Wall thickness determines which hollow metal door frame fits your opening. To measure wall thickness, place a tape measure against the outside face of the finished wall on one side and measure straight through the opening to the outside face of the finished wall on the opposite side. This measurement, taken from sheetrock face to sheetrock face, must match the throat size of the frame you order. An incorrect measurement results in a frame that is either too loose or too tight to install properly.
CDF Distributors’ ProBuilder tool at cdfdistributors.com allows you to select the exact wall thickness during frame configuration, ensuring the throat size matches your wall assembly. For assistance determining the correct frame depth for your project, call (855) 769-9895 or email sales@cdfdoors.com.
What Is Wall Thickness and Why Does It Matter?
Wall thickness is the total distance measured from the outside face of the finished wall material on one side of a partition to the outside face of the finished wall material on the opposite side. In commercial construction, this dimension includes the stud depth plus the thickness of the wall finish (typically sheetrock) on each side. Wall thickness is the single most important measurement when selecting a hollow metal door frame.
Throat size is the internal width of the door frame, measured from the inside face of one frame return to the inside face of the opposite return. When a frame is installed correctly, the throat size wraps precisely around the finished wall. The throat size of the frame must match the wall thickness exactly. If the throat size is larger than the wall thickness, the frame will be loose and leave visible gaps. If the throat size is smaller than the wall thickness, the frame will not slide over the wall at all.
This relationship between wall thickness and throat size applies to all drywall wrap-around frames regardless of wall construction type, stud material, or wall finish. Getting this measurement right before ordering eliminates the most common cause of frame returns and jobsite delays.
Understanding Nominal vs. Actual Stud Dimensions
Stud dimensions in construction use nominal sizing, which does not reflect the actual measured dimension of the stud. This distinction is critical when calculating wall thickness because the stud depth is the largest component of the total measurement.
A 2x4 metal stud has an actual depth of 3-1/2”, not 4”. This follows the same convention used in wood framing, where a 2x4 wood stud also measures 1-1/2” by 3-1/2”. The nominal designation describes the stud before finishing or manufacturing tolerances are applied. When calculating wall thickness, always use the actual stud dimension.
The following table shows common stud sizes with their actual dimensions for both metal and wood framing.
Nominal Size | Actual Depth (Metal Stud) | Actual Depth (Wood Stud) |
2x4 | 3-1/2” | 3-1/2” |
2x6 | 5-1/2” | 5-1/2” |
2x3 | 2-1/2” | 2-1/2” |
2x8 | 7-1/4” | 7-1/4” |
Sheetrock Thickness and Its Effect on Wall Thickness
Sheetrock (drywall) is installed on each side of the stud wall and adds directly to the total wall thickness. The two most common sheetrock thicknesses in commercial construction are 1/2” and 5/8”. While the difference between these two options appears minor, it compounds when applied to both sides of the wall.
With 1/2” sheetrock on each side, the wall finish adds 1” to the stud depth. With 5/8” sheetrock on each side, the wall finish adds 1-1/4” to the stud depth. That additional 1/4” is enough to require a different frame throat size. Ordering a frame based on assumed sheetrock thickness rather than measured sheetrock thickness is a frequent source of error.
In fire-rated wall assemblies, 5/8” Type X sheetrock is typically required. Some fire-rated assemblies require double layers of sheetrock on one or both sides, which increases wall thickness further. Always measure the actual finished wall rather than relying on plan specifications alone, as field conditions may differ from drawings.
Installation Specifications
The wall thickness measurement determines the frame throat size needed for your installation. The following table summarizes common wall assemblies and their resulting wall thicknesses. Each combination produces a specific total that must be matched to the frame throat size.
At a Glance: Common Wall Assemblies
The table below covers the most frequently encountered wall assemblies in commercial interior construction. Use the total wall thickness column to select the matching frame throat size when configuring your order.
Stud Type | Stud Depth | Sheetrock (Each Side) | Total Wall Thickness |
2x4 Metal Stud | 3-1/2” | 1/2” | 4-1/2” |
2x4 Metal Stud | 3-1/2” | 5/8” | 4-3/4” |
2x4 Metal Stud | 3-1/2” | 5/8” + 5/8” (double layer) | 6” |
2x4 Wood Stud | 3-1/2” | 1/2” | 4-1/2” |
2x4 Wood Stud | 3-1/2” | 5/8” | 4-3/4” |
2x6 Metal Stud | 5-1/2” | 1/2” | 6-1/2” |
2x6 Metal Stud | 5-1/2” | 5/8” | 6-3/4” |
2x6 Wood Stud | 5-1/2” | 1/2” | 6-1/2” |
2x6 Wood Stud | 5-1/2” | 5/8” | 6-3/4” |
Note: The wall assembly referenced in CDF’s installation video uses a 2x4 metal stud (3-1/2” actual depth) with 5/8” sheetrock on each side, producing a total wall thickness of 4-7/8”. The frame throat size for this assembly is 4-7/8”.
What Happens When the Frame Depth Does Not Match
Selecting a frame with a throat size that does not match the wall thickness creates installation problems that cannot be corrected in the field without replacing the frame.
