8 Steps to Measure Clearance for Custom Underbed Storage in Camper Vans

Imagine sliding a custom-built drawer under a newly finished van bed platform, only to have it jam against a hidden wheel well slope or a stray wiring loom. Every millimeter of “garage” space under a camper van bed is precious, but uneven metal ribs and curving walls make measuring a minefield. Getting these dimensions right before cutting wood saves hours of frustration and prevents wasted materials.

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Why Precision Underbed Measurements Matter in a Van

Camper van interiors are notorious for lacking straight lines. Unlike a standard home, a van tapers from bottom to top, features structural steel ribs that protrude at odd intervals, and has a floor that mimics a corrugated metal roof. Trying to build custom underbed storage boxes using rough estimates will inevitably lead to stuck drawers, annoying rattles while driving, and wasted space.

Furthermore, the underbed area—often called the “garage”—is the heart of a van’s utility systems. This zone typically houses heavy battery banks, fresh water tanks, water pumps, and complex electrical hubs. Precise measurements ensure your slide-out cargo trays and storage bins clear these vital systems without pinching wires or blocking access to emergency shutoff valves.

Every inch saved by tight, accurate tolerances translates to more living space or extra gear storage. A mismatch of just a quarter-inch can prevent a heavy-duty drawer slide from locking, rendering an entire slide-out assembly useless. Taking the time to map this space with specialized tools ensures your build remains quiet, functional, and highly optimized.

8 Steps to Map Your Van Underbed Storage Space

To get a flawless fit, follow this systematic mapping process before purchasing or cutting any storage materials:

• Step 1: Strip to the subfloor. Remove all loose gear and temporary items so you can measure directly from your actual finished floor to the lowest point of the bed frame.
• Step 2: Establish a level baseline. Park the van on flat ground and use a level to identify any natural slopes in the vehicle chassis.
• Step 3: Mark the wheel wells. Outline the exact footprint of the wheel arches on the floor, including any insulation or boxing you plan to add.
• Step 4: Identify static obstacles. Note the location of structural ribs, exposed wiring harnesses, heater ducting, and plumbing lines.
• Step 5: Measure maximum height. Take vertical measurements at multiple points from the floor to the bottom of the bed slats, noting the lowest clearance point.
• Step 6: Determine maximum depth. Measure from the back doors to your living area partition to find the maximum possible length for drawers or slides.
• Step 7: Map the wall curves. Use specialized profile tools to capture the tapering angle of the van’s walls at the exact height of your proposed boxes.
• Step 8: Subtract clearance tolerances. Deduct at least 0.5 inches from your width measurements and 1 inch from your height measurements to allow for vehicle flexing and easy installation.

Once these steps are complete, transfer your measurements to a highly detailed sketch. Having this reference map ensures that every piece of plywood or aluminum framing you cut fits the space perfectly the first time.

Tape Measure – Stanley FatMax 25-Foot Tape Measure

A high-quality tape measure is the foundational tool for establishing the main boundaries of your underbed storage area. You need a tool that can extend across the full width and length of the van interior without buckling or requiring a second set of hands to hold the end.

The Stanley FatMax 25-Foot Tape Measure is the gold standard for this task because of its impressive 11-foot standout. This rigidity allows you to measure the distance from the back door seal to the living area partition solo, without the tape collapsing mid-measurement. The high-impact ABS case survives drops onto bare metal van floors, while the easy-to-read, wide blade ensures you don’t misread a tick mark in dim garage lighting.

• Blade Width: 1-1/4 inches for easy reading
• Standout Length: 11 feet of rigid reach
• Casing: Shock-resistant ABS with armor coating
• Best Use: Measuring primary spans, bed height, and drawer depth

When using this tape, remember that the end hook is designed to slide slightly to account for its own thickness during inside and outside measurements. Keep this hook clean and free of metal filings that can collect in a van build environment. This tape is perfect for anyone tackling a full van build, though it might be heavier than necessary for light-duty organizers who only need to measure pre-made storage bins.

