GRECH STRADA – Roof Seal and Skylight Maintenance

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Roof Seal and Skylight Maintenance for GRECH STRADA

The Grech Strada’s roof is a hybrid system — the Sprinter’s factory steel roof transitions into a custom composite fiberglass upper section, and that seam is your number-one leak point. Grech uses a butyl-based lap sealant at the factory, but UV exposure and thermal cycling crack it within two to three seasons, especially around the Maxxair vent frame, solar panel mounts, and the fiberglass-to-steel transition seam that runs laterally just above the rain gutters. Unlike a pure EPDM membrane roof, you’re working with a fiberglass substrate in the upper section, which requires compatible products and different prep. Budget a full day for a thorough inspection and reseal, and plan to do this every spring before travel season begins.

Required Parts

Step-by-Step Instructions

Step 1: Set Up Safely and Assess the Roof from Ground Level

Before climbing up, position the van on level ground with the parking brake set and the Fiamma F45s retracted fully — a partially extended awning arm is a shin-height hazard when you’re working on the roof edge. Use a ladder tall enough that you’re stepping onto the roof rather than lunging, and lay down a non-marring foam kneeling pad to protect the fiberglass section. Never kneel directly on the Maxxair vent frame or the solar panel wiring conduit that runs along the driver-side roof edge toward the forward panel junction box. From the ground, use a flashlight at a low angle to spot obvious sealant cracking, lifting edges, or discoloration — water stains show as tan or brown halos around penetrations. Photograph every penetration point before you touch anything: Maxxair vent (front-center of roof), solar panel mounting feet (typically four panels in two rows), and the fiberglass transition seam. These photos become your before-and-after reference and are invaluable if you later need to file a warranty claim with Grech Motors. Check that the Victron system is not in active charging or inverting before you work near any roof-mounted solar connections.

Step 2: Clean the Entire Roof Surface Thoroughly

Proper adhesion starts with a chemically clean surface — skipping this step is why most DIY reseals fail within one season. Apply the Dicor rubber roof cleaner and degreaser full-strength to the fiberglass composite section using a soft-bristle brush, scrubbing in circular motions. Work in three-foot sections and rinse with clean water before the cleaner dries; dried cleaner residue will prevent sealant from bonding. For the steel section near the perimeter gutters and Fiamma awning mounting rail, the same cleaner works, but pay extra attention to the area where the stainless steel awning bracket fasteners penetrate the Sprinter body — Grech uses a factory sealant bead here that often holds road grime and early-stage galvanic corrosion residue. Use a stiff plastic brush (not wire) around the fastener heads to remove any white oxidation product, which is a sign of galvanic reaction between the stainless fasteners and the galvanized Sprinter body. Rinse the entire roof and allow it to dry completely — minimum two hours in direct sun, four hours if overcast. Moisture under new sealant causes bubbling and adhesion failure. Run your hand across the surface; it should feel chalky-clean with zero oily or slick spots before you proceed.

Step 3: Remove and Inspect All Existing Lap Sealant at Penetrations

Work methodically from the front of the roof to the rear, starting with the Maxxair vent frame, then each solar panel mount foot, then the fiberglass-to-steel transition seam. Use only the plastic putty knives from your kit — metal scrapers will gouge the fiberglass composite and create stress fractures that become future leak points. Slide the plastic blade under the existing lap sealant at a shallow angle and peel it away in strips. Grech’s factory sealant is a white or off-white butyl compound; if it’s still pliable and tacky underneath the surface skin, it may still be sealing, but remove it anyway if it’s visibly cracked or lifting at the edges. On the Maxxair vent, check the four corners specifically — thermal expansion cracks almost always initiate here first. Around the solar panel feet, look for any cracking in the underlying tape layer beneath the sealant; if the tape has lifted even slightly, moisture has likely entered. At the fiberglass transition seam, probe gently with a finger — soft or spongy spots indicate moisture intrusion into the composite layup, which requires more extensive repair. Bag your old sealant waste rather than letting it blow off the roof edge onto a neighbor’s vehicle.

