Filling in a Garage Door Opening: Rain Screen Siding System
Drainage and airspace allows liquid water to drain out and air to circulate
Garage doors are often filled in when they’re on a tuck-under one-car garage—because it’s a lot easier opening a door with a knob when walking into a daylight basement.
The first and most important place to start is in the grade of the ground butting into the wall. If it is sloping toward the house, dig it out and slope it away.
Use pressure-treated framing lumber wherever the framing contacts concrete and regular framing lumber in between. Also, use pressure-treated wall sheathing on the bottom of the wall and regular sheathing above.
This video is not about door flashing, so we’ll skip that step and say "install the door."
At the base of the wall sheathing and under the door sill run a generous bead of sealant. Slide metal flashing under the door sill to bed into the sealant. Add another short bead of sealant as a dam along the edge of the door. This will seal the base flashing to the sill flashing. Continue base flashing on the other side of the door.
Seal the top of the flashing to the wall sheathing with flashing tape.
Now you can install a weather-resistive barrier and rainscreen drainage mat. Some products come as a single package, some come separately. At the bottom of the drainage mat, use bug screen to keep the bugs out. Overlap upper sections over the lower sections and wrap the corners tightly.
Add trim over the wrapped corners and get ready for siding.
Keep the bottom piece above the flashing enough that water can drain out from behind. Finish siding the wall and detail the top of the assembly. Install a block of wood at the top of the wall, tucking bug screen behind the siding. Install trim at the top. The backing block should be thick enough to allow a quarter inch of airgap for ventilation.
Walls that let water escape and promote drying tend to stick around.
—Will Schwarz is a remodeling contractor in Marshfield, VT. This animation summarizes a five-part series following an actual project.