6 Best Self Leveling Shims For Uneven Van Roof Mounting

Van roofs are rarely as flat as they appear, often featuring deep corrugations and subtle curves that make mounting heavy equipment a genuine headache. Without proper leveling, brackets sit unevenly, creating stress points that jeopardize the integrity of the vehicle’s exterior shell. Investing in the right shims ensures a secure, flat foundation that prevents water intrusion and hardware fatigue over the long haul.

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Rhino-Rack Self-Leveling Spacers: Best Kit

Rhino-Rack delivers a polished, off-the-shelf solution that eliminates the guesswork typically associated with roof rack installation. These spacers are engineered to interface perfectly with their existing mounting hardware, making them the go-to for those who value system compatibility. They offer a reliable, professional finish that keeps the rack platform perfectly level despite the curvature of a Sprinter or Transit roof.

The primary benefit here is structural consistency. By utilizing a kit designed for specific vehicle footprints, the risk of “crushing” the roof panel during tightening is significantly reduced. This is the top choice for builders who prefer a turn-key solution and want to avoid the time sink of custom fabrication.

Choose this kit if a clean, factory-grade aesthetic matters and if the project budget allows for purpose-built components. It is not the most cost-effective option, but it is the most reliable for those installing high-end roof racks.

Unaka Gear Co. Flexible Mounts: Best for Curves

Unaka Gear Co. has carved out a niche by understanding the unique geometry of modern van roofs. Their flexible mounts are designed to conform to the roof’s arc without fighting against the chassis, making them essential for high-top vans with pronounced side-to-side curvature. These mounts act as a bridge, distributing the load of solar panels or roof decks across the van’s structural ribs.

These mounts are particularly useful because they accommodate slight variances in mounting surface angles. When the roof is not perfectly parallel to the ground, these mounts absorb the discrepancy, ensuring the attachment points stay rigid and true. This prevents the “twisting” effect that often leads to cracked sealant and leaks later on.

If the van build involves a curved roof profile, skip the generic hardware store brackets. These mounts offer the necessary geometry to prevent panel rattling and structural strain. They are worth every penny for the peace of mind provided by their precise fit.

Solar Panel Z-Bracket Leveling Kit: Best for PV

Solar Z-brackets are the industry standard for a reason, but they often require extra shimming when the roof corrugation is deep. A dedicated leveling kit for these brackets usually includes HDPE spacers that fit perfectly under the bracket base. This ensures that the bracket sits flush against the roof while the solar panel remains perfectly horizontal.

These kits are specifically helpful for mid-van installations where the solar panel must sit across a single, narrow ridge. By elevating the bracket, the mounting hardware gains enough clearance to bolt through the roof safely without hitting the floor of the valley. It is an uncomplicated approach to a common electrical mounting problem.

These kits are the ideal choice for budget-conscious solar installs where Z-brackets are already being utilized. While they may not provide the extreme structural rigidity of a full rack system, they are perfectly sufficient for securing lightweight solar arrays.

DIY Solutions Silicone Wedges: Best Budget Pick

When the budget is tight, food-grade silicone or high-density plastic wedges can be trimmed to fit the irregular gaps between a mount and the roof. This is a classic “old-school” van builder technique that requires patience and a steady hand. Because these wedges are soft and malleable, they conform to the roof shape as the bolt is tightened, effectively creating a custom-fit gasket.

However, be warned: this method requires more “elbow grease” and attention to detail than pre-made kits. The wedges must be trimmed with precision to ensure the mounting foot does not rock or vibrate under load. It is a labor-intensive process that relies entirely on the builder’s ability to create a level plane manually.

Opt for this route only if the build schedule is flexible and the desire to save money outweighs the convenience of a kit. For a reliable outcome, use high-durometer silicone that will not compress too much over time.

80/20 Extrusion Adjustable Feet: Pro-Builder Pick

For those building modular rack systems using 80/20 aluminum extrusion, adjustable feet are non-negotiable. These feet allow for micro-adjustments in height, which is critical when mounting a complex frame that spans multiple roof ridges. By adjusting the leveling bolt, the builder can dial in the height for every single attachment point, ensuring a perfectly flat load-bearing surface.