Step 4: Apply EternaBond Tape to All Seams and Problem Areas

EternaBond RoofSeal tape is your primary mechanical seal for the fiberglass transition seam and any areas where the old sealant showed tape lifting underneath — it bonds to virtually everything and will outlast lap sealant by years. Cut the 4-inch tape to length before removing the backing liner; it becomes difficult to handle once the adhesive is exposed. For the lateral fiberglass-to-steel transition seam, cut a single continuous run if possible, centering the tape so two inches lap onto each substrate. Peel back the first six inches of backing liner, press the tape in place, then slowly pull the liner while pressing firmly with your palm to prevent air pockets. The J-roller is non-optional here — use firm, overlapping passes with the roller to press the full tape width to full adhesion, especially at the tape edges. A partially adhered edge is worse than no tape because it creates a water-collection channel. Around the Maxxair vent frame, run a continuous strip around the full perimeter, overlapping corners by at least two inches. At solar panel feet, apply a 6-inch square patch over each foot before applying lap sealant on top. Tape applied at temperatures below 50°F will not achieve full adhesion — if it’s cold, use a heat gun on low to warm the surface and tape.

Step 5: Apply Self-Leveling Dicor Lap Sealant Over All Tape Edges and Fasteners

The self-leveling Dicor sealant flows into gaps and surface texture that tape can’t conform to, making it an ideal topcoat over your EternaBond edges and a standalone sealant for fastener heads. Load the tube into the drip-free caulking gun — the drip-free mechanism prevents sag-drips that cure into trip hazards on the roof surface. Cut the tube nozzle at a 45-degree angle to produce a 3/8-inch bead. Apply a continuous bead along all four EternaBond tape edges, not just the two outer edges — the inner edges where tape meets vent frame or panel foot also need to be sealed. Feather the bead slightly inward with a gloved finger so it tapers to nothing at the edge rather than creating a raised dam. Cover every fastener head that’s visible on the roof — Maxxair vent screws, solar panel rail bolts, and any exposed sheet-metal screws from the Grech composite attachment points. At the Fiamma awning bracket fasteners on the roof-to-body transition, apply sealant generously over each fastener head and the area around it where the bracket contacts the body; this slows the galvanic corrosion process. Allow Dicor to skin over for one hour before applying roof coating.

Step 6: Apply EPDM Primer and Roof Coating to the Full Fiberglass Section

The Liquid Rubber EPDM/TPO primer is mandatory on the fiberglass composite section before applying the EPDM roof coating — without it, the coating will peel within one season because fiberglass has low surface energy. Use a clean 3-inch paint roller to apply the primer in thin, even coats across the entire fiberglass upper section, including up to two inches past the fiberglass-to-steel transition seam onto the steel roof. Work from the rear of the roof toward the front so you’re not rolling over wet primer. Allow the primer to become tacky — typically 20 to 40 minutes depending on temperature — before applying the EPDM roof coating. Do not let the primer fully dry to a hard film before coating; it needs to be in the tacky window for proper inter-coat adhesion. Apply the EPDM coating with the same 3-inch roller in slow, deliberate strokes, maintaining a wet edge to avoid lap marks. One gallon will cover the Strada’s composite section in two coats; apply the second coat perpendicular to the first after the first coat is touch-dry (about one hour). Keep coating away from the Maxxair vent lid mechanism and the solar panel glass surfaces — mask these off with tape beforehand.

Step 7: Final Inspection, Skylight Function Check, and Documentation

Once all sealant and coating are fully cured (24 hours minimum, 48 hours before water exposure), perform a systematic final inspection from the roof. Press firmly along every EternaBond tape edge — no flex or lifting should be detectable. Run a wet rag along the fiberglass transition seam and check the van’s interior headliner immediately beneath for any moisture transfer. The Grech Strada’s interior headliner is secured with Velcro-backed panels near the roofline; gently press the panel near the transition seam inward and look for any moisture staining on the backing. Open and close the Maxxair vent through its full range of motion to confirm the sealant bead hasn’t bridged into the lid mechanism — a small gap should be visible between your sealant and the moving lid. Check that solar panel output is normal through the Victron display in the electronics bay behind the driver seat; adhesive or coating on the panel glass surface will reduce output measurably. Update your maintenance log with today’s date, products used, and specific areas addressed, and set a calendar reminder for a visual inspection every six months. Annual reapplication of Dicor sealant at penetrations is your best insurance against water intrusion in this hybrid roof system.

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