This was off the top of my head and spur-of-the-moment. Our back sliding glass door and small doggie door face west where we get some 50 – 60 mph winds at times. A 20 mph wind will make the doggie door flap swing open about 4". Add pouring rain and it's a dash to put the hard plastic door down to stop a wet mess inside the house.

Because it's a small door, I made the two vertical side pieces just a little taller than the actual doggie door. It just happens to be a nice height for a little table.

I added a roof to stop the rain and had some unused Tupperware lids for cute little windows.

The nice thing out this design is you can make it for any size doggie door. For our Chihuahua to a large German Shepherd sized door.

Step 1: Materials and Tools

Material list
Pressure treated plywood
Cedar or pressure treated 2X2
Tupperware lids
Rebar
Zip ties
Deck stain
Construction adhesive
Deck screws
Caulk
Seal-A-Meal bag and sand

Tools: You could make this with nothing else but a jigsaw and a drill with a screwdriver bit. A circular saw is helpful for the straight cuts. A heavy duty stapler is also needed.

Step 2: Cut It Out and Put It Together.

Once you decide the overall size, cut the two sides pieces.
I used a piece of cardboard that I cut with a razor knife to make a pattern to fit the door and the brick wall.
Screw 2X2's across the bottom and top of both side pieces.
Screw the vertical 2X2 corner piece to one of the side boards then connect the two sides by screwing the other side board to the vertical 2X2 in the corner.
To cut the roof support brace lay your brace board across the top of the side boards to make your cut marks. Once cut, screw the brace to both side boards.
Use a big piece of cardboard to make a pattern for the roof. Mark and cut the roof. Screw the roof to the 2X2's attached to the sides.
Windows are optional of course. But if you have some extra plastic cookware lids trace an opening the size of the container the lids went to. That way there will be a lip to glue the lid to the sides.
Deck stain actually makes pressure treated wood looks nice so buy a small can. When it rains the water really beads up.
After the stain dries glue the windows in place with construction adhesive.
Mark the inside corner and corner next to the wall for the rebar
1. *Locate any underground water pipes or electrical wires first.
2. If you have a slab etc. you'll need a drill with a long masonry bit to drill holes first.
3. Hammer the rebar far enough to wood pieces.
4. Drill some holes and secure the rebar with zip ties.

Step 3: Let Your Dog Test It Before Adding the Flap

Before adding the flap, let your dog get used to using the vestibule before adding the plastic flap.

I made the flap using a Seal-A-Meal bag and filled the bottom with a little sand. You may find it easier to just cut the zip ties and flip the vestibule over to staple the plastic rather than reach inside to staple it.

Caulk the edges of the wood that butt up next to the door and wall.