Quick Answer: Standard shipping container floors are 1.125-inch marine-grade plywood (Keruing or Apitong hardwood) treated with an insect-selective pesticide. For storage use, seal the existing floor with marine epoxy. For occupied conversions such as an office, ADU, or tiny home, replace the plywood with a new subfloor over closed-cell foam, and always seal the original before living above it. Tell us your delivery address and we will quote real costs, no anchored numbers, just honest pricing. Real Brantford yards, real reviews (4.9 / 124+), real 1-3 day delivery across Ontario. Family-operated since 1995.
In This Guide
- What Is a Shipping Container Floor Made Of?
- Are Shipping Container Floor Pesticides a Health Concern?
- How Do You Read the CSC Plate to Find Your Floor Treatment?
- How Strong Is the Container Floor Structure?
- Should You Seal, Overlay, or Replace the Floor?
- How Do You Fully Replace a Container Floor?
- What Drives Container Floor Replacement Cost?
- How Does Ontario’s Climate Affect Container Floors?
- What Brantford-yard customers actually choose
- When Does a Container Floor Genuinely Need Replacing?
- Frequently asked questions
Reading time: about 13 minutes.
What Is a Shipping Container Floor Made Of?
A shipping container floor is 1.125 inches of marine-grade tropical hardwood plywood bolted to a steel cross-member frame every 12 inches. The plywood is the wear surface; the cross-members carry the structural load. Treated with an insect-selective pesticide for ocean transit, the combined system is rated for roughly 1,200 kilograms per square metre of distributed weight.
Walk into any standard 20 or 40-foot dry van and you are standing on 1.125 inches of marine-grade plywood. The plywood is typically made from tropical hardwoods, most commonly Keruing (Dipterocarpus species) or Apitong (Dipterocarpus grandiflorus), sometimes Mengkulang or Bintangor depending on the manufacturer. These hardwoods were chosen for the original shipping use because they are dense, strong, and naturally moisture-resistant. They are also stiffer than softwoods, which matters when a forklift drops a 1,500-kilogram pallet on them mid-ocean.
The plywood is laid in panels approximately 4 feet by 8 feet, bolted into steel cross-members through the floor every 12 inches. The cross-members themselves are the structural elements that carry container load. The plywood is a wear surface, not the floor structure.
Why containers came with this exact floor
Shipping containers were designed for international freight. The floor needed to take forklift loads, survive saltwater, resist fungal growth in tropical climates, and ship cleanly through dozens of port jurisdictions. Marine-grade hardwood plywood treated with insect-selective preservative was the engineering answer. Every container made in Asia since the 1970s has shipped with some version of this floor.
Paul LeBlanc, owner, Van Blanc Ent. Inc.: “People come into the Brantford yard worried the floor is rotten or poisonous, and nine times out of ten it is neither. That marine plywood was built to cross the Pacific loaded with cargo. I have walked floors on 20-year-old boxes that are still tight. The real question is what you are putting on top of it, not whether the wood will hold.”
Are Shipping Container Floor Pesticides a Health Concern?
Shipping container floor pesticides are the single most common worry Van Blanc hears about, and for storage the honest answer is that they are not a meaningful concern. The plywood is treated to stop insects, not to harm people. The history behind the treatment is worth knowing before you decide whether to seal or replace, especially if you are weighing a second-hand box against a factory-fresh one.
Older containers (pre-2000s, mostly retired now): Some used chromated copper arsenate (CCA), a wood preservative containing arsenic. CCA-treated wood is no longer used in shipping container manufacture and most containers carrying CCA-treated floors have been scrapped or had floors replaced. If you’re buying a container manufactured before 2000, the CSC plate (described below) is the place to check.
Modern containers (2005 and later): Industry standard treatments are insect-selective compounds: Basileum SI-84, Taelilium 400, Radaleum FHP-60, or similar permethrin-based formulations. These compounds are biologically targeted to insects (termites, wood-boring beetles, marine borers) and have very low mammalian toxicity. Vapor pressure is low enough that off-gassing is minimal even in a sealed container.
