How to Lay Out an Entry Ramp

Why this matters

A ramp is mostly arithmetic, and the arithmetic is unforgiving in one direction: every inch of rise you under-measure becomes a foot of ramp you did not plan for. Measure 21 inches when the true rise is 23 and the ramp is two feet short, which you discover when the last section lands steeper than everything before it, exactly at the bottom where a wheelchair user is braking or a caregiver is pushing hardest. The layout below is done on paper before a post hole is dug, so the lot, the permit and the person can each say no while saying no is still cheap.

Whether a ramp is even the right answer (versus regrading a path, a platform lift, or using a different door) is decided in the assessment: see related, The Accessibility Walkthrough With the Person Who Lives There and Accessible Entries and Outdoor Paths. This article starts once a ramp is chosen.

Step 1: Measure the rise where the ramp will land, not at the bottom step

The rise is the vertical distance from the top of the door threshold (or the porch surface the person rolls onto) down to the ground where the ramp ends. Not to the ground at the foot of the existing steps, which is usually higher than the ground twenty feet out, because yards slope away from houses on purpose.

How to measure it properly:

1. Set a straight board or a long level on the porch surface at the door and extend it out level, or use a laser level or a water level for longer distances.
2. Measure down to grade at the foot of the steps, then again at roughly where you expect the ramp to end.
3. Use the larger figure for the layout, then re-check it once the layout tells you where the ramp actually ends. If grade falls another inch over the extra length, the run grows again; recompute until it stops moving.

What breaks if you skip it: the error compounds. At 1:12, every inch of rise the ground drops adds a foot of ramp, which lands even lower, which adds a little more.

In this example: the porch is 21 inches above grade at the foot of the steps. Measured out at 20 feet along the walk, grade is within 1/4 inch of the same level, so 21 inches holds.

Step 2: Compute the run from the slope, and pick the slope for the person

Slope is rise over run, written as a ratio. 1:12 means one inch of rise for every 12 inches of horizontal run. It is the steepest ramp the IRC permits as a general rule (R311.8.1, as adopted by your jurisdiction; it allows steeper only where 1:12 is technically infeasible), and it is the maximum the 2010 ADA Standards use at 405.2, which in a private home is a reference, not a requirement.

1:12 is a ceiling, not a target. A strong manual-chair user handles it; a person with weaker arms, a caregiver pushing a heavy power chair up in the rain, or a walker user going down may need 1:16 or 1:20. Ask, and if you can, have the person try a rented modular ramp section at the slope you plan before you commit lumber to it. See related, The Ramp That Met Every Number and Still Did Not Work.

The 2010 ADA Standards also limit a single run to 30 inches of rise before a landing (405.6). At 21 inches you could do it in one run, which matters for the next step.

Step 3: Plan landings and turns, then fit it to the lot

Landings are the flat rests. You need one at the top (where the person turns to open and get through the door), one at the bottom, and one at every change in direction.

• The IRC requires landings at least 3 feet by 3 feet at the top and bottom, where a door opens onto the ramp, and where the ramp changes direction (R311.8.2, as adopted).
• The 2010 ADA Standards use a landing at least 60 inches long and at least as wide as the ramp, and 60 by 60 inches where the ramp changes direction (405.7). A wheelchair needs that 60 inches to turn, and 36 inches is too tight to get a chair turned and a storm door opened.

Use 60 inches. The IRC minimum is what passes inspection; the ADA reference is what a wheelchair can actually turn on.

Width: the 2010 ADA Standards use 36 inches of clear width between handrails (405.5), so with rails on both sides the deck itself is wider than 36 inches by the rail brackets and posts.

Here is the layout on paper, first straight and then folded to fit:

RISE  21 in at 1:12 -> RUN = 21 x 12 = 252 in = 21 ft

STRAIGHT
  top landing     60 in
  run            252 in   (one run, rise 21 in, under 30)
  bottom landing  60 in
  total          372 in = 31 ft out from the house
  lot: 24 ft from wall to sidewalk -> does NOT fit

L-TURN, two equal runs
  rise per run    21 / 2 = 10.5 in
  run each        10.5 x 12 = 126 in = 10.5 ft
  top landing     60 x 60 at the door
  run 1          126 in along the house wall
  turn landing    60 x 60
  run 2          126 in toward the sidewalk
  bottom landing  60 in
  along house     60 + 126 + 60 = 246 in = 20.5 ft
  out from house  60 + 126 + 60 = 246 in = 20.5 ft
  path length     60+126+60+126+60 = 432 in = 36 ft
  check: 20.5 ft out fits the 24 ft lot

Two numbers in that block are worth noticing. The fold costs 60 inches of extra path for the turn landing, so the person travels 36 feet, not 31, to cover the same 21 inches. And the L needs 20.5 feet of clear wall along the house front, which this house has only because the door sits near one corner. A door in the middle of a 30-foot front could take the turn either way; a door at an inside corner could not take it at all, and that is where a switchback (two runs folded back on themselves around a 60-by-60 landing) or a lift comes in.

