Pet Doors to install "Through Glass"

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Pet door to install through glass

General Information About Pet Doors "Through the Glass"

The first thing to realize regarding a pet door for glass doors is that you cannot cut tempered glass!! If you attempt to cut tempered glass, it will shatter! So for a cat door in glass door or doggie door glass door your probably looking at getting it replaced.

The second thing to realize regarding "In-The-Glass" pet doors from Pet Door Guys is how convenient their system makes installing a doggie door directly through the dual-pane glass of your sliding glass door. An in glass pet door cost will vary, but the standard units are around $1,000 and then you would be responsible for paying the installer.  Below is our suggestion for how to put a dog door in a glass door:

How to Install a Dog Door Directly into Glass Doors

Things you will Need:

  • Pet Door

  • Professional glazier (Highly recommended)

  • Glass door

  • Mounting adaptor (if electronic)

  1. Consult with a local glazier to make sure your glass door can be cut. This is especially important if your glass is dual pane or tempered.

  2. Measure your pet from feet to shoulder to get a correct flap size

  3. Choose from pet doors that have the ability to be installed in the glass. You can contact our pet door experts for help!

  4. Order the dog or cat door with

  5. The glazier will need to take your glass door and cut according to the pet door’s rough cut

  6. If your pet door is electronic, be sure to install an adaptor with the pet door; glass can interfere with the door’s signal.


Note: It is not always recommended to install a pet door directly into your sliding glass door as the protruding frame of the pet door can cause your slider not to close properly. If you have a French Door with individual panes, your installer can simply remove one pane of glass. For these doors, we highly recommend the Hale Custom Doors.

Check Additional Information for more information on glass installation for cat and doggie doors


Read commonly asked questions about "Through the Glass" Pet Doors below >>

Click below to expand:


Manufacturer Return Info

Looking to cut a hole in your glass?How do you tell if your glass is tempered? Tempered glass usually has an indicia, or 'bug' as it is called in the trade, in one corner. If you see a bug, the glass is tempered.If you don't see a bug, well.... it may be a plate, which you can cut, and it may not. Older houses are more likely to have plate glass; newer houses probably have tempered. Dual-pane, insulated glass units are almost certainly tempered and shouldn't be cut into anyway. Countries outside the USA would appear to have more plate glass.

Plate glass can be easily cut with a glass cutter. Problem is, it isn't very strong. Some pet doors are specially designed to spread the force over a wide area but they're only meant for cats or for small (and non-hyper) dogs.

The best approach is to have a professional glazier from a local glass shop get you a new piece of glass with the circular cut-out required done for you. This can work for dual-pane glass as well as single pane.

Another way to put a pet door "in the glass" is to replace the glass with 'Lexan'--the generic name is polycarbonate--which looks like glass but which can be drilled and sawed like wood. Use a minimum thickness of 3/16" if possible. Also, look for 'scratch resistant' Lexan. In addition to glass, these cat flaps are fine candidates for any thin material including plywood or screen.

The best way to put a pet door through your glass is with a pet door designed to do so! We sell Pet Doors Guys units, which will replace an entire pane of glass in your sliding glass door with a new piece of glass with pet door pre-installed.

Q: When I purchase a “Through the Glass” dog door, is the entire sliding glass dog door included?

A: No, when you purchase a “through the glass” dog door it comes with the glass panel only. The framing of the sliding door is NOT included in the purchase. Since this unit will replace your current glass inside your framing, there will be an installation process you or a hired professional will need to follow.  As well as filling out the appropriate order form.

Through the glass pet doors are a great option!

Q: How long does it take to get the “Through the Glass” models?

A: It takes about 2-3 weeks for these type of pet doors to be manufactured, then allow 1-5 business days for transit time from the west coast. When it ships out we email you the tracking information, so you’ll know when to expect delivery and can schedule for an installer to come out.

Q: Why is it so expensive to solely purchase the pet door for glass door?

A: “Through the glass” units can be pretty expensive because you’re getting a custom unit made entirely to your specifications, that’s why we highly recommend hiring an installer to get all of the measurements, as these custom doors are non-returnable. Some of the extra options can add to the cost as well, say if you need the Low E coating or added tint.

Q: What are the benefits to the through glass units?

