FHB Logo Facebook LinkedIn Email Pinterest Twitter X 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
  • Restoration
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In
HOUSE+

Using Liquid Flash at a Wall-to-Foundation Connection

Brian Pontolilo demonstrates how to air-seal where the concrete foundation, mudsill, and ZIP System sheathing all meet.

By Brian Pontolilo

Sponsored by ZIP System

For the house my wife and I are building in northwest Connecticut, we used ZIP System sheathing on the walls. Like many of today’s water-resistive barriers, ZIP System is great because it allows you to really efficiently take care of your water management and air-sealing at the sheathing level. Today, we’re working on the transition from the foundation to the wood framing above using liquid flashing.

The mudsill is a critical transition for a number of reasons. First of all, this is an area that’s going to see a lot of water. Rain splashes on these walls, and you can tell that this is the case when you’re building a house because you see the dirt getting splattered up there all the time. Secondly, we have dissimilar materials—wood and concrete—coming together and both behave differently, so this is an area prone to air leaks.

We took a little bit of a belt-and-suspenders approach down there at the mudsill. First of all, when we were installing the mudsill, we made sure to use a capillary break and we put beads of sealant on both the bottom and the top of that capillary break. This is to keep water out, but even more importantly for air-sealing. Where the wall comes down and meets the foundation, we’re sealing the joint between the concrete, the mudsill, and the sheathing with Huber’s Liquid Flash. The process is pretty simple.

First, we cleaned off the concrete and the sheathing by taking a broom and knocking off any splatter from dirt that made its way up there during the building process.

Second, we cleaned off the ZIP tape that comes down to the bottom of the sheathing with a little bit of acetone to get the release agent off of the tape. Then, we put a bead of tape along the foundation. We used duct tape for this, which is what we found sticks best to the green concrete. That’s just to give us a nice crisp line where the liquid flash ends on the foundation, because it will be a little bit visible. We don’t care as much at the sheathing since it’s going to be behind the siding.

The critical place to get the liquid flash is right into that joint. In a perfect world, your mudsill will be flush with the outside of your foundation, but that doesn’t happen all that much. In this project we had as much as a 3/8-in. overhang, so we needed to really make sure that we got a lot of sealant up in that area. I got a bead right in that corner where the concrete, the mudsill, and the sheathing all meet. Then I put a bead of seal along the concrete and spread that out with the spreader that ZIP supplies. I put a bead along the sheathing and I spread that out again nice and even.

Huber calls for 12 mils of thickness, but they also say that as long as you can’t see the substrate below, you’ve applied enough of the liquid flash. In other words, if you can see the concrete or if you can see the ZIP, apply some more. The last thing to do—before the liquid flash cures—is to pull the tape off for a nice, crisp line.


RELATED STORIES

  • How to Air-Seal Mudsills
  • Installing ZIP System Sheathing: Sheathing-to-Foundation Connection
  • Straightforward Air-Sealing Strategies

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

View Comments

  1. architectpaul | Aug 31, 2022 02:52pm | #1

    Nice work BP! And, yes, definitely pull off the duct tape when before the flashing sets....or even begins to skim over I would guess. But if you're too late perhaps running a box cutter blade along the top edge of the tape would do the trick, assuming you can see it.

  2. [email protected] | Oct 31, 2023 11:50pm | #2

    Great video, Brian! By the way, whose idea was it to cut your hair? You're so much sexier with that hippie hair than the new buzz cut you're sporting in the podcast. Just a woman's perspective, lol.

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

A Classic Paint Sprayer Gets a Thoughtful Refresh

The Titan Impact X 440 offers great coverage with minimal overspray.

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

  • Install Denim Insulation Like a Pro
  • Old House Air-Sealing Basics
  • A Closer Look at Smart Water-Leak Detection Systems
  • Building for Resilience with Glass-Mat Sheathing

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
  • Install Denim Insulation Like a Pro
  • FHB Podcast Segment: A Cost-Effective Approach to Insulating and Air-Sealing Floor Trusses
  • FHB Podcast Segment: Old Home Insulation Troubles - How to Find the Right Contractor
  • FHB Podcast Segment: Building a Paintable Surface Over a Traditional Stone Wall
View All

Walls

View All Walls Articles
  • Insulation for Homes in the Wildland Urban Interface
  • Making and Installing Wood Wall Paneling
  • FHB Podcast Segment: Sometimes Spray Foam Makes Sense, Sometimes It Doesn't
View All Walls Articles

Fine Homebuilding Magazine

  • Issue 332 - July 2025
    • Custom Built-ins With Job-Site Tools
    • Fight House Fires Through Design
    • Making the Move to Multifamily
  • Issue 331 - June 2025
    • A More Resilient Roof
    • Tool Test: You Need a Drywall Sander
    • Ducted vs. Ductless Heat Pumps
  • Issue 330 - April/May 2025
    • Deck Details for Durability
    • FAQs on HPWHs
    • 10 Tips for a Long-Lasting Paint Job
  • Issue 329 - Feb/Mar 2025
    • Smart Foundation for a Small Addition
    • A Kominka Comes West
    • Making Small Kitchens Work
  • Issue 328 - Dec/Jan 2025
    • How a Pro Replaces Columns
    • Passive House 3.0
    • Tool Test: Compact Line Lasers

Fine Home Building

Newsletter Sign-up

  • Fine Homebuilding

    Home building tips, offers, and expert advice in your inbox.

  • Green Building Advisor

    Building science and energy efficiency advice, plus special offers, in your inbox.

  • Old House Journal

    Repair, renovation, and restoration tips, plus special offers, 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

Follow

  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X
  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences
  • About
  • Contact
  • Advertise
  • Careers
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2025 Active Interest Media. All rights reserved.

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

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
  • Project Guides
  • 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

Online Learning

  • Courses
  • Project Guides
  • Reader Projects
  • Podcast

More

  • FHB Ambassadors
  • 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

  • X
  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok

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