Stains around top-floor windows
Dormer flashing letting water in.
Mansard roof and dormer repair in New York, NY
A mansard is a steep roof that acts like a wall, wrapped around the top floor and broken by dormers. Its leaks start at the dormers and the gutter at its base, and the work happens on a near-vertical face.
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- Slate and shingle mansards
- Dormers and gutters
Quick answer: Mansard roof repair in New York, NY covers the steep lower slope of slate or shingles, the dormers set into it, and the flat roof and built-in gutter above and below it. Most mansard leaks start at dormer flashing or at the gutter along the base, so those are checked before the slate or shingles are blamed.
What the job involves
How a mansard sheds water
A mansard has two roofs: a steep, almost vertical face covered in slate or shingles, and a low-slope or flat roof on top. Water from the flat top runs to an edge, and water on the steep face runs down to a gutter, often built into the cornice at the base.
The weak points are the transitions. Dormers break the steep face with cheeks, sills and heads that all need flashing. The joint between the flat top and the steep face needs its own detail. And a built-in gutter that has rusted or lost its lining sends water into the wall below.
Cost factors
What mansard repair costs depends on
Access
Scaffolding or a lift for the steep face is often the biggest cost.
Covering
Slate, imitation slate or asphalt shingles.
Dormers
Each dormer has cheeks, a sill and a head to flash.
Built-in gutter
Relining or rebuilding the gutter at the base.
Flat top
The low-slope roof above often needs work at the same time.
Historic review
Landmarks approvals for visible faces.
Variations of the job
Mansard work we do
Slate mansards
Slipped and broken slates on the steep face are replaced with matching slate on hooks or bibbed nails, worked from staging or a lift because the face is too steep to walk.
Shingle mansards
Asphalt or imitation-slate shingles on the steep face are repaired or replaced using the maker's steep-slope fastening, since standard nailing patterns assume a walkable pitch.
Dormer flashing
Step flashing at the dormer cheeks, head flashing above the window and apron flashing below it are rebuilt, usually in copper or coated metal to suit the roof.
Local conditions
Second Empire row houses around Mount Morris Park
The masonry row houses around Mount Morris Park in Harlem include Second Empire designs, the style that put mansard roofs with dormers on so many late 19th-century blocks. They sit inside a historic district, so the slate, dormers and metal on a visible mansard face are repaired to match, and the scaffolding or lift the work needs is planned alongside any Landmarks review.
Timing
How long mansard work takes
The repair itself is often a matter of days. Access takes longer to arrange: scaffolding or a lift, sidewalk protection on a street-facing mansard, and any required approvals come first.
Because access is a large part of the cost, it usually makes sense to do the dormer, gutter and face repairs in one setup rather than coming back for each leak.
How it runs
How mansard repair runs
- 1
Set up access
Staging, brackets or a lift, and sidewalk protection where needed.
- 2
Check the gutter and flat top
The two most common sources of mansard leaks.
- 3
Repair the dormers
Cheek, head and apron flashing rebuilt.
- 4
Repair the face
Slate or shingles replaced to match.
- 5
Photograph
Every repaired area, before the access comes down.
Warning signs
Signs a mansard is failing
Slipped slates on the steep face
Nails rusting through.
Water streaks below the cornice
The built-in gutter is leaking.
Peeling paint on dormer trim
Water getting behind the dormer cladding.
A sagging or loose gutter
Supports rusted or the lining failed.
Leaks at the top of the wall
The joint between the flat top and the steep face.
Questions we hear
Mansard roof questions
Dormer flashing is the most common cause: the step flashing at the sides, the head flashing above and the apron below. Sealant around the window rarely fixes it.
Often. The steep face cannot be walked, so work is done from staging, roof brackets or a lift, and street-facing work may need sidewalk protection.
A gutter formed inside the cornice at the base of the roof and lined with metal. When the lining rusts or cracks, water goes into the cornice and wall instead of the leader.
Physically, yes, but in a historic district that change is unlikely to be approved, and good slate outlasts shingles anyway. Repair is usually the better path.
If it is near the end of its life, yes. The access is already set up, and the joint between the flat top and the steep face gets rebuilt once.
Related services
Related roofing work
Sheet Metal Cornice Repair
Rusted and loose pressed-metal cornices resecured, patched or rebuilt in sections, with the roof edge behind them made watertight.
Learn moreShingle Roof Repair
Missing tabs, valley leaks and lifted ridge caps on pitched roofs, matched as closely as the age of the roof allows.
Learn moreShingle Roof Replacement
Tear-off to the deck, ice barrier at the eaves and valleys, and architectural shingles fastened to the maker's nailing pattern.
Learn moreMansard leaking around the dormers?
Call and we will look at the dormers, the gutter and the face together.