A: The "through the glass" units don't take up the space for you to walk through like a patio panel pet door would.  This is a huge benefit if you have a smaller retrofit slider, as now you don’t have to worry about trying to squeeze through sideways.  Additionally, the "through glass" doggie doors utilize your existing lock, so you will not have to worry about how to go about securing your home.

Through the glass vs. patio panel

In terms of appearances benefits, it also utilizes your current door frame, so you don't have to worry about matching a new frame with your current door and frame. The constantly open sliding glass door will leave you with extra framing blocking your view outside! When in the glass, you do not experience this issue. The Endura Flap Pet Door included is great for insulation so it compliments the dual pane glass in most new sliders.  

Through the glass vs. Patio Panel

Q: Why are certain doggy doors suitable for glass installation and others are not?

A: With certain through glass pet doors the self framing range may not accommodate the thickness of the glass. There are also other variable measures of different types of doggy doors that may not be suitable for through the glass installation. The doors specifically made for a through the glass installation also help spread the force over a wider area. This is an important feature because it prevents the glass from breaking around the door. If you were to install a pet door that does not properly accommodate with a glass installation location, you may encounter problems with your existing glass, with cracking or even potentially shattering due to consistent ramming into the frame while entering/exiting. This problem typically comes from having a larger animal that is more hyper, because as they enter and exit the door they are more likely to hit the sides of the panel. If the door installed was not acceptable for through glass installation it may cause the surrounding glass to break after an extended period of contact. This is why we typically like to recommend using a through the glass pet door if you have cats or smaller, less hyper dogs. With a larger dog we would recommend going with a Pet Door Guys “In the Glass” because they both come with the surrounding glass framing and are more secure than just installing a pet door into your sliding glass door that you cut a hole into.

      framing increases stability        Through the glass increases stability

Pet Door Guys “In the Glass”

Q: Why can't I just cut into any glass door or window?

A: You can not just cut into any glass or window because their are different types of glass that require different procedures to properly cut or replace.  If you attempt to cut into "tempered" or dual pane glass, it will shatter. So how do you tell if your glass is tempered? Tempered glass usually has an indicia, or 'bug' as it is called in the trade, in one corner of the glass panel. If you see a bug, the glass is tempered. If you don't see a bug, well.... it may be plate glass, which you can cut, or it may not. Older houses are more likely to have plate glass; newer houses probably have tempered. We always like to recommend hiring a professional when it comes to cutting or installing glass units. Cutting glass on your own is a health and safety risk.

Q: Can you walk me through this process of ordering the through glass units?

A: First, you’ll want to go over all the information located on the “details” tab of the product you chose and make sure to check out the Placement Guide which will show you where the pet door should be installed based on your current sliding glass door situation.

Next, you will want to Review Sizing Suggestions, Adding Step-Over, and After Installation in order to find the appropriate size opening for your pet.  Make sure that when you do get an installer that you give them all this information too, so that they are able to correctly fill out the order form that they will send to us.

Next you purchase the product via our PetDoors website, and we hold the order for you until we receive that order form. Your total for merchandise, shipping and any sales tax will be shown for the glass unit, however the charges from your local glass shop are not included since you would pay them separately.

You will then need to contact a local glass shop to have them do the measuring, installation, and filling out of the order form. The installer will come out and take apart your sliding glass door frame (a very easy job), takes width, height and thickness measurements then re-installs your glass slider. After that they finish filling out their portion of the order form.

That completed Order Form needs to be emailed (or faxed) to use. Our email is .

Once we have the order placed and the form we fax it over to the manufacturer so they can build the unit!

We ship the completed through glass dog door directly to the installer and they come back out and switch the current unit for the one with the dog door.  Done!

Q: Can I install one of the glass units myself?

A: Depending on how handy you are it might be possible, although it is not the best idea to DIY because they are custom ordered, so you can’t return them if the measurements are off.  We highly recommend that you have a glass company do it for you, unless you are a trained professional.

Q: Do you offer electronic options for “Through the Glass” pet doors?

A: Yes, the SureFlap Microchip Pet Door and the Cat Mate Elite 355 Super Selective Cat Doors can be installed through the glass. However, these two options are not specifically made for a through glass installation and depending on your glass type would require replacing it or cutting it.  On the other hand, the Pet Door Guys pet door option is specifically made for a through glass installation and comes with the glass framing and the panel, but is not an electronic door option.