Laser Measure – Bosch Blaze GLM 50 C Laser Measure

While a physical tape is great for short runs, measuring long spans or checking if your bed frame is square across the van is much easier with a laser. A laser measure allows you to take instant, highly accurate measurements across the entire length of the chassis without dealing with sagging tape blades.

The Bosch Blaze GLM 50 C Laser Measure offers accuracy up to 1/16 of an inch over a 165-foot range, making it incredibly precise for tight-tolerance van builds. It features built-in Bluetooth that syncs measurements directly to a smartphone app, allowing you to quickly create digital floor plans of your underbed space. The backlit color display is highly visible in dark van corners, and the inclinometer function helps you measure angles and slopes simultaneously.

• Measuring Range: Up to 165 feet
• Accuracy: ±1/16 inch
• Connectivity: Bluetooth compatibility with Bosch MeasureOn app
• Power Source: 2 AAA batteries

Keep in mind that highly reflective surfaces like bare steel or silver polyiso insulation can scatter the laser beam and cause error readings. Placing a small piece of blue painter’s tape on your target area provides a solid, matte surface for the laser to bounce off of accurately. This tool is a game-changer for solo builders who want to verify dimensions quickly, but it is not a complete replacement for a traditional tape measure when marking short cut lines on wood.

Profile Gauge – Saker Contour Gauge Profile Tool

The metal walls of a camper van are full of complex, swooping curves and structural bumps. To build storage boxes that hug the walls and maximize every square inch of space, you must be able to duplicate these irregular shapes onto your building materials.

The Saker Contour Gauge Profile Tool simplifies this process by using a series of thin, sliding pins that conform to any shape they are pressed against. Once you press the tool against a curved van rib or wheel well, the heavy-duty locking mechanism holds the pins firmly in place, allowing you to trace the exact profile directly onto your plywood. The 10-inch length is ideal for mapping around standard van metal framing and plastic trim pieces.

• Length: 10 inches for versatile profiling
• Material: High-quality, durable ABS plastic
• Lock Mechanism: Metal lock to prevent pin shifting
• Depth Reach: Up to 5.11 inches for deep profiles

Over time, dust and wood shavings can get trapped between the plastic pins, making them stiff or difficult to slide. Periodically blowing the tool out with compressed air and adjusting the tension screws on the sides will keep it operating smoothly. This tool is indispensable for builders who want a clean, professional “scribe” fit against the van walls, but it is unnecessary if you are building simple, free-standing rectangular boxes.

Digital Caliper – Mitutoyo 500-196-30 Digimatic

When installing heavy-duty drawer slides or fabricating custom metal mounting brackets for your underbed storage, fractions of a millimeter matter. Standard tape measures cannot accurately measure the thickness of sheet metal, bolt diameters, or the exact clearance gap of a drawer slide.

The Mitutoyo 500-196-30 Digimatic caliper delivers unmatched precision using its advanced AOS (Advanced Onsite Sensor) electromagnetic sensor, which is highly resistant to dirt, oil, and water. The digital screen displays measurements in inches or millimeters down to 0.0005 inches, allowing you to verify slide clearances with absolute certainty. The hardened stainless steel construction ensures the tool remains accurate even after years of use in a dusty workshop.

• Range: 0 to 6 inches (150mm)
• Resolution: 0.0005 inches / 0.01mm
• Battery Life: Approx. 3.5 years under normal use
• Sensor Type: Advanced Onsite Sensor (AOS) for environmental resistance

This is a high-end, professional-grade instrument that must be handled with care. Dropping it on concrete or storing it loose in a toolbox can damage the precision-ground jaws and throw off the calibration. It is an essential investment for builders working with tight tolerances and metal hardware, but it is excessive for rough carpentry and simple plywood storage bins.

