Slide Out Seal and Gasket Replacement for RV Slide Rooms
Written by RV Systems Lead, RV Systems and Electrical Lead, OCRV Center. Reviewed by Structural Repair Lead
In shortA seal that stays crushed flat instead of springing back has taken a compression set and will never seal again. Full runs replace at $400 to $3,000.
What is involved in replacing slide out seals and gaskets?
Slide out seal replacement swaps the wiper, bulb, corner and D seal runs that weather a room at both ends of its travel. Owners from Rancho Santa Margarita bring the coach to our Yorba Linda bays, where each run comes off whole, the flange is cleaned to bare substrate, and the new rubber is bedded and hose tested.
- Rubber that will not spring back has compression set and is finished
- Seals are replaced as complete runs, never spliced mid wall
- Butyl goes under the mounting flange, self leveling sealant goes on top
- A hose test on four faces confirms the repair before pickup
- Price range
- $400 to $3,0002 to 14 labor hours, mechanical and electrical department
- Labor rate
- $260 per hourSeal work is performed by the systems team, not the body shop
- Typical turnaround
- 2 to 5 shop daysOne room in a day is realistic, a quad slide coach is not
- Estimate
- $150 writtenComes off the invoice once you authorize the work
- Seal types replaced
- Wiper, bulb, D seal, corner molding, slide topper fabric
- Hazmat and disposal
- $45 flatApplies when solvent based adhesive is used on the run
Last verified
Rubber is a consumable. Nobody sells an RV that way, but every seal on a slide room is a part with a service life, and in southern California that life is shorter than the brochure suggests. Ultraviolet exposure, ozone and eight months parked in a storage lot with the room retracted will finish a bulb seal long before the mechanism that drives the room shows any wear at all.
The tell is simple and you can check it yourself. Press a bulb seal with your thumb and let go. Healthy rubber pushes back and returns to its original height. Rubber that stays dented is done. That condition is called compression set, it cannot be reversed with conditioner, and once it happens the seal is holding nothing back.
The three seal types on a slide room and what each one does
Most owners talk about the slide seal as though there is one. There are at least three profiles working on a typical room and they do unrelated jobs. The wiper is the blade that lies against the outside face of the room and sweeps it clean as the room travels. It handles rain running down the sidewall and it handles nothing else.
The bulb seal is the hollow round profile that compresses when the room is fully retracted, which is the only condition where it seals. The D seal, named for its cross section, sits on the inner flange and does its work when the room is fully extended. Read those two sentences again and the diagnostic follows on its own: a leak that only happens when you are parked is a D seal problem, and a leak that only happens on the freeway is a bulb seal problem.
Corner molding ties the runs together at the four intersections. It is the smallest part on the list and it accounts for a disproportionate share of the water we trace, because a butt joint between two straight extrusions is a hole unless somebody deliberately closed it.
- Wiper: sweeps the room face during travel, works in motion
- Bulb: compresses when the room is in, seals for transit and storage
- D seal: seals the inner flange when the room is fully extended
- Corner molding: closes the butt joints where straight runs meet
What does a failed slide out seal look like from inside the coach?
The first evidence is almost never a puddle. It is a smell. Sponge rubber that has stopped sealing lets humid air move through the wall cavity, insulation holds it, and the coach smells like a basement within a day of being closed up. Owners who store in Rancho Santa Margarita and open the unit up on a Friday afternoon usually notice this months before they see any water.
Visible evidence comes next and it shows up at the floor line. Look at the strip of flooring immediately inboard of the slide, where the room floor meets the main floor. Darkening, a lifted vinyl edge or a soft feel underfoot means water has been arriving there for a while. At that point the seal is a symptom and the floor edge is the problem, which is a different repair and a different department.
- Musty smell within twenty four hours of closing the coach
- Darkened flooring in the strip inboard of the slide opening
- Daylight at the top of the room when it is fully out
- Wind noise from the slide wall above forty five miles per hour
- Rubber crumbs on the ground under the opening
Compression set, ozone and eight months in a storage lot
Compression set is the single reason we replace more seals than we repair. Sponge rubber is a matrix of closed cells, and holding those cells crushed for a long enough period lets the cell walls take a new shape permanently. A room left retracted from October to May is a bulb seal held under load for roughly two hundred days without a break. The rubber does not recover.
Ozone attack runs alongside it and looks different. Ozone cracking appears as fine parallel fissures on the outer radius of a bulb, perpendicular to the direction of stretch. Coastal Orange County air plus strong ultraviolet exposure gets EPDM there faster than most owners expect, and the two mechanisms compound: cracked rubber sets faster, and set rubber cracks faster.
