a full replacement is frequently the correct outcome on those files once the damage is scoped honestly. What complicates them is betterment: a carrier is paying to restore a twelve year old roof, and some policies depreciate that component.
The other recurring issue is teardown discovery. The scope written before the membrane came off was written blind, and rotted decking or a corroded truss found underneath is exactly what a supplement exists for. Those get approved when there are dated photographs of each truss bay and a written note tying the finding to the original loss. They stall when there are not.
Units we reskin most often
Towables dominate this work. Travel trailers and fifth wheels carry large flat roofs with many penetrations and often the thinnest decking, and they tend to spend more of their lives parked outdoors than motorhomes do. Park models are their own category, because a unit that has stood on one pad for fifteen years under trees has usually accumulated everything a roof can accumulate.
What is included
- Complete rooftop teardown
- Air conditioners, vents, antennas, racks, solar and edge trim are all removed and tagged, not worked around.
- Membrane removal and adhesive cleanup
- The old sheet comes off and the residual adhesive is removed so the new membrane bonds to substrate rather than to a failed bond line.
- Full decking inspection rafter by rafter
- Every truss bay is probed and photographed, and the photographs go in the file before any new material covers them.
- Decking replacement in full sheets
- New material lands and fastens on rafters with staggered joints, matched in thickness to the original build.
- New membrane laid in one piece where length allows
- Rolled out from the centre so no air is trapped, bonded with the system matched to the material, and trimmed at the edges.
- Every penetration rebedded and resealed
- New butyl under each flange, correct air conditioner gasket for the final roof thickness, self leveling sealant on top of all horizontal flanges.
- Membrane family conversionwhere applicable
- Changing from EPDM to TPO or the reverse, which requires a different adhesive system and sometimes different edge trim.
- Solar array removal, storage and refitwhere applicable
- Panels, mounts and wiring are removed, catalogued and reinstalled on new mounting points with fresh sealing.
How the work runs
Strip the roof completely
4 to 10 hours
Every rooftop item is removed and tagged, including air conditioners, all vents, the antenna, racks, solar and the edge trim. Working around a fixture is how a roof job ends up with a leak six inches from a brand new membrane.
Peel the membrane and clean the substrate
4 to 12 hours
The old sheet comes off and residual adhesive is scraped and solvent cleaned back to decking. New adhesive bonded onto old adhesive is only as strong as the failed layer underneath it, which is not strong at all.
Assess and replace decking
6 to 30 hours
Each truss bay is probed and photographed. Replacement goes in as full sheets landing on rafters, joints staggered so no two fall on the same member, thickness matched to the original so the roofline stays true.
Lay and bond the new membrane
4 to 14 hours
Adhesive is applied at the coverage rate the product specifies, the sheet is rolled from the centre outward so no air is trapped, and the edges are trimmed and dressed. Flash and open times are respected rather than estimated.
Reset every penetration and flood test
4 to 14 hours
Vents and appliances go back on fresh butyl, the air conditioner receives the correct gasket for the finished roof thickness, and all horizontal flanges are sealed. Then the roof is flooded and held with a technician watching inside.
What this costs
$3,500 to $18,000+
20 to 80 labor hours at $210 per hour, body and paint.
- Body supplies at $5 per body hour.
- Hazmat and disposal $45 flat when chemicals, refrigerant or LP is involved.
- 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 short travel trailer with sound decking and two vents sits at the bottom of the range.
- A forty five foot fifth wheel needing full decking, two air conditioners reset and a solar array refitted sits at the top.
- Rafter repair found after the decking comes off is a genuine scope change and it is quoted as one, with photographs.
