GRECH STRADA – Roof Seal and Skylight Maintenance

Roof Seal and Skylight Maintenance for GRECH STRADA

Is that lap sealant around your Strada’s roof seam already cracking, or are you trying to get ahead of it before water starts seeping in? Either way, you’re looking at exactly what I find every time I get called to one of these vans: that fiberglass-to-steel transition just above the rain gutters has become a thermal stress point where the factory sealant loses the battle against UV and temperature swings. The Strada’s hybrid roof — Sprinter steel bottom, custom composite fiberglass upper section — is solid engineering, but that lateral seam is where water quietly works its way into the ceiling cavity if you’re not staying on top of it. What I’ve written here comes straight from roof calls I’ve actually made, not from a parts manual, so you’ll see what’s really happening and why each step matters when you’re doing this yourself.

Required Parts

• Self-leveling Dicor lap sealant (white, 10.3 oz tube) Dicor 501LSW-1 EPDM Self-Leveling Lap Sealant, 10.3 oz – White
• EternaBond RoofSeal tape (4″ × 50 ft roll) EternaBond RoofSeal White 4″ x50′ MicroSealant UV-Stable Roof Repair Tape
• EPDM rubber roof coating – 1 gallon HENG’S Industries Rubber Roof Coating, 1 Gallon, EPDM Waterproof UV-Resistant
• Dicor rubber roof cleaner and degreaser – 1 gallon Dicor RP-RC-1GL Deep Cleaning Rubber RV Roof Cleanser Spray Refill, 1 Gallon
• Plastic putty knife set (for removing old sealant without tearing membrane) Rerdeim 5-Piece Putty Knife Scraper Set, 1″–5″
• Professional drip-free caulking gun Newborn 930-GTD Drip-Free Smooth Hex Rod Cradle Caulking Gun, 10:1 Thrust Ratio
• Liquid Rubber EPDM/TPO primer – 1 gallon Liquid Rubber EPDM and TPO Primer, 1 Gallon – RV Roof Basecoat
• 3-inch paint roller kit (for applying roof coating) ROLLINGDOG Small Paint Roller Kit, 3 Inch with Tray and Stir Bar
• J-roller (for pressing EternaBond tape to full adhesion) POWERTEC 12″ Long Handle J Roller, 1-1/2″ Diameter, 3″ Wide

Step-by-Step Instructions

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

Before you climb the ladder, position the van on level ground with parking brake engaged and the Fiamma F45s pulled in completely — a half-extended awning arm is exactly shin-height and will catch you when you’re up there working. Get a ladder that lets you step onto the roof instead of having to lunge, and bring a non-marring foam kneeling pad to protect the fiberglass surface. Never kneel directly on the Maxxair vent frame or the solar panel wiring conduit running along the driver-side roof edge toward the forward panel junction box. Get down on the ground and use a flashlight at a shallow angle to spot visible sealant cracks, lifted edges, or discoloration — water stains show up as tan or brown halos radiating from penetrations. Photograph each penetration before you touch anything: the Maxxair vent in the front-center, the solar panel mounting feet (usually four panels arranged in two rows), and the fiberglass transition seam. Those photos give you a before-and-after comparison and come in handy if you need to file a warranty claim with Grech Motors later. Make sure the Victron system isn’t actively charging or running the inverter before you get near any roof-mounted solar connections.

Step 2: Clean the Entire Roof Surface Thoroughly

Sealant sticks only to a chemically clean surface — this is where most DIY reseals fail and fall apart inside a year. Spray the Dicor rubber roof cleaner and degreaser at full strength across the fiberglass composite section using a soft-bristle brush, working it in circular motions. Clean in manageable three-foot sections and rinse with fresh water before the cleaner dries; leftover cleaner residue blocks sealant adhesion. On the steel section near the perimeter gutters and where the Fiamma awning mounting rail bolts to the Sprinter body, use the same cleaner but scrub extra carefully around the stainless steel fastener heads — Grech applies a factory sealant bead here that traps road grime and early corrosion residue. Scrub stainless fasteners with a stiff plastic brush (never wire) to clear any white oxidation, which signals galvanic reaction between the stainless fasteners and the galvanized Sprinter body. Rinse the complete roof and let it dry fully — two hours minimum in direct sunlight, four hours if the sky’s cloudy. Moisture trapped under new sealant creates bubbles and breaks the bond. Once dry, run your hand across the surface; it should feel chalky-clean with no slick or oily spots before you move to the next step.

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

Methodically work from the front of the roof toward the rear: start at the Maxxair vent frame, move through each solar panel mount foot, and finish at the fiberglass-to-steel transition seam. Use only plastic putty knives from your kit — metal scrapers will gouge the fiberglass composite and create stress risers that turn into future leak paths. Slide the plastic blade under the existing lap sealant at a low angle and peel it away in long strips. Grech uses a white or off-white butyl compound at the factory; if it’s still pliable and tacky below the surface crust, it may technically still be sealing, but pull it off anyway if it’s visibly cracked or lifting at the edges. Focus on the Maxxair vent’s four corners — thermal expansion cracks always start there first. At the solar panel feet, check whether the underlying tape layer beneath the sealant has lifted; if it has, moisture has already gotten underneath. Run a gentle finger along the fiberglass transition seam and feel for soft or spongy spots, which mean moisture has penetrated the composite layup and you’ll need more involved repair work. Bag your old sealant instead of letting it scatter onto a neighbor’s rig.