For storage use, the residual chemistry is not a meaningful health concern. For occupied conversions where people will breathe the interior air for hours per day, sealing or replacing the floor is the standard, prudent choice. The cost of sealing is small enough that the prudent step is taken even when the actual risk is low. Buyers who want to skip the question entirely often start from a a brand-new single-voyage box, where the floor has made a single voyage and shows minimal wear before any conversion work begins.
The straightforward answer for occupied use
If the container will become an office, ADU, tiny home, retail shop, or any space where people occupy interior air for hours per day, seal the floor with marine epoxy. This costs little in materials, takes a weekend, and eliminates any meaningful pesticide off-gassing concern. For pure storage use (feed, equipment, contractor tools), the original treated floor is acceptable as-is.
How Do You Read the CSC Plate to Find Your Floor Treatment?
The CSC plate is how you find out what your shipping container floor was treated with. Every certified shipping container carries a Consolidated Safety of Containers (CSC) plate near the cargo doors. The plate lists manufacturer, build date, container number, gross load rating, and a section called “Timber Component Treatment” that names the chemical applied to the plywood floor.
Common treatments listed on modern CSC plates:
- BASILEUM SI-84 (BASF) – permethrin and additional insecticide formulation, common since the mid-2000s
- TAELILIUM 400 – permethrin-based, common on Hyundai and CIMC builds
- RADALEUM FHP-60 – permethrin-based with anti-fungal additive
- K-OTHRINE – deltamethrin-based
If the plate shows any of the above, you are dealing with a modern insect-selective treatment and the standard sealing approach applies. If the plate shows CCA, arsenic-based compounds, or no treatment listed (older containers), consult an environmental services professional before residential conversion.
How Strong Is the Container Floor Structure?
The container floor structure is a steel grid that sits underneath the plywood and carries the real load. The two long perimeter beams run the length of the container (bottom rails), and steel cross-members span the width of the container at regular intervals. On a 40-foot container, the cross-member spacing is typically 12 inches, which puts roughly 40 cross-members under the full floor.
The cross-members are channel steel, typically 6 inches deep and 4 millimetres thick. They are welded to the bottom rails and form the structural floor frame. The plywood sits on top and bolts down to the cross-members every 12 inches.
The combined floor system is rated for a uniformly distributed load of about 1,200 kilograms per square metre (approximately 245 pounds per square foot). Point loads on the floor (forklift wheels, equipment legs) require careful placement to keep the load over a cross-member rather than between them. This is rarely an issue in residential or office conversions but matters in heavy industrial storage.
What “rated load” actually means for residential conversion
A typical residential floor (living room, bedroom) carries roughly 200 kilograms per square metre maximum design load including all furniture and occupants. The shipping container floor is rated for six times that. Floor structural capacity is never the limit in a residential container conversion. Plywood condition, moisture, and surface finish are the limits.
Should You Seal, Overlay, or Replace the Floor?
Whether you seal, overlay, or replace the container floor depends entirely on how you will use the box. Storage gets the cheap option. Occupied conversions get the premium option. Most uses in between fall somewhere in the middle.
Option 1: Seal the original floor (storage and light-occupied use)
Marine epoxy coating applied directly to the existing plywood. Reduces moisture absorption by 60 to 80 percent, seals in any residual pesticide off-gassing, adds wear resistance. Steps:
- Empty the container. Sweep, vacuum, then mop with isopropyl alcohol or warm water. Dry 24 hours.
- Sand any rough spots, splinters, or raised grain with 80-grit sandpaper.
- Apply rolled-on marine epoxy in two thin coats with a phenolic-core roller. Recoat at 4-8 hours between coats.
- Cure 72 hours before loading.
Materials: 5-gallon marine epoxy kit, rollers, gloves, ventilation. For a 40-footer this is the lowest-cost path: doing it yourself is mostly the price of the epoxy kit, while contracting the same job adds labour for the prep, sanding, and two-coat application.
