There are several methods of how to install a newel post but the first step is cutting the stair newel post to the correct height.  This height depends on the standard handrail height for your balustrade which is based on the building codes for your area.  Typically floor level balustrades must be at least 36” high or 42” high, depending on local codes and stair guardrails must be between 34” and 38”.  While these are the typical requirements as established by the International Residential Code, they do vary by area so make sure you know the building codes that apply to stair installation in your area before you proceed.

Calculating the newel post height is the first step in newel post installation.  The two most common scenarios are floor level posts and posts at the start of a stair.  A third scenario is installing newel posts with winder treads but this is a little more complicated so I will address this in a future post.  So stay tuned 🙂

When using turned newel posts the objective in all scenarios is to have the stair handrails terminate into the center of the top block.  If you are using box newels then there may or may not be a space that is visually defined by a molding as the “top block”.   If your newel post does not have this then there is no real rule, the handrail simply terminates somewhere near the top of the newel post.  In the other scenarios, when there is some type of visual top block the calculation is fairly simple.  Using the following formula will center the stair handrail in the top block.

Floor level newel post heights are calculated to place the stair handrail in the center of the top block using the following formula:  Post Height  =  Bottom of Rail Height  + (Rail ÷ 2) + (Top Block ÷ 2) + Cap Mold (If applicable)

**Remember if you are using a turned newel post or a box newel post without cap molding then this measurement will not be part of the formula.  Also, you must add the shoe thickness if newel post does NOT sit on top of shoe.

The following example is using a box newel post and 2 ⅛” – 6701 large traditional handrail with a finished stair handrail height of 37” and the post sitting atop the shoe:

34.875  +  (2.125 ÷ 2) + (6  ÷  2)  +  1.25   =   40.1875 or 40 3/16” to the Top of the Block (Bottom of Post Cap)

Newel Post Heights at the start of the stair are calculated as follows.  The following example is assuming a 37” high stair rail.

1. Mark the top block where the center of the stair handrail will terminate into the newel post.
2. Figure where the top of the handrail will be, you can do this by placing a piece of the handrail on the stair tread nosings then plumbing up to get the thickness of the handrail on the pitch.  Then divide this number in half and add that distance to the center mark from above.  This is where the top of the rail will be.
3. Set stair newel post in place with the mark facing up the stairs and mark the tangent line of the stair tread nosings  – – – – as shown on the bottom block.
4. Measure down from the mark for the top of the rail 37” and mark the post again.
5. Measure between the 37” mark on the bottom block and the tangent line and cut that amount “X” off the bottom of the post.  You now have your starting newel.

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