There is one prevention that actually works and it costs nothing. Run the rooms out for a few hours every month or two while the coach is in storage, if the lot allows it, and treat the rubber with a water based protectant rather than anything petroleum derived. That single habit is the difference between replacing seals at year twelve and replacing them at year six.
Note
Silicone and petroleum dressings are not maintenance. They soften the rubber, then leave it distorted and contaminated so the correct adhesive cannot bond during a later repair.
How we replace a wiper, bulb and D seal run
Work begins with water rather than with tools. The opening gets chalked, then a garden hose is directed at one face at a time while somebody watches from inside with a light. Pressure washers are never used for this, because a pressure washer will drive water past a seal that is perfectly serviceable and send the whole diagnosis in the wrong direction.
Once the entry face is known, every run on that opening comes off, not just the failed one. Mixing heights around a single opening is what causes the second visit. The flange gets scraped back to clean substrate, rebedded in butyl, and the new profile is set with the fastener line hand torqued so the flange is not crushed out of shape.
- Chalk the opening and hose one face at a time
- Remove all runs from the affected opening intact
- Scrape the flange to clean substrate and rebed in butyl
- Match profile by bulb diameter, leg length and flange thickness
- Set the run, seal horizontal flanges, cycle eight times, retest
Slide toppers, corner joints and where the water really enters
A slide topper is a small awning that unrolls over the roof of the room as it extends. Its job is to keep pine needles, jacaranda debris and standing water off the top of the room. When the topper spring loses tension the fabric sags, water collects in the middle, and every rainfall dumps that pool directly onto the top bulb seal. No seal profile made is designed to take a concentrated column of water.
The other under reported entry point is the fastener line. A mounting flange screwed dry into a sidewall gives water thirty or forty individual paths into the wall cavity, and the rubber above it can be brand new and perfect. This is why we rebed rather than reuse. If somebody quotes a seal job without mentioning what happens under the flange, the quote is for rubber and not for a repair.
Before you proceed
Water that has been arriving at the slide floor edge for two seasons is a structural question, not a rubber question. We take a moisture reading before new seals go on so nobody pays twice.
What does slide out seal and gasket replacement cost?
Seal work bills from the mechanical and electrical department at $260 per hour. A single accessible run on one room is a two hour job. Four runs on each of three rooms, with corner moldings and two toppers retensioned, is a full week of bay time, and the honest range has to hold both of those.
Rubber itself is inexpensive relative to the labor, which surprises people. Parts carry standard markup and sales tax applies to parts and materials, labor is not taxed, and a solvent based adhesive on the job adds the $45 hazmat and disposal line. The $150 written estimate comes off the invoice once you authorize the work.
On cost
Coaches built before 2005 sometimes use profiles that are no longer produced. Sourcing from Steele Rubber costs days rather than dollars, and we say so at estimate rather than at day six.
Is a failed slide seal an insurance claim?
By itself, no. Rubber that aged out is maintenance and every carrier scopes it that way. Where coverage does enter the picture is the consequence: if a covered storm event drove water past a seal and into the floor, the resulting damage can be a claim even though the seal that let it in is not. The distinction is worth understanding before anybody files.
What decides those files is the documentation captured before parts come off. Moisture readings at the floor edge, dated photographs of the failed run, and a note of the storm date are what let an adjuster connect a wet floor to an event rather than to eight years of neglect. We capture that on every seal job whether a carrier is involved or not.
Rooms and units we do this work on
Seal wear tracks storage habits far more than it tracks brand. A destination trailer that sits on one pad in a canyon park for nine years and a fifth wheel that gets used forty weekends a year will show completely different seal conditions at the same age, and the one that sits is usually worse.
What is included
- Full run removal on all four sides
- Top, bottom and both jambs come off together so the new rubber sits at one consistent height around the opening.
- Flange cleaning to bare substrate
- Old adhesive, hardened butyl and corrosion are removed with plastic scrapers and denatured alcohol rather than a razor blade.
- Fresh butyl under every fastener
- The mounting flange is rebedded, which is where a surprising share of slide leaks actually originate.
- Profile matching against the original
- Bulb diameter, flange thickness and durometer are matched to the room, not to whatever kit is on the shelf.
- Hose test on four faces
- Water is directed at the top, both jambs and the bottom in sequence with a spotter inside, using a garden hose rather than a pressure washer.
- Slide topper inspection and retensionwhere applicable
- Checked while the room is out and quoted separately if the fabric or spring is the actual water path.
- Interior floor moisture readingwhere applicable
- A pin meter reading is taken at the slide floor edge so a hidden rot problem is caught before new rubber hides it.
