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
Ask the Experts

Fitting Out-of-Level Prehung Doors

Use these two methods for measuring and cutting to install a door when the floor isn't level.

By Andy Engel Issue 303 - November 2021
  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles
Level the head. Prehung doors have equal-length jamb legs, but old floors are often out of level. To install a door in this situation, start by getting the head level with a shim beneath the jamb leg on the low side, which will help you to determine how much you need to cut from the opposite leg. If the floor is out in the other direction, scribe and cut the jamb legs to level the door.

I’m new to installing prehung doors. I’m finding that I sometimes can’t get the head level without raising one of the legs off the floor with a shim. Is there a better way to accomplish this?

—Diana via email

Contributing editor Andy Engel replies: Assuming both jamb legs (by the way, the term “jamb” comes from the French word for leg) are the same length, this means your floor isn’t level. I work on a lot of old houses and encounter this condition all the time.

For ease, take the door out of the frame, and then put the frame in the opening. Stick a couple of shims between the studs and the jambs at the head to hold the frame in place, then check the head for level. Raise the low side by inserting a tapered shim between the bottom of the jamb leg and the floor. When the head is level, make a pencil mark on the shim where it meets the bottom of the jamb. The thickness of the shim at this point is the amount you need to cut from the bottom of the other jamb leg for the head to sit level.

using shim to measure cut
Use a shim to measure the cut when one jamb is higher than the other.

using a compass to measure cut
Use a compass to measure the cut when one side of the same jamb needs to be trimmed.

In old houses, it’s common for the floor to be out of level in both axes and under both jamb legs. The process is a little more involved here. Start the same way, with the door frame shimmed into the opening and the head level. Take a compass—the cheap metal kind with the sharp point that kids can’t take to schools anymore works best—and open the gap between the metal point and the pencil point to the widest space between either of the jamb legs and the floor. Hold the compass with the point on the floor directly below the edge of the jambs, and scribe lines on each jamb leg. This is the line you’ll cut. It should be zero at the point the jambs are highest above the floor, and at the maximum where the jambs touch the floor.

Make the cut with whatever works— miter saw, handsaw, or jigsaw. In many cases, it’s good to back-bevel the cut slightly—the old floor will be higher in the spots where earlier door jambs were located than between them because of previous floor sanding.

Drawings: George Retseck

From Fine Homebuilding #303


RELATED LINKS:

  • Troubleshooting a Prehung Door Installation
  • How to Trim the Bottom of a Door
  • Jigs for Jambs (and Other Door-Hanging Devices)

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

  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

More Ask the Experts

View All
  • Installing Prefinished Cabinet Molding
  • Tall Deck on a Sloped Lot
  • Hard-to-Use Electrical Outlets
  • HVAC for a Slab-on-Grade House
View All

Up Next

Video Shorts

Featured Story

Ducted vs. Ductless Heat Pumps

Choosing the right heating and cooling system means finding the best fit for your home's size, layout, and climate—and balancing trade-offs in efficiency, comfort, and cost.

Featured Video

SawStop's Portable Tablesaw is Bigger and Better Than Before

The 10-in. Jobsite Saw PRO has a wider table, a new dust-control port, and a more versatile fence, along with the same reliable safety mechanism included in all SawStop tablesaws.

Related Stories

  • Breathing New Life into Original Windows
  • Mortising a Hinge without a Router
  • Fastening an Exterior Door With Brick Mold
  • Tom Gensmer, Remodeler and Window-Repair Expert

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

Video

View All Videos
  • Fastening an Exterior Door With Brick Mold
  • FHB Podcast Segment: Proper Flashing for Marvin Windows
  • A Closer Look at Pella's Steady Set Window Installation System with Mike Guertin
  • Details for Integrating an Addition
View All

Window and Door Installation

View All Window and Door Installation Articles
  • Mortising a Hinge without a Router
  • Fastening an Exterior Door With Brick Mold
  • Tom Gensmer, Remodeler and Window-Repair Expert
View All Window and Door Installation Articles

Fine Homebuilding Magazine

  • 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 2024
    • How a Pro Replaces Columns
    • Passive House 3.0
    • Tool Test: Compact Line Lasers
  • Issue 327 - November 2024
    • Repairing Damaged Walls and Ceilings
    • Plumbing Protection
    • Talking Shop

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 81%

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

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