# Roof and Water A roof leak is a location problem before it is a repair problem. Water enters at a penetration, a seam, or a failed membrane field, then travels to the place you noticed it. Classifying the entry point tells you whether you are buying sealant, a membrane, or a subfloor. ## Three entry points, and why the stain is not one of them Almost every water call starts with a stain, and a stain is the least informative thing in the whole sequence. It marks where water finally met something absorbent enough to show it. Entry was higher, and on a crowned roof it was usually also to one side, because water runs to the low edge before it finds a hole. Three things let it in. A penetration, meaning anything cut through the membrane: vents, fans, the air conditioner gasket, an antenna base, a skylight, a refrigerator vent, the screws holding a rack. A seam, meaning the joints at the front and rear caps and along the drip rails. Or the membrane field itself, where material has gone chalky and thin. The three fail on different schedules, and that is what makes the classification worth making. Penetrations fail first and fail often, because they are sealant rather than material, and sealant is a consumable with a service life measured in a couple of seasons on a coach parked in coastal sun. Seams fail next, and they fail structurally rather than cosmetically, because a cap joint that has opened is a joint that is now moving. Membrane fields fail last and fail slowly. An owner told the roof needs replacing when what has actually failed is four penetrations has been given a membrane price for a sealant problem. ## The point where the cost stops being gradual The cost curve on water is a step, and the step is the moment water reaches the decking. Above it, everything is sealant and labour: a roof recoat and reseal runs $750 to $4,500 and buys back a working surface. Below it, the problem stops being a roof. Wet decking has to come out, decking is structural, and the roof comes off to reach it, so membrane replacement runs $3,500 to $18,000 or more. If the water got past the decking and into the floor, water damage restoration and subfloor replacement runs $750 to $15,000 and the interior comes apart to get at it. Nothing about the stain on a ceiling panel tells you which side of that step you are on. A moisture meter does. ## What a recoat can and cannot be asked to do Recoating is the most oversold operation in this trade and genuinely useful when it is honest. It works when the decking reads dry, the seams are sound, and the membrane is intact but tired. It does nothing at all over wet decking, which is the version owners are most often sold, because a coating applied over trapped moisture seals the moisture in and buys a season of not knowing. This shop declines that job and says why. A recoat over a wet roof is money spent to postpone a measurement, and the postponement gets charged later at membrane and subfloor prices. The related decision, when a membrane is genuinely finished, is what replaces it. EPDM, TPO and fiberglass behave differently under coastal ultraviolet, walk differently, and take sealant differently at penetrations. That choice belongs on its own document at posted rates when it is an upgrade rather than a repair, because a coach that arrived with one material and leaves with another has been changed as well as fixed, and a settlement summary is a poor place to discover that. ## The habit that decides most of the above Everything on this page is decided by a habit that costs an afternoon twice a year. Sealant looked over on a six month cycle, from a ladder rather than from the ground, with photographs and a note of the date. It is not maintenance theatre. It is the only record that will later exist about what condition a roof was in before an event, and it is what separates a claim where an assumed service life can be questioned from a claim where it cannot. It also finds four penetrations while they are still four penetrations. ## Two neighbouring problems filed elsewhere Two things get confused with a roof leak constantly, and both are filed in other sections. A slide that leaks is a seal and geometry problem rather than a roof problem. A wet cabinet under a sink is plumbing. Both produce the same soft floor and the same smell as a roof leak, so the first job at intake is establishing which of the three is actually running, because the search patterns share nothing at all. ## Related - [Water Enters High And Leaves Low](https://ocrv.guru/blog/roof-and-water/water-enters-high-and-leaves-low/) - [Six Months Is The Sealant Inspection Interval](https://ocrv.guru/blog/roof-and-water/six-months-is-the-sealant-inspection-interval/) - [A Recoat Over Dead Membrane Buys One Season](https://ocrv.guru/blog/roof-and-water/a-recoat-over-dead-membrane-buys-one-season/) - [Hail Dents The Roof And Bruises The Deck](https://ocrv.guru/blog/roof-and-water/hail-dents-the-roof-and-bruises-the-deck/) - [The Vent Flange Fails Before The Membrane](https://ocrv.guru/blog/roof-and-water/the-vent-flange-fails-before-the-membrane/) - [EPDM, TPO And Fiberglass Age Differently](https://ocrv.guru/blog/roof-and-water/epdm-tpo-and-fiberglass-age-differently/) --- Source: https://ocrv.guru/blog/roof-and-water/ 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/.