How the work runs
Chalk and hose the opening
1 hour
The room goes out, chalk marks the suspect runs, and water is applied one face at a time with somebody watching from inside. Finding the entry point before anything comes apart is what keeps this from becoming a guess and a parts bill.
Strip the old runs
1 to 3 hours
Every run comes off in one piece where possible so the original profile can be measured and matched. Old butyl under the flange is scraped back to clean substrate, because new rubber over hardened butyl sits proud and leaks at the fastener line.
Match profile and dry fit
1 hour
Bulb diameter, leg length and flange thickness are compared against the original before anything is bonded. A profile that is close but not correct will look right and hold pressure for about one rainy season.
Bed and set
2 to 6 hours
Butyl goes under the flange, fasteners are torqued by hand rather than by driver clutch, and horizontal flange edges get self leveling sealant. Vertical flanges get non sag product, since self leveler on a vertical run simply migrates.
Cycle and retest
1 to 3 hours
The room runs a minimum of eight full cycles so the new rubber takes its set against the face, then the hose test is repeated in the same four face sequence and the results go in the file.
What this costs
$400 to $3,000
2 to 14 labor hours at $260 per hour, mechanical and electrical.
- Parts at $100 or less carry 100 percent markup. Parts over $100 carry 35 percent. Special order parts require a full non refundable deposit at order.
- Sales tax of 7.75 percent applies to parts and materials. Labor is not taxed.
- A 50 percent deposit is taken at authorization on any job over $2,000, with an additional 25 percent when parts arrive on any job over $10,000. Final balance is due at pickup.
- A single bulb run on an accessible dinette room sits near the bottom of the range.
- Four runs on each of three rooms, with two slide toppers retensioned, sits near the top.
- Obsolete profiles on coaches built before 2005 sometimes have to be sourced from Steele Rubber, which adds days rather than dollars.
How estimating is billed
- Written repair estimate: $150, credited in full against an authorized repair.
- In depth diagnostic, scan and programming: $285 per hour, one hour minimum, credited in full against an authorized repair.
- In shop pre purchase inspection: $400 to $1,200 depending on unit size and systems count.
- Insurance walk ins are accepted during posted hours. All inspection and estimating work is performed in shop at the Yorba Linda facility.
What you will notice first
- A dark stain on the carpet or vinyl right where the slide floor meets the main floor
- Daylight visible along the top of the room when it is fully extended
- A musty smell that shows up within a day of closing the coach up
- Whistling from the slide wall at freeway speed with the room in
- Crumbs of dry black rubber on the ground under the slide opening
- The wiper blade folded under itself instead of lying flat after the room comes in
- Chalky white bloom or green mildew along one seal run
- Water beading on the inside face of the slide fascia after a rain
How this fails, and what we do about it
| Failure mode | How we diagnose it | The fix |
|---|---|---|
| Bulb seal compression set | Measure uncompressed height against the profile spec with the room out. A one inch bulb that measures five eighths under no load has lost its recovery and is passing air and water. | Replace the entire run around the opening. A partial replacement leaves new rubber at full height fighting old rubber at reduced height, and the room will not sit flat. |
| Wiper blade rolling under | Watch the last six inches of retraction. If the blade tucks under instead of sweeping across the room face, the blade has lost stiffness or the room is sitting low against it. | Fit a new wiper run, then correct room height and pitch so the blade contacts the face at the angle it was extruded to contact. |
| Corner joint leak | Water shows up at one interior corner only, and the flange there has a butt joint where two straight runs meet. Chalk and a hose confirm it in about four minutes. | Use a molded corner where one exists for the profile. Where it does not, bond the joint with a compatible cyanoacrylate and seal the flange underneath with fresh butyl. |
| Adhesive backed seal releasing | The seal lifts away from the flange with light finger pressure and the exposed metal is clean rather than torn. That is adhesive failure, not rubber failure. | Switch to a kerf or track mounted profile where the opening allows it, so the seal is held mechanically instead of relying on tape in 110 degree bay temperatures. |
| Slide topper fabric pooling water onto the seal | The topper sags in the middle and water sheds inboard onto the top bulb seal every time it rains, which is not what the top seal was designed to handle. | Retension or replace the topper fabric and roller spring first. Replacing the seal underneath a sagging topper buys a season and no more. |
Why it happened
- Compression set from long term storage with the room retracted, which loads the bulb seal continuously for months with no recovery period
- Ultraviolet and ozone attack on exposed EPDM sponge rubber, which shows first as surface crazing along the outer radius of the bulb
- Petroleum based dressings applied by a previous owner, which swell the rubber, then leave it soft and permanently distorted
- Adhesive backed seal releasing from the flange in summer heat, usually starting at a corner and peeling toward the middle
- A room that travels out of square, which drags the wiper blade sideways and shaves the working edge off one side
- Screws through the mounting flange installed dry, with no butyl underneath, so the leak is at the fastener rather than the rubber
Parts and brands we work with
- Trim-Lok bulb, D and wiper profiles in EPDM sponge and dense rubber
- Steele Rubber Products replacement runs for older coaches with obsolete profiles
- AP Products and Clean Seal slide out seal kits
- Lippert factory seal kits keyed to specific room widths
- Carefree of Colorado and Dometic slide topper fabric and roller assemblies
- Dicor 501LSW self leveling lap sealant and 551 non sag for vertical flanges
- Butyl tape in 1/8 by 1 inch for bedding a mounting flange
What not to try yourself
- Coating a hardened seal with silicone spray to make it soft again. Silicone does not restore recovery height and it contaminates the flange so the correct adhesive will not stick later.
