How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

Is all cloth wiring dangerous?

Friday, January 31, 2020

Electrical wiring insulation has gone through multiple upgrades over the years, primarily for fire resistance. Wiring up until the mid-20th century was insulated with rubber embedded with cloth, which some electricians call “rag wiring.” The material had two safety problems: 

1) The rubber hardens, cracks, and pieces start to break off over time, especially in a hot attic.

2) The cloth-rubber combination has a low thermal resistance and can melt or catch fire when the wires overheat.

    Thermoplastic insulation was introduced in the 1950s for wiring, and it has a higher thermal resistance than the cloth-rubber. The cable bundle was still wrapped in cloth and, although the newer insulation is safer, it can be difficult to differentiate from the older wiring. It’s important to be able to tell the difference, because some insurance companies do not want to write homeowner’s policies on old homes with cloth-rubber insulated wiring because of the fire risk, but consider the thermoplastic insulated wire in a cloth-sheathed cable acceptable. Others consider cloth-covered wiring okay as long as the cloth/rubber insulation is not deteriorated.

    Here’s some more examples below. 

   Newer non-metallic cable has a nylon/plastic sheathing and an example is at the yellow arrow above. Also, since 1986, the formulation for the thermal resistance of the plastic insulation was improved to withstand a temperature of 90º C (equivalent to 194º  F). 

    The older cloth-sheathed cable, although it has thermoplastic insulation on the individual wires, deteriorates and can fray over time in an attic, like in the photo below.

    So, if an inspector tells you that you have cloth wiring, be sure to get clarification as to whether it is cloth/rubber insulation (often bad for insurance) or cloth-sheathed cable with older thermoplastic insulation (not great, but  more acceptable).

    Also, if you have wiring that looks like this in the attic or crawl space of your home, it’s called “knob-and-tube,” and the insurance company will definitely want it replaced. See our blog posts What is "knob and tube" wiring? and What is rag wiring? to learn more. 

    If your old wiring is deemed unacceptable by an insurance company based on a home inspector’s four-point inspection report, you still have the option to hire an electrician to report on their professional opinion of the condtion of the wiring—which may sway the underwriter to drop the objection and offer to insure the property without replacement of the wiring—or not.

• • • • • • • • • • • • • • • • • • • • • • • • • • •

Here’s links to a collection of our other blog posts about ELECTRICAL WIRING:

Which house appliances need a dedicated electrical circuit?

Can a short circuit cause a high electric bill?

What is the maximum spacing requirement for securing NM-cable (nonmetallic-sheathed cable)?

Is it alright to just put wire nuts on the end of unused or abandoned NM-cable or wiring?

What causes copper wires to turn green or black in an electric panel?  

What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?

Why is it unsafe to bond neutral and ground wiring at subpanels?

Should I get a lightning rod system to protect my house?

Why is a strain relief clamp necessary for the cord connection to some electric appliances?  

Does a wire nut connection need to be wrapped with electrical tape?

What is the minimum clearance of overhead electric service drop wires above a house roof?

What are the requirements for NM-cables entering an electric panel box? 

What is the color code for NM cable (Romex®) sheathing?

Why are old electrical components not always "grandfathered" as acceptable by home inspectors?

How can I find out the size of the electric service to a house?

Can old electrical wiring go bad inside a wall? 

What is an open electrical splice?

What are the most common electrical defects found in a home inspection? 

What is the life expectancy of electrical wiring in a house? 

What is an "open junction box"? 

How dangerous is old electrical wiring? 

What is a ground wire? 

I heard that aluminum wiring is bad. How do you check for aluminum wiring?  

What is the code requirement for receptacle outlets in a closet?

   Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Water Heaters

Water Heater Age

"What Are The

Signs Of..."

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests



When It First

Became Code

"Should I Buy A..."

Park Model Homes


Shingle Roofs




Wind Mitigation

Roof and Attic

"Does A Home


Pool and Spa

"What Is The Difference Between..."




Concrete and

Concrete Block

Metal Roofs


Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants


Older and

Historic Houses

Crawl Spaces

Mobile-Manufactured Homes

Building Permits

Life Expectancy

Clay Soil





Exterior Walls

& Structures


Common Problems

HUD-Code for

Mobile Homes

Garages and Carports

Flat (Low Slope) Roofs

Electrical Panels

Sprinkler Systems

Electrical Receptacle Outlets

4-Point Inspections

Hurricane Resistance

Frequently Asked Questions (FAQ)

Home Inspection

Heating and Air Conditioning

Building Codes

Fireplaces and Chimneys

Inspector Licensing

& Standards

Energy Efficiency

Washers and Dryers



Doors and Windows



Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps


Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.






Air Conditioner & Furnace Age/Size


Electrical Switches





Water Intrusion

Electrical - Old

and Obsolete


Foundation Certifications

Tiny Houses

About McGarry and Madsen



Buying a home in North/Central Florida? Check our price for a  team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.

Moisture Problems

Crawl Spaces