How to Clean a Cargo Trailer Interior the Right Way

You haul gear all season, close the doors, and forget about it. Then you open the trailer six weeks later and something hits you in the face: a musty odor, suspicious spotting along a lower wall seam, or grit ground into the floor. If you have been there, you already know that cargo trailer interiors do not clean themselves, and moisture-related damage becomes harder to correct the longer it is ignored.

The good news is that cleaning a cargo trailer interior is not complicated. It takes the right sequence, products that are compatible with the installed materials, thorough drying, and a little consistency. A light cleanup after dirty loads and a deeper cleaning once or twice a year can help control odors, reveal leaks early, protect cargo, and preserve the trailer’s condition and resale value.

Start With a Full Cleanout (Don’t Skip This)

Before introducing water or cleaner, remove everything that is not permanently installed. Take out straps, moving blankets, ramps, bungee cords, tools, floor mats, and anything wedged beside the wheel boxes. Inspect those items separately before returning them because a damp blanket, dirty mat, or leaking container can immediately recontaminate a clean trailer.

Sweep loose material from the front toward the rear doors with a stiff-bristle push broom. A shop vacuum is better for fine dust, metal shavings, drywall debris, and material trapped around fasteners or wall edges. A leaf blower can speed up outdoor cleanup, but wear eye and respiratory protection and avoid blowing dust toward people, vehicles, buildings, or neighboring property.

Determine where wash water can safely exit before wetting the interior. Most general-purpose enclosed cargo trailers are not built as wash-down compartments and do not have floor drains. Some specialized trailers may include drains or washable flooring, but a rear door opening should not automatically be treated as a drain. Use as little water as practical, protect electrical equipment, and collect contaminated runoff when the trailer has carried oil, fuel, fertilizer, chemicals, or other regulated material.

Inspect the empty trailer carefully. Water staining near rear doors, roof edges, vents, marker-light wiring, or wall-to-floor joints may indicate a seal or fastener problem. Dark spotting can be dirt, staining, mold, or mildew; color alone cannot identify it. Soft flooring, swelling, delamination, loose fasteners, bubbling coatings, corrosion, or a persistent musty odor deserves attention before washing. Cleaning the visible surface will not correct an active roof, door, or body leak.

Floors First: Steel vs. Treated Wood vs. Aluminum Tread

The correct method depends on the actual floor construction and any covering applied over it. Consult the trailer’s documentation or ask the dealer when you cannot identify the material. Test every cleaner in an inconspicuous area before treating the full floor.

• Painted or coated steel floors (used in certain specialty cargo bodies and custom configurations): Vacuum or sweep first, then scrub with a diluted, coating-compatible detergent and a nylon brush. Do not assume every industrial degreaser is safe for paint or powder coating. Minimize standing water, especially around scratches, seams, welds, and bolt holes where exposed steel can corrode. Rinse sparingly and dry promptly.
• Aluminum tread plate floors or floor coverings (available on some cargo, motorsports, and custom trailer configurations): Use a pH-neutral cleaner that is labeled safe for aluminum. Strong alkaline degreasers, acidic wheel cleaners, bleach, and abrasive pads can discolor or etch aluminum. The raised tread pattern often requires brushing. Use low-pressure rinse water rather than driving a concentrated pressure-washer stream into seams, fasteners, doors, or wall cavities.
• Plywood or engineered-wood decking (common in enclosed cargo trailers, including current configurations that use plywood or proprietary engineered panels): Sweep and vacuum thoroughly. Spot-clean with a lightly damp brush or cloth and a cleaner approved for the flooring. Do not saturate the deck or pressure wash it unless the manufacturer specifically identifies the complete interior as washable. Water entering panel edges, fastener holes, or joints can cause swelling, delamination, decay, and hidden mold. Keep the doors and vents open until the deck is fully dry.

Some trailers have rubber coin flooring, vinyl flooring, removable mats, or other coverings installed over the structural deck. Clean those materials according to their manufacturer’s instructions. Lift removable mats so that both the mat and the floor beneath it can dry. Moisture trapped under an apparently dry rubber mat is a common source of odor and floor damage.

For grease or hydraulic-fluid stains, first absorb free liquid with an appropriate oil absorbent and dispose of it properly. Apply a compatible degreaser according to its label, including its dilution rate and dwell time, then agitate with a nylon brush. Do not automatically apply an undiluted concentrate; it may damage paint, aluminum, adhesives, rubber, or wood. Never wash petroleum products or chemical residue onto the ground or into a storm drain.

