An ADA door threshold is the strip at the bottom of a doorway that must meet strict height and slope rules so wheelchair users, people with walkers, and others with mobility aids can pass through safely. In most cases, the threshold cannot rise more than ½ inch above the floor, and any part above ¼ inch must be beveled. This guide covers everything you need to know, from height limits to fixing a failed inspection.
What Is an ADA Door Threshold?
A threshold is the raised strip you step or roll over at the base of a doorway. It bridges the small gap between the door and the floor.
Thresholds do more than just look neat. They block drafts, keep water out, cut down noise, and give the door frame extra support. But when it comes to accessibility, their main job is to let everyone cross the doorway without tripping or getting stuck.
Building owners, architects, and contractors search for ADA threshold rules mainly to confirm their doors will pass inspection. Threshold height is one of the most common reasons commercial doors fail ADA checks, so getting it right the first time saves time and money.
Why Threshold Compliance Matters
Threshold compliance matters because non-compliant doors create real barriers for people with disabilities and expose building owners to legal risk. A threshold that’s too tall can stop a wheelchair user cold.
ADA Title III lawsuits have tripled since 2013. In 2025 alone, 8,667 federal ADA Title III lawsuits were filed, and California generated 3,252 claims on its own. Threshold violations are one of the most frequent triggers for these complaints.
The good news is that fixing thresholds early is cheap compared to fighting a lawsuit. Adding accessibility features during new construction typically adds less than 1% to total building costs, while a professional compliance audit runs about $2,500 to $7,000 for a commercial property. That’s a small price next to a settlement, which often costs twenty times more than it would have cost to comply in the first place.
Maximum Threshold Height Limits
The maximum threshold height for new construction is ½ inch (13 mm). This is the number most people search for, and it applies to nearly all doors.
There are two exceptions. Exterior sliding doors can have a threshold up to ¾ inch (19 mm) high, even in brand-new buildings, because they need extra height to keep water out. Existing or altered thresholds in older buildings can also go up to ¾ inch, as long as they’re properly beveled.
| Door Type | Max Height (New Construction) | Max Height (Existing/Altered) | Bevel Required Above |
|---|---|---|---|
| Interior swinging doors | ½ inch (13 mm) | ¾ inch (19 mm) with 1:2 bevel | ¼ inch (6.4 mm) |
| Exterior swinging doors | ½ inch (13 mm) | ¾ inch (19 mm) with 1:2 bevel | ¼ inch (6.4 mm) |
| Exterior sliding doors | ¾ inch (19 mm) | ¾ inch (19 mm) with 1:2 bevel | ¼ inch (6.4 mm) |
| Residential dwelling unit sliding doors (CA, 2026) | ¾ inch (19.1 mm) | N/A | ¼ inch (6.4 mm) |
When Is a Bevel Required?
A bevel is required whenever any part of the threshold rises more than ¼ inch above the floor. Below that height, a vertical edge is allowed with no bevel at all.
Think of the bevel as a mini-ramp. It smooths out the transition so wheels and feet don’t catch on a sharp edge. Without it, even a threshold within the height limit can still be a trip hazard.
Inspectors check this closely because a missing bevel is one of the most common reasons doors fail. If your threshold measures more than ¼ inch, plan on a beveled edge on both sides.
What Is a 1:2 Bevel Slope?
A 1:2 bevel slope means the ramp rises 1 unit for every 2 units it runs horizontally. In plain terms, for every inch of height, the bevel needs at least 2 inches of horizontal distance to taper down.
This ratio isn’t arbitrary. It creates a gentle enough angle that a wheelchair can roll up and over without extra effort or risk of tipping.
To check compliance, measure the vertical rise and the horizontal run of the sloped edge. Divide the rise by the run — if the result is 0.5 or less, the slope meets code. A steeper bevel fails inspection even if the overall height is within limits.
Exterior Sliding Door Exception Explained
Exterior sliding doors get a special exception because they need a taller threshold to stop water from getting in. These doors can have a threshold up to ¾ inch, even for brand-new construction.
This is different from swinging doors, which are capped at ½ inch regardless of whether they’re interior or exterior. The extra height on sliding doors accounts for the track hardware and the weatherproofing needed at ground level.
The bevel rule still applies here. Any part of the ¾-inch threshold above ¼ inch still needs that 1:2 slope on each side.
Existing vs New Construction Threshold Rules
New construction must meet the ½-inch limit, while existing or altered buildings get more flexibility. Existing thresholds can stay at up to ¾ inch as long as they’re beveled correctly on both sides.
This exception exists because ripping out and replacing thresholds in older buildings can be expensive and disruptive. Code writers recognized that requiring a full threshold replacement wasn’t always practical.
That said, this exception only applies to thresholds that were already in place or are being altered — not new installs. If you’re putting in a brand-new door in an existing building, the ½-inch rule usually applies.
How to Measure Threshold Height Correctly
Measure from the finished floor to the highest point of the threshold, at the center of the doorway width. Many measurement errors happen because people measure from the subfloor instead.
