On this page (6 sections)
Knowing which roof you actually have
EPDM is a rubber membrane, usually white on the surface with a black core, and it is the most common material on mid market coaches and trailers. It sheds a fine chalky layer as it ages, which is by design: the surface sacrifices itself to ultraviolet and washes away, taking dirt with it. Those white streaks down your sidewalls are the membrane doing its job, and they mean the material is thinning year over year.
TPO is a thermoplastic membrane, typically with a bright white finish and a reinforcing scrim inside. It does not chalk the way EPDM does, it holds its appearance longer, and it can be heat welded at seams, which is a real advantage for repairs. It is also less forgiving of sharp impact and can crack rather than stretch when something drops on it. The two look similar from the ground and behave nothing alike.
Fiberglass and aluminum roofs are the other two families. A one piece fiberglass roof is stiff, walkable, and effectively permanent as a material, but it crazes and it still leaks at every penetration. Aluminum roofs on older trailers use lapped panels with sealed seams, and those seams work every time the trailer flexes. Whichever you have, the sealant is the consumable, not the roof.
Every leak starts at a hole somebody made on purpose
Count the penetrations on a typical roof: an air conditioner or two, a vent fan, plumbing vents, a refrigerator vent, a television antenna, solar mounts, a ladder, marker lights, and the front and rear cap seams. Every one of those is a hole cut through the membrane and the decking, bedded in butyl tape, screwed down, and sealed at the perimeter. The membrane between them is generally in far better condition than the sealant beading each one.
Self leveling lap sealant is designed to flow slightly when applied so it settles into a smooth continuous bead over a horizontal joint. It has a service life measured in a handful of years in this climate before it shrinks, cracks at the edges, and lifts. Non-sag sealant does the same job on vertical surfaces and cap transitions. Neither is permanent, and neither should be applied on top of the old failed layer, which is the most common thing we find.
The air conditioner is the leak nobody inspects. It seals against the roof with a large compressible gasket, and that gasket takes its clamp load from the bolts running down through the shroud into the interior ceiling assembly. Those bolts loosen with vibration and the gasket takes a permanent set. Retorquing them to specification, or replacing the gasket, is routine maintenance that most owners have never had performed.
Deciding between resealing, patching, and replacing
Resealing is the right call when the membrane is sound and the sealant is not. That means stripping the old failed material from every penetration and seam rather than adding another layer over it, cleaning back to the membrane, priming where the product requires it, and laying fresh sealant. Done properly this is a full day of work on a large coach and it prevents the category of damage that costs many times more.
Patching works for isolated damage: a branch puncture, a tear from a low clearance strike, a failed section around a removed accessory. On EPDM we clean, prime, and bond a compatible patch with proper overlap. On TPO we can heat weld a patch into the parent material, which produces a joint as strong as the sheet. What patching cannot do is rescue a membrane that has thinned globally or gone brittle across its whole area.
Full replacement becomes correct when the membrane has aged out, when there are multiple failures across the surface, or when the decking underneath has to come up anyway. Once we are pulling every roof mounted component to get the old membrane off, the incremental cost of new material is smaller than owners expect, and doing it in stages over several years costs considerably more in total labor.
What a full roof replacement involves
Everything comes off: air conditioners, vents, fans, antenna, solar, ladder, racks, and the front and rear cap trim. The old membrane is pulled and the decking is exposed and inspected across its whole area. Luan decking that has been wet is soft, delaminated, or dark, and it comes out. Rafters are checked at the same time, because a leak that softened decking has usually been feeding water into the framing beside it for just as long.
New decking goes down onto sound rafters, then the membrane is adhered with the correct adhesive system for the material and rolled out flat to eliminate air and wrinkles. Wrinkles are not cosmetic on a roof: they pond water and they concentrate stress at the fold. Edges are terminated under the cap and side trim, not just sealed at the surface, so water is directed rather than merely blocked.
Reassembly is where the job is decided. Every component that comes back goes on fresh butyl tape, with fasteners torqued in sequence and perimeters sealed with the correct self leveling or non-sag product for the orientation. We then flood test the roof before the interior ceiling goes back, because finding a missed penetration with water in the shop is trivial and finding it later, through a stained ceiling panel, is not.
What is included
- Full penetration audit
- Every vent, mount, seam, and fastener inspected and photographed, including the air conditioner gasket and clamp bolts.
- Old sealant stripped, not layered
- Failed lap sealant removed to the membrane and primed where the replacement product requires it.
- Decking and rafter inspection
- Substrate exposed and probed across its full area, with soft luan and compromised framing replaced.
- Membrane replacement in matching material
- EPDM, TPO, or fiberglass system installed with the correct adhesive and rolled flat to eliminate ponding.
- Component rebedding on fresh butyl
- Air conditioners, vents, and racks reinstalled on new tape with sequenced fastener torque.
- Flood test before closing up
- The finished roof is water tested while the interior ceiling is still accessible.
Signs you need this work
- A soft or spongy spot underfoot when you walk the roof
- A stain, bubble, or sag in the interior ceiling panel, often near a vent or air conditioner
- Cracked, shrunken, or lifting sealant beads around roof mounted components
- A musty smell inside that gets stronger after rain or after the unit has been closed up
- Heavy white or black streaking down the sidewalls that returns within weeks of washing
- Visible tears, punctures, or exposed decking anywhere on the membrane
Frequently Asked Questions
How often should a roof be resealed?
Inspect twice a year and plan on resealing penetrations roughly every two to four years in Southern California sun, sooner if the unit lives outdoors uncovered. Self leveling lap sealant is a consumable with a finite service life, not a permanent finish. The inspection matters more than the interval: cracked or lifting beads mean it is time regardless of how recently the work was last done.
Can you tell if there is damage without tearing the roof apart?
Largely, yes. We walk the roof for soft areas, take moisture meter readings through the interior ceiling and along the wall tops, and inspect every penetration and seam. That gives a reliable picture of where water has been. Confirming the extent of decking damage does require lifting membrane, which is why an estimate on a leaking roof is written after inspection rather than from photographs.
Is a roof coating a real alternative to replacing the membrane?
A liquid coating is a legitimate product for extending the life of a sound but weathered membrane, and it is a poor substitute for replacement when the membrane has failed or the decking is wet. Coating over trapped moisture seals the water in and accelerates rot underneath. We inspect and read moisture first, then tell you whether coating buys real time or just hides the problem.
Will a claim cover roof damage?
Sudden damage from an impact, a fallen branch, or a storm event is normally treated as a covered loss. Deterioration from age and deferred resealing is generally considered maintenance and falls to the owner. Where both are present, and they often are, the scope has to separate them clearly. We document the difference with photographs so the covered portion is not lost in a general denial.
How long does a full roof replacement take?
On a 35 to 40-foot unit, generally two to three weeks. Stripping components, removing the old membrane, and replacing decking is the bulk of it, and any framing or wall top repair discovered underneath extends it. Adhesive and sealant cure times also set part of the schedule. Simple resealing of all penetrations on a sound roof is typically a one to two day job.
Can I just have the leak fixed and leave the rest?
You can, and sometimes that is the right economic decision on an older unit. Be aware that sealant across a roof ages at roughly the same rate, so a failure at one penetration usually means the others are close behind. We are happy to repair a single point, and we will note in writing which other locations are already showing cracking so the next visit is not a surprise.
Related services
- Fiberglass and Delamination Repair
Sidewall separation, cap cracks, soft spots, and laminate rebuild.
- Water Damage Restoration
Leak tracing, subfloor replacement, and structural drying.
- Air Conditioning Service
Rooftop and ducted AC replacement, soft start install, and airflow repair.