Knob & Tube Wiring in St. Louis

Knob & Tube Wiring in St. Louis Homes

The concentration of knob and tube wiring in the St. Louis area follows the city's development history closely. Older neighborhoods in St. Louis City and the inner-ring suburbs of St. Louis County are where this wiring is most consistently found. Communities like Affton, Overland, and University City, along with older pockets of St. Charles and Pacific in Franklin County, all have housing stock from this era.

In many cases, knob and tube wiring has been partially updated over the years. For example, a former owner of a home may have rewired the kitchen and bathrooms while leaving the bedrooms and attic runs untouched. This partial work can complicate things, because mixed systems sometimes create grounding and compatibility issues that need to be sorted out as part of the remediation process. A thorough inspection documents exactly what's present before any plan is developed. 

The Risks of Knob & Tube Wiring 

Knob and tube wiring gets its name from the ceramic knobs used to anchor wire runs and the ceramic tubes threaded through joists to protect the wire where it passes through wood. The system was functional for its time, but it has three fundamental problems by today's standards.

First, it has no ground wire. Modern electrical systems use a ground conductor to redirect fault current away from people and devices safely. Knob and tube has two conductors (hot and neutral) and nothing else. This means that any outlet or device on a knob and tube circuit cannot be properly grounded, which limits the protection available and rules out the use of GFCI outlets on those circuits without additional work.

Second, the insulation on knob and tube wire was typically made from rubber and cloth, both of which become brittle and crack with age. A wire installed a century ago and never touched may look intact from a distance, but the insulation condition up close often tells a different story. Damaged insulation in a wall cavity or attic is a serious fire risk.

Third, knob and tube wiring depends on free air circulation to dissipate heat. Decades of attic insulation additions, a common energy upgrade in older St. Louis homes, can bury knob and tube runs and prevent that heat from escaping, creating another pathway to overheating and fire.