Hand Railing & Retrofit is a topic that has been around for years.
More and more insurance carriers are less agreeable to allow older railings that have horizontal or wider slats stay in place if they are going to insure the property.
The issue is referred to as the ” Ladder Effect”are not up to code
There has been much discussion over the years about the safety of horizontal infill on guardrails because of what is perceived as the “ladder effect” that horizontal or decorative infill patterns create. In fact, the first edition of the International Code Council’s (ICC) Residential Building Code (IRC), issued back in 2000, included wording that restricted the use of horizontal and decorative patterns. However, the International Code Council’s Code Technology Committee (CTC), after detailed research and discussion with industry experts, removed the “ladder effect” wording a year later in the first IRC Supplement issued in 2001. And any wording referring to “ladder effect” has never returned. It’s also important to note, that the ICC’s Commercial Code (IBC) has never had any wording that restricted the use of horizontals or decorative infill patterns. (http://www.feeneyinc.com/site/resources_dealers/binder_docs/Intl_Building_Codes.pdf)
If you have a building with wider railings and you are facing the cost of retro fit, you may want to consider the wire mesh in the video. Ask your insurance carrier if this would be satisfactory.
I found the manufacturer; https://www.jakob-usa.com/wire-mesh-2/. The representative on the phone was very helpful and able to provide price ranges depending on possible solutions.