Schedule Appointment
Austin Pro Calender Icon
Appointment
phone icon
Call Us
Austin Pro Siding, Windows, Roofing, Patio Covers Logo

Sizing Replacement Windows: Key Considerations

By
austin pro
Written by Austin Pro Management
July 22, 2024

Sizing replacement windows bears as much consideration as choosing the materials and comparing energy efficiency ratings. In today’s post, Austin Pro Siding, Windows & Roofing discusses the factors that need to be considered when sizing replacement windows.

Wall Openings

The wall openings are the parts of the exterior wall framing where the windows are anchored to. This is one of the first things a replacement window contractor will take a look at during a consultation. In addition to determining the dimensions of the replacement window frame, the opening’s condition is also determined in case parts require repairs or, if the new window is expected to be heavier, improvements in structural support.

There’s no way to get an exact measure of the actual window opening because it’s hidden behind the window trim — unless the project involves an already-removed window. Window replacement contractors base their window measurements on the window frames and get rough measurements. Generally, the resulting window frames are fractions of an inch smaller than the rough window opening. Resulting gaps between exterior wall and window frame are shimmed and caulked during installation.

Window Style

Window replacement is an opportunity to switch to a different window style. Depending on your chosen style, the new windows may have features that affect the resulting frame and sash sizes. For example, double-hung windows have a counterbalancing mechanism within the frame that makes the sashes easier to lift when opening. Another example is picture windows, which do not have sashes and therefore may need slimmer frames.

Mulling Windows

Mulled windows are essentially two or more windows that are installed in the same opening. Exterior wall framing typically has provisions for window expansion, which means if you have two or more windows alongside each other, chances are the gaps between the windows can be removed to create a bank of mulled windows, or even a single large window.

Austin Pro Siding, Windows & Roofing is one of the most trusted replacement window companies serving communities in Austin. Give us a call at (512) 550-0000 or fill out our contact form to schedule a consultation.

Enhance Your Home’s Value and Efficiency with Affordable Replacement Windows
February 28, 2026
Enhance Your Home’s Value and Efficiency with Affordable Replacement Windows

New windows offer a high ROI. Discover affordable replacement options that boost property value and energy efficiency simultaneously.

How to Match Your Window Trim With Your Home’s Interior
February 28, 2026
How to Match Your Window Trim With Your Home’s Interior

Create a cohesive look by coordinating your interior window trim with your home’s decor.

Is Your Austin Brick House Quietly Leaking Water Behind the Walls After Every Storm?
July 14, 2026
Is Your Austin Brick House Quietly Leaking Water Behind the Walls After Every Storm?

Austin brick homes look solid, but hidden moisture intrusion behind brick veneer causes thousands in damage every year — often undetected until it's too late. Learn the 6 most common water entry points, the warning signs you can spot yourself, and when a targeted repair versus a full fix is the right call. Austin Pro Siding helps homeowners stop the damage cycle before the next storm hits.

Is a Metal Roof Actually Worth It in Austin Now? The 2026 Break-Even Math on Heat, Insurance, and the New Tax Law
July 14, 2026
Is a Metal Roof Actually Worth It in Austin Now? The 2026 Break-Even Math on Heat, Insurance, and the New Tax Law

A standing seam metal roof in Austin costs roughly double a shingle roof — but in 2026, rising cooling bills, tightening insurance rules, and the expanded homestead exemption are quietly changing the calculus. Here's the honest break-even math for Austin homeowners who plan to stay put.

Next-Gen Door Security Technologies
February 28, 2026
Next-Gen Door Security Technologies

Upgrade your safety. Explore the latest security technologies available for modern entry doors.

Reflective Roofing: A Game-Changer for Texas Home Efficiency
February 28, 2026
Reflective Roofing: A Game-Changer for Texas Home Efficiency

A game-changer for Texas efficiency. Learn how reflective roofs keep your attic cool.

Reasons to Choose Energy-Efficient Windows for Your Home
February 28, 2026
Reasons to Choose Energy-Efficient Windows for Your Home

Stop wasting money. Here are the top reasons to switch to energy-efficient windows now.

When Should You Replace or Repair Your Damaged Siding?
February 28, 2026
When Should You Replace or Repair Your Damaged Siding?

Rot or cosmetic? We help you determine if your siding damage can be fixed or needs replacement.