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Your Position: Home - Security & Protection - Buying Guide on Fire-Rated Glass for Your Needs

Buying Guide on Fire-Rated Glass for Your Needs

Author: Geym

Mar. 07, 2024

The U.S. Fire Administration reported almost

1.3 million fire-related incidents

in the country in 2019, causing 3,704 deaths, 16,600 injuries, and US$14.8 billion in losses. These numbers led to a growth in awareness about fire safety products in buildings, anticipating a boost in the country’s fire-rated glass consumption in the coming years.

This surge and growth in awareness and application evolved the fire rated glass market to offer various products that suit different consumer needs. If you’re unsure which fire rated glass is best for your project or don’t know where to start, our fire rated glass buying guide below can help.

What is Fire Rated Glass?

Fire rated glass is a type of glass that offers a level of protection in the event of fire, and while it doesn’t extinguish the fire, having them installed can benefit you in different ways.

1. Contains fire, smoke and radiant heat

Keep flames, smoke and in some cases dangerous radiant heat from spreading and have enough time to get out of a burning room or building. The official term for this is compartmentation, which means that the glass restricts fire damage to a specific area, preventing it from spreading and causing more damage.

2. Withstands heat

 Fire rated glass can withstand high temperatures better than other glass types. For example, standard window glass will shatter at around 250°F, but fire rated glass can survive high temperatures without breaking.

By slowing the spread of fire, fire rated glass ultimately preserves human life and protects your property and assets.

3. Easy integration

Due to the rise in the demand for fire rated glass, manufacturers now make it easy to integrate it into any commercial, institutional or residential projects without having it look out of place.  Advanced versions can also perform multiple functions such as energy efficiency, hurricane resistance, bullet resistance, blast resistance, attack resistant, and more.  Decorative options are also available.  

Fire rated glass is now an essential part of building plans. They can be either fire-protective or fire-resistive. Let’s take a look at the difference.

Fire-Protective vs. Fire-Resistive

Fire rated glass can either be fire-protective or fire-resistive. Here’s a summary for both to give you an idea of which one you need in your project.

  • Fire-protective glass

Fire-protective glass is a type of fire rated glass designed to compartmentalize flames and smoke but not prevent radiant heat transfer, meaning that objects or people on the other side of the glass will feel the heat. It is also subject to application, area, and size.

It is tested to  NFPA 252/257 or UL 9/10C, typically up to 45 minutes.  Fire-protective glass is usually for openings and doors. Some examples of fire-protective glass are specially tempered glass, specialty fire protective, wired glass, and glass-ceramic.

  • Fire-resistive glass

Fire-resistive glass also compartmentalizes flames and smoke but prevents the transmission of radiant heat through glazing, which means objects on the other side of the glass don’t get hot enough to combust. Furthermore, fire-resistive glass is not limited in application or size, unlike fire-protective glass. 

It is tested to ASTM E-119 or UL 263 and typically 60-120 minutes. They are used in wall (including butt-glazed), door and floor applications. Some examples include fire resistive tempered units and annealed multilaminates. 

For a more in-depth look at the differences between fire-protective and fire-resistive glass and specific examples for each, check out our separate article here.     

Types of Fire Rated Glass

Fire Protective Glass

  • Wired Glass

For a long time, wired glass or wire mesh glass was the only type of fire rated glazing available on the market. It’s made from a wire grid mesh incorporated into a sheet of glass. The wire holds the glass in place in the face of a fire.

However, regular wired glass breaks and causes jagged edges. Safety wired glass has a film covering the glass so that if it does break, it won’t be penetrated, reducing injury.   are 

 With clear, safe and economical and USA-made fire rated glass options that today, designers, contractor and owners have moved away from using wired glass for safety and aesthetic reasons.   

  • Ceramics 

Ceramics resists high levels of heat by letting the heat through unabated. . Since it can handle temperature changes, it’s often used for cooktops and fireplace doors.

Ceramics are brittle and break easily.  Like wired glass, they would have to be filmed or laminated to meet safety standards, adding to its already high cost. Ceramics also have a noticeable amber or greenish tint.

