Wet Subfloor Traced To One Slide Seal

A slide opening carries more than one seal, and they do different jobs. The bulb seal makes the compression joint when the room is closed. The wiper, a thin flexible lip standing proud of the opening, rides against the room face while it moves and while it sits extended. Rain running down a sidewall arrives at the top wiper first, and on a room that is out, the top wiper is the only thing between the weather and the inside of the wall cavity.

Wipers fail differently from bulbs. A bulb goes hard and takes a set, which an owner can see and feel. A wiper keeps its shape and loses its curl, so it stops pressing against the room face and starts merely touching it. Touching is not sealing. There is no gap to photograph and no split to point at, and a wiper in that condition will pass any inspection done by looking rather than by pressing a fingertip along the lip and feeling for return pressure.

The consequence is that water does not run down the outside of the room where it would be seen. It gets behind the room face, into the space between the room and the opening, and from there it is inside the structure of the coach with no route back out to daylight.

The room does not run on open air. It runs in and out of a boxed opening with a floor of its own, formed by the coach's floor structure and closed at the sides by the opening framing. That box has a low point, because nothing on a coach is dead flat and because the box is built to shed anything that gets into it toward one end. Water arriving past a failed wiper lands in that box and starts moving toward the low corner immediately.

What the box does not have is a drain, on most builds. It was never designed to carry water, only to stop draughts and to give the room something to run on. So the water reaches the low corner and stops there, held against the underside of the interior floor by nothing more than the fact that there is nowhere else to go. It sits in contact with the edge of the subfloor sheet, which is the one part of a coach's floor that has no laminate skin on it.

Subfloor on a coach is plywood or a laminated panel, laid in sheets that butt against each other on a frame member. Those butt joints are the fast route. Water sitting at the low corner of a slide box wicks into the exposed edge of the nearest sheet, travels along the joint, and can arrive at a point well away from where it entered because a joint runs the width of the coach. Two metres of travel along a butt joint is unremarkable and takes one wet season.

The floor above it stays dry the whole way. Vinyl, laminate and most carpet backings are vapour barriers, so nothing reaches the surface where a foot would find it. Meanwhile the underside is sealed by the belly wrap, which is doing exactly what it was built to do and holding road spray out, and in doing so holding this water in. A coach's floor is a sandwich with a barrier on both faces, which makes it excellent at staying dry from outside and very poor at drying once wet from inside.

The soft spot, when it finally appears, forms where the plywood has been wet longest and where the load is highest. That is often a doorway threshold or the base of a cabinet, neither of which is anywhere near a slide. An owner who finds a soft threshold and starts looking at the door seal is following the evidence correctly and looking in the wrong place.

Distance is not the only thing that misleads. Direction does too, because a butt joint runs across the coach and the low corner of a slide box can be on either end of it. A soft area on the kerb side of a coach whose only slide is on the road side is not evidence against the slide, it is evidence that the joint carried the water the full width. Ruling out a slide because the wet floor is on the wrong side is one of the more common reasoning errors on this fault, and it costs a season every time it happens.

The first honest signal on this route is a musty smell in a closed coach that clears within minutes of opening a window. It comes from the underside of the subfloor and reaches the cabin through the gaps that every floor has, around plumbing penetrations, under cabinet kick panels, at the base of a slide sill. There is nothing to see because there is nothing on any visible surface.

Owners routinely dismiss it, and the reason is reasonable: a closed coach smells closed. The distinguishing feature is season. A stored coach that smells the same in July as it did in February has a storage smell. One that develops a smell after the rainy season and loses it by late summer has water on a cycle, and a slide seal is the most common single origin of that pattern on a coach that has slides.

Once a floor comes up, the evidence of where water entered is gone, and on an insurance claim that evidence is worth more than any description of it. These six take ten minutes and they should exist before a shop, an adjuster or an owner opens anything.

• The full width of each slide opening with the room extended, taken square on, so the wiper line is visible along its whole length
• A close photograph of the top wiper at both ends and at the centre, with a fingertip pressing the lip so the return, or the absence of it, is visible
• The low corner of the slide box, taken from below with the room out and a light behind the camera
• The soft area itself with a tape measure laid from it to the nearest slide sill, so the distance is on the image rather than in a sentence
• Any staining at the base of a cabinet kick panel or at a doorway threshold, however faint
• The exterior sidewall above the slide, showing what the water was running down before it reached the wiper

Working from the soft spot outward is the natural instinct and it fails here, because the soft spot is the end of the route and the route runs under a sealed floor. A repair that replaces the wet section of subfloor without addressing the wiper produces a coach that is genuinely dry for a season and wet again the following spring, in a slightly different place, because the joint carried the water somewhere new.

We do not write water estimates from photographs, and this is the clearest example of why. A set of images of a soft threshold proves the floor is wet. It carries no information about which of two or three slide openings supplied the water, and that is the entire question. Insurance walk-ins are welcome and we write the estimate here, with the rooms run out and the wipers checked by hand before anybody talks about flooring.

Slide out seal replacement runs $400 to $3,000 depending on how many openings are involved and which seal profiles the coach uses. Water damage restoration and subfloor replacement runs $750 to $15,000. That gap is the reason this post exists, and it is not a scare figure: the low end of the restoration band is a defined area of subfloor caught in its first season, and the high end is a coach where the joint carried water across most of the floor over several years.

Diagnostic time posts at $285 per hour with a one hour minimum, credited against an authorised repair. On this fault that hour is spent running every room out, pressing along every wiper, and putting a moisture meter along the slide sills and the butt joints rather than at the soft spot, because the soft spot is already known and tells nobody anything new.