- Frame too large (throat size exceeds wall thickness). The frame returns do not press tightly against the wall surfaces. This leaves a visible gap between the frame face and the sheetrock on one or both sides. The frame may feel loose or shift after installation. Caulking can address minor cosmetic gaps, but structural looseness compromises the compression anchor function and reduces the frame’s holding strength.
- Frame too small (throat size is less than wall thickness). The frame physically cannot slide over the finished wall. The returns will not clear the sheetrock edges, making installation impossible without removing wall material or replacing the frame with the correct throat size.
In both cases, the project is delayed while the correct frame is ordered and shipped. Measuring wall thickness accurately before ordering prevents this outcome entirely.
Tools and Materials
- Tape measure: for measuring wall thickness from sheetrock face to sheetrock face
- Calipers or depth gauge: for verifying sheetrock thickness independently when the edge is accessible
- Notepad or measurement log: for recording measurements at multiple points along the opening
- Straightedge or level: for confirming the wall surface is flat at the measurement point
- Flashlight: for inspecting the stud cavity if sheetrock thickness is uncertain
Step-by-Step Measurement Process
Step 1: Locate the Measurement Point
Identify the door opening where the frame will be installed. The measurement must be taken at the opening itself, where the finished wall is exposed on both sides. Do not measure at a location away from the opening, as wall thickness can vary due to furring strips, uneven sheetrock application, or different sheetrock thicknesses on each side of the wall.
Step 2: Measure from Outside Face to Outside Face
Place the tape measure against the outside face of the sheetrock on one side of the wall. Extend the tape straight through the opening to the outside face of the sheetrock on the opposite side. Read the measurement. This is your total wall thickness.
For the wall assembly shown in CDF’s reference video (2x4 metal stud with 5/8” sheetrock on each side), this measurement is 4-7/8”: the 3-1/2” stud plus 5/8” sheetrock on each side (5/8” + 3-1/2” + 5/8” = 4-3/4”). Note: the actual measurement in the video is 4-7/8”, which accounts for minor construction tolerances in the stud and sheetrock installation.
Cross-section diagram showing: sheetrock (left side) + metal stud cavity + sheetrock (right side), with dimension lines indicating individual component thicknesses and total wall thickness measurement from outside face to outside face. This diagram requires CDF approval before inclusion in the production file.
Step 3: Take Multiple Measurements
Measure the wall thickness at a minimum of three points along the opening: near the top, at the middle, and near the bottom. Wall thickness can vary if sheetrock was applied unevenly or if the studs are not perfectly straight. If measurements differ, use the largest measurement as your wall thickness for frame selection. A frame throat that matches the widest point will seat properly at all points.
Step 4: Verify Sheetrock Thickness Independently
If the sheetrock thickness is not known from project specifications, verify it by examining an exposed edge at the opening, an electrical outlet cutout, or another access point. Measure the sheetrock thickness directly with a tape measure or calipers. Confirm whether the sheetrock is 1/2” or 5/8”. Check both sides of the wall, as different thicknesses can be installed on each side, particularly in fire-rated assemblies where one side may have a double layer.
Step 5: Calculate and Confirm
Verify your measurement by calculating the expected wall thickness from the component dimensions. Add the stud depth plus the sheetrock thickness on each side. Compare this calculated value to your tape measurement. If the two values do not agree within 1/8”, re-measure or investigate the wall construction for unexpected conditions such as furring strips, adhesive layers, or non-standard sheetrock thickness.
Example calculation: 2x4 metal stud (3-1/2” actual) + 5/8” sheetrock (left) + 5/8” sheetrock (right) = 4-3/4” calculated. Field measurement of 4-7/8” indicates minor construction tolerance, which is normal. Use the field measurement (4-7/8”) when ordering the frame.
Step 6: Select the Matching Frame Throat Size
Use the wall thickness measurement to select the frame with the matching throat size. The throat size is listed in the frame specifications and is selectable during configuration in CDF’s ProBuilder tool. The throat size and wall thickness must be identical. There is no tolerance or adjustment range; the values must match.
Common Mistakes to Avoid
Avoid these errors when measuring wall thickness for frame selection:
- Measuring stud depth only. The stud depth is not the wall thickness. Wall thickness includes the sheetrock on both sides. A 2x4 stud is 3-1/2”, but the finished wall is 4-1/2” to 4-3/4” or more depending on sheetrock thickness.
- Assuming sheetrock thickness without verifying. Assuming 1/2” sheetrock when the actual installation is 5/8” results in a wall thickness error of 1/4” (1/8” per side, both sides). This is enough to require a different frame.
- Measuring at only one point. Wall thickness can vary across the opening due to uneven sheetrock application or stud irregularities. Always measure at a minimum of three points.
- Using nominal stud dimensions for calculation. A 2x4 stud is 3-1/2”, not 4”. Using the nominal dimension adds 1/2” of error to the calculation.
- Measuring before the wall finish is complete. If sheetrock has not been installed on both sides, the measurement will not reflect the final wall thickness. Measure only after all wall finishes are applied.