Walls: Aluminum Panels and the Seam Problem

Many enclosed cargo trailers use plywood, engineered-wood panels, vinyl-faced panels, or other interior liners. Smooth aluminum or aluminum tread plate may be offered as an interior option, while the corrugated or smooth aluminum visible outside the trailer is exterior skin and should not be confused with the interior wall liner. Current Wells Cargo FastTrac configurations, for example, list 3/8-inch PlexCore high-performance interior sidewalls, while Legend offers different liners and finishes depending on the model and selected options.

For painted, vinyl-faced, or metal liners, begin with a microfiber mop or soft sponge and warm water containing a small amount of mild detergent. Keep moisture away from unfinished panel edges. Work from top to bottom so runoff does not cross areas you have already cleaned. Use a lightly damp cloth rather than flowing water on bare plywood or other absorbent wall material.

Pay particular attention to wall-to-floor joints, corners, wheel-box edges, trim channels, roof bows, and areas around doors and vents. Dust and moisture can collect in these locations, but dark or gray residue is not automatically mold. If suspected growth returns after cleaning or appears near a stain, locate and correct the moisture source rather than repeatedly treating the surface.

For a small affected area on a hard, nonporous surface, scrub with detergent and water and dry it completely. Wear gloves and eye protection; an N95 respirator is prudent when disturbing visible mold. Porous materials can be difficult or impossible to clean completely after mold grows into them. Swollen, soft, delaminated, or extensively contaminated wood panels may require professional evaluation and replacement rather than surface treatment.

Do not rely on vinegar or bleach as a universal mold treatment. Products can react with metals, coatings, adhesives, rubber, and other cleaners. Never mix bleach with ammonia, acids, vinegar, or any other cleaning product. If a registered disinfectant is needed for a specific contamination problem, use only a product labeled for the surface and follow its ventilation, protective-equipment, dilution, contact-time, rinsing, and disposal directions exactly.

After cleaning, wipe seams, trim, and fastener recesses with dry towels and keep the trailer ventilated. A fan can improve air movement, provided it is suitable for the environment and its electrical connections remain dry. Do not close the trailer until the flooring, wall liners, mats, trim channels, and cargo restraints are completely dry.

Odor: What Causes It and How to Actually Eliminate It

Persistent trailer odor can come from mold growth, spilled liquids, wet cargo, rodents, food residue, fuel or chemicals, damp wood, floor coverings, or water trapped behind a liner. Fragrance sprays may temporarily mask an odor, but they do not remove its source and may transfer scent or residue to sensitive cargo.

After cleaning, ventilate the trailer until all surfaces are dry. Baking soda or a commercial odor absorber may help with residual odor, but neither substitutes for removing contaminated material or repairing a leak. Calcium-chloride moisture absorbers such as DampRid collect liquid brine, so place them in a stable container where they cannot tip, leak onto metal, contact cargo, or be reached by children or animals. Follow the product label and do not leave an open container unsecured while towing.

If odor persists, inspect beneath removable mats, along the underside of the floor, around roof and side vents, inside accessible cabinets, and near door seals and wall penetrations. A portable dehumidifier can help dry a stationary trailer when humidity is high, but it must be connected and drained safely according to its instructions. Keep household electrical equipment away from wash water, do not overload an extension cord, and never operate fuel-burning equipment inside an enclosed trailer.

Indiana’s warm, humid summers can slow evaporation, particularly when a trailer is parked in shade with the doors closed. Use actual moisture readings when possible rather than assuming a surface is dry because it feels dry. A pin-type moisture meter can help compare suspicious wood panels with known-dry areas, although readings must be interpreted for the particular material.

A clean appearance is only part of the job. Finding the leak or wet material, removing contamination, and drying the assembly completely are what prevent recurring odor, corrosion, swollen decking, and damage to the cargo carried inside.

Mildew Prevention: The Maintenance Habits That Matter

Cleaning removes surface contamination; moisture control helps prevent it from returning. Never close a trailer immediately after washing or after transporting wet equipment. Open the rear and side doors while the trailer is parked securely, or use installed vents, until every surface and removable item is dry. Secure doors against wind and do not leave an open trailer unattended where people, animals, rain, or theft present a risk.

Before adding a roof vent, confirm that the trailer does not already rely on sidewall vents and ask the manufacturer or an experienced trailer shop whether a roof opening is appropriate. Vent size, roof-bow spacing, reinforcement, sealant, wiring, warranty requirements, and installation method vary by trailer. Cutting an unsupported opening or using the wrong sealant can create the leak the vent was intended to prevent. Roof vents are standard on some specialized configurations and optional on many general cargo models; model length alone does not establish what equipment is installed.

