FHB Logo Facebook LinkedIn Email Pinterest Twitter Instagram Tiktok YouTube Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In
How-To

GFI outlets on wooden decks

By Rex Cauldwell Issue 119

Q:

I’ve been told that GFI outlets are not a shock deterrent on wooden decks. I work at a home center in San Diego where customers routinely purchase GFIs to replace the outlets on their boats. Is this application any different than a wooden deck, except when wet? What about RVs? Would you describe the way that the GFI functions in these situations so that I can give my customers good, informed advice about benefits and/or risks?

Danny Morgan, San Diego, CA

A:

Rex Cauldwell, a plumbing and electrical contractor in Copper Hill, Virginia, and author of Wiring a House , replies: GFIs do not need a ground to work. They compare the supply current in the black wire with the return current in the white wire. If a ground fault occurs, the circuit opens faster than a heartbeat, and the current stops flowing. But for the current to stop flowing, there has to be a ground fault.

A ground fault occurs when the hot-wire electrons are being taken to ground (earth), as opposed to going back to the panel via the white wire. Therefore, if you are on a dry insulator (such as a dry wooden deck) and you put your body across the black to white wires, the current flows out of the black wire, through you and into the white wire and back to the panel. No ground fault occurs. The GFI does not trip, and you will be toast.

If someone is on a boat dock and the dock is dry, and he puts himself between the black and white wires, the GFI will not trip. Again, he will be toast. The same is true with RVs. However, if a person is standing on the ground or on a wet dock or a wet deck, some electrons will flow to ground, the GFI will trip and try to save his life.

Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters
×

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

New Feature

Fine Homebuilding Forums

Ask questions, offer advice, and share your work

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Up Next

Video Shorts

Featured Story

The Fine Homebuilding Interview: Lloyd Alter

This author and architect discusses achieving carbon reduction in the home-building industry through radical sufficiency and using less.

Featured Video

A Modern California Home Wrapped in Rockwool Insulation for Energy Efficiency and Fire Resistance

The designer and builder of the 2018 Fine Homebuilding House detail why they chose mineral-wool batts and high-density boards for all of their insulation needs.

Related Stories

  • Dialing In a Job-Site Tablesaw
  • Protect Deck Joists
  • Flashing-Free Deck Ledger
  • Podcast 591: Members-only Aftershow—Hidden Costs of Construction

Discussion Forum

Recent Posts and Replies

  • |
  • |
  • |
  • |
  • |
  • |
View More Create Post

Highlights

Fine Homebuilding All Access
Fine Homebuilding Podcast
Tool Tech
Plus, get an extra 20% off with code GIFT20

"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Video

View All Videos
  • Podcast 591: Members-only Aftershow—Hidden Costs of Construction
  • Podcast 573: Vibrating Washers, Rot Behind Deck Ledgers, and Tightening Vented Crawlspaces
  • Podcast 549: Members-only Aftershow—Patios vs. Decks
  • Podcast 527: Sloping Decks, Brick-Filled Framing, and Skylights
View All

Decks

View All Decks Articles
  • Flashing-Free Deck Ledger
  • Podcast 573: Vibrating Washers, Rot Behind Deck Ledgers, and Tightening Vented Crawlspaces
  • Best Deck for a Steel Roof
  • Protect Board Ends to Prevent Rot
View All Decks Articles

BOOKS, DVDs, & MERCH

Shop the Store
  • 2022 Fine Homebuilding Archive
    Buy Now
  • Pretty Good House
    Buy Now
  • Code Check Complete 3rd Edition
    Buy Now
  • 2023 Tool Guide
    Buy Now
  • Shop the Store

Fine Homebuilding Magazine

  • Issue 318 - October 2023
    • Make Mudsills Square and Level
    • Turn Up the Heat With Induction Cooktops
    • The Fine Homebuilding Interview: Lloyd Alter
  • Issue 317 - Aug/Sept 2023
    • Finishing Drywall With Seamless Results
    • A Flat Roof in a Cold Climate
    • Compact Cordless Shop Vacs
  • Issue 316 - July 2023
    • Timber-Framed Solar Canopies
    • Build a Transom Above a Stock Door
    • Understanding Toilet Design and Efficiency
  • Issue 315 - June 2023
    • How to Craft a Copper Roof
    • 5 Lessons from Building in a Cold Climate
    • The Advantages of Cellular PVC Siding
  • Issue 314 - April/May 2023
    • 7 Options for Countertops
    • Tool Test: Wood-Boring Bits
    • Critical Details for Ductless Heat Pumps

Fine Homebuilding

Follow

  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok
  • twitter

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences

Taunton Network

  • Green Building Advisor
  • Fine Woodworking
  • Fine Gardening
  • Threads
  • About
  • Contact
  • Advertise
  • Careers
  • Copyright
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2023 The Taunton Press, Inc. All rights reserved.

X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

Shop the Store

  • Books
  • DVDs
  • Taunton Workshops

More

  • FHB Ambassadors
  • Reader Projects
  • Podcast
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok
  • twitter

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 70%

Subscribe

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in