# Sealant on a six month cycle: what to look at in spring, and what in autumn Two inspections a year, in spring and autumn, on a fixed date rather than when something stains. Sealant fails on a schedule set by ultraviolet exposure and thermal movement, not by rainfall. Coastal Southern California owners lose more roofs to eight dry months of sun than to the wet ones. ## Why the two passes look for different things Put both inspections in a calendar with a reminder and treat the date as fixed. The spring pass, ideally March or April, is a damage assessment: it looks for what the wet season found and exploited. Standing water at a low seam, a lifted termination bar, sealant that has taken up water and gone soft, a vent flange that has moved. Anything found in spring gets fixed while the weather is dry and stable enough to cure a repair properly. The autumn pass, September or October, is preventative and it is the more important of the two on this coast. Eight months of high ultraviolet load and daily thermal cycling between a hot roof and a cool night have worked every joint on the unit, and the autumn pass is where you catch the sealant that has gone chalky, shrunk back off a flange or cracked along a movement line before the first rain finds it. A joint that looks marginal in October is an open joint in January. Coastal air adds salt to that, which attacks fasteners and bright trim under the sealant rather than the sealant itself. ## Self levelling belongs on the roof, non sag belongs on the walls Two families of sealant, and putting one where the other belongs is the single most common owner error on a roof. Self levelling sealant is formulated to flow out and settle into a smooth bead under its own weight, which is what you want on a horizontal surface where it has to seal an irregular flange and shed water. Dicor self levelling lap sealant is the reference product for that job and it is what most factories use around roof penetrations. Non sag sealant is formulated to stay where it is put on a vertical or overhead surface. It belongs on sidewall seams, window frames, compartment door frames, cap side seams and anything on a slide. Put self levelling on a sidewall and it runs, leaving a thin unsealed section at the top of the joint and an ugly tail below it. Put non sag on a roof flange and it holds a ridge that stops water rather than shedding it, which puts a pond exactly where you were trying to prevent one. Eternabond tape occupies a third position: a butyl based sealing tape used to bridge a seam or a tear, excellent as a repair and difficult to remove afterwards, so it is a considered choice rather than a default. ## Reversion, chalking, and a seam that holds a pond Learn three failure signatures and the inspection becomes fast. Reversion is sealant that has gone backwards chemically and is now soft, tacky or gummy, often darker than it should be, and it will take a fingerprint or pick up dirt in a way cured sealant does not. Reverted sealant has lost adhesion whether or not it looks continuous, and pressing it usually opens a gap at one edge. Chalking is the opposite failure and it is what ultraviolet does. The surface goes pale, matt and powdery, and a finger drawn across it comes away dusty. Chalking on the top surface alone is cosmetic. Chalking with a visible crack, or with the bead shrunk back off a flange edge, is a joint at the end of its life. A pond seam is the third: any place water stands after rain or a wash instead of moving, usually just uphill of a flange, an air conditioner or a bar that has lifted slightly. Ponding is not itself a leak, and it is the condition under which every marginal joint becomes one, so mark it and correct the geometry rather than just adding sealant on top. ## The roof penetrations, in inspection order Work the roof front to back in a fixed sequence, every time, so nothing gets skipped when you are interrupted. Start at the front cap seam where the cap laps the roof, which takes the most flex and the most direct airflow at speed. Move to the air conditioner and check the gasket compression and the shroud fasteners rather than the sealant, because that unit seals by gasket and an over tightened or flattened gasket is the failure. Then each roof vent flange, then the skylight dome and its flange, then the refrigerator vent, then the antenna base, then each ladder mount, then the termination bar along both sides, then the rear cap seam. Note the condition of each in a fixed order in your log rather than writing prose, because the value of the log is comparison across passes rather than description. Look at the flange edge specifically, not the middle of the bead: sealant fails at the edge where it meets the flange or the membrane, and a bead that looks perfect across its face is often lifted along one side. Press each one. Sound sealant is firm and does not move. Anything that gives, tacks or shows a dark line at the boundary goes on the list. - Front cap to roof seam - Air conditioner gasket and shroud fasteners - Roof vent flanges - Skylight dome and flange - Refrigerator vent - Antenna base - Ladder mounts - Termination bar, both sides - Rear cap to roof seam ## Sidewalls, slide flanges, and the joints nobody checks Come off the roof and work the walls with the same discipline. Every window frame, along the top edge and down both sides to the sill, with attention to the mitred corners where a frame gasket opens first. Every compartment and baggage door frame. Every entry door frame and the awning rail above it. Every fastener that passes through the sidewall, including the ones holding an awning, a ladder, a rack, a light or an owner fitted accessory, because