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

Fine Homebuilding Project Guides

Insulation

Guide Home
  • Energy Efficiency
  • Air-Sealing
  • Choosing Insulation
  • Installing Insulation
  • Water Management
How-To

Air-Sealed and On Piers

Carpenter Tim Holton and his crew came up with an up-in-the-air solution for sealing an addition with an elevated floor.

By Tim Holton Issue 285 - Aug/Sept 2019
  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

Synopsis: Carpenter Tim Holton describes a project in which his team added a sunroom to the back of a client’s home, and the site’s unique requirements made a piered foundation with deck-style footings the best solution. He details the process of building the floor frame on the pressure-treated foundation attached to concrete piers, and then lifting the floor to sheathe it from beneath. Using this method, the crew was able to forgo excavating machines and minimize damage to the yard and surrounding areas.


As a remodeling contractor, I often find myself with unique projects that take some outside-the-box thinking, and this job was no different. My customers wanted to add a 12-ft. by 16-ft. sunroom to the back of their home, and property lines, patios, gardens, and a septic system made it near impossible to get excavation equipment and concrete trucks to the location.

After some research and talking with inspectors and other respected contractors, I decided to build the addition on deck-style footings and a subframe of built-up pressure-treated beams. This is not the standard foundation for sunrooms in our area, but the pros greatly outweighed the cons in this situation. We were able to hand-dig each footing 42 in. deep and place 18-in. concrete forms in the holes, then wheel the concrete around from the driveway to fill the forms. By forgoing excavating machines and distributing the soil from the footing holes to the gardens, we minimized damage to the yard and surrounding areas.

Since the addition is a conditioned space without a crawlspace or basement, we had to come up with a way to seal the floor from air and moisture. We placed a 6-mil polyethylene vapor barrier and stone on the ground under the floor system to help prevent ground moisture from wicking and diffusing up through the bottom. We kept the floor approximately 6 in. above our stone and vapor barrier to allow some airflow under the space.

thick rigid foam in each joist bay and along the rim joists, and sealed the perimeter of the strips with spray foam

That just left air-sealing. After many hours of figuring, we devised a way to build a standard floor, raise it up, sheathe and tape it, and lower it back down. We rented two manually operated material lifts, each with a 1000-lb. load capacity, from our local supplier and used them to raise up the floor frame. Once it was up at a comfortable working height, we could sheathe it from below—similar to hanging drywall on a ceiling, albeit nailed as in normal wall construction. Once the underside was sheathed and the seams were taped, we lowered the structure back into place, nailed it off, insulated it, sheathed the top side, and continued with our wall framing just as if we were building on a standard floor system. (We didn’t tape the perimeter of the sheathing to the floor frame, but it wouldn’t hurt to do so.)

To fully insulate the floor, we placed strips of 1 1/2-in.-thick rigid foam in each joist bay and along the rim joists, and sealed the perimeter of the strips with spray foam. Fiberglass- batt insulation fills the remainder of the joist cavity, and 3/4-in. AdvanTech subflooring caps the floor system. Wire mesh attached to the perimeter framing and buried 2 in. deep in the soil around the perimeter will help keep rodents out.

This method of construction is an unorthodox approach and presents some challenges, but on a tight site such as this, it can be a better and more cost-effective option than a traditional foundation.

See these articles that demonstrate techniques similar to what Tim used:

How to Insulate a Cold Floor — For better energy performance, homes built on piers, rooms above garages, and cantilevered bays need properly air-sealed and insulated floors.

Get Your Deck Joists Right — Learn how to calculate cantilevers and determine simple spans—plus find a series of installation tips for creating robust joist connections, weatherizing, and more.

From Fine Homebuilding #285

To view the entire article, please click the View PDF button below.

View PDF
Previous: Creating a Sealed Crawlspace Next: Installing ZIP System Sheathing: Sheathing-to-Foundation Connection

Guide

Insulation

Chapter

Air-Sealing

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

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Insulation

Insulation

Trusted, comprehensive guidance from the pros for a home that is healthy, comfortable, and energy efficient

View Project Guide

View All Project Guides »

Become a member and get unlimited site access, including the Insulation Project Guide.

Start Free Trial

Energy Efficiency
  • Understanding Energy and Houses
  • Building Energy-Efficient Homes
Air-Sealing
  • Air-Sealing Basics
  • Air-Sealing Tools and Materials
  • Foundations and Floors
  • Walls, Windows, and Doors
  • Attics and Roofs
Choosing Insulation
  • Insulation Basics
  • Material Choices
Installing Insulation
  • Insulating Attics and Roofs
  • Insulating Walls
  • Insulating Floors, Footings, and Slabs
  • Insulating Foundation Walls
Water Management
  • Water-Management Principles
  • Materials
  • Installation Methods

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.

  • Home Group
  • Antique Trader
  • Arts & Crafts Homes
  • Bank Note Reporter
  • Cabin Life
  • Cuisine at Home
  • Fine Gardening
  • Fine Woodworking
  • Green Building Advisor
  • Garden Gate
  • Horticulture
  • Keep Craft Alive
  • Log Home Living
  • Military Trader/Vehicles
  • Numismatic News
  • Numismaster
  • Old Cars Weekly
  • Old House Journal
  • Period Homes
  • Popular Woodworking
  • Script
  • ShopNotes
  • Sports Collectors Digest
  • Threads
  • Timber Home Living
  • Traditional Building
  • Woodsmith
  • World Coin News
  • Writer's Digest
Active Interest Media logo
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

You have 1 free article remaining.

Get complete site access, including thousands of videos, how-to tips, tool reviews, and design features.

Start your FREE trial

Already a member? Log in

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

Privacy Policy Update

We use cookies, pixels, script and other tracking technologies to analyze and improve our service, to improve and personalize content, and for advertising to you. We also share information about your use of our site with third-party social media, advertising and analytics partners. You can view our Privacy Policy here and our Terms of Use here.

Cookies

Analytics

These cookies help us track site metrics to improve our sites and provide a better user experience.

Advertising/Social Media

These cookies are used to serve advertisements aligned with your interests.

Essential

These cookies are required to provide basic functions like page navigation and access to secure areas of the website.

Delete My Data

Delete all cookies and associated data