- Sealing a leak by running a bead of caulk along the outside of the seal. That traps water inside the wall cavity instead of letting it drain, and it turns a rubber job into a floor job.
- Splicing a short patch into a run at the leak point. The splice becomes the new leak within a few cycles because the joint sits at a different height than the run either side of it.
- Using a razor blade to strip old adhesive off a painted or gelcoat flange, which cuts the finish and starts corrosion right where the new seal is about to sit.
Which vehicles we do this on
Vehicles we perform Seal and Gasket on
StandardStandard fifth wheel repair concentrates on the pin box and upper deck welds, the floor at the step up transition, the front cap above the pin and the roof front radius seamMulti SlideA multi slide fifth wheel carries three to five rooms, which leaves limited continuous sidewall between openings and mixes Schwintek, rack and pinion and hydraulic mechanisms on one trailerTravel TrailerTravel trailer repair covers A frame tongue welds, the front cap that takes road debris, the roof front radius seam, sidewall delamination starting at a window corner, and equalizer and axle wearClass A GasClass A gas motorhome repair covers the molded front and rear caps, the vacuum bonded laminated sidewalls, the EPDM roof and the F53 chassis underneathClass CClass C motorhome repair centers on the cabover bunk, the joint where the coach body meets the factory van cab, and the stick built or laminated house behind itDestinationDestination trailer repair addresses frame flex at the axle hangers on a long light rail, roof ponding because the unit sits level for months, and sidewall bow from slides left extended all seasonI ask everybody the same question before I quote a seal job: how long does the coach sit with the room in? If the answer is most of the year in a storage lot, the bulb seals are flat and I do not need to look at them to know it. Rubber under constant load with no recovery time is a spring you left compressed for eight months. I would rather sell somebody the correct four runs once than sell them a top run now and watch them come back in April with a wet floor.
Appendix: questions and answers
- How can I tell if my slide seal has taken a compression set?
- Press the bulb with your thumb and release it. Rubber in good condition rebounds to its original height in under a second. Rubber that stays dented has set permanently and will not seal in transit again. Conditioners do not reverse this. The run needs replacing.
- Can you just replace the one seal run that is leaking?
- We can, and on a young coach with one damaged run we sometimes do. On an older unit it is a poor value. New rubber at full height next to old rubber at reduced height holds the room off square against the opening, so the neighbouring run starts leaking within a season.
- Does leaving the slide in during storage really wreck the seals?
- Yes, and it is the leading cause we see. A room retracted from October through May holds the bulb seals crushed for roughly two hundred days with no recovery period. Extending the rooms for a few hours every month or two while stored is the cheapest seal maintenance available.
- What should I put on RV slide seals to keep them soft?
- A water based rubber protectant, applied to clean dry rubber a few times a year. Avoid petroleum distillates and silicone sprays. Both swell sponge rubber, leave it distorted afterward, and contaminate the mounting flange so the correct adhesive will not bond during any later repair.
- How do you find where a slide is actually leaking?
- Chalk on the opening and a garden hose applied to one face at a time, with a technician inside watching under a light. Never a pressure washer. Pressure will push water past a healthy seal and send the whole diagnosis in the wrong direction, which is how good seals get replaced needlessly.
- Do I need to fix the slide topper before replacing the seals?
- If the topper sags, yes. A slack topper collects a pool of water in the middle and empties it onto the top bulb seal every time it rains. No seal profile is built to hold back a concentrated column of water, so new rubber under a tired topper is a short lived repair.
Open a file on this repair
Tell us the vehicle, what happened and whether a claim is open. We will tell you what the scope looks like and what it takes to get you back on the road.
Or call (949) 799-3387