How to measure a door opening to ensure the perfect fit

If you need to replace a door or frame getting all the measurements right is essential to ensure the perfect fit. But then, how exactly do you take door measurements and what exactly do you need to measure? Is the exterior door size the same as the interior size? Do you measure just the door or the frame too? Keep reading to learn how to measure a door opening like a pro.

Understanding door measurements

When it comes to installing replacement doors and frames there are a few measurements you need to take into consideration.

 

·       Door size

The door measurements include the height, width and thickness of the door as well as hinge pitching and strike location. All these measurements need to line up for a door to function properly.

 

The notion of nominal vs actual door size is very important as all commercial doors are undersized from their nominal size by 1/8” on each of the sides and the top and usually by 3/4 “on the bottom. Therefore when we say a 3’0 x 7’0 door, the actual door size is 35 ¾” x 83 1/8” NOT 36” x 84”. Commercial door thicknesses are typically 1 ¾” exact size.

 

Note that the interior of the frame when measured will be the exact size so that a 3’0 x 7’0 frame will measure exactly 36” x 84” when measured inside the frame.

 

Hinge pitching is the distance from the top of the door to the top the first hinge, and then from the top of the 1st hinge to the top of the second hinge, and the top of the 2nd hinge to the top of the 3rd hinge. This measurement should always be done on the frame where the pitch of the top (1st) hinge will be 1/8” larger than on the door to accommodate the 1/8” gap at the top.

 

Similarly lock (or on the frame strike) centerline locations should always be measured on the frame. The measurement is taken from the bottom of the frame to the centre of the strike.

 

·       Frame size

Ideally you can replace both the frame and the door together eliminating the need measure hinge pitching and strike locations and ensuring proper fit. Frame sizing is more about the wall condition than the door.

 

Commercial hollow metal frames typically have a 2” face and have various throat sizes to accommodate different wall constructions. The most common throat size in the industry for welded frames is 4 ¾” to accommodate a 3 5/8” stud wall with either ½” or 5/8” drywall. The most common 3 piece knock down frames size is 4 5/8” or 4 7/8” again to accommodate 3 5/8” studs with either ½” or 5/8” drywall. Many other sizes are available

 

Frames mounted flush in concrete or block walls typically use the same 4 ¾” throat construction.

 

The heights and widths of frames can be easily modified to accommodate various opening sizes.

 

Whether you’re measuring to determine the width or height, it’s always good practice to take a measurement at several different spots along the opening where the frame is being installed and then go with the smallest to ensure the frame will fit. 

 

·       Rough opening

Learning how to measure a rough opening is essential for ensuring the proper fit of your replacement frame in an existing wall.

 

Knockdown frames are typically used for replacement frames in existing stud walls, come in 3 pieces (hinge jamb, strike jamb and head) and are assembled on site during installation. The rough opening should be approximately 1” larger than the nominal size of the frame on each of the 3 sides so that the frame can wrap around the wall while accommodating the 2” face. So a 3’0 x 7’0 knockdown frame should have a 38” x 85” rough opening.

 

Rough openings being cut in concrete for welded frame should be approximately ¼” larger than the nominal frame size on each of the 3 sides so that the frame can slip into the opening for installation.

 

Need help with your replacement door? Visit Remac Door & Hardware. We’ve proudly served construction professionals and contractors for over 35 years offering high-quality products from leading manufacturers, expert advice, professional design-specification services, in-house fabrication and expert installation services. Contact us today to learn more about ourproducts and services or to request a free quote.

 

 

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