How a Louvered Roof Works
A louvered roof is a set of movable slats turned by a crank or motor. Open, they let sun and air through; closed, they overlap into a sealed panel that sheds rain into concealed channels and down the posts. The point is that one structure gives shade, sun and shelter without anything being put up or taken down.
Three positions, one structure
Fully open, the roof is a frame: air moves, light comes straight down, and the space underneath is a patio with a shape rather than a shelter. At an angle, the slats cut direct sun while air still passes between them, which is the position that makes a hot afternoon usable without making the space dark. Closed, they overlap and become a roof.
That third position is what separates a louvered roof from a slatted pergola. A fixed pergola filters light and does nothing about rain. A louvered one closes.
Where the water goes
A closed roof has to send the water somewhere, and the detail that matters is whether it goes off the edge or through the frame. Concealed drainage runs it into channels in the beams and down inside the posts, which means nobody sitting at the perimeter gets the run-off. Structures without it shed a curtain of water exactly where people walk in.
What it does not do
A louvered roof is not a room. Closed, it stops rain falling vertically; wind-driven rain still arrives from the side, which is what curtains and pull-down screens are for. It is not insulation either - the space underneath is outdoor temperature, shaded.
And it needs operating. A roof left closed through a summer is a solid roof, and the adjustability that justified the price goes unused.
Against the alternatives
A gazebo with polycarbonate panels keeps rain off permanently and passes daylight through, with nothing to adjust. A fabric canopy is cheaper and seasonal. A louvered roof sits between them: the most control, and the most mechanism to look after.
Questions
How does a louvered pergola roof work?
Slats pivot on a crank. Open they let light and air through; closed they overlap into a sealed panel that sheds rain.
Does a louvered roof keep rain out completely?
Vertical rain, yes. Wind-driven rain comes in from the sides, which is what curtains and pull-down screens are for.
Where does the water go?
On the structures shown here, into concealed channels and down through the posts rather than off the edge.
Is a louvered roof better than a solid one?
It is more adjustable and more mechanism. A solid or polycarbonate roof does one thing permanently and has nothing to operate.