  • Specialty Tempered Fire Rated Glass

This type of fire rated glass can be a cost-effective alternative to wired glass and ceramics; however, it usually won’t survive the hose stream test, so it also has limited use. In the US, fire rated glass in 20 minute doors does not need to meet the hose stream test.   

  • Specialty Fire-Protective Glass

Specialty fire-protective glass is the most economical fire and safety-rated glazing available while meeting the hose stream test.    It provides excellent clarity (available in low-iron versions) and meets the highest human impact safety requirements. You can use it for interior and exterior applications and is available in specialty architectural make-ups and patterns.

Fire Resistive Glass

  • Annealed Multilaminate

This type is multi-laminated, consisting of alternating layers of annealed glass and transparent  intumescent interlayers. The higher the fire rating, the more layers of annealed glass are needed. They are susceptible to damage of the interlayers from moisture, have smaller sizes, require great care in handling due to breakage, and have other restrictions that limit their use.  All annealed multilaminates are made overseas.  

  • Fire-Resistive Tempered Units

Fire-resistive tempered units consist of specialty tempered glass with the cavity or cavities filled with a clear, semi-rigid intumescent interlayer.  They are more durable compared to annealed multilaminates and are available in larger sizes.  Fire resistive tempered units are made in the USA.  

4 Things to Consider When Shopping for Fire Rated Glass

1. Does the glass have a certified fire rating?

All fire rated glass must be tested, certified, listed and under the follow-up service of a nationally recognized third-party laboratory such as UL on Intertek.  

2. Do you need fire-protective or fire-resistive?

Both fire rated glass types must pass different requirements to be fire-protective or fire-resistive. Always ensure that you know what kind to get and for what purpose.

For example, fire-protective glass is suitable for building codes requiring “opening protective” assemblies, while fire-resistive glass is ideal for building codes requiring an enclosed space is designated as fire-resistant, like a stairwell. Fire protective is typically rated from 20-45 minutes and subject to area and size limitations, while fire resistive is typically rated 60 minutes or more and does not have size or application limitations.  

Lastly, review the testing requirements.  Fire protective glass is tested to NFPA 252/257 or UL 9/10C, which fire resistive glass is tested to ASTM E-119 or UL 263.

3. Does it meet additional performance or design requirements?

Fire rated glass has been in constant innovation, and fortunately for designers and building owners today, the variety in design and performance requirements are more diverse.   Today’s advanced fire rated glass products can also protect against environmental (hurricane) and man-made (ballistic, blast, attack, forced entry) threats.  Decorative and energy-efficient make-ups are also available.  

4. Does it meet Buy America Requirements? 

With USA-made fire rated glass and framing systems being readily available, architects can specify them in government-funded public projects such as transportation terminals, federal buildings, courthouses, and more in order to meet Buy America Requirements.  SAFTI FIRST is the only vertically integrated, single-source USA-manufacturer of advanced fire rated glass, framing, entrances and floor systems.  Our products are made in our state-of-the-art manufacturing facilities in Merced, CA. 

Click here to view SAFTI FIRST’s Capabilities Video: https://vimeo.com/588032343 

What to Look for in a Fire Rated Glass Provider

1. Proven Expertise & Experience

Fire rated glass is a life safety product, and its use is governed by the IBC. Fire rated manufacturers should be experts not only in their products, but in the test standards and code requirements as well.   They must have an excellent track record and an extensive portfolio to back it.

2. High-quality products that are code-compliant

A fire rated glass provider should offer products that meet and exceed the minimum requirements. SAFTI FIRST manufactures fire rated glass products that meet code and creates aesthetically pleasing designs to fit client needs.

3. Fast lead times

Most importantly, fire rated glass suppliers must deliver. The product is not the only thing that matters to clients. Manufacturers should provide the right product and deliver it within an optimal timeframe. Work with a fire rated glass provider that proves their efficiency and delivery.

