How Far Apart Should Stair Rails and Railing Posts Be?

“How far apart” means three different things on a staircase: how far apart the newel posts go, how far apart the balusters go, and how far apart two handrails can be. Short answers: put a newel or stabilizer post about every 8 feet, keep baluster gaps under 4 inches, and leave at least 27 inches of clear width between two handrails. Details below.

By Douglas Lovin, owner of Cheap Stair Parts, 20+ years in stair parts · Updated 10/22/26

Quick answers

Question	Answer
Distance between newel posts	About 8 ft ideally. Add a stabilizer post on longer runs.
Gap between balusters	Less than 4″ (a 4″ ball should not pass through)
Gap on the stair section of the rail	Less than 4-3/8″ under the IRC
Clear width between two handrails	At least 27″
Clear width, one handrail to wall	At least 31-1/2″
Handrail height	34″ to 38″ above the stair nosing
Guard height at a landing or balcony	At least 36″

The code numbers above come from the International Residential Code (IRC), which most U.S. towns use for houses. Your local code can be stricter, so check with your building department before you build.

How far apart should newel posts be?

We tell customers to put a newel support post about every 8 feet. The code does not give a maximum distance between posts. It sets a strength rule instead: a guard or handrail has to hold a 200 lb load. The longer the rail runs without support, the more it flexes, and a wobbly rail is the first thing people notice.

On a long balcony or landing run, you do not have to break the rail with a full newel post. A stabilizer post is a post that goes under the rail for support on longer runs. The rail keeps running over the top of it.

• Rail run up to about 8 ft: posts at each end are enough.
• Rail run of 8 to 16 ft: add 1 stabilizer post.
• Rail run of 16 to 20 ft: add 2 stabilizer posts. We sell handrail up to 20 ft long, so a full 20 ft rail gets 2 stabilizers.

Stabilizer options include the 4000-SP blank stabilizer newel, the 4010-SP-E stabilizer newel and the 4592-SP stabilizer post. For installing posts, see how to install a wood newel post.

How far apart should balusters be?

Balusters (spindles) have to be close enough that a 4″ sphere cannot pass between them. On the sloped stair section, the IRC allows up to 4-3/8″. In practice, most stairs use 3 balusters per tread, which keeps you under the limit on a standard tread.

The triangle under the bottom rail, formed by the tread and riser, has its own rule: a 6″ sphere should not pass through.

For layout, see the baluster measuring and spacing diagram. For horizontal bar railings, see the horizontal bar spacing guide.

How far apart should two handrails be?

The IRC requires stairs to be at least 36″ wide. Handrails can stick out up to 4-1/2″ from each side, which leaves:

• At least 27″ of clear width between two handrails.
• At least 31-1/2″ of clear width between one handrail and the opposite wall.

Wall-mounted handrails also need at least 1-1/2″ between the rail and the wall so a hand fits around it. See how to attach a railing to the wall.

Railing height

Handrails go 34″ to 38″ above the stair nosing. Guards at landings and balconies go at least 36″ high where the drop is more than 30″. See how tall balusters should be.