    You can still have an electronic pet door!                                                         The framing is included!

Glass around Pet Door Separate                                       Glass Framing around Pet Door Included

SureFlap Microchip Pet Door                                                        

Cat Mate Elite 355 Super Selective Cat Doors                         Pet Door Guys

Q: What is the minimum step over on the “Through the glass” units?

A: The minimum step over on the through glass units is 3 3/4" plus however tall the frame of the the sliding door is.  So if your frame is 2” tall than the minimum step over would be 5-¾”.  There are 2" or 4" step over add-on options as well, these will add 2” and 4” to the minimum to raise the step over to accommodate taller pets.  

Q: What is the largest flap size on the through glass units?

A: The largest flap size offered for through the glass units is XL 12" x 23".

Q: Why does it matter where the doggie door is installed in the glass units?

A: If misplaced, the doggie door can get in the way and impair the full function of your sliding door. In the image below, the red arrows indicate examples of improper placement of the dog door in your sliding glass door.

The first(top) arrow shows a single section sliding glass door with the pet door installed on the stable side. This installation would be a problem because the door that slides is on the inner track and if opened it would hit the dog door and would create a loss of walking clearance.

In the second example(arrow #2), the same situation is present, however the dog door is installed in the sliding glass door section and this would cause a problem and not let the pet through if there is a screen present on the outside. Before make an installation like this, make sure your pet has enough clearance and nothing will hinder the pet from entering/exiting.

In the third installation example (arrow#3), the pet door is again installed into the fixed panel of the sliding glass door. This example however is with a 8’ wide door opening. Again, when the sliding glass door is opened, the pet door will stop the slider from fully opening and would cause a loss of walking clearance for people.

The last arrow (arrow#4), is an example of installing a pet door on a 4 section sliding glass door, 2 fixed and 2 sliders. The arrow points to the installation of the pet doors on the fixed panels. This installation location would cause a problem because as either slider is opened you again would lose a significant amount of walking clearance room for yourself. Therefore, take a look at all the examples below without an arrow to get a better idea of what location will work for you and not cause any problems for you, your pet or the sliding glass door.

OX vs. XO layout

Q: What is an "XO" vs "OX" layout?

A: The XO layout is for typical inside sliding wide patio doors, outside sliding doors, three panel doors and wide doors. The OX layout is for four panel doors. A good way to figure this out would be to take a look at this chart.

OX vs. XO layout

Q: What layout would I choose for my dog door if my slider was on the outside and why?

A: You would refer to the XO layout because you do not want the sliding half of your door to hit the doggie door when opening or have the pet flap hit the meeting rail/parked screen when the pet exits.

Q: What is Low “E” coating?

A: It stands for Low-emissivity coating. Low E is applied to the inside of the glass to cut backon the heat and cold transfer. Low outside temperatures combined with moist, warm air inside the house can result in condensation on the inside of any glass window including that in a patio door. Dual pane, low "E" glass can greatly reduce or eliminate this problem. This feature is especially important in cold climates.

Q: What are grids on glass?

A: Grids are crossbars between the glass panes. They sometimes are outside the panes as with your typical French Doors.

Through the glass works great with French Doors.

Q: I would like to get the glass with the doggie door already in it for a French Door, what can I do?

A: To replace your glass, we offer the Pet Door Guys In the Glass Unit. This is just the glass piece which gets inserted into your existing frame.

Q: What does it mean by standard and oversize glass size?

A: Standard Glass Size has a square inch range of 34" x 76" or smaller. Oversized Glass Size would be any range over 34" x 76" and up to 46" x 92". This doggie door for glass door only works with Dual Pane Glass units.

Q: I have a small pet, only 10" to the shoulder and 15Lbs, will the small work?

A: Yes it should work, just be sure that the step over isn't too high for your pet.  For both of the manufacturers the minimum step over would be calculated by measuring the frame of the sliding door from the bottom to the start of the glass then adding 3-¾”.  So if your frame was 2” high then the step over would be 5-¾”. With a small pet at 10” we typically would recommend step over range of 3”-4”. A step over of almost 6” would make it much more difficult for your pet to get through, so reducing the step over as much as you can to get it into that range should be a main concern for you.  Typically you could use a step or a ramp for this.

