What Is the Difference Between Standard 3-Inch and 4-Inch Aluminum Door/Window Frames, and Which One Should You Choose for Your Project?

Four popular aluminum brands in Thailand each have different strengths: ORM is suitable for projects that require the highest TIS standards, SMS Schimmer stands out for industrial-level precision, Fuji Eurotech is ideal for slim Euro Profile applications, and Thai Metal offers good value for project-based work. No single brand is the best for every type of job.

A common problem that the SGQ technician team often finds in repair and renovation projects is aluminum frames that do not fit the wall opening properly. Sometimes the frame is too large, requiring additional wall chiseling. Other times, it is too small and needs to be filled with an unusually thick layer of silicone, which can make the installation less durable and more prone to leakage.

What many people misunderstand is thinking that “aluminum frames” come in only one size. In fact, there are several standard sizes available, and choosing the right size from the beginning can save a lot of time and repair costs.

This article explains the dimensions of aluminum frames (width × depth), their relationship with wall opening sizes, and guidelines for choosing the right frame size based on the type of door or window panel. It does not cover the thickness of the aluminum profile, which is explained separately in another article.

What Is an Aluminum Frame, and How Is It Different from Other Frame Components?

Before discussing sizes, it is important to understand which part of the door and window system the “frame” refers to, because in the construction industry, this term is often used interchangeably with different meanings.

What Components Does an Aluminum Frame System Include?

An aluminum door and window system is divided into 3 main parts:

• Frame: The outer structure fixed to the wall. It supports the weight of the entire system. The frame size is measured by the face width and depth of the profile.
• Sash: The movable part of the system, such as sliding panels, casement panels, or folding panels. The sash moves either inside or outside the frame.
• Glass: Installed inside the sash. The glass thickness must correspond with the glass groove depth of the profile.

The size discussed in this article refers only to the dimensions of the “frame”: the face width and the depth that fits into the wall. It does not refer to the thickness of the aluminum material itself.

Why Is Frame Size More Important Than Many People Realize?

An aluminum frame that does not fit the wall opening properly can cause problems in 3 main areas:

• Appearance: If the gap between the frame and the wall is wider than 15 mm, an unusually thick layer of silicone will be needed. This can make the finished work look rough and untidy.
• Firmness and waterproofing: A wide gap reduces the silicone’s ability to withstand water pressure, increasing the risk of leaks during the rainy season.
• Structural stability: A frame that is too narrow for a heavy or large panel may not be able to support the weight properly. Over time, this can cause the panel to sag or prevent the lock from closing properly.

Based on SGQ’s repair project data: More than 60% of frame leakage repairs are caused by choosing a frame size that is not suitable for the wall opening, rather than by material defects.

How Many Standard Aluminum Frame Sizes Are There? (Table 1)

Aluminum frames in the Thai market are commonly available in 3 standard size groups. Each group is designed for different types of applications.

Note: Dimensions may vary slightly depending on the aluminum brand, such as SMS, ORM, Fuji, or Thai Metal. Please check the selected brand’s catalog before cutting to size.

What Is the Difference Between 3-Inch and 4-Inch Aluminum Frames, and Which One Should You Choose?

The difference between 3-inch and 4-inch frames is not only their size. It also affects their load-bearing capacity and the glass size they can support:

• 3-Inch Aluminum Frame (75 mm): Face width of 75 mm with a depth of approximately 38–45 mm. It can support glass up to 8 mm thick and is suitable for general residential projects with panels not larger than 1.5 meters.
• 4-Inch Aluminum Frame (100 mm): Face width of 100 mm with a depth of approximately 45–55 mm. It can support glass up to 12 mm thick and has a larger section area, allowing it to handle greater bending moments. It is suitable for panels 1.5–3 meters wide.

Based on SGQ technicians’ experience across more than 500 projects: 3-inch frames can support around 90% of general applications. However, if the panel is wider than 1.5 meters or uses heavier insulated glass, a 4-inch frame or larger should always be used. Saving on frame costs is not worth the repair costs that may follow later.

How Is a Euro Profile Frame Different from a Standard Frame?

A Euro Profile frame has 2 key differences from a standard frame: a narrower face width, which allows more visible glass area, and a greater depth, which supports thicker glass and a more complex sealing system.

Important note for renovation projects: Euro Profile frames are not compatible with general standard frames. Wall openings previously fitted with 3-inch or 4-inch frames may need to be resized before switching to a Euro Profile system → See more details about the Euro Profile system.

The Relationship Between Frame Size and Wall Opening Size (Table 2)

Even if the right frame size is selected, incorrect wall opening measurements can still cause installation problems. Below is the standard clearance commonly used in aluminum installation work.

