Our old house, and previous dog door instructable had a large 3 panel sliding glass door. The new house was two one lite insulated doors, and no means for the dog to get out. The result has been several accidents and lost stuffed animals. This project in an overview of what is involved to replace the insulated glass already in place with a dog door and glass combination.
Step 1: Tools and Supplies
For both doors, I have used the Ideal Pet Products Medium Dog Door. It runs $20 on Amazon, and is pretty robust. In our case with this door, I used pressure treated 2x lumber and a pine "veneer" on the inside to make up the difference. As the 2x's are 1-3/8" and the door is 1-3/4". This door also has a metal skin on the outside that needs to be accounted for.
Insulated Tempered Glass Units (more on next step)
Door Door Amazon
Wood, Pressure treated if exposed to outside
Pocket Hole Jig
Arby's Sandwich (for training)
Step 2: Measuring and Ordering Glass
This is the one that puts most people off a project like this, because you can't cut back an insulated tempered unit.
The first thing you need to do is measure the glass opening. If the glass stop can be removed and you are nervous, you can rip out a section to see, but generally in the US the glass is either 3/8" or 5/8" inside of the daylight opening(the visible area of the glass). You can usually tell based on the moulding/glass stop used. The glass I ordered had a 3/8" spacer and I should have ordered 5/8", but it won't make enough difference to notice.
After you have your total opening for the glass, you'll need to figure out the size of your rails (approximately) and the size of your glass. Usually you'll want to leave 1/8" gap around the glass for imperfections in the door and glass.
My glass opening was 20-1/4 x 68. The glass I ordered was 20-1/8" x 50" and 7-7/8" x 13-5/8". This leaves me with a rail somewhere in the area of 4-3/8" (inside dimension), which I can adjust as necessary to make room for mistakes.
Ordering the glass is a simple as calling a glass company. They will want to know the sizes, thicknesses, spacer and a few other things. Mine ran me about $220 or so for the two units. Make certain your order TEMPERED glass. After I ordered the glass, I ran across Onedayglass.com, which was significantly cheaper, but my credit card had already been charged. My glass took about 10 business days to arrive.
Step 3: Removing the Old Glass
This process can be a little arduous, it's like the don't want the glass to come out! You will need to remove the glass stop surrounding the glass on the inside of your door. If you don't see any tell tale brad/nail holes in your door, it might be clamp glazed which means it was assembled with the glass in place.
If this is the case, you may want to rethink the project. You can still do it, but you will need a router and a special bit to run on the shoulder and cut just deep enough so as not to cut the glass. This can be a pain...
After the stop is removed and all the brads are out, you will need to coax the glass out. Using a utility knife and a heat gun works well to soften the silicone. The glass won't just pop out, you can gradually work around the perimeter and peel it out.
After that, clean up where the glass meets the wood to get good seal for the new glass.
Step 4: Test Fit Your Glass, Measure Your Rails
Pretty simple here. Make sure your new glass fits, then determine how wide your rails can be to fit everything together. The side with the dog door won't need any rabbet for the glass, so start with the measurement of just the shoulder, then determine how much you have to add for the rabbet/moulding.
Step 5: Install Rails
After the rails are cut and rabbeted, I used a pocket hole jig to get the holes started, then 3" drywall screws to hold everything tight. I did the cross rail first, then the vertical bar second so everything was very tight. Your rails are set inside the original rabbet for the glass, so they have butt joints on the ends.
Now double check your glass fits before continuing.
Step 6: Install Glass and Temporary Stop
Now it's just a matter of running a bead of silicone and setting the glass in place. I used a brad nailer and some temporary glass stop to hold everything together while the silicone set. You can see these in the inside picture
Step 7: Paint/Stain, Install Dog Door and Train Dog
Paint or stain the interior/exterior as necessary. I used spray paint to match the exterior and Minwax Walnut stain and some polyurethane to match the interior. It didn't take long to dry on the inside.
Installing the dog door is simple. If your dog has never experienced a dog door, I suggest getting an Arby's sandwich and coaxing them through a few times. Tillie remembered pretty quickly, though there is a much larger drop off than before.