What is the steepest ramp the IRC allows at a house?

It depends on the ramp. A ramp that serves the required exit door can be no steeper than 1 in 12 (1:12, or 8.3%). Any other ramp at the house can be up to 1 in 8 (1:8, or 12.5%). So the exit ramp is the strict one.

When do I need a handrail on a ramp?

You need a handrail on at least one side once a ramp is steeper than 1:12. If the ramp is 1:12 or flatter, the IRC does not require a handrail. When one is required, the top of the handrail sits 34 to 38 inches (864 to 965 mm) above the ramp.

How big do the landings have to be?

A landing at least 3 ft by 3 ft (914 mm by 914 mm) goes at the top and bottom of the ramp, wherever a door opens onto the ramp, and wherever the ramp changes direction. The landing width across the ramp is at least 36 inches.

Is there a maximum rise before I have to add a landing?

Not in the residential IRC. R311.8 only calls for landings at the top and bottom, at doors, and where the ramp turns. There is no code-set limit on how much a single straight run can climb, as long as the slope and handrail rules are met. (Commercial ramps under the IBC and ADA are different.)

Does the IRC even apply to my job?

Only if your state or town has adopted it. The IRC is a model code with no force on its own. Editions in use range from 2015 to 2024, and some places amend the ramp slope. Always confirm the edition and any local changes for your jurisdiction.

In this section

US Ramp Slopes (IRC R311.8)

The IRC's 1:12 maximum for an egress ramp, the steeper 1:8 allowed elsewhere, landings and when a handrail is required.

IRC 2021 Clause IRC R311.8

The requirement

The ramp serving the required exit door can be no steeper than 1:12 (8.3%). Any other ramp at the house can be up to 1:8 (12.5%). So the exit-door ramp is the strict one. The rest get more room.

1:12 means 1 unit up for every 12 along. 1:8 means 1 unit up for every 8 along. The IRC sets both lines:

The ramp	Steepest slope allowed
The ramp serving the required exit door	1:12 (8.3%)
Any other ramp at the house	1:8 (12.5%)

Landings

The flat spot at each end of the ramp is the landing. Each landing must be at least 3 ft by 3 ft (914 mm by 914 mm). You need one:

at the top and bottom of each ramp,
wherever a door opens onto the ramp, and
wherever the ramp changes direction.

Across the ramp, the landing is at least 36 in wide.

Handrails

A handrail is only needed once the ramp gets steep. Steeper than 1:12, and you need a handrail on at least one side. At 1:12 or flatter, the IRC does not ask for one at all.

When you do need a handrail, the top of it sits 34 to 38 in (864 to 965 mm) above the ramp. The IRC does not give the grip size here. How thick the rail is to hold comes from the stair-handrail rule. Check R311.7.8.5.

Is there a maximum rise before a landing?

No, not for a house. This surprises people, so it is worth saying plainly. The residential IRC sets no limit on how far a single ramp run can climb before a landing. You add landings at the top, at the bottom, at doors, and where the ramp turns. That is it. A long straight run of any rise is allowed. The slope and handrail rules above still apply.

Commercial ramps are different. Under the IBC and ADA, a single run is capped at 30 in of rise. That is not the residential IRC rule.

IRC R311.8

Work it out on site

Say you are building the ramp to the required exit door. The door sits 24 in above the ground. How long does the ramp need to be at 1:12?

Pick the slope. An exit-door ramp can be 1:12 at the steepest. That is 1 unit up for every 12 units along.
Do the math. 24 in up × 12 = 288 in, which is 24 ft of ramp run. That 24 ft is just the math of this example, not a code number.
Add the landings. A 3 ft by 3 ft landing goes at the top and the bottom. The house code sets no limit on the run length between them. One straight run is fine here.
Handrail? At exactly 1:12 the ramp is not steeper than 1:12. So the IRC does not require a handrail. Build steeper and it would.

So: about 24 ft of ramp at 1:12, with a 3 ft by 3 ft landing at each end. The slope calculator does this rise-over-run math for you.

Do it in 5 seconds

Part of the US building codes for the trades — the hub, with the state-by-state adoption picture.
Building the stairs that ramp might replace? See the sibling stair and rail articles in the US building codes hub.

Sources

2021 IRC, Section R311.8 — Ramps (R311.8.1 Maximum slope, R311.8.2 Landings required, R311.8.3 Handrails required) — the 1:12 egress-ramp slope, the 1:8 slope for other ramps, the 3 ft × 3 ft landings, and the handrail trigger and 34–38 in height. Confirm at codes.iccsafe.org (also republished at up.codes/s/slope-of-ramps).
Handrail grip size — R311.8.3.2 defers to the stair-handrail grip rule at R311.7.8.5; check that clause rather than a number here.
Adoption caveat: The IRC is a model code with no legal force on its own. It applies only where a state or local jurisdiction adopts it, and adoption is often amended and edition-lagged — jurisdictions run editions from 2015 through 2024, and some amend the ramp slope locally. Always confirm the exact edition and any local amendments for your jurisdiction before you build.

More United States rules

Ramps in other countries

Frequently asked questions

What is the steepest ramp the IRC allows at a house?: It depends on the ramp. A ramp that serves the required exit door can be no steeper than 1 in 12 (1:12, or 8.3%). Any other ramp at the house can be up to 1 in 8 (1:8, or 12.5%). So the exit ramp is the strict one.
When do I need a handrail on a ramp?: You need a handrail on at least one side once a ramp is steeper than 1:12. If the ramp is 1:12 or flatter, the IRC does not require a handrail. When one is required, the top of the handrail sits 34 to 38 inches (864 to 965 mm) above the ramp.
How big do the landings have to be?: A landing at least 3 ft by 3 ft (914 mm by 914 mm) goes at the top and bottom of the ramp, wherever a door opens onto the ramp, and wherever the ramp changes direction. The landing width across the ramp is at least 36 inches.
Is there a maximum rise before I have to add a landing?: Not in the residential IRC. R311.8 only calls for landings at the top and bottom, at doors, and where the ramp turns. There is no code-set limit on how much a single straight run can climb, as long as the slope and handrail rules are met. (Commercial ramps under the IBC and ADA are different.)
Does the IRC even apply to my job?: Only if your state or town has adopted it. The IRC is a model code with no force on its own. Editions in use range from 2015 to 2024, and some places amend the ramp slope. Always confirm the edition and any local changes for your jurisdiction.