OUTSIDE VAN ATERRA – Roof Seal and Skylight Maintenance

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Roof Seal and Skylight Maintenance for OUTSIDE VAN ATERRA

The Outside Van ATERRA’s roof system is a carefully engineered stack of penetrations, seals, and composite materials — and every one of those seals is a potential water entry point if neglected. Outside Van builds on the Mercedes-Benz Sprinter 144″ cargo platform using a fiberglass composite roof overlay, which behaves differently from standard EPDM TPO membranes found on production RVs, so generic RV roof advice only gets you partway there. Your ATERRA will have multiple critical seal zones: the Maxxair fan ring, the Fiamma F45s awning mounting rail, every solar panel roof rack foot (typically 6–8 feet per rack side), any cable entry glands, and the perimeter seam where the composite top meets the factory Sprinter roof skin. Plan to do this inspection twice yearly — spring and fall — and after any significant hailstorm or tree-branch contact.

Required Parts

Step-by-Step Instructions

Step 1: Access the Roof Safely and Document Every Penetration

Never step directly onto the ATERRA roof without a proper ladder rated for your weight plus tools — the fiberglass composite overlay is strong but not designed as a walking surface, and concentrated point loads near the edges can crack the layup. Use a wide, padded ladder stabilizer that hooks over the Sprinter rain gutter channel to prevent ladder sway. Before touching anything, do a slow walk-around from ground level with a flashlight, then photograph every roof penetration from above once you’re up. On a typical ATERRA, you’ll find the Maxxair fan centered toward the rear third of the roof, the solar panel rack running fore-aft along the roof centerline, the awning mounting rail along the driver’s side roofline, and one or two cable entry glands (usually near the fan or rear rack cross-member) feeding the solar and fan wiring down through the Sprinter’s B-pillar or D-pillar. Cross-reference these locations against your van’s specific build sheet — Outside Van sometimes relocates components based on customer spec. Number your photos so you can track each seal point through the repair process. This documentation step saves enormous time when you’re identifying which sealant was applied where and in what sequence.

Step 2: Clean the Entire Roof Surface Before Inspection

You cannot accurately inspect a dirty roof — road grime, oxidized sealant, and bird debris all mask early cracks and lifting edges. Start by blowing off loose debris with compressed air or a soft-bristle brush, working from front to back. Mix the Dicor rubber roof cleaner and degreaser at the dilution rate printed on the jug — typically 4:1 with water for general cleaning, full-strength for grease spots near the solar wiring conduit where cable management zip ties sometimes trap road oil. Apply with a soft mop or microfiber applicator and scrub in sections, keeping the cleaner wet for at least three minutes before rinsing. Do NOT use petroleum-based solvents, bleach, or abrasive pads on the fiberglass composite top — they’ll degrade the gel coat and any existing EPDM coating layer. Pay extra attention to the gutters that form along the Fiamma awning mounting rail; Outside Van welds or bonds a drip edge there that traps debris and holds moisture against the sealant bead. Rinse thoroughly with fresh water from a garden hose on low pressure — high-pressure washing can force water under lifted sealant edges and into the Sprinter’s factory roof skin cavities below. Let the roof dry completely (minimum two hours in direct sun) before proceeding to inspection.

Step 3: Inspect Every Seal Point Systematically

Work through your numbered photo list methodically, pressing lightly along every sealant bead with a gloved finger. Healthy Dicor self-leveling sealant stays slightly flexible and won’t crack under fingertip pressure; failed sealant feels brittle, shows surface crazing, or lifts away from the substrate in ribbons. At the Maxxair fan ring, inspect the full 360-degree perimeter bead where the flange meets the composite roof — this joint sees the most thermal cycling because the fan lid opens and closes daily. At each solar rack foot, Outside Van applies both butyl tape beneath the foot and a topcoat bead of self-leveling Dicor around the perimeter; check for any gap between the Dicor cap and the rack foot edge, which indicates the butyl underneath has cold-flowed away. Along the Fiamma awning rail, run your finger under the rail edge where it meets the Sprinter’s drip gutter — this hidden joint is the single most common water entry point on ATERRA builds. Probe cable gland boots with a fingertip for stiffness or cracking. Mark any suspect areas with a paint pen. Also inspect the seam where the composite roof overlay meets the factory Sprinter roof skin at the perimeter — look for any separation or bubbling of the EternaBond or sealant used there by Outside Van during the original build.

