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The Published Dimensions
There is a precise, public dimensional standard for this. It governs facilities covered by the ADA rather than private homes, which makes it a reference rather than a requirement — and a good one.
Quick answer
The ADA standards give exact heights, diameters and clearances for bathtub grab bars. They apply to public accommodations rather than to houses, but they are the only dimensioned published reference available, which is why they are worth reading before fitting one.
Source: US Access Board, ADA Standards, Chapter 6: Bathing Rooms.
What the standard says for a bathtub
| Element | Dimension |
|---|---|
| Grab bar height, to top of gripping surface | 33–36 in |
| Lower back-wall bar, above the tub rim | 8–10 in |
| Circular bar diameter | 1¼–2 in |
| Clearance from the wall (absolute) | 1½ in |
| Control end wall bar | 24 in minimum |
| Back wall bars (two, parallel) | 24 in minimum each |
| Head end wall bar | 12 in minimum |
A removable in-tub seat or a permanent seat at the head end is also required; removable seats are 15 to 16 inches deep and 17 to 19 inches high.
Source: US Access Board, ADA Standards, Chapter 6: Bathing Rooms.
And the scope, which matters
These are the ADA standards. They apply to facilities covered by the ADA, not to private dwellings. Nothing here says a house must meet them, and anybody who tells you a home grab bar is "ADA required" is wrong.
What they are is a set of dimensions worked out carefully by people who had to get it right, available free, and a better reference than guessing.
The one that surprises people
The 1½ inch clearance from the wall is an absolute dimension rather than a minimum. Closer and a hand cannot get round the bar; further and an arm can pass behind it, which is its own hazard.
What actually holds a grab bar up
Not the tile, and not a hollow wall. A bar has to land in framing or in blocking installed for it, and that is why fitting one properly is a job rather than a purchase.
It is also the one moment when it costs least: while the wall is already open for other work.
Where to put it, given the research
At the exit. CDC found 37.3% of bathroom injuries happened bathing, showering or getting out, against 2.2% getting in, so a handhold positioned for the way out is doing most of the available good.
Source: CDC, MMWR: Nonfatal Bathroom Injuries Among Persons Aged ≥15 Years, United States, 2008.
Changing a tub is mostly about what is behind it.Tell us what you want done and we will route you to a contractor in your area, found from your ZIP code, who can look at the wall and the floor before quoting. No charge to you, and we will not ask you why. Anything else needing a plumber is fine to bring up while we have you.
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