The threshold at your mother’s patio door stands 1 3/4 inches (4.4 cm) above the concrete slab. It has been there since 1998, and nobody thought about it once until the day the wheelchair came home. Now it’s the reason she can’t reach the garden without two people lifting the chair over the frame.
That’s where most people are when they start looking at an aluminum threshold ramp. Not planning a construction project. Standing in a doorway with a tape measure, trying to work out whether a piece of metal with a slope on it will fix the next ten years of somebody’s afternoons.
Here’s the good news. A threshold ramp is the cheapest piece of access hardware you can buy, and the easiest one to install. Here’s the part nobody mentions in the listing. Most of them are sold by length and height alone, and the thing that decides whether yours works is usually the door hanging above it.
So measure four things before you order anything: the rise, the door, the wheel, and the weather. The rest of this page is about those four.
The rise is a real measurement, not the number on the listing
Put a level or a straightedge across the top of the threshold and measure down to the ground on both sides. Do it at three points along the width, because thresholds settle. On a 36-inch (91 cm) opening you can easily find a quarter inch of difference between one end and the other, and that difference is exactly what makes a ramp rock under a chair.
Record the highest point. That’s your design rise, not the average.
Some typical numbers, so you know whether yours is normal. A sliding patio door track usually sits 1 to 2 inches (2.5 to 5 cm) proud of the slab. An interior door over wall-to-wall carpet lands around 3/4 inch. A garage-to-house step is often 4 to 6 inches (10 to 15 cm), and that one is already too tall for most threshold ramps. A shower curb runs about 4 inches and needs its own kind of solution.
Then hold your number against the limits that govern a doorway in a public building. Changes in level up to 1/4 inch (6 mm) can be vertical. Anything between 1/4 and 1/2 inch (6 to 13 mm) has to be beveled at no steeper than 1:2. Anything above 1/2 inch has to be ramped. The Access Board’s guide to ramps and curb ramps says it plainly: ramps are required to span changes in level greater than half an inch. Your private patio door isn’t bound by that rule, but the numbers are still a decent sanity check on how abrupt a transition a wheel can survive.
One measurement people skip: the ground on the low side. A ramp doesn’t only raise the high point, it also drops the effective floor at the bottom edge by the thickness of the material. If your walk slopes away from the door, the ramp’s low lip can end up hanging in the air with nothing under it. Slide a hand underneath before you commit to a length.
The door swing decides more than the slope does
A door that swings inward needs clear floor for the whole arc of the leaf. Drop a 12-inch-wide ramp on the inside of that doorway and the door either lands on it or drags across the high edge and stops halfway open. This is the single most common reason a threshold ramp gets packed up and sent back.
A storm door or screen door on the outside has the same problem in reverse. Those doors hang low, with a sweep or a bottom expander designed to sit about a half inch off the sill. Put a ramp under them and the door won’t latch, or the sweep tears itself off within a month of daily use.
Measure the gap between the bottom of the door leaf and the floor while the door is closed. On most residential doors it’s 3/4 inch to 1 1/2 inches. The height of your ramp at the point where the door passes has to stay under that figure, which usually means the ramp goes outside an inward-swinging door, or the door gets trimmed and re-hung.
Sliding patio doors are their own case, because the track is part of the floor. The ramp has to bridge the track without sitting on the roller channel, or the panel won’t slide. Plenty of aluminum threshold ramps are built with a notch or a bridge plate for exactly this, and it’s worth reading the product drawing instead of the marketing photo. A track that’s 1 1/2 inches deep is a different problem from a flat sill with a 3/4-inch lip.
Run the arithmetic for your own doorway. A 1-inch rise at 1:8 needs 8 inches of horizontal run, which is 8 inches of floor the door leaf has to clear and 8 inches of walking surface you didn’t have before. Multiply that by every doorway in the house and the geometry stops being abstract. It also explains why a ramp that looked small online turns out to dominate a hallway.
If the arithmetic doesn’t fit, the honest answer is often a small landing outside the door with a longer ramp beyond it. That’s a bigger job, and it’s still cheaper than a repair bill and a bad fall.
Slope is the number to check before price
Slope is rise divided into run. A 1:12 ramp climbs 1 inch for every 12 inches of length, and that’s the maximum allowed on an accessible route in the 2010 ADA Standards. A 1:8 ramp climbs 1 inch for every 8 inches, which is steeper and shorter, and it’s common on portable threshold products because the whole thing has to fit on a porch or a landing.
