PVC Window Jamb Extensions – Finish with casing, never worry about water damage again.

Why Choose Our Traditional PVC Jamb Extensions?

Built for performance. Designed with precision. Trusted by contractors.

Moisture-Resistant & Durable
Made from premium-grade PVC that resists warping, swelling, and rot — ideal for Canadian climates.
Custom-Cut to Fit
Let us save you the frustrations of dealing with oversized windows and crooked walls - you simply give us your measurements and we will build you a jamb to fit.
Glossy Finish – No Painting Required
High-quality, factory-applied glossy finish that matches PVC windows — no need for painting after installation.
Easy to Install
Whether you're a first time renovator or an experienced finisher completing a window wall, our PVC solution makes it easy.
3/4” Standard Thickness
Our jamb extensions are built to a 3/4” standard depth — optimized for most framing and drywall configurations.
Superior to MDF and Drywall
No flaking. No swelling. No mold. Just clean, professional results that outperform lower-grade trim products.

We make finishing windows simple

Send Us Your Measurements
Using the guides under "resources", send us your length, height and depth at each corner. For a quick estimate, fill out our quote calculator and then send it our way to place your order.
We Manufacture Your Jambs and Ship Quickly
Depending on the quantity of windows you need, we ship out windows in roughly 2 weeks. To save on shipping, we dissassemble your jamb and ship it flat.
Re-Assemble and Install
Simply re-assemble and install in place using the supplied silicone and installation clips. Once the silicone is set, remove the clips and your window is ready for casing!

How to Measure

To get an accurate quote, you'll need your total square footage and jamb depth. Here's how:

1. Measure Window Width & Height

Flat Window: Measure from outer edge to outer edge of the frame for both height and width.

Drywall Return (U-Channel): Hook your tape measure to the inside of the drywall return and measure from inside to inside.

2. Determine Jamb Depth

Measure from the window (or inside edge of drywall return) to the outer edge of the drywall to determine your required jamb depth.

3. For More help, see "resources"

See specific window measurements needed for your window type or contact us for help with your measurements. Contact us if you have an existing jamb that needs an extension.

Installation instructions for window jam extensions, including removing jams from packaging, dry fitting the jam, and applying silicone to the window. The image shows step-by-step directions with photos of the product and window installation process.
Instructions and images showing the process of installing window clips and preparing for window trim. The first image shows clips installed around a window, and the second image shows a finished window ready for trim.
A close-up of a new white window frame installed in a house under construction, with the window looking out to a striped striped exterior surface.
Image of a window with a white frame and a windowsill, view of the wall inside the room, part of the brown exterior wall.
A man wearing a blue t-shirt and a tool belt is applying painter's tape around a window frame to prepare for painting or drywall finishing.
Living room with large floor-to-ceiling windows showing a sunny outdoor deck and green landscape, wooden ceiling, and hardwood floor.
Interior view of a spacious living room with large, floor-to-ceiling windows showing a blue sky with clouds and green landscape outside; wooden ceiling and floor; sliding glass door opening to a deck with outdoor furniture.
A person wearing a glove is applying caulk along the edge of a window frame.
Close-up view of a window with a white sill and a screen, showing part of a tree outside under a partly cloudy sky.
A rectangular window set into a white wall with a view of trees and neighboring houses outside, with some wooden planks leaning against the wall on the right.
Interior view of a bathroom or laundry room with a window and an unused custom cabinet space.