Here’s a simple process:
- Locate the center of the doorway opening.
- Place a ruler or caliper flat on the finished floor surface.
- Measure straight up to the highest point of the threshold.
- Record the number and compare it against the ½-inch or ¾-inch limit that applies to your door type.
- Re-measure any time new flooring is installed, since carpet or tile can change the effective height.
Common Threshold Materials and Their Uses
Aluminum is the most common material for commercial ADA thresholds because it’s affordable, lightweight, and resists corrosion. Other materials serve more specific needs.
| Material | Best For | Pros | Cons |
|---|---|---|---|
| Aluminum | Most commercial applications | Lightweight, affordable, many profiles | Can dent over time |
| Bronze | High-end commercial, institutional | Durable, premium look | Expensive, heavier |
| Brass | Upscale commercial | Sophisticated appearance | Expensive, needs polishing |
| Stainless steel | Industrial, corrosive environments | Very strong, modern look | Expensive |
| Vinyl / PVC | Interior, residential | Good insulator, affordable | Less durable |
| Rubber | Flexible sealing | Pliable, tight seal | Wears quickly |
| Wood | Residential, historic buildings | Traditional look | Not ideal for commercial use |
Types of ADA-Compliant Thresholds
The main threshold types are saddle, bumper, interlock, thermal break, panic, and ramp. Each fits a different situation.
- Saddle thresholds work well for interior corridors and office doors.
- Bumper thresholds give the door bottom something to seat against.
- Interlock thresholds have a groove that captures the door sweep for a tighter weather seal on exterior doors.
- Thermal break thresholds add an insulating barrier, useful for climate-controlled buildings.
- Panic thresholds stay low profile so they clear exit device hardware.
- Ramp or offset thresholds create a gradual slope, often used to fix an existing non-compliant threshold without full replacement.
How to Choose the Right Threshold for Your Door
Choose your threshold based on the door’s location, exposure to weather, and traffic level. Interior doors usually only need a simple saddle threshold.
Exterior doors need more thought. If water resistance is a priority, an interlock or thermal break threshold paired with a proper door sweep works best. For retrofits where the existing threshold can’t be replaced, a ramp threshold is often the easiest fix.
Material choice should match the environment too — aluminum for general commercial use, stainless steel for industrial or corrosive settings, and bronze or brass when appearance matters as much as function.
Installation Best Practices for Compliance
Good installation starts with a clean, level surface and ends with a dry fit before anything gets fastened permanently. Skipping these steps is how new installs end up failing inspection.
- Prepare a level, debris-free substrate before setting the threshold.
- Dry-fit the threshold to confirm height and bevel direction.
- Fasten securely using anchors suited to the substrate (concrete, wood, or metal).
- Confirm level landings exist on both sides of the doorway.
- Test the finished install by rolling a wheelchair or walker over it.
Why Do Doors Fail ADA Inspection at the Threshold?
Doors most often fail inspection because the threshold is too tall, lacks a required bevel, or has become a trip hazard from wear. These are avoidable problems.
| Failure Type | Cause | Solution |
|---|---|---|
| Threshold too tall | Profile exceeds ½ inch | Replace with compliant threshold |
| Abrupt vertical edge | No bevel above ¼ inch | Install beveled threshold or ramp |
| Trip hazard | Worn or dented surface | Replace threshold |
| Incorrect weather seal | Non-ADA profile used | Use compliant interlock/thermal break threshold |
| Uneven floor transition | New flooring changed height | Re-measure and adjust |
How to Fix a Non-Compliant Threshold
The fastest fix for a too-tall or unbeveled threshold is usually to replace it with a code-compliant profile, or add a ramp threshold over the existing one. Don’t just cut down the old threshold — without a proper bevel, it can still fail.
If full replacement isn’t possible right away, an offset wheelchair ramp threshold can bridge the gap while keeping the required 1:2 slope. This is a common solution for older buildings.
Always re-measure after the fix to confirm the new height and bevel angle actually meet the ½-inch or ¾-inch limit that applies.
Threshold Ramps and Offset Wheelchair Transitions
Threshold ramps, also called offset wheelchair ramps, are low-profile add-ons that bridge height differences while keeping a gentle slope. They’re especially useful when a threshold can’t be replaced outright.
These ramps typically maintain the same 1:2 slope required for beveled edges. One detail people often overlook is the horizontal offset — the ramp needs enough clearance so it doesn’t interfere with the door sweep or the door stop.
Door Sweep and Threshold Interaction
Door sweeps and thresholds need to work together, not against each other. A sweep that drags on a new threshold — or a ramp that binds against the sweep — will keep the door from closing properly.
Interlock thresholds are designed specifically to mate with certain sweep profiles, creating both a weather seal and a smooth surface. When installing any new threshold, always check that the door still opens and closes freely afterward.
Weather Sealing Without Sacrificing Accessibility
You don’t have to choose between a tight weather seal and ADA compliance. Interlock and thermal break thresholds are built to do both.