Option 2: Overlay with rubber, vinyl, or engineered floor (mid-range occupied use)
Add a wear surface and moisture barrier over the existing plywood without removing it. Common overlays:
- Industrial rubber sheet (3/8 inch). The most economical overlay per square foot installed. Bombproof for workshop or garage use. Easy to clean.
- Sheet vinyl (commercial grade). A step up in cost per square foot installed. Better appearance for office or retail use.
- Engineered hardwood click-lock. The most expensive overlay per square foot installed. Residential appearance for ADU or studio conversions. Requires underlayment.
- Luxury vinyl plank (LVP). Mid-range per square foot installed. Cost-effective residential look with moisture resistance.
For a 40-foot container (about 310 square feet of floor), the overlay total depends on the material you pick and whether you install it yourself or contract it out: rubber sits at the low end of the range, sheet vinyl in the middle, and engineered hardwood at the top.
Option 3: Full floor replacement (premium occupied conversions)
Remove the original plywood, install a new subfloor system, finish with engineered floor of choice. This is the path for residential conversions where you want a known-clean, properly insulated floor under occupants, and it is often bundled into a wider yard conversion build alongside venting, doors, and electrical rough-in. The mechanics of cutting and converting a box are covered separately; the floor steps and cost drivers are below.
How Do You Fully Replace a Container Floor?
A full container floor replacement means lifting out the original plywood, prepping the cross-members, insulating, and laying a new subfloor and finish surface. It is a 2 to 4 day project for a competent DIY team or a 1-2 week contracted job depending on scope. The sequence is straightforward but the prep work matters.
Tools and materials
- Reciprocating saw with bi-metal blades (Sawzall or equivalent)
- Cordless drill with 1/2-inch impact-rated socket
- Pry bar, large flat-tip screwdriver
- Wet-dry vacuum
- Pressure washer (for cleaning cross-members)
- Wire brush and rust converter for cross-members showing surface rust
- Closed-cell spray foam for insulating between cross-members (2-3 inches)
- Pressure-treated 2×6 or 2×8 lumber for new joist supplements (optional, for very heavy loads)
- 3/4-inch marine plywood or 23/32-inch tongue-and-groove subfloor
- Self-tapping metal screws (No. 12 by 2 inch minimum)
- Polyurethane construction adhesive
- Finish flooring of choice (engineered hardwood, LVP, tile, etc.)
Removal sequence
- Locate and remove the existing floor bolts. Original floors are bolted to cross-members through plywood. Look for hex-head bolts every 12 inches in a grid pattern. Use the socket and impact driver to back them out. Some will be rusted; cut these with the reciprocating saw.
- Lift the plywood panels. Pry up at the corners and lift each panel out. A 4×8 panel weighs roughly 60-80 pounds wet. Get help if needed.
- Inspect cross-members. Look for surface rust, deep pitting, deformation. Wire-brush any rust and apply rust converter then primer. Replace any deformed cross-members (rare; usually only needed on heavily abused containers).
- Vacuum and clean. Years of dirt and pesticide residue collect between cross-members. Vacuum thoroughly, then wipe with damp cloth. Dispose of debris as construction waste, not household garbage.
New subfloor install
- Spray-foam insulate between cross-members. 2 inches of closed-cell spray foam adds R-12 to R-14 to the floor, blocks moisture from the ground, and stiffens the floor structurally. On a 40-footer this is a small line item relative to the finished floor above it.
- Optional: supplemental 2×6 joists. For heavy loads or very long spans, add pressure-treated 2x6s parallel to the cross-members, secured with metal joist hangers. Most builds skip this step.
- Lay subfloor panels. 3/4-inch marine plywood or 23/32-inch tongue-and-groove. Stagger seams. Apply polyurethane construction adhesive on top of cross-members before placement, then screw down every 12 inches into the cross-members.
- Seal the seams. Polyurethane seam sealer or tape every joint to prevent moisture penetration.
- Install finish floor. Engineered hardwood click-lock, LVP, tile, sheet vinyl, or rubber mat per use case.
