Roofing in Chicago splits between low slopes behind parapets and steeper asphalt on bungalows, and lake wind works on both. Coping joints, pitch pans, and seams fail on the flat work. Tabs, ridges, and chimney saddles fail on the pitched work. Water then runs across a top-floor ceiling that may be plaster over wood lath. Check the alley side; the bad slope is often hidden from the sidewalk.
Ponding after a rain means the drain, the scupper, or the slope itself has quit. A parapet snow ridge will send melt under the flashing in a January thaw. Ice at the north wall is common. So is a blown-off coping cap after a straight east blow. Granule loss on a bungalow still matters, but do not describe a pitched roof as if it were a gravel deck. Name the system you actually have.
Brick chimneys in this city leak at the step flashing and at the crown, then telegraph a stain down an interior chase. On a two-flat, a party wall can make the leak feel like the neighbor's until you are underneath. Skylights and old hatches on flat roofs are punctures with gaskets that age out. Satellite mounts and loose rails do the same. Say what is fastened to the membrane before anyone walks it.
A repair that does not include the drain, the metal edge, and the way the parapet is counterflashed is a repair you will meet again. Debris, old gravel, and wet insulation change the weight and the dry-in plan. If the deck is soft under a known pond, the surface product is not the whole scope. Temporary cover matters when another lake storm is stacked behind this one. Keep foot traffic off a wet membrane.
Say bungalow or flat roof, leak or blow-off, and which floor is stained. Mention the parapet if water is coming from the wall rather than the field of the roof. Chicago wind will test the edge you leave open. Call the number on this page.