Q: Does the flap in the glass units insulate well?

A: Yes, the Pet Door Guys glass units use the Endura Flap, which provides excellent insulation.

Q: Can you change the flap in the glass units if it wears out?

A: Yes, you can purchase replacement Endura Flaps on the website, it might sound strange, but you will need to purchase the one for the Door/Wall Mount since that includes the hole plugs.  However, they can be a little difficult to replace because you must remove the whole frame in order to get the new flap into place properly.

Q: What do you need to put the SureFlap Microchip doors in glass?

A: You need to purchase the "through glass" installation kit that comes with the adapter needed for installation of the doggy door. This installation kit will help simplify the process of installing the pet door in  glass/material that is not already compatible with the SureFlap pet door.

Q: How do I put a dog door in a glass door?

A: There are a few different approaches depending on your situation and glass type. If you have single pane non-tempered glass, you can cut the glass (must be a circle) and install the pet door through that. If you have dual pane or tempered glass this cannot be cut (it will shatter) so it must be replaced. You can have a local glass company get you a new piece of custom glass with a notch already in it, and then install a pet door through that. The other option would be to get the new glass unit with a pet door already installed, this way your glass company just has to take some measurements of your current unit and then switch them out for you. This would be similar to the process you would take if the glass broke and you had to replace it. A good option for this would be Pet Door Guys or Advanced Windows.

Q: Why do all the dog door glass door pictures show the pet door under the handle on the operating panel?

A: Most sliding glass door's operating panel slides inside the home. Due to the pet door's frame thickness it needs to be on the operating panel if it slides inside the home. The pet door needs to be placed under the handle because if it's placed on the other side, the center post of the fixed panel or screen door may prevent the pet door from opening properly.

Q: Can I install any glass door with doggie door?

A: No. There are numerous things that have to be considered when installing dog door in glass door. It is best to consult with a Customer Service Representative and a local glazier for guidance and details.

Q: Can I personally install dog door in glass?

A: We do not recommend this installation process for homeowners to do unless they have glazier skills. It is a complicated process, but easy for glaziers to do.

Q: What pet door for glass doors can I install in my current glass door?

A: We recommend that you consult with a glazier (glass company) to see if your glass can be cut. Most doors are made with tempered glass and cannot be cut. If it can't be cut the Pet Door Guys and Pet Door Products offer replacement glass solutions.

Q: Can I have my glass cut to install a pet door for glass?

A: No, a pet door for a glass door involves having a new piece of glass made to replace your existing glass. We recommend keeping your old glass because the process can be reversed should you not need a pet door in the glass any longer.

Q: I need to know how to install a doggie door in a sliding glass door, can you help?

A: To install a glass door with pet door you should hire a local glazier. You can not cut your existing glass. The Glazier help you measure and install your pet door. A video on how to install a dog door in sliding glass door can be found here:

Q: I want a doggy door in glass door. What are my options?

A: We have two custom order options that can replace an existing insulated glass unit. They are the Pet Door Guys - "In The Glass" and Pet Door Products - "In The Glass" pet doors.

Q: Can I buy a sliding glass door with doggie door built in?

A: We offer two "In the Glass" pet door options that replace your existing glass panel with a new one that has the pet door built in. This is less hassle than replacing your entire sliding glass door. Check out Pet Door Guys or Pet Door Products

Q: Does have anything for my newer vinyl framed sliding glass door?

A: A newer type of dog door for sliding door are built specifically for installation in vinyl framed sliding glass door tracks. We think they're a great choice because, with vinyl frames themselves, they look more like they "belong" and will generally engage with the lock on your sliding glass door. However, there are disadvantages as well. They're relatively hard to install, they're not easily removable, and they come in a very limited range of flap sizes and 'step-over' heights. Based on our customer experience we find some prefer the vinyl specific option, while others have decided on the more general-purpose dog doors for sliding glass door to get a broader range of feature choices. The best two pet panels recommended specifically for vinyl sliding doors would be:

Q: On my doggie door sliding glass door panel, what do I do about the gap between the operating panel and fixed panel?