This is the preferred method for anyone mounting heavy expedition gear, storage boxes, or roof decks. The adjustability allows for fine-tuning the rack’s aerodynamics, ensuring it sits as low as possible to reduce wind noise. It transforms a custom rack build from a “guess and check” exercise into a precise engineering project.

If the goal is a fully custom, high-durability roof rack, do not settle for fixed mounts. These adjustable feet are essential for managing the uneven load distribution of heavy gear. They represent a pro-level investment that pays off in structural integrity.

Hein’s All-Purpose Roof Spacer: The OG Choice

For many in the van community, Hein’s spacers are the benchmark. These are CNC-machined to match the specific contours of nearly every major van model, from the Ford Transit to the Ram ProMaster. They provide a flat, solid foundation by filling the valley of the roof corrugation completely, effectively turning an irregular roof into a flat mounting surface.

The advantage of these spacers is their thickness and material density; they don’t deform under the pressure of a bolted-down rack. Because they are custom-profiled, they eliminate the need to stack multiple shims or use excessive amounts of sealant. They are the definition of “do it once, do it right.”

If the van model is well-supported by this brand, this is unequivocally the best way to shim a roof. The time saved during installation and the long-term reliability make them superior to almost every other option. They are a staple of the van-building community for a reason.

Do You Actually Need Roof Leveling Shims?

Not every installation requires aggressive shimming, but almost all benefit from it. If the mounting bracket is thin and the roof corrugation is deep, fastening the bracket directly to the roof will cause the metal to deform or “oil can” under the tension of the bolt. This deformation creates a pathway for water to bypass the sealant and enter the interior.

Furthermore, leveling shims distribute the load. By spreading the weight over a larger area of the roof’s valley rather than a single point, you minimize the risk of stress fractures in the sheet metal. For heavy items like roof decks or solar arrays, shims are a vital component of a safe, long-lasting installation.

How to Install Shims Without Causing Leaks

The golden rule of van roof mounting is that the shim is not the seal; the sealant is the seal. When installing, always apply a high-quality polyurethane sealant, such as 3M 5200 or Sikaflex, between the shim and the roof, and between the shim and the mounting bracket. This creates a “sandwich” of protection that keeps the mounting hardware isolated from the elements.

Ensure all surfaces are cleaned with isopropyl alcohol before application to guarantee the sealant adheres to the metal. After tightening the bolts, a small bead of sealant should squeeze out from the perimeter of the mount. Smooth this out with a gloved finger to create a tapered, waterproof edge that sheds water rather than pooling it.

Choosing Shim Material: Plastic vs. Rubber

The material choice largely depends on the intended load and the amount of vibration expected. Plastic or HDPE shims are rigid and provide a rock-solid foundation, which is ideal for mounting structural rack systems. They do not compress, so once the bolt is tightened, the height remains constant.

Rubber or EPDM shims, conversely, offer a degree of vibration dampening. These are excellent for solar panels, where the goal is to reduce the mechanical stress transferred from the van body to the delicate PV cells. However, avoid soft rubber that may degrade or compress significantly over time, as this can lead to loose hardware.

Sealing Your Roof Mounts: A Pro’s Guide

Sealing is the most critical step in the entire process. Regardless of the shim used, use a non-sag, moisture-curing sealant that remains flexible as the van chassis flexes during travel. Rigid adhesives or standard hardware store silicones are prone to failure and can lead to silent leaks that rot the van interior over months or years.

Always apply enough sealant to completely encapsulate the bolt holes and the perimeter of the shim. When the bolt is tightened, the sealant should fill every void between the mounting foot, the shim, and the roof. If the process is done correctly, the mount becomes a permanent, integral part of the roof architecture.

Selecting the right shim is the difference between a build that requires constant maintenance and one that lasts for the life of the vehicle. Prioritize structural fit and waterproof integrity, and the rest of the build will follow with confidence. With the right foundation secured, you are ready to move on to the next phase of your conversion with a roof that stays dry and reliable regardless of the road ahead.