- Ignoring double-layer sheetrock in fire-rated walls. Fire-rated assemblies may require two layers of 5/8” sheetrock on one or both sides, which adds 5/8” to 1-1/4” to the total wall thickness beyond a standard single-layer assembly.
- Measuring away from the door opening. Wall thickness at a different location on the same wall may differ from the thickness at the opening due to furring, additional layers, or construction variance. Always measure at the actual opening.
Wall Thickness in Fire-Rated Assemblies
Fire-rated wall assemblies frequently use different sheetrock configurations than standard partitions, which directly affects wall thickness and frame throat size selection. Fire-rated drywall wrap-around frames are available in 20-minute, 45-minute, 60-minute, 90-minute, and 180-minute (3-hour) ratings. The door, frame, and all hardware must carry matching fire labels for the assembly to be compliant.
Common fire-rated wall configurations include single-layer 5/8” Type X sheetrock on each side (for lower ratings) and double-layer 5/8” Type X sheetrock on each side (for higher ratings). A double-layer assembly on a 2x4 metal stud produces a wall thickness of approximately 6”, compared to 4-3/4” for a single-layer assembly with the same stud. The frame throat size must be selected to match the actual finished wall thickness, not the stud depth or a standard assumption.
CDF rivets fire labels onto every fire-rated frame assembly before shipping. Verify all fire rating requirements with project specifications and the Authority Having Jurisdiction (AHJ).
Configure Your Assembly
CDF’s ProBuilder tool at cdfdistributors.com allows contractors and facility managers to select the exact wall thickness during frame configuration. ProBuilder displays available throat sizes and matches them to your wall assembly, ensuring the frame fits your opening. Wall thickness is a required field during configuration, and ProBuilder will only present frame options compatible with your specified dimension.
For assistance determining the correct wall thickness or frame throat size for your project, call (855) 769-9895 or email sales@cdfdoors.com. CDF’s sales team is available Monday through Friday, 7:30 AM to 4:30 PM CT.
Frequently Asked Questions
What is the difference between wall thickness and throat size?
Wall thickness is the total distance from the outside face of the finished wall on one side to the outside face of the finished wall on the opposite side. Throat size is the internal width of the door frame measured from one return to the other. These two measurements must be identical for the frame to fit correctly. The frame throat wraps around the finished wall, so the throat size must equal the wall thickness.
How do I measure wall thickness if the wall is not finished yet?
If the wall finish has not been installed, you cannot measure the final wall thickness directly. Instead, calculate the expected wall thickness by adding the stud depth plus the planned sheetrock thickness on each side. Confirm the sheetrock specification with the project drawings or the drywall contractor. For a 2x4 metal stud (3-1/2”) with 5/8” sheetrock on each side, the calculated wall thickness is 4-3/4”. CDF recommends verifying by field measurement once the wall finish is complete.
Does sheetrock thickness really make a difference in frame selection?
Yes. The difference between 1/2” and 5/8” sheetrock on each side adds 1/4” to the total wall thickness. For a 2x4 metal stud wall, 1/2” sheetrock produces a wall thickness of 4-1/2” while 5/8” sheetrock produces 4-3/4”. These require different frame throat sizes. A 1/4” discrepancy is enough to make a frame either too loose or impossible to install.
What wall thickness do I have with a 2x4 metal stud and 5/8-inch sheetrock?
A 2x4 metal stud has an actual depth of 3-1/2”. With 5/8” sheetrock on each side, the calculated wall thickness is 4-3/4” (3-1/2” + 5/8” + 5/8”). In practice, field measurements may read 4-7/8” due to construction tolerances. Use the field measurement when ordering the frame.
Can I use shims to adjust if my frame throat size does not match?
No. Shimming is used to plumb and level the frame within the opening, not to compensate for a throat size mismatch. If the throat size does not match the wall thickness, the frame must be replaced with the correct size. There is no field adjustment that corrects a throat size discrepancy.
Where should I measure wall thickness on the opening?
Measure at the door opening itself, at a minimum of three points: near the top, at the middle, and near the bottom. Wall thickness can vary across the height of the opening. If measurements differ, use the largest measurement to select the frame throat size.
Do wood stud walls and metal stud walls have different wall thicknesses?
Not necessarily. A 2x4 wood stud and a 2x4 metal stud both have an actual depth of 3-1/2”. The wall thickness depends on the stud depth plus the sheetrock thickness on each side. The same stud depth with the same sheetrock produces the same wall thickness regardless of stud material. The measurement and frame selection process is identical for both.
About This Guide
This measurement guide reflects CDF Distributors’ standard specifications and field-tested procedures used by commercial contractors nationwide. The wall thickness measurement method described in this guide is demonstrated in CDF’s reference video, available on CDF’s YouTube channel at youtube.com/@CDF_Distributors.
For questions about wall thickness measurement, frame throat sizes, or to configure a door and frame assembly for your project, contact CDF at (855) 769-9895 or sales@cdfdoors.com. Configure your assembly online at cdfdistributors.com using ProBuilder.