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
- Multiple soft areas underfoot in different parts of the roof
- Membrane that tears further when you probe an existing repair
- A patchwork of tape and sealant applied over several years by several people
- Ceiling panels sagging or delaminating in more than one room
- Water appearing in different places depending on which way the unit is parked
- Edge trim screws that no longer hold anywhere along one side
- A roof that has been coated at some point and is now peeling in sheets
- Staining around every single penetration rather than around one
How this fails, and what we do about it
| Failure mode | How we diagnose it | The fix |
|---|---|---|
| Widespread decking rot | Pin meter readings elevated across multiple zones, soft response underfoot in more than two places, and lauan that crumbles at several probe points. At this stage cutting out sections leaves more joint than sheet. | Replace decking in full sheets that land and fasten on rafters. Sheet joints are staggered so no two land on the same truss, exactly as the original build did it. |
| Membrane past service life | The sheet tears rather than stretches when probed, and existing patches have failed at their edges. Age plus ultraviolet exposure has taken the elongation out of the material everywhere. | Full sheet replacement. Patching a brittle membrane relocates the failure to the patch perimeter, which is why those repairs come back so consistently. |
| Rafter damage found after stripping | With decking off, aluminum tube trusses are checked for corrosion at the sidewall junction and wooden rafters for rot at their ends. Both fail at the perimeter first, where water collected. | Section and replace the affected truss, or sister a new member alongside it. This is a supplement item on an insurance file and it is why teardown photographs matter. |
| Air conditioner gasket mismatch after new decking | New decking of a different thickness changes the distance the air conditioner has to compress its gasket. Refitting the original gasket then either crushes it or leaves it loose. | Measure final roof thickness and fit the correct gasket, 3/8 or 1/2 inch, then torque the mounting bolts to the specified compression rather than to feel. |
| Edge trim and insert strip failure | The aluminum edge rail has elongated screw holes along one or both sides, and the insert strip has shrunk back from the corners leaving the fastener line open. | Replace the rail and the insert, bed the rail on butyl, and seal the top edge with non sag rather than self leveling product since this is a vertical face. |
Why it happened
- Decades of accumulated penetration leaks, each small, each feeding water into the same lauan sheet from a different direction
- A membrane past its practical service life, where the sheet has lost elongation and any new patch simply moves the failure point an inch
- OSB decking that has swollen at the sheet joints, which loses fastener grip across the whole roof rather than in one place
- An incompatible coating applied years ago that trapped moisture against the membrane and prevented normal drying
- Storm or impact damage over a large enough area that repair and replacement price out close to each other
- A previous repair done with Eternabond over dirty sealant, which now cannot be removed without taking substrate with it
Parts and brands we work with
- EPDM sheet in 45 mil with matched water based or solvent based bonding adhesive
- TPO and Alpha Systems SuperFlex membrane for heat welded installations
- Lauan decking in 1/8, 1/4 and 3/8 inch and OSB where the original build used it
- Aluminum edge and corner trim, plus insert strip where the original design used one
- Air conditioner gaskets in 3/8 and 1/2 inch to suit final roof thickness
- Butyl tape and Dicor 501LSW self leveling sealant for every reset penetration
- Fan-Tastic and MaxxAir vents where the originals are not worth refitting
What not to try yourself
- Laying a new membrane over the old one to save the strip out labor. The bond is only as good as the failed adhesive underneath, and the old sheet hides the decking condition that was the reason for the job.
- Reusing the original air conditioner gasket after changing decking thickness. Either it crushes and cracks the shroud mounts or it never compresses and the opening leaks straight into the ceiling.
- Screwing new decking into old fastener holes. Lauan does not hold twice in the same hole, and a roof deck that lifts at the fasteners will telegraph through the membrane within a year.
- Doing this work outdoors. Adhesive flash times, ambient humidity and any breeze all change the outcome, and a partially bonded roof is worse than the one it replaced.
Which vehicles we do this on
Vehicles we perform Full Replacement 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 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 underneathClass 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 itPark 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 skirtingEvery full roof I have ever done has had at least one surprise in it, and the surprise is always in the same place: the last two feet before the rear cap, or right where the front cap seam meets the sidewall. Water collects at the ends. So I tell people at estimate that the decking number could move once we are down to it, and I photograph every truss bay before anything covers it back up. Nobody has ever argued with a photograph. What people object to is a number that changes with no explanation attached, and that is fair enough.
Appendix: questions and answers
- How many days does a complete RV roof replacement take?
- Six to fifteen shop days for most units. Stripping every rooftop component, peeling the membrane, replacing decking, bonding a new sheet and rebedding all the penetrations each take real hours, and adhesive open and cure times cannot be compressed to suit a pickup date.
- Can a new membrane be installed over the existing one?
- It should not be. The new bond is only as strong as the failed adhesive layer beneath the old sheet, and leaving the original membrane in place hides the decking condition that usually motivated the job. Every roof we replace is stripped to the substrate before anything new goes down.
- Can I switch from an EPDM roof to TPO during replacement?
- Yes. It means a different adhesive system, heat welding equipment instead of bonding, and sometimes different edge trim for the sheet thickness. Owners usually make the change because TPO does not chalk, so the black streaks that run down the sidewalls of an EPDM equipped coach stop appearing.
- Why does new decking change the air conditioner gasket?
- Because the gasket has to fill the gap between the air conditioner base and the finished roof, and changing decking thickness changes that gap. Reusing the original where the roof is now thicker crushes it. Reusing it where the roof is thinner leaves it loose. We measure and fit 3/8 or 1/2 inch accordingly.
- Can the price go up once the old roof is off?
- It can, and the reason is always decking or rafters that were invisible until the membrane came away. We photograph every truss bay before covering it and quote any additional work separately with those photographs attached. What we do not do is absorb a discovery quietly and hand you a larger number at the end.
- What happens to my solar panels during a roof replacement?
- They come off. Panels, mounts and wiring are removed, catalogued and refitted on new mounting points with fresh butyl and sealant afterward. Working around an array guarantees a leak next to a brand new roof, and the mounting feet are one of the most common penetration leak sources we find.
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