How Much Clearance Should Be Allowed Between the Frame and the Wall on Each Side?

The standard clearance is 10–15 mm on each side around the frame. This is not only for installation convenience, but also for 3 engineering reasons:

• Thermal Expansion: Aluminum expands by approximately 0.024 mm per 1°C per 1 meter. In Thailand’s climate, where temperatures can vary by 30–35°C per day, a 1-meter frame can expand by up to 0.7–0.8 mm. The clearance helps accommodate this expansion.
• Construction Tolerance: Brick walls or concrete walls usually have a standard tolerance of around ±5 mm. Clearance helps accommodate this variation.
• Space for Silicone and Insulation: A 10–15 mm gap provides enough space for applying high-quality silicone with sufficient thickness to effectively prevent water and wind leakage.

How Should You Choose a Frame If the Existing Wall Opening Is Not Standard?

Renovation work on houses aged 10–20 years often comes with problems such as distorted wall openings or non-standard dimensions due to structural settlement. In this case, there are 2 possible approaches:

• If the wall opening is off-standard by less than 15 mm: Choose the closest frame size, then use packers or shims to level the gap before applying silicone. This method can be done without chiseling the wall.
• If the wall opening is off-standard by more than 15 mm: The wall must be chiseled or filled to the required size first. It is not recommended to force an oversized frame into a smaller opening, as this can affect the locking performance and overall tightness of the system.

How to Measure a Wall Opening Correctly Before Ordering a Frame: Measure the opening width at 3 points: top, middle, and bottom. Then measure the opening height at 3 points: left, middle, and right. Use the smallest value of each dimension for calculation, because any swollen or warped section of the wall will obstruct the installation at the narrowest point.

Choosing the Frame Size Based on the Panel Type (Table 3)

The panel type is another factor that determines the suitable frame size, because each system supports weight and pressure in different ways.

What Frame Size Is Required for a Large Sliding Door?

For sliding doors wider than 2.4 meters, there are key factors that must be calculated before choosing the frame size: the total weight of the panels and glass, and the load placed on the rollers and sliding track.

For example, a 2-panel sliding door with a total width of 3 meters and a height of 2.2 meters using 8 mm glass has a total glass area of approximately 6.6 sq.m. × the weight of 8 mm glass (approximately 20 kg/sq.m.) = around 132 kg of glass weight. When combined with the aluminum panel weight of approximately 15–20 kg, the track and frame must support a total weight of more than 150 kg. In this case, a 3-inch frame is definitely not sufficient → See more details about sliding door systems.

Does a Folding Door Frame Require a Special Size?

Folding or bi-fold doors have a more complex load-bearing structure than sliding doors. When all panels are folded together, the total weight is concentrated at the upper and lower fixing points. Therefore, the frame must have:

• Sufficient depth for installing the top track or bottom track of the folding door system, which usually requires a minimum depth of 55–65 mm.
• A 4-inch frame or larger to provide enough space for embedding the track and securing the bolts firmly.
• The supplier must be informed that the project is for a folding door system, because the profile holes for wiring and track fixing are different from standard frames → See more details about folding door systems.

Common Mistakes When Choosing Aluminum Frame Sizes

Based on SGQ’s repair and renovation experience, these are the 2 most common mistakes. They are easy to prevent if you know them in advance.

Why Can a 1-Inch Measurement Error in the Wall Opening Cause a Major Installation Problem?

1 inch (25 mm) may sound small, but it means the gap between the frame and the wall increases by another 12–13 mm on each side. This can turn the gap into 22–28 mm per side, which exceeds the range that silicone can seal effectively.

Long-term effects:

• Silicone that is too thick will crack faster than normal. High-quality silicone works best at a thickness of 6–12 mm.
• The silicone around the frame may need to be repaired every 2–3 years instead of every 5–7 years.
• The risk of water leakage increases during the rainy season.

Correct measuring method: Measure 3 points for each dimension: width at the top, middle, and bottom; height on the left, middle, and right. Use the smallest measurement, then subtract 20–30 mm for the total clearance on both sides. The result is the frame size that can be ordered.

Are Aluminum Frames and Wooden Frames Different in Standard Size?

They are very different, and this is a common trap in old-house renovation projects:

• Old Standard Wooden Frames: They usually have a face width of 4–5 inches (100–125 mm), but a shallower depth because wood does not require grooves or tracks for hardware.
• 4-Inch Aluminum Frames: The face width may be the same, but the depth is greater. Aluminum frames also include grooves for rubber seals, locking hardware, and tracks, so the dimensions that fit into the wall are different.

Conclusion for Renovation Projects: Do not measure the existing wooden frame and order an aluminum frame in the exact same size. Always measure the actual wall opening after removing the old frame first.