each of those is a hole in the laminate with a bead of sealant as its only defence. Slides need their own pass. Check the flange sealant all the way around each slide opening, and check the wiper, bulb and D seals on the slide itself for compression set, tearing and hardening. Run the slide out and look at the top seal from outside: a wiper seal that has taken a permanent curl no longer wipes, and every extension pushes water past it into the wall. Look at the underside of the slide floor and the seal at the bottom flange, which is the joint that gets least attention and does most of the damage when it fails, because water entering there goes straight into the subfloor. ## What an owner actually needs to own The list is short and it is worth having in a box before the first pass rather than assembling it on the roof. A stable ladder. A torch bright enough to rake light across a seam. A plastic putty knife and a plastic scraper, plastic rather than steel so a membrane survives the process. Denatured alcohol or a cleaner that contains no acetone, and low lint cloths. Low tack painter's tape for masking a bead and for marking findings. Nitrile gloves. A phone for photographs and a notebook or a note file for the log. Consumables: one tube of self levelling lap sealant matched to your membrane type, one tube of non sag for the walls, and a roll of butyl sealing tape held in reserve for a tear rather than used as routine maintenance. Buy the sealant the same season you use it, because a tube that has been in a hot garage for two years is not the product on the label. Check the membrane type before buying anything, since a sealant formulated for EPDM is not necessarily correct on TPO, and the wrong chemistry can attack the membrane it is meant to protect. ## When a recoat is the answer, and when the deck under it is already gone A recoat and reseal is the right answer when the membrane itself is sound and the failure is at the joints and the surface. Sealant renewed at every penetration, a coating applied over a membrane that has gone chalky but not brittle, ponding corrected where it can be. That work runs $750 to $4,500 plus, across 4 to 20 hours, and it is the cheapest money on a coach: a roof kept sealed on a schedule almost never becomes a structural repair. A recoat is the wrong answer when the deck under the membrane has already taken water. Coating a soft deck buys a season and hides the evidence for the season after that, and the repair that follows is larger for the delay. The tells are a deck that gives underfoot, a ripple that follows a framing line, a stain on an interior ceiling panel, or a fastener that has begun to back out because the wood no longer holds it. At that point the honest answer is a membrane replacement with deck repair underneath, $3,500 to $18,000 plus across 20 to 80 hours on a motorhome, and on a trailer roof $500 to $14,000 across 3 to 70 hours. The spread on both is real, because the number is set by how much deck comes out rather than by the square footage of the membrane. ## The log, and why it is worth more than any single inspection Keep one file, in one place, with one entry per pass. Date, weather in the preceding week, membrane type, and then the fixed list of penetrations and wall joints with a one word condition against each: sound, chalked, cracked, reverted, ponding, resealed. Add the photographs from that pass and note which products went on which joints, including the date on the tube. Nothing prose, nothing subjective, the same fields every time. Two payoffs, and both arrive years later. The first is that comparison across passes is the only way to see a joint moving slowly, which is what sealant does before it fails. A bead described as chalked in three consecutive autumn entries is a decision, where the same bead seen once is a shrug. The second is a claim. Betterment and depreciation on a roof rest on an assumed service life that is usually a template default, and a dated log with photographs is the only thing an owner can put against that default. It is also the single most useful document you can hand a shop on arrival, and the reasoning behind those deductions is set out at /insurance-help/deductible-and-depreciation/. ## Questions ### How often should RV roof sealant be inspected? Every six months, and after any hail or any low clearance contact. Six months is not arbitrary: a Southern California summer takes a lap sealant bead through roughly 180 heat cycles, and that is about how long it takes a hairline separation at a fastener to open into a path. Walk the roof, look at every penetration perimeter, and press each bead with a thumb. Chalky, cracked or lifted beads get cut out and rebedded, not overcoated. ### What is the difference between Dicor lap sealant and Eternabond tape? Different jobs. Dicor self levelling lap sealant is a flowable bead for horizontal penetrations, and it is designed to be maintained: cut out, clean, rebed, every few years. Eternabond is a butyl tape that bonds permanently across a seam and is very difficult to remove without damaging membrane. Tape belongs on long seams and repairs. Sealant belongs around fittings you will need to service again. Using tape around an air conditioner makes the next removal expensive. --- Source: https://ocrv.guru/the-center/guides/sealant-inspection-on-a-six-month-cycle/ OCRV Center, 23281 La Palma Ave, Yorba Linda, CA 92887. (949) 799-3387. Serving Laguna Niguel, California. All work performed in shop. No mobile or roadside service. Licences: California Bureau of Automotive Repair ARD00288521; EPA CAL000367879. Published ranges are ranges, not quotes. Every figure traces to https://ocrv.guru/prices/.