4. Great customer support

Working with fire rated glass can sometimes be complex. The product is manufactured and assessed and should also meet client size, use, and design expectations. A reliable manufacturer will provide clients with excellent customer support to help them choose the fire rated glass that meets their requirements.

Click here to read some of our Customer Testimonials: https://safti.com/testimonials/ 

5. Amazing problem-solving

Every client has a different need; sometimes, even the most seasoned fire rated glass provider will have difficulty solving problems. The important thing to look for is the eagerness and willingness to solve a client’s problem.

Know Which Fire Rated Glass Best Suits Your Needs

The best way to ensure that you’ll get a fire rated glass according to your need is by knowing how to choose the best one. Remember that requirements are to be met, and each type has a specific use.

SAFTI FIRST manufactures world-class, USA-made fire rated glass and glazing solutions. We provide quality products that enhance the fire protection of your projects without compromising on aesthetics or architectural appeal.

We have various fire rated glass and glazing solutions to help take your project to the next level. Contact us today!

Door Glass and Frames Buying Guide

Key Diagrams/Pictures

Most common glass sizes:

Door glass & frame kit (includes the insulated glass “IG” unit, the interior and exterior plastic door glass frame, screws, and screw caps):

Additional reading:
What kind of yellow paint should I get to paint the lines ...

Cross section of clear insulated glass unit:

Cross section of 3 pane decorative glass unit:



Adding or upgrading door glass is the best way to immediately boost the curb appeal and value of a home. Door glass also helps an entryway bring light into the home and allows you to see outside without opening the door. Door glass comes in a range of styles including clear, decorative, internal mini-blinds, grills between the glass, venting, and frosted or opaque. These styles provide a range of privacy, aesthetics, and functionality to an entryway. Decorative door glass is most often found in front entry doors. Clear glass, glass with blinds, venting glass with a removable screen, and glass with internal bars or grills are typically used for side doors, patio doors, kitchen doors, and man-doors to a garage or shed.

Door glass is most often found in exterior doors. However, some interior doors do have single pane glass (for example pantry doors or French doors with 15 lite style for a living room or dining room). Glass on interior doors can help a room feel larger, provide increased visibility, and can be a safety feature by reducing the chance of opening a door into someone on the other side!


Modern door glass for exterior doors is double or triple paned for energy efficiency and tempered for safety. Door and side lite glass is required by law to be tempered. Some glass is laminated for additional security or severe weather resistance. Low-e or low-emissivity glass has a special coating that can help improve energy efficiency by reflecting non-visible light. In cold weather, low-e glass reflects heat back inside the home. In warm weather, low-e glass reflects solar heat off of the outside of door glass and helps to keep the interior of the home cool. In general, the largest energy efficiency gain comes from switching from single pane glass to double pane insulated glass. Then switching to thicker glass or triple paned glass will drive significant energy savings, and the savings from low-e glass declines. We only advocate for low-e glass in extreme climates and with very large pieces of glass that receive direct sunlight.

The vast majority of modern door glass is easily replaceable and held into doors or sidelites with plastic or vinyl frames. These frames screw together and clamp or sandwich glass into the door or side lite. This style of securing door glass into a door is sometimes called "lip-lite." The exterior frame seals against the outside face of the door with a bead of caulking and the frame seals against the exterior pane of glass with another bead of caulking, together creating a tight seal. The interior frame is the one with the screw holes and after the glass & frames are installed and the screws are tightened, caps cover the screw heads on the interior frame.