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

EternaBond RoofSeal tape is the primary mechanical seal for your fiberglass transition seam and any spots where you found tape lifting beneath the old sealant — it bonds to almost everything and will outlast lap sealant by several years. Cut the 4-inch tape to the length you need before you peel back the backing liner; once the adhesive’s exposed, it becomes a fight to handle. For the lateral fiberglass-to-steel transition seam, try to run one unbroken strip if you can, positioning it to lap two inches onto each substrate. Pull back the first six inches of backing liner, press the tape down, then slowly remove the liner while pushing firmly with your palm to eliminate air pockets. The J-roller is non-negotiable — roll it over the full tape width with firm, overlapping strokes to ensure complete adhesion, paying special attention to the tape edges. A partially stuck edge creates a water trap that’s worse than no tape at all. Around the Maxxair vent, run tape around the entire perimeter in one continuous line, overlapping the corners by no less than two inches. Over each solar panel foot, lay a 6-inch square patch before you add lap sealant on top. If you’re applying tape and it’s below 50°F, warm the surface and tape with a heat gun on low to achieve full adhesion.

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

Self-leveling Dicor flows into gaps and rough texture that tape can’t bridge, making it the perfect cover for your EternaBond edges and a solid sealant on its own for fastener heads. Load the tube into a drip-free caulking gun — the drip-free design keeps sag-drips from curing onto your roof where they’ll trip you up. Cut the tube nozzle at a 45-degree angle for a 3/8-inch bead. Run a continuous bead along every EternaBond tape edge, including the inner edges where the tape meets the vent frame or panel foot — those edges also need coverage. Feather the bead inward slightly with a gloved finger so it tapers out rather than forming a raised ridge. Seal every fastener head 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 where they attach to the roof-body transition, apply sealant generously over the heads and around the bracket contact point; this slows galvanic corrosion. Give Dicor an hour to skin over before applying roof coating.

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

The Liquid Rubber EPDM/TPO primer is essential on the fiberglass composite section before you coat it with EPDM — without this primer coat, the roof coating will peel off within a year because fiberglass doesn’t accept adhesives easily on its own. Roll the primer on with a clean 3-inch paint roller, applying thin, even layers across the entire fiberglass upper section and extending two inches past the fiberglass-to-steel transition seam onto the steel roof. Work from back to front so you’re not rolling over primer you just laid down. Wait until the primer gets tacky to the touch — usually 20 to 40 minutes depending on conditions — before you apply the EPDM roof coating. Don’t let it dry all the way to a hard film; it has to be tacky for the coating to bond properly to it. Apply the EPDM coating with the same 3-inch roller using slow, deliberate strokes and keeping a wet edge to prevent lap lines. One gallon covers the Strada’s composite section in two coats; apply the second coat perpendicular to the first once the first coat is touch-dry (around an hour). Keep the coating off the Maxxair vent lid mechanism and the solar panel glass — mask these with tape before you start rolling.

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

After all sealant and coating have fully cured (24 hours minimum, better to wait 48 hours before water exposure), get back on the roof and do a complete walk-through inspection. Press firmly on every EternaBond tape edge — you should detect zero flex or lifting. Wipe a wet rag along the fiberglass transition seam and immediately check the interior headliner directly beneath it for any moisture seeping through. The Strada’s interior headliner panels are Velcro-backed near the roofline; gently press the panel in near the transition seam and look at the back side for any discoloration from moisture. Open and close the Maxxair vent through its complete range to confirm your sealant bead hasn’t extended into the lid pivot — there should be a small gap visible between the sealant and the moving lid. Pull up the Victron display in the electronics bay behind the driver seat and verify solar panel output is normal; any adhesive or coating on the glass will show up as a drop in power output. Log today’s date, the products you used, and which areas you worked on in your maintenance records, and set a phone reminder to do a visual inspection every six months. Reapplying Dicor sealant at penetrations once per year is the best protection against water getting into this hybrid roof design.

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The Lap Sealant That Actually Stays Put on Grech Strada Roof Transitions

That fiberglass-to-steel transition on the Strada is ground zero for water entry every single time — the factory lap sealant shrinks and cracks faster than you’d expect, and by the time the failure becomes visible, slow roof rot has already started. This sealant is the product that actually holds through the thermal cycles.

What works

• Self-levels during the cure, so you don’t have to feather it perfectly — it settles to its own grade and resists the thermal cycling that splits rigid sealant compounds.
• EPDM-based formulation matches the existing roof coating, delivering better adhesion than silicone or polyurethane products applied over factory seals.
• The 10.3 oz cartridge is calibrated for one complete transition lap with nothing left over — you actually use what you purchase instead of storing a half-full tube until it hardens.

What doesn’t

• Takes a long window to reach full cure (48-72 hours), meaning you can’t immediately expose it to foot traffic or bake it in direct sun while it’s still setting.
• Demands a caulking gun with solid mechanical advantage — weak guns make you work harder and produce uneven beads, which undermines the self-leveling benefit.

I’ve had jobs where I applied this sealant, thought the bead looked too thin, and wanted to add a second pass — but the self-leveling does its job if you trust the process and let it cure undisturbed. Get the Dicor 501LSW-1 EPDM Self-Leveling Lap Sealant, 10.3 oz – White and stick to the cure schedule.

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