Flat Stock Trim & Moulding: S4S or S3S Finished Boards

August 22, 2022

By: The Finished Space

Some types of moulding are extravagant and ornate. They pack a punch and dazzle with their details. These types of moulding often serve a specific decorative purpose to help bring an aesthetic to life.

Then, on the other end of the spectrum, there are the simple trim and moulding types. These finishing touches are easy to miss if you don’t know they’re there. However, despite their subtle appearance, they are essential to a finished room. Flat stock trim is one such moulding type.

Flat stock moulding might not make an immediate impact, but you’re sure to notice if it’s not there. So, what is flat stock trim and moulding, and what is it used for? In this article, we’re going to discuss flat trim, including the difference between S4S moulding and S3S moulding. Then, we’ll chat about how you can use flat moulding strips in your space to make it more aesthetically pleasing.

What is Flat Stock Moulding and Trim?

Dining Room Table

Flat stock moulding is true to its name. It’s a type of trim that is flat on all its sides. In other words, there are no distinctive shapes, profiles, or designs on flat stock moulding. Instead, it’s simply a flat and finished wooden board.

Some common wood types for flat stop moulding include:

  • Solid Pine

  • Fingerjoint Pine

  • S4S Moulding or S3S Trim

  • Oak

  • Poplar

  • Fingerjoint Poplar

  • Maple

  • MDF (medium-density fiberboard)

Flat stock moulding is incredibly versatile and can be used for various purposes. For example, you can use it for your baseboards, window casings, door casings, shelves, window ledges, decorative elements, and more.

Sometimes, you might hear flat stock trim referred to as S4S or S3S. Why is that, and what do those terms mean?

S4S and S3S Finished Boards

Option M - Vintage Industrial - Office - Architrave - 2022

S4S and S3S are acronyms that stand for Surfaced 4 Sides and Surfaced 3 Sides, respectively. S4S boards are flat on all four sides. Conversely, S3S boards indicate that two faces are planed, one has been processed, and the fourth edge is left rough.

Whether you need S4S or S3S depends on how you use the flat stock trim and how many edges will be exposed.

5 Ways to Use Flat Stock Trim In Your Home

If you aren’t sure how to use flat stock trim in your home, these ideas should help. Here are five unique ways to use flat stock moulding to enhance your home’s aesthetic and tie the whole look together.

1. Use Flat Stock Door Trim for an Art Deco Aesthetic

Masonite - Logan - Two Panel Black Door in Living Room with Yellow Chair

A flat stock door trim is a great way to create a subdued or art deco aesthetic. Flat door casings are a terrific way to finish a look without drawing too much attention. However, if you choose a bold color, you can take a flat door trim to new heights.

2. Use Flat Wood Trim for Floating Shelving

Another fantastic way to incorporate flat wood trim into your home is with stylish floating shelves. You can create an architecturally interesting shelf or one that flows naturally along the edges of the wall. Either way, you can use flat wood trim to create a shelf whose only limit is your imagination’s creativity.

3. Create Texture with Flat Moulding Strips

Black 3 Panel Door and Black Accent Wall Bedroom.png

Create a coffered wall or intricate paneling with flat moulding strips. Flat moulding strips are a terrific way to add texture and design to an otherwise plain area. Who says that flat moulding strips have to be boring? Not us!

4. Combine Flat Stock Window Trim and a Flat Stock Door Casing for a Cohesive Look

It’s very common to see flat stock window trim and flat stock door casing used together. Using a bunch of flat stock trim in the same room can really help tie the entire look together to create a truly cohesive final aesthetic. Paint them the same color for cohesion, or toy around with contrasting colors to maximize the impact.

5. Combine a Flat Stock Baseboard and Flat Stock Casing

Interior Glass Panel Door

Flat stock baseboards are incredibly common. If you don’t like the look of a flat baseboard by itself, you can use it to create stacked baseboards. When combined with a matching flat stock casing, flat baseboards can add a layer of sophistication and design to any space.

Get High-Quality Flat Stock Moulding At Metrie

If you’re ready to add some flat trim to your home’s design – you’ve come to the right place. At Metrie, we specialize in designing beautiful finishing touches to complement any aesthetic. In fact, we work with the world’s top designers to ensure our customers always have access to the best trim and moulding on the market.

If you aren’t sure what types of moulding work best for your space, check out our innovative design tool, Option {M}. It helps match moulding styles with trendy design aesthetics.

If you’d like a little more inspiration before diving in, check out our design gallery for more inspiration.