Door glass frames are typically made of plastic or vinyl (wood is rare/only found on very old doors). Plastic is the most common and comes in several types with different advantages/weaknesses:

  • PC/ABS blend: Medium/high expense. Excellent durability and resistance to impact. Takes paint/stain very well without any primer needed. Best option for handling “high heat” or direct sunlight, especially if your door is behind a storm door that traps heat or is painted black and tends to get hot.
  • ABS: Very rigid but prone to cracks under force, medium expensive, takes paint/stain well. Can handle moderate heat/sunlight. Typically used on lower quality decorative door glass.
  • Polypropylene (glass filled): Less expensive, moderate durability and heat/sun resistance. Can be painted or stained after using a primer that is for use with plastics/for use with polypropylene.
  • Polypropylene (talc filled): Very cheap, low durability the tendency to crack at the corners. Can handle moderate heat/sunlight. Can be painted or stained after using a primer that is for use with plastics/for use with polypropylene.
  • Polystyrene: Very cheap, was used from ~1970 through the 1990s. Cracks, warps, discolors easily, especially if in direct sunlight.
  • Vinyl: The most durable & expensive. Can be painted/stained but doesn’t take paint/stain as well as ABS or PC/ABS. Can handle direct sunlight well.

Except for vinyl frames, which are extruded and stapled together, the other door glass frames (the plastic ones) are made in large injection molds.

Insulated door glass units are made by taking two pieces of tempered glass (sometimes with a third piece of decorative glass in between them), installing an aluminum spacer around the edges of the glass, and then sealing the unit with a strong sealant (typically a black rubber-like substance called butyl and/or other sealants like polysulfide, etc.). To prevent condensation on the inside of the glass, drying beads or “desiccant” lines the inside of the aluminum spacer and absorbs excess moisture. Sometimes a thin, flexible metal tube protrudes through the sealant. This tube is for equalizing the pressure inside the unit if the unit is built at a low altitude and installed at a high altitude or vice versa. Insulated door glass comes in three standard thicknesses: ½” thick (typically for clear glass/glass with external grills), ¾” thick (very rare, used for some decorative door glass mare around ~1970-1985), and 1” thick (standard for decorative glass and glass with internal blinds). When replacing the door glass frames and keeping the existing glass, it is critically important to measure the glass thickness and select the frame designed for that glass thickness (i.e., a frame for 1” glass won’t fit a ½” piece of glass, even if the width and height are correct).

Decorative door glass often has “caming,” or inlaid metal. Caming typically comes in 3 colors or finishes: black (also known as lead or patina), silver (also known as nickel or satin nickel), and brass. Today, most caming is made of zinc with different finish colors. Recently, decorative glass with wrought iron caming has become popular. Of course, glass with “lead” caming in no longer made with actual lead due to the safety and environmental complications of lead. In addition to caming, decorative glass typically has some combination of etched, frosted, hammered, beveled, patterned, or glue-chip glass.   

Older doors (typically pre-1970) may have single pane door or door glass that is held into the door with wood trim (sometimes called “sticking”) and nails that is flush to the face of the door. Glass installed into a door in this fashion (without a screw-together plastic or vinyl frame) is known as “flush glazed.” Some very high end (mostly premium wood doors) still use a “sticking” method or “flush glazing” method to install door glass. Interior doors that have glass are typically flush glazed. See image below for a comparison of lip lite to flush glazed. Note that sometimes lip-lite style products can be used to replace a flush glazed unit, as long as the cut-out dimensions match.

Our product offering

Note: All of our door glass and frame kits are designed for exterior doors that are 1.75” thick

Decorative Door Glass

  • Traditional styles (e.g., Stratford, Wexford, Saxon, etc.)
  • Modern styles (e.g., Connecticut, Paxton, Portland, Austin, etc.)
  • Wrought iron styles (e.g., Charleston)
  • Decorative door glass is typically 1” thick (measuring the full unit -- two clear panes sandwiching a decorative pane)

Door Glass with Internal Blinds

  • Internal blinds are a great option for controllable privacy and light, without the hassle of external blinds that tangle and break (internal blinds use a magnetic operator that is very durable and reliable – the blinds themselves are protected in between the panes of glass)
  • Blinds can be raised/lowered and tilted (except the 7x64 size which is tilt only)
  • Glass is 1” thick