Run your own numbers. A 1-inch rise at 1:12 needs 12 inches of ramp, and at 1:8 it needs 8. A 2-inch rise needs 24 or 16 inches. A 3-inch rise needs 36 or 24. Suddenly a “3-inch threshold ramp” is a two-foot-long object, and you need to know where those two feet are going to live before it arrives.
Steeper is faster to fit and harder to use. Self-propelling a manual chair up 1:8 takes real shoulder work, and coming back down the chair wants to run. A caregiver pushing from behind has better leverage on 1:8 than the occupant does, which is why so many of these ramps are bought by the person pushing rather than the person riding.
If the user propels themselves and lives alone, favor the longest ramp the space allows, even if that means a custom length. If someone always pushes, a steeper aluminum threshold ramp is workable for a rise under 3 inches. Write the number on a sticky note if you have to. Slope is the spec that changes how the doorway feels every single day, and it’s the one nobody puts on the box.
There’s a related trap with width. A ramp that’s 36 inches wide fits a standard chair with a couple of inches to spare, but it leaves no room for a foot to land beside the wheels when someone walks up next to the chair for balance. On a doorway that gets two-person transfers, go wider than the chair.
Casters, footrests, and the scooter problem
A wheelchair’s front casters are usually 5 to 8 inches in diameter, and they find every lip in the world. A ramp that rises smoothly but starts with a vertical quarter-inch edge will stop a small caster dead, and the chair pivots around that point instead of rolling over it. The leading edge matters as much as the slope number printed on the side.
Footrests are the second casualty. They hang forward and low, often 2 to 3 inches off the ground, and they meet the ramp surface at the transition where the angle changes fastest. A footplate that catches will lift the front of the chair, and if the rear wheels are still on the flat at that moment, the whole thing can go over backward. Look for a ramp with a gradual toe at the bottom rather than a squared-off end.
Mobility scooters bring a different problem: ground clearance. A four-wheel scooter often runs 3 to 4 inches of clearance under the chassis, with anti-tip wheels hanging behind the rear axle. On a short, steep threshold ramp those anti-tip wheels touch down before the drive wheels reach the top, the rear tires lose traction, and the scooter spins in place. If you’re buying for a scooter, test the actual machine on the actual ramp, or pick a longer and gentler unit.
Walkers and rollators are the quiet third case. Their wheels are small, their frames are light, and they tip forward easily. A ramp that’s perfectly fine for a 200 lb wheelchair can be genuinely sketchy for a 90-year-old with a rollator, because nothing holds the front down. For rollator use, a gentle slope and a textured surface matter more than the load rating.
None of this shows up in a product listing. All of it shows up in the first week.
Aluminum grade, weight, and what February does to it
Almost every threshold ramp on the market is made from 6061 aluminum in a T6 temper, a precipitation-hardened alloy with good corrosion resistance and reasonable weldability. The Aluminum Association publishes the alloy and temper designations if you want to read what the four digits actually mean. In practice, 6061-T6 weighs about one-third as much as the same volume of steel, needs no paint, and grows its own thin oxide layer within minutes of being cut.
Weight is the spec that decides whether the ramp gets used. A 3-foot aluminum threshold ramp typically lands between 10 and 20 lb (4.5 to 9 kg), light enough for one person to lift with a hand on each side. A 4-foot version can push 30 lb, and at that point it stops being portable and starts being furniture. If it has to move daily, weigh it before you buy. If it’s going to live in one doorway for a decade, weight matters far less than stability.
Surface is the next decision. Punched or perforated deck plate drains well and grips in rain, but the holes pack with grit, grass clippings and road salt over a winter, and once they’re packed the texture is gone. Extruded plank decks with raised ribs shed water and clean out with a broom. Rubber-topped ramps feel better underfoot and run quieter, and the rubber will eventually lift at the edges.
Winter is where cheap aluminum shows its age. Road salt and de-icing brine attack the surface, and bare aluminum touching a steel threshold or a steel door frame sets up a galvanic couple that eats the softer metal. Rinse the ramp in spring, and slip a nylon washer or a plastic shim between aluminum and steel wherever the two meet. It’s a two-dollar fix that prevents a corroded mess three years later.
Painting is usually a mistake. The mill finish holds up better than most rattle-can jobs, and paint that chips gives water a place to sit. If you want a different color, have it powder coated, or buy it anodized and accept the limited palette.
Keeping it where you put it
Most threshold ramps rely on friction and gravity, which is fine for a 1-inch rise on a level slab. It’s not fine on a sloped walk or a smooth garage floor, where a chair pushing up will slide the whole assembly forward an inch at a time until the top edge drops off the threshold. You’ll feel it as a jolt, and then you’ll find the ramp a foot out of place.
