Your shed sits on a 4 inch (10 cm) concrete pad, and the floor deck lands about 9 inches (23 cm) above the grass. Not a cliff. Just enough that you lift the mower coming out and lift it again going back in, twice a week, from April to October.
So you laid a scrap 2×10 across the gap. It worked for a season. Then came three days of rain in late March, the bottom edge went soft where it touched the dirt, and one Saturday the board folded in the middle with the mower halfway up. Nobody got hurt. The mower got dropped. That’s the afternoon most people start shopping for an aluminum shed ramp.
This is the easy version of the ramp problem. You’re not chasing ADA compliance for a public building. You’re not fitting a wheelchair through a bathroom door. You’ve got a short rise, a known load, and one hard constraint that nobody mentions until it bites: the door swings out.
Get four numbers right and the rest is shopping. Get them wrong and you’ll own an aluminum shed ramp that’s too steep for a wheelbarrow, too short for the door, or too narrow for the mower deck.
Measure the rise where the wheels actually land
Everyone measures the wrong thing first. They put a tape on the shed floor from inside, read 9 inches, and order an aluminum shed ramp for a 9 inch rise. Then it arrives and the top lip sits on the door sill instead of under it, and the real climb turns out to be 10 and a half inches.
Measure outside, on the ground the ramp will actually rest on. Then measure up to the top of the surface the wheels roll onto, which is the shed floor deck, not the door threshold and not the siding trim. If your shed has a 1 inch (2.5 cm) saddle sill, that inch counts. Write the number down in inches and in centimeters, because half the listings you’ll compare use one and half use the other.
Do it in two spots. The ground along the shed wall is rarely level, and a ramp that’s flush at one corner can hang 2 inches in the air at the other. If the pad has settled, your effective rise changes across the width of the doorway.
Now multiply. One inch of rise needs 12 inches of run at a 1:12 slope, which is the number the 2010 ADA Standards use for public buildings. Nine inches of rise at 1:12 is 108 inches, or 9 feet (2.7 m) of ramp outside a garden shed. Almost nobody builds that. It’s worth knowing the reference anyway, because it tells you how much you’re giving up when you shorten things.
At 1:8, the same 9 inches needs 72 inches (1.8 m). At 1:4, it needs 36 inches (0.9 m), and 1:4 is roughly where a walk-behind mower starts to feel like work instead of a roll.
If you want the longer version of this math, including how capacity and slope interact once a person is on the ramp, the aluminum ramp buying guide walks through it with worked examples.
Build a small list before you look at a single product page:
- 6 inch rise (15 cm): 48 in at 1:8, 24 in at 1:4
- 9 inch rise (23 cm): 72 in at 1:8, 36 in at 1:4
- 12 inch rise (30 cm): 96 in at 1:8, 48 in at 1:4
- 18 inch rise (46 cm): 144 in at 1:8, 72 in at 1:4
That table is the whole sizing argument in four rows. Longer is gentler and takes more yard. Shorter fits the space and asks more of your legs.
The slope depends on what’s rolling up, not on code
An aluminum shed ramp doesn’t have one correct angle. It has an angle that suits the wheels. Change the wheels and the answer changes, which is why two neighbors with identical sheds can both be right with ramps of different lengths.
A 21 inch push mower with 8 inch rear wheels rolls up 1:4 without complaint. The wheels are big enough to bridge the transition at the bottom, and you’re pushing, not carrying. A loaded wheelbarrow is a different animal. Most of the weight sits on two small wheels and two handles, and once the slope passes about 1:5 you start fighting it with your arms instead of your legs.
A hand truck with a fridge on it wants something closer to 1:6, and two people. A snowblower wants width more than it wants a gentle slope, because the auger housing is wide and the thing is top heavy. An ATV or a riding mower wants a deck wide enough that you’re not steering with one wheel off the edge.
Here’s the honest part. Aluminum gets a reputation as the non-slip option, and that reputation is only half earned. Punched deck plate and extruded traction ribs do grip better than wet pressure-treated lumber. But at 1:4, with wet grass clippings tracked onto the deck, no pattern saves you. You’ll feel the wheels break loose before the mower slides, and you’ll learn to blow the deck off before you push anything heavy up. Steep plus wet is the failure case for every material.
So pick the slope for the worst load you’ll actually move, not the average one. If the wheelbarrow comes out twice a year and you’re willing to make two trips, size for the mower and stop worrying. If you’re hauling firewood or bagged soil, add a foot or two of length and thank yourself later.