What breaks if you skip it: a ramp designed straight and then bent on site to miss a bush or a property line, with the turn squeezed into a 48-inch landing a chair cannot turn on.

Step 4: Check the permit, the setbacks and the edges before you buy lumber

Permit. A ramp at an entry door almost always needs a building permit. The IRC's exemption for small low decks (R105.2, as adopted) applies only to decks that are not attached to the dwelling, are 30 inches or less above grade, and do not serve the required exit door. A ramp to the front door serves the exit door, so the exemption does not reach it, whatever its height. Some jurisdictions run an expedited accessibility permit; ask.

Setbacks and the lot. A ramp that extends toward the street can push into a zoning setback. Some cities exempt accessibility ramps from setbacks or approve them administratively; others require a variance. Check before you draw the final layout, and check with an HOA if there is one. If the customer is a tenant, the landlord's permission and the Fair Housing Act's modification rules come first: see related, Reasonable Modifications for Tenants.

Rails and edges. Plan these on the drawing because they change the footprint:

• Handrails. The IRC requires a handrail on at least one side of a ramp steeper than 1:12 (R311.8.3, as adopted), so a ramp at exactly 1:12 may pass without one. The 2010 ADA Standards use rails on both sides of any run rising more than 6 inches (405.8). Each run here rises 10.5 inches; put rails on both sides, continuous through the turn landing.
• Guards. The IRC requires guards where the walking surface is more than 30 inches above grade within 36 inches horizontally (R312.1.1, as adopted). This ramp tops out at 21 inches, so no guard is required, but the rail posts still need to be framed in.
• Edge protection. Keep a wheel from rolling off the side. The 2010 ADA Standards use either a curb or barrier low enough that a 4-inch sphere cannot pass under it, or a surface extending 12 inches past the inside face of the rail (405.9). A 2x4 curb along the deck edge is the usual answer.
• Cross slope. No more than 1:48 side to side on the run and the landings (405.3 and 405.7.1 in the 2010 ADA Standards). A ramp that tilts sideways steers a chair into the rail.

Step 5: Set the footings below frost and plan the structure off the layout

A ramp is a long, low deck, and it moves the way decks move: on frost heave and on settling footings, not on its lumber.

• Footing depth. Bottom of footing below the frost depth your jurisdiction sets (IRC R403.1.4, as adopted). In a cold region that can be several feet down; in a mild one, a foot. A ramp on blocks set on the lawn heaves in its first winter and the transition at the porch develops a lip.
• Post spacing comes from the beam and joist span tables for the lumber you use (the deck provisions in IRC R507, as adopted, are what most departments apply to a wood ramp). Lay out footings at both ends of each landing and at intervals along each run that the beam span allows.
• At the house. Either ledger-attach to the house's rim with the flashing and fastening R507 calls for, or set a row of posts a short distance off the foundation and keep the ramp free-standing. The free-standing version avoids a new penetration and a leak path at the rim; the ledger version saves a row of footings.
• Dig safely. Call the one-call utility locate before digging, wait for marks, and hand-dig inside the tolerance zone around any mark. If a line is struck, stop, keep everyone back, and for gas, leave the area and call the utility's emergency number from a distance; do not try to plug it or start an engine nearby.

In this example: the jurisdiction's frost depth is 36 inches. The L takes footings at the four corners of the top landing (two of them shared with run 1), at the four corners of the turn landing, at the bottom landing, and two intermediate pairs along each 10.5-foot run where the beam span requires them. The ramp is free-standing, with its first row of posts 12 inches off the foundation, which moves the bottom landing out to 246 + 12 = 258 inches, 21.5 feet, still inside the 24-foot lot.

The joint at the door. The last half inch is where ramps fail their user. The 2010 ADA Standards use a maximum vertical change of 1/4 inch, or 1/2 inch beveled at 1:2 (303.2 and 303.3); see related, Thresholds and Changes in Level. Build the top landing to meet the threshold, not the porch surface below it.

How to know the layout worked

Before the deck boards go on, set a 2-foot level with a 2-inch shim at one end on each run: a 1:12 ramp is exactly 2 inches of drop over 24 inches. Check three places on each run, plus the cross slope. After the boards go on, have the person use it: up, the turn, and down, with whoever pushes them. Watch the turn landing in particular; if they back and fill to get around it, it is too small, whatever the drawing said.

References

• IRC Sections R105.2, R311.8, R312.1.1, R403.1.4 and R507, as adopted by your jurisdiction; check numbering for your edition.
• 2010 ADA Standards for Accessible Design, 303, 405 and 505, used as a dimensional reference only in a private home.
• Your state's one-call utility locating service, before any digging.
• See related: Ramp Slope, Rise and Landings; The Ramp That Met Every Number and Still Did Not Work; Thresholds and Changes in Level; Reasonable Modifications for Tenants.