At least annually, and after any branch strike or roof damage, inspect rear-door seals, side-door seals, roof seams, vents, exterior trim, marker lights, fasteners, and wiring penetrations. Also inspect the roof from a safe position without standing on it unless the manufacturer identifies it as walkable. Sealant and weatherstripping are not universal parts, and replacement cost and installation time vary considerably. Match the original profile and use a manufacturer-approved sealant rather than choosing a part by appearance alone.

Store the trailer with its roof and door openings closed against rain while maintaining ventilation through properly designed vents. Park on a firm, well-drained surface and, when practical, position the trailer so water does not pool around damaged seals or enter through an open door. Do not create an unsafe off-level condition merely to encourage drainage.

Organization: A Clean Trailer Stays Clean Longer

Loose gear can scuff liners, damage doors, block vents, collect moisture, and become dangerous cargo during sudden braking or a collision. Organizing the interior should improve both cleanliness and load securement, but every rail, shelf, hook, and fastener must be appropriate for the trailer structure and the intended load.

• E-track rails: E-track can provide flexible attachment points when the track, connectors, fasteners, backing, and supporting structure are properly rated and installed. Track may be steel or aluminum, and its usable capacity depends on the entire installation rather than the rail alone. Do not fasten load-bearing track only to a thin interior liner. Factory-installed and optional cargo-control packages vary across the trailers available at Spencer Trailers.
• Rubber floor mats: Removable rubber mats can protect compatible flooring and improve traction, but they may also trap grit, chemicals, and moisture. Choose a material suitable for the cargo, avoid reducing required clearance around doors or equipment, and remove the mats periodically to clean and dry both sides.
• Overhead shelving: Shelves and cabinets keep small items off the floor, but their capacity is specific to the product, mounting method, trailer structure, and load distribution. Use the manufacturer’s published rating, install reinforcement where required, secure the contents, and remember that high-mounted weight can affect stability.
• Wall hooks and track systems: Hooks are useful for lightweight straps, bungees, and moving blankets. Mount them into appropriate structural members or approved backing, not merely into plywood or decorative liner unless the system is expressly designed for that installation. Heavy tools and equipment should be restrained with rated cargo-control hardware.

Quick Q&A

Can I pressure wash the inside of my cargo trailer? Only when the trailer manufacturer and the installed floor and wall materials permit it. Many general-purpose enclosed trailers contain plywood or engineered-wood decking, absorbent wall liners, exposed electrical components, and joints that are not designed for pressure washing. A concentrated stream can force water behind panels, damage coatings, and enter lights, switches, connectors, locks, bearings, or door hardware. Sweeping, vacuuming, controlled scrubbing, and a low-volume rinse are safer for most interiors. If pressure washing is approved, use the lowest effective pressure, a wide fan tip, adequate distance, and prompt drying.

My trailer smells like mildew but I don’t see any growth. What’s happening? The source may be under a mat, inside wet wood, behind a liner, around a roof penetration, beneath the floor, or in a stored strap or blanket. Remove all cargo, inspect accessible areas, correct leaks, and dry the trailer thoroughly. If the odor returns, the floor feels soft, panels are swollen, or staining continues to spread, ask a qualified trailer repair shop or mold-remediation professional to investigate instead of removing structural panels without a plan.

Does the brand of trailer affect how easy it is to clean? Construction and options matter more than the name on the front. A smooth, nonporous liner can be easier to wipe than unfinished wood, while removable rubber flooring may simplify some cleanup but conceal moisture if it is never lifted. Aluminum framing can resist frame corrosion, but aluminum surfaces still require compatible cleaners and the floor or interior liner may be wood-based. Compare the exact floor, wall liner, vents, seams, cargo-control system, and access points on the individual trailer. Talk to us at Spencer Trailers (812) 829-0226 and we will help match the configuration to the cargo you actually haul and the way you plan to maintain it.

The Last Step Most People Skip

After the trailer is clean, dry, inspected, and reorganized, record the date and any problems you found. A piece of removable tape inside the door works, or keep a simple note with the trailer’s maintenance records. Include leaks, damaged seals, coating chips, soft flooring, loose tie-down hardware, and products used. The next time you open the trailer, you will know when it was cleaned and whether a previously observed stain or odor has returned.

Trailers that are cleaned and inspected regularly are more likely to age well. A 7×16 or 8.5×24 enclosed trailer represents a substantial investment, but its actual price depends on manufacturer, frame material, GVWR, axle configuration, interior height, doors, flooring, electrical equipment, cargo-control options, and current market conditions. A few careful hours each year can protect the floor, liners, hardware, cargo, and resale condition. If you are shopping for an enclosed trailer that suits your maintenance needs, browse our current inventory or stop by 291 West State Hwy 46 in Spencer. We will show you the materials and options on the actual trailer so you can choose a configuration that fits the work you expect it to do.