Pairing a compliant threshold with the right door sweep and gasketing keeps water and drafts out while staying within height and bevel rules. For extra water resistance, newer products like the ADAptive water-rated accessible sill combine sealing performance with full accessibility compliance.
How Often Should Thresholds Be Inspected?
Thresholds should be inspected quarterly in high-traffic commercial buildings and at least once a year everywhere else. Regular checks catch problems before they become code violations.
During an inspection, verify fastener tightness, check the bevel is still intact, and look for wear or rounding at the leading edge. Any time flooring is replaced, re-measure the threshold height, since new carpet or tile can change the numbers.
State and Local Code Variations (California, Florida)
Federal ADA standards set the baseline, but some states add their own rules. California’s 2025 Standards for Accessible Design, effective January 1, 2026, keep the ½-inch general limit and ¾-inch limit for sliding doors serving dwelling units, with specific exceptions for certain occupancy types not on accessible routes.
Florida Building Code adds extra water-resistance testing requirements for thresholds. If your project is in a state with its own accessibility code, always check whether it’s more stringent than the federal ADA standard — the stricter rule applies.
ADA vs Fair Housing Act: Residential vs Commercial
ADA Title III governs commercial and public buildings, while the Fair Housing Act covers residential multifamily housing. These are two separate sets of rules, and mixing them up is a common mistake.
If you’re working on an apartment complex, Fair Housing Act rules likely apply instead of, or alongside, ADA. A local accessibility specialist can clarify which standard governs your specific project.
Common Mistakes to Avoid During Installation
The most common threshold mistakes are easy to prevent once you know what to look for.
- Installing a threshold over ½ inch in new construction.
- Skipping the bevel on any edge above ¼ inch.
- Assuming all exterior doors qualify for the ¾-inch exception (only sliding doors do).
- Measuring from the subfloor instead of the finished floor.
- Cutting down a non-compliant threshold instead of replacing it properly.
- Letting loose fasteners cause the threshold to rock or shift.
Expert Tips for Long-Term Compliance
A few habits go a long way toward staying compliant year after year.
- Measure twice before ordering or installing any threshold.
- Use a bevel gauge to confirm the slope is 1:2 or gentler.
- Test the finished threshold with a wheelchair or walker.
- Document every inspection with photos, measurements, and dates.
- Bring in an accessibility consultant early in the design phase for larger projects.
Latest Updates: 2025–2026 ADA Threshold Standards
The 2010 ADA Standards for Accessible Design remain the controlling federal standard through 2026, with no physical-accessibility updates published since 2012. Most of what’s changed recently is happening at the state level and in enforcement trends.
California’s 2025 Standards took effect January 1, 2026, keeping the familiar ½-inch and ¾-inch limits with added exceptions for certain dwelling unit doors. Meanwhile, ADA door threshold Title III lawsuits have kept climbing, reaching 8,667 federal filings in 2025. On the product side, manufacturers have introduced water-rated accessible sills and improved offset ramp transitions, giving building owners more options for retrofitting older doorways without a full replacement.
How Much Does Compliance Cost vs Litigation Risk?
Compliance is almost always cheaper than the cost of a lawsuit. Adding accessibility features to new construction typically adds less than 1% to total building costs, and a full third-party compliance audit runs $2,500 to $7,000 for a commercial property.
Settlement costs, by comparison, often run twenty times higher than what proactive compliance would have cost. Given that ADA Title III filings have tripled since 2013, addressing threshold issues now is a far better investment than waiting for a complaint.
FAQs
What is the maximum height for an ADA-compliant door threshold? For new construction, the max is ½ inch (13 mm). Exterior sliding doors and existing/altered thresholds can go up to ¾ inch (19 mm) if properly beveled.
Do all thresholds need to be beveled? No. Thresholds ¼ inch or less can have a vertical edge. Anything taller must be beveled at a 1:2 slope or gentler.
Can an existing threshold be ¾ inch and still be ADA compliant? Yes, as long as it’s an existing or altered threshold (not new construction) and has a beveled edge on each side with a 1:2 slope.
Are exterior sliding door thresholds treated differently under ADA? Yes. They can be up to ¾ inch even in new construction, due to the need for extra water protection.
How do I measure threshold height for ADA compliance? Measure from the finished floor to the highest point of the threshold, at the center of the doorway.
What materials are ADA-compliant thresholds made from? Aluminum is most common, along with bronze, brass, stainless steel, vinyl, PVC, rubber, and wood.
Why do commercial doors fail ADA inspection at the threshold? Common reasons include excess height, missing bevels, worn surfaces creating trip hazards, and incorrect weather sealing profiles.
Can I install a threshold ramp to fix a non-compliant threshold? Yes. Offset wheelchair ramps can bridge height differences while maintaining the required 1:2 slope, especially useful when full replacement isn’t practical.
Do interior door thresholds have different ADA requirements than exterior? Height and bevel rules are the same, but exterior thresholds usually need extra weather sealing and corrosion-resistant materials.
How often should ADA thresholds be inspected? Quarterly for high-traffic commercial buildings, or at least annually otherwise, with re-checks after any flooring changes.