Insights > Article > Posted: 2025-Dec-05, Updated: 2025-Dec-08

What is Window and Door Casing - What are the Options?

Windows and doors do more than open to the world; they complete a space

Windows and doors are critical for comfort, performance, and energy efficiency, but what truly makes them feel like part of your home is how they’re finished. The casing (the decorative trim that frames the opening) around them isn’t just decoration: it hides gaps, improves insulation, enhances visual appeal, and connects the architectural elements of your interior into a cohesive whole, making each opening feel intentional and complete.

At Bayview Windows, we know premium installation isn’t just about great products; it’s about the details. That’s why we offer not only high-quality windows and doors but also tailored trim solutions that elevate your home’s character while ensuring a polished, professional finish.

Bayview's current standard trim

All windows come with our sleek 2.25-inch flat MDF trim, included in your base installation. Installed with a brad nailer and professionally filled with MDF filler, the trim is left smooth and ready for paint. Keep in mind that MDF filler may shrink slightly over time and could need refilling by the homeowner before painting to ensure a perfect finish.

Note: future material changes

We continuously monitor the construction market to ensure we provide the best value and quality. While MDF is our standard today, Bayview Windows reserves the right to substitute the standard trim material (e.g., transitioning to finger-jointed pine or similar) should the market costs for wood and millwork fluctuate significantly. Any change would be communicated clearly and would be chosen to maintain our commitment to quality and value.

Often an overlooked opportunity
Custom trim options

For homeowners looking to elevate the look and feel of their space, window and door casing is one of the most impactful, and often overlooked, finishing details. It adds depth, character, and a sense of architectural permanence, turning a simple opening into a defined design feature.

Because every home has its own style, the right casing helps your new windows blend seamlessly into your interior, creating a polished, cohesive look that feels intentional and complete. When planning your project, be sure to ask your Bayview Windows sales consultant about our interior trim, framing options, and trim suppliers. A small detail that can make a remarkable difference.

Why custom trim elevates your home’s character

In modern home-building, standard trim prioritises simplicity and cost-effectiveness. Choosing a premium, customised trim resolves this by:

Adding Visual Weight: Giving windows and doors the authority needed to balance the room’s scale.
Creating Shadow Lines: Profiles catch the light, transforming a flat opening into a beautiful three-dimensional feature.
Ensuring Historical Accuracy: Matching your trim to the period or architectural style of your home instantly raises its architectural value.

Material Matters: MDF vs. Solid Wood Trim

The material you choose will impact the final look, durability, and cost of your custom trim.

Feature	Medium-Density Fibreboard (MDF)	Solid Wood (Pine, Poplar, etc.)
Cost	Lower. Most budget-friendly option.	Higher. Reflects the cost of natural lumber.
Finish	Best for Painting. Extremely smooth, resulting in a flawless, professional paint finish.	Best for Staining. Natural grain patterns are visible.
Stability	Very Stable. Does not typically warp or twist.	Reactive. It can slightly expand or contract with humidity changes.

Trim styles: from classic to contemporary

Before visiting a supplier, understanding a few classic styles can help you find the perfect match for your taste:

Style	Description	Ideal For
Colonial/Classic	Often features a curved edge called an ogee or s-curve. Elegant, balanced, and timeless.	Traditional homes, formal living spaces.
Craftsman	Distinguished by simplicity, featuring thick, flat trim, often paired with a substantial header.	Bungalows, Arts and Crafts homes.
Federal/Georgian	Characterised by intricate details, often built up with multiple layers of moulding.	Heritage homes, grand rooms.

Bayview’s custom finish advantage: Our process

Step 1: You Choose the Millwork

We will happily refer you to our trusted local millwork suppliers. These experts carry vast catalogues of profiles.

We provide you with a list of (List of Approved Millwork Suppliers).
You Select: The specific profile, material, and quantity required.
Recommendation: We recommend ordering (Percentage Overage for Waste) extra material to account for cuts and waste.