The same slope logic applies indoors, just with a chair instead of a mower. If your household also needs a ramp at a front door or a garage step, the piece on sizing an aluminum wheelchair ramp covers the part where the person pushing sets the limit, not the load.
One more thing about grade. A 1:4 slope is 25 percent. A 1:8 slope is 12.5 percent. Those percentages are what you’ll see in product listings, and the difference between them is not subtle when you’re the engine.
Your door swings out, and that changes the plan
This is the constraint that ruins more shed ramp purchases than slope does. Standard shed doors are outswing, single or double. An outswing door needs clearance on the outside, right where you just put a ramp.
The fix is a low-profile top lip. The ramp’s transition plate slides under the door, and the door swings over the top of it. That works, but only if the plate is thin enough. A quarter inch (6 mm) plate clears almost any door. A one inch lip does not, and you’ll find out when the door won’t close and the bottom corner is scraping aluminum.
Check three clearances before ordering:
- Gap under the door bottom to the shed floor: this is the maximum lip thickness you can use
- Height of the door bottom above the outside grade: the swing arc needs to clear the ramp deck
- Distance from the hinge side to the ramp edge: a door swinging across a ramp corner binds
If your door sits tight to the floor with no gap, you have two options. Cut a shallow notch in the sill and drop the plate into it, or mount the ramp so the plate sits on the floor inside the doorway and the deck runs out under the door. The second one means the door can’t close while the ramp is in place, so it only works for a ramp you leave set up.
Double doors add a middle post in most sheds. If yours has one, a single wide ramp means the post is now standing in the ramp, and your ramp becomes two narrow ramps with a gap between them. Measure the clear opening, not the door width.
If the ramp is serving a doorway someone in the house uses with a walker, the rules change again, and permits can enter the picture for anything that reads as a permanent structure. The guide to handicap ramp permits and placement is the one to read before you pour anything.
There’s an upside to a low lip, and it’s worth planning for. A 9 inch rise with a thin plate at the top and a mitered bottom edge is a ramp you can walk over in shoes without noticing. Get the lip wrong and every trip through that door becomes a small stumble, which is a strange thing to build into your own yard.
Width, edges, and the ramp that slides out from under you
Deck width is where people economize and regret it. A 30 inch (76 cm) deck fits a push mower with room to spare. A 24 inch deck fits it technically, and every trip you’ll be lining up the wheels like you’re parking a car.
If a riding mower or an ATV ever goes in that shed, go wider. Thirty six inches (91 cm) is the number that stops feeling tight. Wider decks cost more and weigh more, so don’t buy 48 inches for a wheelbarrow and a rake.
The ramp also has to stay where you put it. An aluminum shed ramp on a smooth concrete pad will skate. Every push up the slope pushes the deck away from the shed, and after a month you’re resetting it every time. Fix it with two anchors through the bottom flange, or a lip that hooks over the pad edge, or a rubber mat underneath if you want it removable. Bolting is the version that ends the problem.
Side edges matter more than most listings admit. A flat deck with no raised edge is fine for a mower. It’s not fine for a wheelbarrow you’re wrestling, because the wheel can walk off the side at knee height and dump a load of gravel onto your foot. A 2 inch (5 cm) turned-up edge rail does real work here, and so does a slight texture change at the border so you can feel the edge with your foot.
Check the cross slope too. A ramp that’s flat side to side is what you want. If the ground under it falls away, shim the low side or the whole deck twists, and a twisted aluminum deck will rock under load and eventually work its anchors loose.
One more width note for anyone loading a riding mower. Measure the outside of the rear tires, not the deck. A 42 inch deck on a mower with a 46 inch track won’t fit a 44 inch ramp, and the listing will happily sell you one.
Aluminum vs pressure-treated: the ten-year bill
Wood is cheaper on the day you buy it. A pressure-treated 2×10 and a couple of blocks costs less than any metal ramp you’ll find, and for a 9 inch rise that’s a real temptation. It also has a predictable lifespan in ground contact, and the end grain sitting in wet dirt is where it goes first.
Steel is the other option. Strong, cheap per pound, and it will rust anywhere the coating gets scratched, which on a shed ramp is the bottom edge and the area under the door where snow sits.
Aluminum sits in the middle on price and at the front on service life. Common ramp stock is 6061-T6, an alloy with good corrosion resistance and no need for paint. The Aluminum Association publishes the temper and alloy data if you want the metallurgy, but the practical version is simple: it doesn’t rot, it doesn’t need refinishing, and it weighs roughly a third of what the same steel ramp would.
