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How To Install A Wider Prehung Exterior Door

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Today I am sharing how to install a wider prehung exterior door at the ranch house. Increasing the width of a front door will create an open front entry feel allowing for more natural light with the addition of sidelights.

The original front door at the ranch house was 36″x80″ and over 70 years old. Needless to say, the door needed to be updated.

We will be showing how we replaced a 36″ door with a 51″ door and the transformation is amazing!

A typical front entry door is 36″ wide by 80″ high. But what if you want to update your home with a wider door? Maybe a door with glass to let in the natural light? The cost to widen an exterior doorway will vary but it’s well worth the investment.

old brown front door with raised panels and small glass windows at the top

Prehung Exterior Steel Door

The first step to replacing an existing door is to select a door style.

We decided the Novatech prefinished steel entry door was the perfect choice for this home from the Remodelers Outlet in Fall River, Massachusetts. To allow more natural light into the home, we opted to install a black door with 3/4 lite portrait glass and 1 sidelight.

The art deco glass will provide a nice contrast with the white board and batten exterior siding as well as privacy.

black exterior front entry door with art deco glass and sidelight how to install a wider prehung exterior door

In a perfect world we would have added 2 sidelights but the door space available would only allow for a 55″ wide rough opening.

The door was custom assembled right in Fall River at the Remodelers Outlet. You can order online for pickup or delivery is available to select Massachusetts areas. They sell everything you need for just about any home improvement project at “outlet” prices!

black exterior front entry door with art deco glass and sidelight

Can You Widen An Exterior Door?

Yes! You can widen an exterior door opening. Replacing an older style front door with a front door with sidelights is the easiest way to modernize a front entry way. This will require widening the rough opening (frame) of the doorway.

Exterior doors come in a variety of sizes and styles. There are literally hundreds of options but a few of the most popular include, full or partial glass, sidelights (the long skinny windows beside the door) or a transom (the windows above the door) feature. Letting the “light” in via glass built into the door is a feature that many homeowners desire. Most of the time, upgrading to a bigger door in an older home, requires a front door remodel to fit a larger door.

How To Measure For a Wider Prehung Exterior Door

The original front door opening was 36 x 80. As you can see below, we didn’t have a lot of room on the left side so our new door size was limited.

36x80 rough opening front door, how to install a wider prehung exterior door
Original 36 x 80 front door opening

The new door we ordered was 51″x80″ which included a sidelight. To accommodate the larger door, Jim needed to increase the rough opening of the doorway.

How do you measure for a wider entry door?

To measure for a wider prehung door, be sure to leave 1 – 1 1/2″ greater for each dimension (height and width) than the door frame of the new door. This will allow for an easy fit and room for shimming (to get the new door level). Any gaps can be filled in with spray foam insulation and covered with the door trim.

When measuring the width and height, take your time to achieve accurate measurements.

how to measure the rough opening of a front door black exterior front entry door with art deco glass and sidelight, how to install a wider prehung exterior door
Measure front door width

Here is the door new door in all it’s glory!

front door makeover with a black prehung door

Door Installation Tip

Do yourself a favor and pay the extra money for a prehung door. Unless you are replacing the exact size door that requires no change in frame or rough opening, the savings in your brain cells will be worth it! Click through this post, why we choose prehung doors, to see why prehung is the best. The same is true for interior and exterior doors.

How to Install a Prehung Exterior Door

Modernize your home with a bigger front door! Learn how to install a wider prehung exterior door by cutting the existing rough opening wider and higher to accommodate a larger front entry door.
Print Instructions
measure the width of door rough opening

Supply List

  • New Exterior Door
  • Pressure treated wood (for header and sill if replacing)
  • 2×4's to reframe the door
  • Sawzall
  • Level
  • Hammer
  • Prybar
  • LocTITE insulation foam
  • Cordless drill
  • Nail gun
  • construction screws

Instructions : Step by Step

  • Remove the old door
    man removing old brown raised panel exterior door with 4 square windows at top
  • Measure the rough opening for the new door
    Cut new opening 1" – 1 1/2" higher and wider to leave room for leveling with shims.
    how to measure for a wider front entry door
  • Cut the new rough opening using a sawzall
    cutting a front door rough opening with a sawzall to make the door opening wider
  • Using a hammer and pry bar, remove the old trim, 2×4's and existing frame
    reframing front door rough opening for a new wider door
  • We installed a new header and replaced the rotted sill
    cutting a front door rough opening and door jamp with a sawzall to make the door opening wider
  • Be sure to use pressure treated wood for sill and header
  • Frame new door opening with 2×4's to match existing frame
    *2×4 construction was "code" in our area during the time this house was built.
    frame front entry rough opening nailing 2x4s to wall and joist
  • Add flashing tape around the door
    Flashing tape provides and extra layer of protection from air and water penetration
    add flashing tape around front entry rough opening to prevent air and water penetration
  • Install new door
    1. A prehung door comes completely assembled, including the hinges, frame and exterior trim. Simply add the door to the new opening, level and nail or screw to door frame.
    2. Use wood shims to level the door on the sides, bottom and top if necessary. Be sure to use a level to ensure proper installment
  • Fasten door to frame
    Use a cordless drill and nail gun
    prehung black exterior white interior door with sidelight and white vinyl trim
  • Seal new door with foam insulation
    We used LocTITE foam insulation to seal around the gap between the door and frame to make it weather tight
  • Install interior trim around new door
    white interior front entry door with art deco privacy glass and sidelight
  • Add exterior trim around new door
    Our prehung door included vinyl trim


Our door was factory finished with black exterior paint with a white interior. You will pay extra for a factory finish but many times it’s worth it!
Author: Jessica Bruno
Cost: varies depending on scope of work

This ranch renovation project has been one of my favorites! It’s the cutest house and I am loving all the new updates. If you have an older home with an outdated, narrow front door, consider replacing it!

Replacing an existing front door with a more modern style is a great way to increase curb appeal and add character to a front entrance. I highly recommend this home improvement project if budget allows!

Disclosure: This complimentary door is from Remodelers Outlet. All opinions and words are 100% my own. This how to install a wider prehung exterior door tutorial is for demonstration purposes. Be sure to consult with a licensed general contractor regarding any structural changes.

Meet Jessica

What started as a hobby, Jessica’s blog now has millions of people visit yearly and while many of the projects and posts look and sound perfect, life hasn’t always been easy. Read Jessica’s story and how overcoming death, divorce and dementia was one of her biggest life lessons to date.

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