Where Roof Water Goes: Downspouts, Stained Walls and Flat Roofs

Yes, because the rain that does fall arrives at once: about 53 percent of El Paso's yearly precipitation falls in July, August and September, per the National Weather Service, in short summer storms rather than a steady season.

A roof concentrates that water. Everything that lands on it leaves along the eaves, so a house with no gutter puts a whole roof's rain into a narrow strip of ground beside its own wall, storm after storm. A dry year hides the damage. The first hard storm shows it.

Where the yard can take the water and send it on, which on most lots means open ground that falls away from the house. A downspout aimed at a side yard that already drains toward the lot line moves the problem next door, so a narrow side yard usually gets an extension that carries the water out to the front or back of the lot instead. The rules on where yard runoff may go are on the hardscaping page: where runoff may go in El Paso.

A downspout over a driveway lands on the slab's surface, away from its edges and corners, with the slab's fall carrying the water off, because water dumped at a slab edge soaks the ground the slab sits on, as the concrete flatwork page explains. On pavers it washes the joints first, so that spot needs a hard landing, as the paver driveway section explains. A buried leader pipe only helps if its far end comes out somewhere lower. Each downspout's route is drawn on the scope before a hole is drilled for its strap.

Often because the roof above it has no gutter, or a gutter that overflows at that spot. Rock and soil built up against the wall cause the same band from below, by holding water against the weep screed. Water falling from the eave hits the ground, throws mud and minerals back onto the lowest part of the wall and carves a trench along the drip line, and each storm makes the trench deeper and the band of stain taller. Washed-out soil also takes the fall of the ground with it, so the next storm pools against the foundation instead of running away from it.

The bottom of the wall is the part the code means to keep clear. A framed stucco wall ends in a weep screed at or below the foundation plate line that lets trapped water drain out (IRC R703.7.2.1), and anchored brick veneer drains through weep holes just above the flashing at its base (IRC R703.8.5 and R703.8.6). Mud splashed into either one blocks the way water is supposed to leave the wall. A gutter stops the splash at its source. A white, powdery bloom on brick or block is a different problem, efflorescence, and the yard side of the repair is on the landscaping page.

Usually not along its edges, because a parapet roof drains through canales and scuppers that pass through the wall. What it often needs is a place for that water to land. A canale throws a whole roof section's flow to one spot, and a scupper can get a conductor head and a downspout so the water comes down the wall in a pipe instead of a stream. The roof side of canales and scuppers, the seals and the slope, is on the roofing page. Many El Paso houses mix the two, with a pitched porch or garage roof against a flat main roof, and the pitched part gets a gutter of its own.