The single floor-replacement tip that saves the most money
Spray-foam insulate the cross-member voids BEFORE installing the new subfloor. Buyers who skip this step end up with cold floors in winter and condensation issues from below, and retrofitting insulation later requires lifting the subfloor again. The 2-inch closed-cell foam adds only a modest amount to project cost and saves multiples of that in long-term floor performance.
What Drives Container Floor Replacement Cost?
Container floor replacement cost moves on the same handful of levers: how many square feet you are covering, the finish material, and whether you do the labour or contract it. The bigger the box, the more material and labour each option consumes. The table below ranks the relative effort and cost of each approach (lower is cheaper, higher is more involved) so you can see how the choices stack up across sizes.
| Approach | 20ft (about 160 sq ft) | 40ft (about 310 sq ft) | 40ft HC (about 310 sq ft) |
|---|---|---|---|
| Sweep and leave | No cost | No cost | No cost |
| Seal with marine epoxy (DIY) | Very low effort, very low cost | Low effort, low cost | Low effort, low cost |
| Seal with marine epoxy (contracted) | Low effort, low cost | Low effort, low-to-mid cost | Low effort, low-to-mid cost |
| Rubber sheet overlay (contracted) | Low effort, mid cost | Mid effort, mid cost | Mid effort, mid cost |
| Sheet vinyl overlay (contracted) | Low effort, mid cost | Mid effort, mid-to-high cost | Mid effort, mid-to-high cost |
| LVP / engineered overlay (contracted) | Mid effort, mid-to-high cost | Mid effort, high cost | Mid effort, high cost |
| Full replace, foam insulated, subfloor only (DIY) | High effort, mid cost | High effort, mid-to-high cost | High effort, mid-to-high cost |
| Full replace + LVP finish (contracted) | High effort, high cost | Highest effort, high cost | Highest effort, high cost |
| Full replace + engineered hardwood (contracted) | High effort, highest cost | Highest effort, highest cost | Highest effort, highest cost |
The two largest customer segments at Van Blanc fall at the extremes: simple seal jobs done DIY for general storage upgrades, and full insulated replacements with LVP or engineered finish contracted out for ADU or tiny-home conversions. The middle-tier overlay options are common in container offices and retail conversions.
How Does Ontario’s Climate Affect Container Floors?
Ontario’s climate puts two specific stresses on a container floor: hard freeze-thaw swings and ground moisture. Both shorten floor life if you ignore them, and both are manageable with sealing, insulation, and proper site prep.
Freeze-thaw cycles and the floor. Ontario containers see 60-90 freeze-thaw cycles per year between October and April. The original plywood absorbs moisture and releases it slowly. In a stationary Ontario container, the plywood floor is the wettest part of the box in spring as condensation drips down and pools at the floor-to-wall transition. Sealing or replacing the floor addresses this directly. The container condensation guide goes deeper on the moisture mechanism.
Cold-weather subfloor performance. Without insulation between cross-members, the floor becomes a thermal bridge in winter. Container offices in Sudbury or Ottawa with un-insulated floors show condensation on cold floor patches and noticeable heat loss through the floor. The 2-inch closed-cell foam fix solves this for a modest materials outlay, and it works best when paired with the wall and ceiling approach covered in our cold-climate insulation breakdown.
Salt and moisture from ground contact. Containers set directly on damp earth or on snow-melt-prone surfaces wick moisture into the floor structure from below. Elevation on concrete blocks (4-6 blocks per side, 6-8 inches off the ground) plus a drained gravel pad eliminates most of this, as our guide to setting a container base explains in full.
Brantford-yard observation
Christian: “Customers ask us if they need to replace the floor before using the container. The honest answer for storage is almost always no. The factory marine plywood is robust enough for 20 to 30 years of stored-goods use if you keep the moisture out. For a tiny home or office build, replacing is worth it because you want known-clean, insulated, and finished to the surface you want. For a feed barn or contractor storage, sweep it and use it.”
What Brantford-yard customers actually choose
Across 30 years of Ontario container deliveries, the floor decisions Van Blanc customers make break out roughly:
- 60 percent: Leave the original floor as-is. Storage use where the plywood condition is acceptable. No work needed.