Torpedo Level – Empire EM81.9 True Blue Level

No van floor is perfectly flat, and installing storage slides or cabinet doors on an unlevel surface leads to drawers that slide open on their own or doors that bind. A torpedo level helps you establish a true horizontal baseline relative to the vehicle’s chassis, ensuring smooth operation of all moving storage parts.

The Empire EM81.9 True Blue Level features high-contrast e-Band vials that make it incredibly easy to read in the low-light conditions under a bed platform. Its heavy-duty aluminum frame is highly durable, and the integrated neodymium magnets allow you to stick the level directly to the van’s steel ribs for hands-free adjustments. The top-read window provides a clear view of the level bubble from above, which is crucial when working in cramped underbed spaces.

• Length: 9 inches, perfect for tight spaces
• Vials: 3 high-contrast e-Band vials (plumb, level, 45-degree)
• Frame: All-metal aluminum frame with V-groove edge
• Magnets: Powerful neodymium magnets for steel surfaces

Remember that before you trust your level readings, you must park the van on a surface that is as close to level as possible. If the vehicle is parked on a steep incline, use levelling blocks under the tires first to normalize the suspension. This tool is a fundamental necessity for any drawer slide installation, though it is less critical for simple drop-in plastic storage tubs.

Angle Finder – General Tools 822 Digital T-Bevel

Not all corners in a camper van meet at a clean 90-degree angle. The transitions from the floor to the walls, or the slopes of custom wheel well covers, often feature obtuse or acute angles that are difficult to measure and replicate on a miter saw.

The General Tools 822 Digital T-Bevel combines a traditional bevel gauge with a digital LCD display that reads angles instantly. This tool allows you to measure the exact slope of a van wall, lock the blade at that specific angle, and read the precise degree measurement on the screen. This takes the guesswork out of setting your miter saw blade, ensuring your wooden joints fit tightly without unsightly gaps.

• Blade Length: 8 inches
• Display: Large LCD with hold function
• Accuracy: ±0.3 degrees
• Range: 0 to 360 degrees

The digital display relies on a CR2032 button cell battery, which can drain more quickly in freezing winter temperatures inside an uninsulated van. Keep a spare battery in your tool bag so you are never left without the digital readout mid-build. This tool is highly recommended for anyone building custom sloped cabinetry, but you can skip it if your storage layout relies entirely on pre-built, square framing.

Carpenter Pencil – Irwin Strait-Line Mechanical

Precise measurements are only useful if you can mark them clearly onto your building materials. Standard wooden pencils dull quickly on rough plywood, break their tips when dropped, and require constant sharpening with a utility knife.

The Irwin Strait-Line Mechanical carpenter pencil solves these frustrations by utilizing thick 18-gauge lead that resists breaking under heavy pressure. You never need to sharpen it; simply click the end cap to advance fresh, sharp lead when needed. The flat, rectangular body prevents the pencil from rolling off your workbench or sloping van floor, keeping it right where you need it.

• Lead Size: 18-gauge heavy-duty lead
• Body Design: Flat, anti-roll rectangular shape
• Refills: Easily reloadable with replacement leads
• Best Use: Marking cut lines on plywood, framing, and metal

Because the lead is quite thick, it can leave a slightly wider line than a standard mechanical drafting pencil. To maintain high accuracy, always cut on the “waste side” of your pencil line rather than directly down the center of it. This is a cheap, indispensable upgrade for any DIYer, though it is not ideal for fine, highly detailed drafting work on paper blueprints.

Utility Knife – Milwaukee Fastback Folding Knife

A reliable utility knife is essential for a variety of tasks during the measuring and fitting phase of your custom storage build. From scoring clean cut lines on plywood to cutting out cardboard mockups of your drawers to check clearance, a sharp blade is used constantly.

The Milwaukee Fastback Folding Knife is designed with a press-and-flip opening system that allows you to open the blade with one hand while holding your measuring tape or wood with the other. The tool-free blade change mechanism lets you swap out dull blades in seconds, ensuring you always have a razor-sharp edge. It also features a integrated wire stripper and gut hook for added utility around electrical wiring tasks.