Step 2: Bayview’s Professional Installation

Our experienced installers will treat your chosen millwork with the meticulous attention to detail it deserves:

Acclimatisation: The millwork must be delivered and acclimatised inside your home for (Acclimatisation Hours: 48 or 72) hours before our team begins work.
Precision Installation: We ensure perfect mitring, seamless layering, and flawless integration with the wall and window frame.
Joint Integrity: We use glue and precise nailing to guarantee the stability of your custom millwork. We offer a (Warranty Statement on Mitre Joint Integrity).

The Result: Your Bayview Windows installation is finished with a piece of custom architectural millwork that elevates the entire visual character of your home.

Common Interior Window Casing Options

The term "casing" generally refers to the decorative trim piece(s) that cover the gap between the wall and the window frame.

1. Simple/Flat Casing (Modern & Craftsman)

Definition: A single, flat board that frames the window. It is the simplest and most modern look.
Aesthetic: Clean, minimalist. The thickness (depth) often provides the primary visual interest, rather than curves or profiles.
Example: Bayviews standard 2.25" MDF trim is a form of flat casing.

2. Profiled Casing (Traditional & Colonial)

Definition: A single trim piece that features a curved, moulded, or shaped edge. It is the most common casing used in traditional homes.
Aesthetic: Classical elegance. Profiles often include features like an ogee (S-curve) or a bead (small rounded ridge).
Variation: Can be combined with back bands (see below) to look thicker.

3. Back Band Casing (Built-Up/Layered)

Definition: A secondary, smaller profile used in conjunction with a main casing (either flat or profiled). The back band is applied along the outside edge, where the main casing meets the wall.
Purpose: To make the entire casing assembly look wider and deeper, giving the window more visual weight and a custom, "built-up" appearance.

4. Plinth Block (Block Casing)

Definition: A square or rectangular block of wood, usually thicker and wider than the casing itself, used at the bottom corners of the door/window frame, where the vertical casing meets the baseboard.
Purpose: Provides a visual transition and a strong, structural base. It also simplifies the mitring (cutting) process, as the casing and baseboard simply butt up against the block instead of needing complex angle cuts with each other.

5. Architrave/Header (Top Trim)

Definition: The horizontal trim piece that sits directly above the window (or door). In premium millwork, the architrave is often the most substantial and decorative element.
Aesthetic: When flat, it provides a simple shelf or visual cap. When decorative (built-up with multiple profiles), it is often called a Pediment and serves as a formal crown, adding significant architectural weight.

6. Picture Frame Casing

Definition: The simplest modern approach where the four pieces of trim (two verticals, one top, one bottom) are cut at 45-degree angles (mitred) on all four corners, just like a picture frame.
Aesthetic: Very clean, symmetrical, and consistent.

7. Apron and Stool Casing (Traditional Sill)

Definition: This style uses a decorative ledge (stool) that runs horizontally across the bottom of the window opening, similar to a traditional windowsill, supported underneath by a decorative piece called an apron.
Aesthetic: Traditional, offers a functional shelf for small items, and breaks up the casing's vertical lines. Unlike Picture Frame casing, the side casings stop at the stool.

These elements can be mixed and matched to create nearly limitless custom looks, which is why your Custom Finish Advantage process is so valuable!

Frequently Asked Questions (FAQ)

Q1: What exactly is included in Bayview Windows' standard trim installation?

Our standard installation includes 2.25-inch flat MDF trim, which is included in your base price.

Q2: Does Bayview Windows add a markup to the custom trim material cost?

No. You purchase the millwork directly from the supplier we refer you to. Our quote to you covers only the professional installation labour.

Q3: How much more expensive is custom trim installation compared to the standard trim?

The additional cost is for the specialised labour time required. Our custom trim labour is charged (Flat Rate or Hourly Estimate) to account for the increased complexity of cutting and layering profiled trim.

Q4: Who is responsible for painting or staining the new custom trim?

The finish work (painting or staining) is the responsibility of the homeowner or your painter. Our service leaves the trim ready for finishing, which includes (Priming Status: Yes or No) before we leave the job site.

Q5: Does Bayview take care of disposing of the old trim and millwork off-cuts?

We will remove and responsibly dispose of all old trim. We (Haul Away/Do Not Haul Away Off-Cuts) the scrap materials (off-cuts) generated from installing your new custom millwork.