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RV Moisture and Leak Survey: Find Where the Water Gets In

By the Apex RV Repair service team · Over 5,200 RV repairs completed since 2008 · Specifications on this page are taken from the manufacturer documents listed in Sources

Mobile service across Florida · Last updated: September 01, 2026

An RV moisture and leak survey is a non-destructive inspection of the coach water barrier - the roof membrane, its sealant terminations, the cap seams, and every window, vent and slide flange - plus the wood and foam behind them. Nothing is opened and nothing is repaired. Readings are mapped through the finished surfaces to locate where water is entering, and the deliverable is a written report with a moisture map.

What an RV Moisture and Leak Survey Actually Is

A moisture and leak survey is a non-destructive inspection of the coach water barrier and the wood, foam and framing behind it. Nothing is removed and nothing is repaired on this visit. Moisture is mapped straight through the finished surfaces with an impedance scanner, and a pin-type probe is used only where a small hole is already acceptable. The output is a document rather than a fix: a labeled moisture map, meter readings tied to named locations, photographs of every failed sealant termination, and a ranked list of likely entry points. It is booked on its own, separate from a purchase or an insurance claim. A snowbird who leaves a fifth wheel parked from April to November has no way of knowing whether the roof held while they were gone, and the coach will not volunteer it. By the time the sidewall shows a mark, the answer has already cost money. The survey answers one question only: where is the water getting in.

Why the Survey Starts on the Roof and Works Downward

Water enters high and leaves low, so a survey run in any other order finds the puddle and calls it the leak. The sequence starts on the roof deck with a pinless impedance meter, an instrument that senses through a finished surface instead of into it, and Extech rates its MO257 to between 20 and 40 mm below that surface on a relative 0 to 100 scale rather than an absolute moisture percentage. Every self-leveling lap sealant bead, the front and rear cap seams, the air conditioner gasket, the roof vent flanges, the antenna base, the ladder mounts and the solar bracket feet get scanned and recorded. Then the upper sidewall and awning rail, then windows, doors and slide flanges, then the lower skirt, the basement compartments and the belly. Each level is scanned before the one beneath it. That way a wet reading downstairs can be attributed to something already found upstairs, instead of being written up as a second, separate leak that does not exist.

The Stain Inside Is Almost Never Under the Hole Outside

Owners typically describe a brown ring on a ceiling panel, a soft corner behind the dinette, or a musty smell that comes back after every rain. That location is the exit, not the entry. Water that gets past a failed sealant bead does not fall straight down. It runs along the underside of the roof decking until it meets a rafter, tracks sideways into the wall cavity, then follows the aluminum framing down to the first horizontal surface that will hold it. In a laminated sidewall it can travel several feet before anything shows. So the stain is treated as one data point. Our technicians work the perimeter around and above it, widening the scan until readings drop back to the dry baseline taken on a known sound area of that same coach. The entry point sits at the top edge of the wet zone, not the middle of it, and it is frequently on the far side of a seam.

Pressure and Smoke Testing to Prove the Path

Scanning shows where water is sitting. It does not prove how the water got there, and on a coach with a dozen candidate terminations above the wet zone that difference is the whole job. Two tests close the gap. A controlled water test runs a hose on one area at a time, starting at the bottom of the suspect zone and moving up in stages with a second person watching inside, because wetting a whole wall at once tells you nothing about which bead failed. A smoke test works the other way: the coach is lightly pressurized with a blower and filled from a fogger, and the smoke escapes through the openings from the inside out. Smoke reads well on window flanges, slide flanges and the seam where the sidewall meets the roof edge. It is far less useful on a roof designed to vent. Neither test replaces the meter, and both are run only after the dry baseline is recorded.

What Thermal Imaging Shows, and What Fools Both Instruments

A thermal camera does not see water. It detects infrared energy leaving a surface and renders it as a temperature map, so it can flag moisture only indirectly, when a wet area happens to sit at a different temperature from the dry material beside it. That leaves two hard limits. If the coach and the surrounding air have equalized overnight there is no differential left to render, and a soaked wall images the same as a dry one. Under Florida sun the opposite failure appears: a shaded awning line, a slide topper, an aluminum stud behind a laminated panel and a vinyl decal all read as anomalies that have nothing to do with water. The meter has its own blind spot. Its reading is relative, not a percentage, and Extech instructs that the MO257 be recalibrated whenever it moves to a new area, so it means nothing without a dry baseline from that same coach and material. Where the roof will not give one, the map is built from the ceiling panels inside. Imaging points; the meter decides.

