A sill is the solid stone at the bottom of a door or window opening. It catches rainwater, directs it away from the facade, and protects the opening from wear and tear. You’ll find sills under the front door (door threshold), under the window (window sill) and under the garage door (garage threshold). Inside, a transom marks the transition between two spaces. In Belgium, blue stone has been the standard material for generations.
When building or renovating a home, a great deal of attention is often paid to windows, doors, and exterior cladding materials. Yet there is one element that is often underestimated but plays an important role both technically and aesthetically: the threshold.
A well-chosen sill not only provides a beautiful finish for windows and doors, but also protects the facade from water seepage and dirt. But which sill should you choose for your door or window?
A threshold serves several purposes:
Without a proper threshold, water can more easily seep into the facade or under the window and door frames. That is why windows and doors almost always have a natural stone threshold posted.
When it comes to thresholds, people very often choose Belgian blue stone. This natural stone has several advantages:
In addition, natural stone has a natural texture and character. This makes every threshold unique.
➡ Discover our Belgian blue stone thresholds.
Depending on the application, there are different types of thresholds.
Window sills are installed beneath windows and ensure that rainwater is drained away from the facade. They usually protrude a few centimeters beyond the facade so that water does not run down the masonry.
Depending on the architectural style and the desired finish, there are various types of window sills.
Flat threshold
A flat window sill has a clean, simple profile. This type is often used in modern homes and on minimalist facades.
Flat threshold with an upstand
This type features a small raised edge on the back. This raised edge helps prevent water from seeping under the window frame.
Drainage threshold
A drainage threshold has a slight slope so that rainwater drains away more easily. A drip groove is often included on the underside as well.
Drainage threshold with cushions
In more traditional homes, thresholds are sometimes finished with so-called “cushions” at the ends. This gives them a more traditional and decorative look.
👉 Would you like to learn more about the different types, sizes, and installation of window sills?
Be sure to read our article “”Everything You Need to Know About Window Sills Made of Blue Stone".
➡ Check out our solutions for window sills made of blue stone.
For exterior doors, people often opt for a wider and thicker threshold. It must not only drain water but also be sturdy enough to withstand heavy use.
In modern homes, door thresholds are often sleek and minimalist ...while in traditional homes, a more pronounced profile is typically chosen.
➡ Discover our door thresholds made of natural stone.
Thresholds can be manufactured with various finishes. The choice affects both the appearance and the comfort of use.
Common finishes include:
The right choice often depends on the home's architecture and the type of window and door frames.
The thickness of a threshold depends on its application and span.
Typical thicknesses are:
A thicker threshold provides extra stability and durability, especially for larger openings.
The price of a door sill depends on various factors, such as:
As a general guideline, you can usually expect to pay approximately €40 to €120 per running meter, depending on the dimensions and model.
A natural stone threshold is an investment that will last for decades. Thanks to its strength, durability, and natural look, Belgian blue stone remains one of the most popular materials for windows and doors.
Choosing the right size, finish, and installation ensures that your thresholds blend perfectly with the architecture of your home and remain beautiful for years to come.
Are you unsure about the right dimensions or finish for your thresholds?
Our team would be happy to help you choose the right solution for your project.
For a front door, people usually choose a threshold made of Belgian blue stone. This material is highly wear-resistant, frost-resistant, and can withstand heavy use. A thicker threshold measuring approximately 8 to 10 cm provides extra stability and durability.
A window sill must be wide enough so that it protrudes a few centimeters beyond the facade. This ensures that rainwater drains properly and does not run down the facade. Often, a overlap of approximately 3 to 5 cm provided.
The term "natural stone thresholds" usually refers to a drip groove included. This small groove prevents rainwater from running back up the facade along the bottom of the sill. This helps keep the facade better protected against moisture and dirt.
The price of a threshold depends on various factors, such as length, width, thickness, and finish. As a general guideline, you can expect to pay for a threshold made of Belgian blue stone approximately €40 to €120 per running meter, depending on the model and dimensions.
Natural stone thresholds are easy to maintain. Regular cleaning with water and a mild cleaning product is usually sufficient. Avoid harsh products that can damage the stone’s natural texture.
The thickness of a threshold depends on its application and span. For window sills is usually about 5 cm used. For door sills For larger openings, people often choose 8 to 10 cm, so that the threshold is sturdy enough and cannot bend.
For larger windows or sliding windows, a thicker sill may be recommended to ensure extra stability. The correct thickness is therefore usually determined based on the width of the opening and the type of window frame.