Hurricane Impact & Security Glass

  • Some parts of the country (e.g., Florida & Texas) have requirement for door glass to be able to withstand certain storm/wind/projectile impacts
  • Door glass installed in these areas must meet requirements (e.g., Miami Dade County or FL15419 code approval – seefloridabuilding.org)
  • Clear glass and select decorative styles are available in hurricane impact rated with high-impact vinyl frames. Hurricane glass is expensive, with prices 3-5x that of standard glass.
  • Hurricane glass comes with added benefit of security glass (significantly enhances resistance to break-ins) as well as sound reduction (laminated glass provides significant sound-proofing)

Clear Door Glass

  • We offer a broad variety of clear door glass sizes and external grills or divider options
  • Clear glass (no dividers) gives a more modern look
  • Clear glass with external grids or grills gives an iconic, traditional look
  • Glass is typically ½” thick (some select clear styles are 1” thick

Glass with Internal Grills (also known as “grids” or “dividers” or “grilles”)

  • Modern look & easy to clean (because you don’t have to clean around external grids)
  • Available with white or bronze internal grids (tan and black also available for special order)

Venting Door Glass

  • Great for a kitchen or side door where airflow (e.g., to let in a nice breeze on a summer day or to let out the smoke/smells from cooking) is desired
  • Two insulated glass units (fixed one up top and a sliding one below) – you can slide the window open. Includes a removable screen.

Replacement Door Glass Frames

  • Materials: We offer door glass frames in only high quality materials. In general, our decorative glass options and frames for 1” thick glass are typically PC/ABS. Frames for ½” glass (and the frames on our clear glass product offering) is typically the high quality glass-filled Polypropylene. Some sizes (typically less common sizes) use high-quality vinyl frames.
  • Shapes/Sizes (see measuring door glass down below): We offer door glass frames in rectangular, oval, round top, arch top, and fanlite shapes
  • Colors: We offer white and tan frames. Tan frames are only available for 1” thick glass in select shapes/sizes. We recommend tan frames if you plan to stain your door glass frames because the tan base will require fewer coats of stain to reach the desired color. However, PC/ABS white frames can be stained easily (you just might need an extra coat or two to reach the desired color)
  • Profile: Most of our frames have a profile known as an “R” profile or a colonial or traditional profile (see picture below). Flat (also known as shaker or quaker or craftsman) profile frames are becoming more popular and are offered with our craftsman style door glass and on select decorative styles.         


Traditional “R” Frame         Shaker Flat Frame

Replacement cycle

Door glass should be replaced every 10-15 years, or as desired for a new look. Often times the door slab itself is in great shape but decorative door glass can look dated or tired. Fresh glass and a new coat of paint for the door will result in a door that looks brand new at a small fraction of the cost of replacing the entire door system. This makes door glass replacement an excellent project when renovating a home or preparing a home for sale/going on the real estate market.  

We also often help with glass replacements when:

  • The insulated glass unit seal fails and the glass becomes fogged/filled with condensation
  • The glass is broken (e.g., a rock from a lawnmower, someone accidentally bumps the glass, or the glass is broken in a forced entry)

Door glass frames should be replaced if they become warped, cracked, chipped, discolored, or otherwise broken. The polystyrene frames installed on many older doors crack and deteriorate within ~2-5 years, and even faster in direct sunlight. New frame materials hold up much, much better but still require replacement every 8-15 years, depending on exposure to sunlight, the elements, and normal wear and tear. Often, full lite door glass frames can become cracked or broken at the bottom as a result of pets pawing or chewing on the frames.

Installation instructions

  1. Door Glass Installation(see video)
  2. Remove screw caps to expose screws (should be on the inside of the home, if installed properly). If the caps are painted over and difficult to remove, try a small flathead screwdriver and mallet/hammer to cut or knock them free.
  3. Use a utility knife to score around the interior and exterior door glass frames to cut through any existing paint
  4. With a friend outside holding the glass firmly into the door, remove screws. If screws strip out, try a stripped screw tool or you can use a drill to drill out the screws
  5. Remove interior frame
  6. Remove exterior frame and glass unit
  7. Clean the opening
  8. Place the new glass unit & exterior frame assembly into the cut-out opening. The exterior frame does not have screw holes and typically comes pre-caulked to the insulated glass unit. Install this assembly from the outside of the home.
  9. While a friend holds the exterior frame and glass unit into the door from outside of the home, attach the interior frame (the one with screw-holes)
  10. Fasten screws tightly (no harder than a good twist by hand, set power drills to lowest torque setting, do not exceed 15 in-lbs of torque)
  11. Cover screws with provided screw caps (if no caps are available, you can also use white putty and smooth over with your thumb, then add wood grooves with a fingernail)
  12. Door Glass Frames Installation Instructions