Check what the ramp offers for anchoring. Rubber feet hold on concrete and fail on gravel. Pre-drilled holes let you run a masonry screw or a Tapcon into the slab, which is permanent and effective, and needs a hammer drill and a bit you may not own. Adhesive plates hold on clean concrete and let go after a freeze-thaw cycle. For a rental unit, removable is the only option, and in that case plan on a rubber mat underneath.
Shimming is normal. Very few thresholds are dead level across the width, and a ramp that rocks will eventually crack at a weld or walk itself out of position. Use solid plastic or aluminum shims, not folded cardboard, and check the ramp with a level again after you’ve rolled something heavy across it once.
One detail that earns its keep: run a bead of exterior sealant along the top edge where the ramp meets the threshold, if the door is exposed to weather. Water that gets under the ramp in winter freezes, expands, and lifts the whole assembly. Five minutes in October saves a repair in March.
If the ramp sits on a wooden porch instead of concrete, use screws rather than adhesive, and check that the boards under it are sound. A ramp bolted into a soft or rotten board will pull out the first time a loaded chair rolls onto it, and it will do that without warning.
When a threshold ramp is the wrong answer
Here’s the honest part. An aluminum threshold ramp solves transitions up to about 4 inches, and past that it stops being a threshold ramp and becomes a poor imitation of a real ramp. A 6-inch rise at 1:8 is 48 inches long, which is a piece of equipment sitting in your doorway rather than a plate you step over.
Anything above roughly 6 inches needs the full treatment: a proper slope at 1:12, level landings at the top and bottom, handrails on both sides at 34 to 38 inches, and usually a permit. The 2010 ADA Standards for Accessible Design spell out the run limits, the 30-inch maximum rise between landings, and the 60 by 60 inch landing size. Those rules exist because a long steep ramp is where chairs tip backward and where caregivers hurt their backs.
There are also sites where no ramp works well. Loose gravel, a steeply crowned driveway, a doorway at the bottom of outdoor stairs, or a threshold that ices over every January. In those cases the answer is usually to change the route rather than the hardware. A different door, a poured pad, or a platform at the right height beats a ramp that has to fight the ground.
And if the person using it has limited trunk control, or drives a power chair with a high center of gravity, get advice from an occupational therapist before you buy. A ramp that suits one chair and one user can be risky for another, and no product page can tell you which case you’re in. That’s not a sales pitch, it’s just true.
There’s a cost angle too, and it usually decides the question for you. A custom 1:12 ramp with landings and rails runs into real money and weeks of waiting, while a threshold ramp is a same-week purchase. When the rise is under 3 inches, spending the difference on a wider doorway or a better door closer will buy more usable access than a longer ramp ever would.
For a business entrance, the calculation is different. An accessible route that doesn’t meet the slope rules is a compliance problem, not a convenience problem, and a portable plate in front of a commercial door tends to walk away or get left in the wrong place. Talk to whoever handles the building before you buy hardware for a doorway the public uses.
What to have in hand before you order
Five numbers, written down. The rise at the highest point of the threshold. The width of the opening between the jambs. The clearance under the door leaf when it’s closed. The diameter of the front casters. The slope of the ground on the low side, which you can eyeball with a level and a ruler.
With those five, you can choose a length honestly, confirm the door will still close, and know whether the thing has to be anchored. Without them you’re guessing at the one dimension that decides whether the aluminum threshold ramp makes the doorway usable or just makes it look accessible.
Most buyers skip the door clearance and the caster size. Those are the two that generate complaints, and they’re both measurable in under a minute with a tape and a pencil. The ramp itself rarely fails. The doorway around it does.
Ask the seller for the loaded weight and the rated capacity in writing, per ramp rather than per pair. If a listing won’t state a rating at all, treat that silence as information. Returns on a 30 lb item are annoying enough that most people keep a ramp they can’t use, which is the worst outcome of the whole process and the easiest one to avoid with two minutes of measuring.
If you’re still working out the wider picture, the aluminum ramp buying guide covers length, capacity and slope math from the ground up. The piece on sizing a wheelchair ramp to the chair and the pusher goes deeper into the human side of that decision. If a permit or a public entrance is involved, read permits, placement, and what a ramp won’t fix first. For a vehicle instead of a doorway, the folding aluminum ramp guide covers hinge wear and the loading ramp guide handles trailer decks. You can browse current stock in the shop or read more on the blog.