A: Many panels like the Endura Flap Thermo Panel comes with a Draft Stopper to seal that gap. If not, you can purchase a Draft Stopper

Q: What is the shortest dog sliding door available?

A: It is a Custom Thermo Panel Small flap with a height of 35 inches. Other Custom Thermo Panel minimum height sizes are: Medium 42 inches, Large 48 inches and Extra Large 46 inches.

Q: I need a doggy door for glass door that is on hinges what are my options?

A: Dual-pane, single sheet of glass versions you will need to order a Pet Door Guys In the Glass replacement glass unit. If you have a traditional french door with individual panes, you'll need to order a Hale Custom Dimension pet door.

Q: What slider doggie door do you recommend for windows that slide left to right?

A: We have a couple of dog door solutions that can be custom made to any height they are the Thermo Panel and Quick Panel

Q: What is the largest sliding doggie door?

A: Dog doors in glass largest size vaires by manager. The largest available is the Hale Standard Patio Panel or Omni Panel. The Giant size is 15 1/2" wide x 27 1/2" high.

How to install a Dog Door in a Glass Door?

You will essentially be ordering a new piece of glass to install a doggie door into your sliding glass door. We highly recommend hiring a professional glazier who knows how to remove and replace the glass in a sliding glass door. 

Step One: Check Out Our Placement Guide

First, check that one of the installation options is suitable for you. They are:

  • 2 Panel Slider: Installation in either side of the inside track panel. When using the center-post side, it is important to ensure the screen will not interfere with the action of the pet door flap.

  • 3 Panel Slider: Installation may be in either side of the inside track slider of jamb of the 3rd panel. The same concern applies to the screen as stated above.

  • 4 Panel Slider: Installation may be on either side of either inside track panel

For diagrams, check out our Placement Guide here.

Step Two: Contact a Glazier

Contact a local glazier you'd like to work with to help you measure and later install your in-the-glass unit. They will come out to get the measurements of the actual glass that is in your sliding glass door, including whatever glass might be hidden! Usually a quick search online should suffice, but this List of Installers is also a good place to start (Note: is not affiliated with these installers and not all of them are glaziers).

Step Three: Measure Your Pet!

Measure your pet to get an accurate flap size. The In the Glass unit comes with a 3 ¾” step over in addition to any step over your frame has right now. Take this into account! Here is a Measuring Guide to help you out.

Step Four: Order Online

Place the order on this page to receive the order form asking for your custom dimensions. Your order is on hold until we receive this order form. The form is emailed directly as you complete your order.

Step Five: Custom Dimensions Form

Be sure to enter an email with your order. As soon as your order is completed, you will receive an email with an order form. You will need to fill out this form and send it back to This is where your custom dimensions come in. Your order will be on hold until we receive your dimensions.

Step Six: Shipping & Installation

We then arrange with the factory to custom-build your new piece of glass with the pet door in the lower corner specified by you.

Here is a video that roughly summarizes the process of receiving and installing the In-Glass Pet Doors:

You can also have a glazier cut a hole in your existing glass if your glass is not tempered, and install a pet door through the glass yourself. This is particularly common to do with smaller pet doors intended for cats!

What does this mean?

Installing a pet door through your glass is a great alternative to a patio panel insert. You order a piece of replacement glass for your glass door, and that new piece of glass has a pet door at the bottom already built in! All your glazier needs to do is remove your old glass, and replace it with the new glass. 

How it works

Why would you want this?

Panel inserts are great for a lot of situations, and can be completely temporary which is ideal for renters. The problems that arise are:

  1. You cannot use your sliding glass door's existing lock to reliably lock the sliding glass door! With a pet door in the glass, your slider functions and locks like normal.
  2. Your view is going to be obstructed by the additional framing that overlaps when your sliding glass door is always in the "open" position. 
     Before and After
  3. If you have a smaller sliding glass door, you might not be able to get outside when the pet panel is installed
     Before and After

When your pet door is installed right through the glass, nothing has to change for you! The sliding glass door will still open and close normally, and your pets will be able to enjoy the luxury of coming and going as they please. 


You can also have a glazier cut a hole in your existing glass if your glass is not tempered, and install a pet door through the glass yourself. This is particularly common to do with smaller pet doors intended for cats!

Do you have a question that wasn't answered? If you do, please email it to us!