Remove your old door glass and frames from your door

  1. Remove screw caps to expose screws (should be on the inside of the home, if installed properly). If the caps are painted over and difficult to remove, try a small flathead screwdriver and mallet/hammer to cut or knock them free.
  2. Use a utility knife to score around the interior and exterior door glass frames to cut through any existing paint
  3. With a friend outside holding the glass firmly into the door, remove screws. If screws strip out, try a stripped screw tool or you can use a drill to drill out the screws
  4. Remove interior frame
  5. Remove exterior frame and glass unit

Prepare your glass and door

  1. Clean the opening in the door
  2. Remove caulking from your glass (and clean from the face of the door). We recommend Goo Gone if you have sticky or stubborn caulking
  3. Clean your glass with Windex and let dry for at least 20 minutes
  4. If your new outside (exterior) plastic frame (the side without the holes for screw caps) is pre-caulked, skip this step. Otherwise, add a bead of silicone caulk (available in our accessories section) to where the exterior door glass frame seals with the exterior pane of glass. Then add a bead of caulk to where the exterior door glass frame seals with the exterior face of the door.
  5. Within 10 minutes of applying caulk to the exterior door glass frame, press the frame down onto the glass (glass should be laid flat on risers like a block of wood with a towel to allow the frames to fully seat onto the glass). Push glass and exterior frame together and wipe any excess caulking that squeezes out
  6. Let caulking sit (preferably for a few hours or overnight) to harden. This will make installation into the door easier as the glass and frame will slide less, however this step is not required

Install into door

  1. Install the new glass unit & exterior frame assembly into the cut-out opening. Install this assembly from the outside of the home.
  2. While a friend holds the exterior frame and glass unit into the door from outside of the home, attach the interior frame (the one with screw-holes)
  3. Fasten screws tightly (no harder than a good twist by hand, set power drills to lowest torque setting, do not exceed 15 in-lbs of torque)
  4. Cover screws with provided screw caps (if no caps are available, you can also use white putty and smooth over with your thumb, then add wood grooves with a fingernail)
  5. Finishing (painting or staining) Door Glass Frames

NOTE: We do recommend using painters tape and painting the frames prior to installation (painting on a flat surface prevents running)

White Polypropylene Frames (see instructions in box – will say “white frames” and not have a tan dot in the upper right hand corner)

  • Your frame is maintenance free and does not require painting.
  • If you choose to paint this frame follow below steps with frames at room temperature:
    • First lightly sand frames and clean with mild detergent mixed with water. Let dry.
    • Next, apply adhesion promoting primer made for use with polypropylene. We recommend: Sherwin-Williams UPO 7228 Low VOC Adhesion Promoter – clear plastic adhesion promoter, Rust-Oleum Brands 249058 White Ultra Cover 2X Enamel Spray Primer, PPG SXA 1050 plastic adhesion promoter, or BASF R-M AM865 plastic adhesion promoter.
  • After primer dries, apply thin coats of an exterior grade acrylic latex paint. Let paint dry completely between coats. Apply clear top coat at paint manufacturer’s recommendation.
  • CAUTION: Apply paint in a well-ventilated area and follow all paint manufacturer's cautions, warnings and instructions.