- 20 percent: Seal with marine epoxy. Mid-range storage uses where the customer wants longer floor life and easier cleaning. DIY.
- 10 percent: Overlay with rubber, vinyl, or engineered floor. Workshops, light-occupied uses, retail pop-ups. Usually contracted out.
- 10 percent: Full replacement with insulated subfloor and finish floor. Container offices, ADUs, tiny homes, hospitality builds. Almost always contracted out.
Christian LeBlanc, second-generation operator: “We have customers who have stored grain or feed in the same container for 20 years and never touched the floor. The plywood is dark from use, the surface is scuffed, but the box is dry and tight. Replacing that floor would have been wasted money. We have other customers building tiny homes where every detail matters, and full replacement is the only right answer. The path depends on the use, not on any blanket rule.”
When Does a Container Floor Genuinely Need Replacing?
A container floor genuinely needs replacing in five situations, and in nearly every other case sealing is enough. Here is when Van Blanc tells customers to replace rather than seal or overlay:
- Visible rot or delamination. The plywood is structurally compromised. Replacement is the only honest fix.
- Heavy chemical contamination from prior use. Container was used to ship hazardous materials and absorbed residue cannot be cleaned. Disclosure on the CSC plate or container history is the indicator.
- Residential or occupied conversion with sensitive occupants. Children’s spaces, healthcare uses, food prep areas. Replace and start clean.
- Heavy industrial point loads. Customer plans to install machinery exceeding the original floor’s point-load rating, requiring supplemental joists and a new subfloor.
- Pre-2000 container with CCA-treated plywood and residential intent. Older arsenic-based treatments warrant replacement before any occupied conversion.
In every other case (cosmetic wear, surface staining, the buyer’s general unease about pesticide treatment), sealing is the right answer. Replacement adds to the project cost and is not required by code, function, or honest expert judgment in most cases.
Worth the drive to Brantford
Buyers visiting our Brantford yard at 90 Morton Avenue East can walk containers at every grade and see what 1-year, 10-year, 20-year, and 25-year-old container floors actually look like in person. Christian or Paul will walk through which condition fits your planned use and whether seal, overlay, or replace makes sense for you. With 200 plus containers in stock, you pick the bin and we deliver. Most Ontario container suppliers do not let you choose. We do.
Go Deeper: Detailed Topic Guides
For more depth on specific aspects of this topic, see our spoke articles:
More from this cluster
Deeper reads we’ve added since the original guide:
Frequently asked questions
What is the shipping container floor made of?
Standard container floors are 1.125-inch marine-grade plywood, typically made from tropical hardwoods Keruing (Dipterocarpus species) or Apitong. The plywood is bolted to steel cross-members every 12 inches. The combined system is rated for approximately 1,200 kilograms per square metre (245 pounds per square foot) uniformly distributed load.
Are shipping container floors toxic?
Modern container floors (2005 and later) are treated with insect-selective pesticides (Basileum, Taelilium, Radaleum, K-othrine) that are biologically targeted to insects with very low mammalian toxicity and minimal off-gassing. For storage use, the floor is acceptable as-is. For occupied conversions, sealing with marine epoxy eliminates any meaningful exposure concern.
Should I remove the original shipping container floor?
For storage use, no. The marine plywood is robust enough for 20-30 years of stored-goods use. For occupied conversions (office, ADU, tiny home), replacement is recommended because you want known-clean, insulated, and finished to surface. For light-occupied uses (workshop, garage), overlay with rubber or LVP is the common middle path.
How much does it cost to replace a container floor?
It depends on the path. A DIY marine-epoxy seal is the cheapest option for a 40-footer, mostly the price of the epoxy kit. A contracted overlay with vinyl or engineered floor costs more and scales with the square footage and material. A full replacement with insulated subfloor and finish floor (contracted) is the most expensive and varies with your finish floor choice. The honest number always comes down to size, material, and whether you do the labour or contract it.
What is the best plywood for a container floor replacement?