What the Written Report Has to Contain

A report is useful to an insurer or a buyer only if a third party could repeat it. That means it has to record method, not just conclusions. The minimum is the make, model and mode of every meter used, the dry-baseline reading and where on the coach it was taken, ambient temperature and relative humidity at the time of the survey, the date plus the rainfall in the days before it, a labeled moisture map with a value at each test point, and a photograph of every failed termination with something in frame for scale. The interpretation is then kept separate from the data: which readings are elevated, which entry point each one is attributed to, and how firm that attribution is. A line reading moisture detected in the rear wall is worth nothing in a claim. An adjuster prices scope, and scope comes from mapped extent with numbers behind it.

What It Costs, When to Book It, and What Waiting Turns It Into

A single-slide travel trailer is generally a two hour survey; a 40 foot diesel pusher with four slides and a wet bay takes longer. Book it before June 1 rather than after. The Atlantic hurricane season runs June 1 to November 30, and an open sealant termination heading into it gets tested by every rain band for six months. A Florida coach also never gets a dry season in which to recover. A rig laid up in Ohio spends winter frozen and idle; one parked in Ocala or Miami sits wet all year, so a small entry point compounds rather than pauses. A sealant reset now becomes a delaminated sidewall or a subfloor section later.

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Frequently asked questions

How is a moisture and leak survey different from a pre-purchase inspection?

A pre-purchase inspection covers the whole rig - appliances under load, LP system, tires, slides, brakes - and water intrusion is one chapter of it. A moisture and leak survey does only the water, and does it deeper: a full roof-down scan, a dry baseline, a moisture map and a traced entry point. Owners book the survey when they already know something is wet and need to know where it came in.

Can you find the leak without cutting anything open?

Usually, yes. An impedance scanner reads through finished panels without marking them, so the map is built non-destructively. A pin probe is used only where a small hole is already acceptable, such as inside a basement compartment or under a removable trim strip. If the readings still cannot separate two candidate entry points, the next step is a controlled water test rather than exploratory cutting.

Will a thermal camera show me the leak?

Not on its own. Thermal imaging renders temperature, not moisture, so it only highlights a wet area when that area sits at a different temperature from the material around it. Early morning, before the sun loads the sidewall, is the useful window. Every thermal anomaly still has to be confirmed with a moisture reading before it goes in the report, and unconfirmed anomalies are noted as dismissed.

How long does a moisture and leak survey take?

A single-slide travel trailer is generally around two hours on site. A Class A with multiple slides, a wet bay and a full basement runs longer, because there are more terminations to scan and more places for water to stop. The written report and the moisture map are assembled after the visit, so expect a document rather than a verdict at the door.

Will my insurer accept the report?

An adjuster wants method and extent, not an opinion. A report that names the meter and mode, gives the dry baseline, records ambient temperature and humidity, maps a reading to each labeled test point and photographs each failed termination gives them something to price. What gets rejected is a one-line statement that moisture was found, with no map, no numbers and no attribution.

Should I book the survey before or after hurricane season?

Before. The Atlantic hurricane season runs June 1 to November 30, and an average season produces roughly fourteen named storms. A termination that is already open in May will be loaded by months of rain before anyone looks at it. A survey in spring turns a sealant reset into the whole repair; the same defect found in December is usually a wall or floor job.

Sources

Every figure on this page comes from a manufacturer document or a standards body, not from another repair site. Here is where each one comes from.

  1. Extech MO257 pinless moisture meter - manufacturer specificationsThe instrument facts behind the roof-down scan: a pinless meter takes non-invasive readings through a finished surface with a sensing depth of 20 to 40 mm (0.79 to 1.57 inches), it returns a relative 0.0 to 100.0 value that Extech labels 'Relative only' rather than an absolute moisture percentage, and it self-calibrates in dry air at power-on, which is why every reading in the report is tied to a dry baseline taken on that coach.
  2. Fluke - What is thermal imaging and how a thermal image is capturedThat a thermal imager detects infrared energy emitted by a surface and renders it as a temperature map, which is why it evidences moisture only indirectly and needs a temperature difference to show anything at all.
  3. NOAA National Hurricane Center - tropical cyclone climatologyThe Atlantic hurricane season runs June 1 to November 30, and the 1991-2020 average season produces 14 named storms, 7 hurricanes and 3 major hurricanes - the basis for booking a survey in spring rather than after.

What this usually costs

ItemPriceWhat it covers
Service call$299Includes the trip out to your RV and the first hour on site
Work past the first hourQuoted after diagnosisWe tell you what it will take before we carry on
PartsQuoted per jobSpecial-order parts may need a deposit before we order them
Written estimateNo chargeYou approve the estimate before any work starts

The service call covers the trip out to your RV and the first hour on site. Anything beyond that depends on what we find, and we quote it and get your approval before carrying on.

The price ranges on this page come from our own recent jobs across Florida, not from an industry average. What you pay depends on the rig, the parts it needs and what we find on site, so we give you a written estimate before any work begins and you approve it first.