PC/ABS Frames & Vinyl Frames (see instructions in box – will say “primed tan/white frames” and will  have a tan dot in the upper right hand corner)

  • Painting                                                 
    • First clean with mild detergent mixed with water. Let dry. No other surface prep needed.
    • With the frames at room temperature, apply an exterior grade acrylic latex paint in thin coats, allowing the paint to dry completely between coats. Apply clear top coat at paint manufacturer’s recommendation.
    • CAUTION: Apply paint in a well-ventilated area and follow all paint manufacturer's cautions, warnings and instructions.
  • Staining                               
    • First clean with mild detergent mixed with water. Let dry. No other surface prep needed.
    • Next, with the frames at room temperature, apply an opaque base coat of exterior grade acrylic latex paint. Let dry completely.
    • Apply the stain, work it into the grain with a sponge or cloth, and then wipe off the excess stain. Continue applying coats of stain until you are satisfied with appearance.
    • Apply clear top coat at paint manufacturer’s recommendation.

Special cases/FAQ

  • My glass/frames measures about 2” narrower than what I saw on the website
    • This is a narrow size and is typically used on narrow doors (i.e., 30” wide and narrower). Most styles are available in the NARROW size (see our “Other Sizes” section). Some decorative & other styles can be special ordered in this size as well.    
  • After I installed the new glass/frames some caulking oozed out onto the glass/door—what do I do?
    • If the caulking is still wet, wipe clean with a damp cotton rag. It the caulking is too sticky for that then use a plastic putty knife to scrape off the excess and then use goo-gone to clean up any residuals.



How to measure your door glass to select the correct size for your door

First we recommend to check your door thickness. Most doors measure 1 3/4" in thickness. Our Glass & Frame Kits fit doors that are within 1/16" of 1 3/4" thickness.

Glass Size vs. Cut-out size vs. Outside Frame Size - what's the difference?

Each door has three measurements. The first is the size of the glass, for example 22" wide by 36" tall. The next measurement is called the cut-out or "opening" in the door where the door glass is inserted. This measurement is 1" larger in width and height than the glass, so in this case the cut-out would measure 23" wide by 37" tall. If you are adding glass to a door that does not currently have glass, or if you are expanding the opening in a door to allow for a larger size glass, the cut-out is a key measurement. Finally, the outside frame measurement (see below) is an inch or so wider than the cut out, and since the frame is visible it is the easiest measurement to do. Remember, your actual glass size will be about 2" narrower and shorter than your frame measurement.  

  1. Outside Frame Measurement (actual glass size will be 2" narrower & shorter than outside frame measurement)

Measure the outside length and width of your existing frames (see picture above). Measure along the face of the door from the outside corner to outside corner of the frame (width and height, not diagonally). Frames that measure up to ½” shorter or narrower will work fine (the profile of door glass frames has changed slightly over the years but the actual glass sizes have remained consistent). However, if the existing frame measures more than ¼” larger than the replacement frame the replacement likely will not fit. We also recommend measuring the glass directly and confirming exact measurement for oval frames, as oval frame profiles have varied significantly over the years.

  1. Glass Thickness Measurement (for replacement frame kits, not necessary if you are purchasing a kit that includes the glass)

Measure the exact overall thickness of your insulated glass insert (the full "sandwich" of both pieces of glass and the gap of insulating air in between).  You will need to unscrew enough of the interior frame to squeeze a tape measure in between the frames to determine the glass "sandwich" thickness. Usually a measurement can be taken after unscrewing around a corner of the inside frame -- not the entire frame. The glass "sandwich" will measure either 1/2", 3/4" or a full 1".  If your glass is 3/4", you will have to replace the glass and the frame assembly, since frames for 3/4" glass thickness are discontinued. However, the vast majority of glass is either 1/2" or 1" thick. Most of the time (but not always!) double pane clear or etched glass is 1/2" thick. Decorative "triple glazed" or glass with two clear pieces sandwiching a decorative third piece of glass (often with metal caming inlaid), is typically 1" thick. It can be hard to judge the thickness of your glass without measuring, so we strongly recommend removing screws from one of the top corners of your existing frame and using a small ruler to measure the glass thickness.

Buying Guide on Fire-Rated Glass for Your Needs

Door Glass and Frames Buying Guide






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