It does have weaknesses, and they’re specific. Aluminum dents. Drop a loaded wheelbarrow off the side edge and you’ll put a permanent dip in the deck that catches a mower wheel every time after that. It also gets hot in direct summer sun, hot enough that bare feet on it in August is a bad idea. And it’s slick when wet with anything organic on it, which we already covered but deserves repeating because it’s the one people underestimate.
Cost per year is where the math flips. A treated lumber ramp replaced twice in fifteen years, plus the deck boards, plus an afternoon each time, usually lands near the price of one aluminum shed ramp bought once. If you’re staying in the house, aluminum wins. If you’re selling in two years, wood is defensible.
For buyers outside the US, the calculation adds a line. Aluminum doesn’t care about humidity the way wood does, and coastal air with salt in it is exactly the environment where treated lumber underperforms. That’s worth knowing if your shed is anywhere near water.
Three things that ruin a shed ramp in the first winter
Snow is the test that separates an aluminum shed ramp that lasts from one that doesn’t, and the failures are consistent.
The first is drainage. Water running down the slope hits the bottom edge of the ramp and, if the ground doesn’t fall away from it, pools there. Pooled water plus freeze cycles lifts the ramp and heaves the pad. Give the bottom of the ramp somewhere to drain, even if it’s a shallow gravel trench under the transition.
Shoveling is the next one. A metal snow shovel dragged across a punched aluminum deck will catch on every hole and tear at the plate edges. Use a plastic shovel, or shovel with the blade lifted, or accept that you’re sweeping rather than scraping.
Then there’s ice at the transition. The bottom lip is a small step, and small steps collect meltwater that refreezes overnight. Sand or a coarse grit on the deck through the winter is the boring fix that works. Don’t salt aluminum repeatedly if you can avoid it, because chloride is the one thing that will eventually go after it, especially at cut edges and fastener holes.
Worth doing in fall, before the first freeze: check the anchors, clear the deck, and look at the ground under the bottom lip. Ten minutes in October saves a morning in January.
There’s a fourth problem that isn’t the ramp’s fault at all, and it’s the one that gets people swearing in February. Snow drifts against the shed door and freezes into the gap between the door bottom and the top plate. You go out with a shovel, clear the deck, and the door still won’t budge because there’s a wedge of ice under it. Keep a putty knife or a stiff brush by the door, and clear that gap before the melt refreezes.
None of this is a reason to skip aluminum. It’s a reason to plan the drainage, keep the deck clear, and buy a plastic shovel. The ramp will outlast the shed if you do.
Ordering one: the numbers to write down
Before you look at a catalog, put these on a note and keep it in front of you. Rise in inches and centimeters. Run you can live with. Clear opening between door jambs. Maximum lip thickness the door will clear. Worst load going up, including the wheelbarrow. Whether it needs to come off seasonally.
Then match the load rating to the job. Ramp capacity figures vary a lot between models, and the honest answer is to use the manufacturer’s rating for the specific ramp rather than a rule of thumb. A ramp rated for a wheelchair and a ramp rated for a riding mower are built differently even when they look similar in a photo.
Length is the one place where custom sizing pays off. A 9 foot run at 1:8 is not a standard catalog length in most lines, and cutting a longer aluminum shed ramp down usually voids the rating and leaves you with a raw edge. If your rise lands between two stock sizes, order the longer one and let the extra foot sit at the bottom, where it costs you nothing but grass.
Two practical notes from the workshop side. First, most aluminum ramp suppliers will cut to a specified length if you ask, and the price difference between stock and cut-to-length is smaller than people expect. Second, if you’re buying from a factory overseas, the length that fits your container matters as much as the length that fits your yard. Long one-piece ramps ship badly. Shorter panels that bolt or hook together ship well, which is the same reason folding aluminum ramps exist in the first place.
Measure once more before you order. The 9 inches you wrote down in April is still 9 inches in June, but the ground under it moved, and the door you assumed swings clear might have a sagging hinge. It’s a five minute check, and it’s cheaper than return freight.
If you’d rather compare deck widths and lip styles side by side before committing, the ramp shop lists them by length. And if your shed project turns into a driveway or tailgate problem too, there’s more on the blog.
One last thought. The best shed ramp isn’t the strongest one you can buy. It’s the one that’s still bolted to the same pad in year eight, with a deck you can walk across in slippers without thinking about it.