• Opening Style: One-handed press and flip
• Blade Change: Tool-free quick change
• Body Material: Durable metal frame with wire belt clip
• Safety Features: Lock-back design to prevent accidental closure

Always change the blade as soon as it begins to drag or tear cardboard templates, as a dull blade requires more force and is more likely to slip and cause injury. This is a must-have tool for any builder, though it is designed for utility cuts rather than detailed wood carving or heavy-duty chiseling.

How to Factor Wheel Wells and Wiring into Clearance

Wheel wells are the single biggest spatial obstacle in the underbed garage. To maximize storage, you must decide whether to build asymmetric drawers that stop short of the wheel arches or to build narrow, full-depth drawers that run parallel between them. When boxing in wheel wells with plywood, remember to factor in the thickness of any sound-deadening material (like butyl rubber matting) and thermal insulation you plan to apply to the metal beforehand.

+--------------------------------------------+ |             Bed Platform                   | +--------------------------------------------+ |  [Drawer]   |   Spacer   |   [Drawer]      | |             |  (Wiring)  |                 | |             +------------+                 | |  [Wheel Well]            [Wheel Well]      | +--------------------------------------------+ |               Van Floor                    | +--------------------------------------------+ 

Wiring looms and plumbing lines represent another set of hidden clearance traps. Main 12V DC power cables running from the alternator or solar controller often trace along the lower corners of the van floor. Never jam storage boxes tightly against these wires; vehicle vibration during travel can cause the wood to rub through the wire insulation, leading to dangerous electrical shorts.

Allow for a safety buffer of at least 1 to 1.5 inches of clearance around all wiring harnesses and flexible plumbing lines. Secure loose wiring with insulated P-clips directly to the chassis to keep them from drifting into the path of your drawer slides. If a wire bundle must pass through a storage compartment, protect it by routing it through a rigid split-conduit sleeve or building a small wooden shield over it.

Selecting Materials for Your Custom Storage Boxes

Choosing the right material for your underbed storage boxes requires balancing weight, durability, and moisture resistance. A heavy storage build will sap your fuel mileage and can push your van past its Gross Vehicle Weight Rating (GVWR).

Material	Pros	Cons	Ideal Use
Baltic Birch Plywood	Exceptional strength, holds screws well, looks great raw	Expensive, heavy	Drawer boxes, heavy cargo slides
Lightweight Poplar	Easy to work with, lighter than birch	Dents easily, less structural	Trim pieces, lightweight drawer fronts
Expanded PVC (Sintra)	100% waterproof, lightweight, won’t rot	Flexible, requires extra framing support	Partition walls, wet-gear storage bins
Aluminum Extrusion	Modular, incredibly strong, lightweight	High cost, requires specialized hardware	Main structural frames, slide-out trays

For most van builders, Baltic Birch plywood in 1/2-inch or 5/8-inch thickness strikes the best balance of strength and space savings. Unlike standard construction plywood, Baltic birch features void-free inner plies that hold fasteners securely, even under the constant vibration of road travel. If you are building slide-out trays designed to hold heavy gear like mountain bikes or portable fridges, consider constructing the main tray frame out of 15-series aluminum extrusion to keep weight down while maintaining maximum rigidity.

Regardless of the material you choose, remember that the garage area is prone to moisture from damp gear and condensation. Seal all wooden components with a high-quality polycrylic or marine-grade varnish to prevent warping, mold, and wood rot over time.

Conclusion

Building custom underbed storage in a camper van is a rewarding project that transforms a chaotic cargo hold into an organized, efficient gear garage. By taking the time to map the space systematically, factoring in static obstacles, and utilizing the right precision tools, you can ensure your storage system operates smoothly for years to come. Do not rush the measuring phase—double-check your dimensions, build templates where necessary, and choose your materials wisely to create a functional, durable mobile home.