Why Baltimore Roofs Fail, and What to Watch For

Most roof failures we see in Baltimore aren't mysterious. They start in a handful of spots that are easy to miss from the street: flashing, valleys, flat roof seams, chimneys, and the roof edge where gutters overflow. Our weather doesn't help. Summer storms, humid stretches, and freeze-thaw swings in winter all work on the same weak spots year after year.

Here are the risks we run into most, what to look for, and what usually fixes them.

Rowhome roofs and shared walls

On city rowhomes, roofs and walls are tied together. A problem on your neighbor's roof or at the seam between houses can show up on your side.

• Look for: damp or bubbled drywall near the party wall, peeling paint where the homes meet, stains on the top floor ceiling after a hard rain
• What fixes it: sealing the seam between roofs properly, repointing open mortar joints at the parapet, and sometimes adding a small diverter so water doesn't run toward the joint

Flat roofs on rowhomes also fail at seams and drains, not evenly across the whole surface. A clogged drain or scupper lets water sit, and standing water finds every weak seam.

Slate on older homes

Slate is common on older houses in places like Roland Park, Homeland, and Bolton Hill. It can last a very long time, but freeze-thaw cycles crack individual pieces, and old nails rust out and let slates slide.

• Look for: chipped edges, cracked or missing slates, pieces of slate on the ground or in the gutter
• What fixes it: replacing the broken pieces with matching slate and fixing any flashing nearby. Please don't walk on a slate roof yourself. It's slippery and it breaks under your feet.

Valleys, trees, and clogged gutters

Valleys are where two roof slopes meet, and they carry a lot of water. Leaves, pine needles, and shingle grit pile up there and hold water against the roof.

• Look for: debris sitting in the valleys, stains under the eaves, moss or green streaks near overhanging trees
• What fixes it: clearing the valleys and gutters, trimming branches back from the roof, and repairing any soft spots at the edge

Our gutter cleaning and maintenance page covers the gutter side of this.

Flashing and the chimney joint

If I had to pick one spot where most leaks start, it's flashing. That's the metal at chimneys, walls, vents, and skylights. The shingles can look fine while the metal next to them has rusted, bent, or pulled loose. The joint where the chimney meets the roof is one of the worst for it.

• Look for: rust streaks, bent or missing metal, cracked caulk, and stains near the fireplace or chimney chase inside
• What fixes it: resetting or replacing the flashing, and repointing the chimney if the mortar is part of the problem. Caulk helps, but it's a maintenance item that needs checking, not a permanent fix.

More on that on our roof flashing repair page.

Ice dams and poor attic ventilation

In late winter, snow melts on a warm roof, runs down, and refreezes at the cold edge. That ice can push water back under the shingles. Poor attic airflow makes it worse, and it also cooks shingles from underneath in summer.

• Look for: big icicles on the gutters, wet spots on ceilings along outside walls, a hot, musty attic in July, or frost on the rafters in January
• What fixes it: repairing the damaged edge, adding ice and water shield there during the repair, clearing blocked vents, and improving airflow where needed

What you can check yourself

You don't need a ladder for most of this. Grab a pair of binoculars and walk around the house after a big storm. Then take a look in the attic with a flashlight. Small leaks that sit for a year turn into soft wood and a bigger repair, so it's worth catching them early. For how we track down where a leak is actually coming in, see our roof leak detection and repair page.

If you're not sure what you're looking at, text your address and a few pictures to 443-900-4815 or give us a call. MHIC #154344.