Step 4: Remove Failing Sealant and Prep Surfaces for Repair

Use the plastic putty knife set — never metal tools — to lift and peel away any sealant that failed your inspection. Plastic blades flex with the roof surface contour and won’t gouge the fiberglass composite or scratch the Sprinter’s painted roof skin where the two surfaces meet. Score around the perimeter of old Dicor beads with the thin-edged plastic blade, then peel in long strips rather than scraping across the surface. Old butyl tape beneath rack feet should only be disturbed if you’re fully removing and repositioning a foot — otherwise, leave intact butyl alone and work only on the topcoat Dicor bead. After mechanical removal, wipe each prepared area with isopropyl alcohol (91% or higher) on a lint-free cloth to remove butyl residue and any remaining cleaner film — this step is critical for new sealant adhesion. Let the alcohol flash off completely (about five minutes). If you’re repairing an area larger than about six inches in any direction, or if you found actual lifting or bubbling of the composite overlay, apply the Liquid Rubber EPDM/TPO primer to the bare substrate using a disposable brush and let it tack up per the label instructions (usually 20–30 minutes) before applying any tape or coating. Don’t skip priming on large repairs — it’s the difference between a fix that lasts two years and one that lasts ten.

Step 5: Apply EternaBond Tape to Seams and Large Repair Areas

EternaBond RoofSeal tape is your go-to for any seam repair wider than a finger, any area where two dissimilar materials meet (like the composite-to-Sprinter-roof perimeter), and any location where you found actual separation or lifting. Cut your pieces to length before peeling the backing — EternaBond is aggressive and will bond to itself and anything else the moment the adhesive is exposed. For the perimeter seam between the composite overlay and the Sprinter factory roof, run a continuous strip of the 4-inch tape centered over the joint, pressing down as you unroll to avoid air bubbles. Immediately follow with the J-roller, applying firm downward pressure along the full tape length — two passes minimum, working from center to edges. The J-roller is non-negotiable here: hand pressure alone leaves micro-voids that become leak channels. At rack feet where you’ve removed the Dicor cap bead, cut EternaBond into small squares or strips sized to fully cover the foot perimeter and overlap onto the roof surface by at least two inches in every direction. On the Maxxair fan flange, EternaBond works best as a supplementary layer under a fresh Dicor bead rather than as a standalone fix — the fan flange moves slightly with thermal expansion and pure tape without a cap bead can peel at the edge over time.

Step 6: Reapply Dicor Self-Leveling Sealant at All Penetrations

Load your drip-free caulking gun with the white self-leveling Dicor lap sealant tube — the drip-free mechanism matters because you’ll be working overhead and an uncontrolled bead ruins both the repair and your eye. Cut the tube nozzle at a 45-degree angle to produce a bead roughly 3/8 inch wide. At the Maxxair fan, start at the rear of the flange and run a continuous bead around the full perimeter, maintaining consistent pressure so the bead height stays even. Self-leveling Dicor will flow slightly over the next 30–60 minutes to fill small voids, so don’t try to smooth it with a tool — let gravity do that work. At each solar rack foot, run the Dicor bead around the full perimeter of the foot, slightly overlapping onto any EternaBond you’ve applied. At cable entry glands, work the nozzle tip slightly under the edge of the boot and inject sealant before running a cap bead over the top. Along the Fiamma awning rail, pay special attention to the front and rear end caps where the rail terminates — these corners are high-stress points. Wipe any sealant that strays onto painted Sprinter surfaces immediately with a damp rag; cured Dicor on factory paint requires aggressive scrubbing that risks scratching. Allow the full roof to cure undisturbed for 24 hours minimum before exposure to rain.

Step 7: Apply EPDM Roof Coating and Establish a Maintenance Schedule

If your inspection revealed widespread surface chalking, multiple small cracks across the composite roof field, or areas where the original Outside Van factory coating has worn thin, apply the EPDM rubber roof coating as a protective topcoat over the entire roof surface after all sealant work has fully cured. Stir the coating thoroughly — EPDM coatings settle in the jug and an unmixed application will cure unevenly. Apply the Liquid Rubber EPDM/TPO primer first to any bare fiberglass or previously uncoated areas, then roll the EPDM coating using the 3-inch roller kit in long, even strokes from front to back, keeping a wet edge to avoid lap marks. Two coats are better than one thick coat — apply the second coat perpendicular to the first after the first has skinned over (typically two to four hours depending on temperature and humidity). Keep the coating at least one inch away from freshly cured Dicor beads; some EPDM coatings contain solvents that can soften fresh sealant. Once the coating is fully cured (48–72 hours), record every repair location and date in a maintenance log stored in your van’s glovebox or Victron electrical cabinet alongside your build sheet. Set calendar reminders for biannual inspection — catching a lifted Dicor bead in spring costs you one tube of sealant; catching the water damage it caused in fall costs you weeks of remediation.

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