3/4-inch marine-grade plywood (BS 1088 standard) or 23/32-inch tongue-and-groove subfloor (AdvanTech, Pacific T&G subfloor). Both are designed for moisture exposure and provide stiff, durable subfloor performance. Marine plywood is more expensive but more moisture-resistant. T&G subfloor is the cost-effective standard for most container conversions.
How thick is a shipping container floor?
The plywood layer is 1.125 inches (28 millimetres) thick. The cross-member steel structure underneath adds 6 inches (150 millimetres) of structural depth. Total floor system thickness from the ground to the interior floor surface is approximately 7 to 8 inches including the bottom rails.
Can I install vinyl plank flooring in a shipping container?
Yes. Luxury vinyl plank (LVP) is one of the most popular finish floors for container conversions because it tolerates moisture, installs over existing plywood with underlayment, and matches the floor flexibility containers experience during transport. It is priced per square foot installed and sits in the mid-range of finish-floor options.
How do I know if my container floor has CCA arsenic treatment?
Check the CSC (Consolidated Safety of Containers) plate near the cargo doors. Look for “Timber Component Treatment” section. If it lists CCA, copper arsenate, or arsenic compounds, the floor uses older treatment chemistry. Modern Basileum, Taelilium, Radaleum treatments are insect-selective and considerably lower-risk. Pre-2000 containers more likely to have CCA.
Can I install tile flooring in a shipping container?
Yes, but with caveats. Containers flex slightly during transport and from temperature changes, which can crack rigid tile. For containers that will remain permanent (delivered once and never moved), tile works fine over a stiff subfloor with proper underlayment. For containers expected to move, click-lock LVP or sheet vinyl is more forgiving.
Does a container floor need to be insulated?
For storage use, no. For occupied conversions in Ontario, yes. Without insulation between cross-members, the floor is a thermal bridge in winter, leading to cold floor patches, condensation from below, and noticeable heat loss. 2 inches of closed-cell spray foam in the cross-member voids adds R-12 to R-14 on a 40-footer.
Will the floor sag under heavy loads?
Not in normal use. The original floor system is rated for 1,200 kg/m² uniform load. Point loads (forklift wheels, machinery feet) require careful placement over cross-members rather than between them, but the system handles most residential, office, and workshop loads with significant margin. Heavy industrial applications may require supplemental joists.
How long does a sealed container floor last?
20 to 30 years for the original treated marine plywood if kept dry and properly sealed. The marine epoxy seal extends life by reducing moisture absorption and adding wear resistance. Replacement subfloors using 3/4-inch marine plywood or tongue-and-groove subfloor with proper installation can last 30-50 years in occupied conversion use.
Sources
- International Organization for Standardization. (2022). ISO 1496-1:2013 Specification and testing of series 1 freight containers, Part 1: General cargo containers. iso.org
- International Maritime Organization. (1972, amended). International Convention for Safe Containers (CSC) and Timber Component Treatment Disclosure. imo.org
- BS 1088 Standard. (2024). British Standard 1088: Marine Plywood Manufactured from Tropical Hardwoods Specification. bsigroup.com
- Discover Containers. (2024). Shipping Container Flooring and Pesticides: Should You Remove the Plywood Floor?. discovercontainers.com
- Falcon Structures. (2024). Are Shipping Container Floors Toxic? Health and Safety FAQs. falconstructures.com
Reach Van Blanc in Brantford
We have been supplying shipping containers across Ontario since 1995. Our warehouse is at 90 Morton Avenue East in Brantford, and we deliver across Ontario in 1 to 3 days from our four Brantford yards. No surprise fees, no chase-the-paperwork. Every quote comes with a real lead time, not a hopeful one.
Van Blanc Ent. Inc. 90 Morton Ave E Unit 1B, Brantford, ON N3R 7J7. +1 888-509-6658
Walk our yard before you buy. You can compare original-floor condition across containers of every age and grade, and see exactly what 5, 15, and 25 years of Ontario service does to a marine plywood floor. Christian or Paul will walk through the seal-versus-overlay-versus-replace decision for your specific use. With 200 plus containers in stock, you pick the bin and we deliver. Most Ontario container suppliers do not let you choose. We do.
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