Roof Repair in Princeton, NJ: Slate, Copper and Historic-District Roofs

Princeton’s preservation ordinance says original roofing should be maintained or repaired, and replacement should use the same material and size, so on a historic house slate repair is almost always the starting point. That fits how slate behaves. Quality Pennsylvania and Vermont slate can outlast several sets of nails and flashing, and most Princeton slate roofs we inspect have plenty of sound stone left.

A proper slate repair starts with an inspection from ladders, roof brackets or a lift, never by walking on the slate. We look for slipped pieces, cracked or delaminating slates, rusted nail heads, worn valleys and failed chimney flashing, and tap suspect slates to hear whether they are sound. Then we replace failed pieces with matching slate of the same size, thickness and colour, held with copper hooks or copper nails under the course above. Valleys are relined in copper, and chimneys get new step and counter flashing cut into the mortar joints.

Matching is the hard part. Older Princeton roofs often use slate from quarries that have closed, and some have faded or weathered unevenly. We source salvaged or new slate that matches as closely as possible and, where needed, move original slate from a hidden slope to the front and put the new material out of view.

Repairs that restore a roof to its prior condition count as ordinary maintenance under Princeton’s code, which generally keeps them outside Historic Preservation Commission review. A full replacement, or a switch to a different material, is a visible change that needs review. If a substitute is unavoidable, the ordinance asks for one of the same shape and size. Our slate roof repair page goes deeper on techniques.

Built-in gutters are one of the most common hidden leak sources on older Princeton houses, and relining them is far cheaper than repairing the cornices and walls they eventually rot. Many Western Section and downtown homes have Yankee gutters formed into the roof edge or box gutters built into the cornice, lined with copper or tin-coated terne.

These troughs move every winter. Seams soldered decades ago crack, terne rusts through, and pooled leaves from Princeton’s oaks and maples hold water against the metal. Because the gutter sits inside the structure, a leak can run along a rafter or inside the cornice and appear as a stain several feet away, on a porch ceiling or an upstairs wall.

The repair options are relining with new soldered copper, which matches the original and lasts the longest, or lining with a fully adhered membrane under a copper or painted metal apron where budget is tight. Either way we first remove rotted wood in the trough, rebuild the slope so water reaches the outlet, and re-flash the outlet into a properly sized leader.

Removing a built-in gutter and hanging a modern gutter in front of the eave changes the look of the house. On a Princeton property in a historic district, that kind of visible change can trigger review, and it often makes ice damming worse. We recommend keeping the original system and maintaining it. A fall cleaning, a spring check of seams and outlets, and a quick look after heavy storms like Ida catch most problems before water gets into the walls. Read more on our gutter and roof-edge repair page.

Tree impact is Princeton’s most serious roof emergency, and the first hours after the storm matter most: get people out of affected rooms, photograph everything, and get the roof covered. Sandy in October 2012 closed more than 60 local roads and brought down at least 50 trees on campus alone, and Ida’s tornado in 2021 snapped and uprooted trees along Washington Road.

Safety comes first. A limb resting on a roof can shift, and branches tangled in service lines are dangerous. Stay out of rooms under the damage, keep clear of downed wires and let a tree service remove the weight before roof work starts.

Documentation comes next. Photograph the tree, where it struck, the roof from the ground and every interior stain, crack or wet area, with dates. Keep damaged slates, copper pieces and debris until the adjuster has seen them, because they help prove the materials that need matching.

Then we secure the roof. On slate we use tarps strapped and weighted or fastened through the damaged area rather than nailing through sound slate, which would create new leaks. We check rafters and decking for cracks, brace them if necessary, and keep water out of plaster ceilings, which can collapse when soaked.

The permanent repair follows. If rafters or decking need replacement, that is structural work and needs a permit even on a detached house. Matching slate, cedar or copper may take time to source. Our written report separates storm damage from pre-existing wear, lists slate counts and copper footage, and helps your adjuster price a matched repair instead of an asphalt substitute.

Cedar roofs in Princeton usually fail from moisture, not age, and better drying conditions plus targeted repair can add years before replacement. Cedar shakes and shingles show up on Shingle style and Colonial Revival houses in the older districts and on many newer homes on Princeton Ridge and in wooded parts of the former Township.

Under a full canopy of oaks, beeches and tulip trees, cedar stays wet after rain, collects needles and leaves in the keyways and grows moss. Wet cedar cups, splits and eventually rots, often starting on north slopes and below overhanging limbs. Mechanical damage from falling twigs and squirrels adds up too.

A good repair starts with cleaning: low-pressure washing and hand clearing of keyways and valleys so water drains freely. We then replace split, rotted or missing shingles with matching cedar, re-nail with stainless fasteners, and replace valley and step flashing where it has corroded. Trimming limbs back from the roof lets sun and air reach it, which does more for a cedar roof than any coating.

When cedar is beyond repair, replacement cost is a real question. In New Jersey cedar costs about $17.35 to $20.20 per square foot installed, compared with about $7.95 for architectural asphalt. On a house in a Princeton historic district, switching from cedar to asphalt is a visible material change that the Historic Preservation Commission is likely to review, since the ordinance prefers the same material or a substitute of the same shape and size. Outside the districts the choice is yours, and we give side-by-side prices so you can compare lifespan and appearance honestly.

On a Princeton house in a historic district, adding a skylight, dormer or roof-mounted equipment is an alteration, and whether it needs Historic Preservation Commission review depends mainly on whether it can be seen. Princeton’s code sets two kinds of districts. In a Type 1 district, proposed work visible from anywhere within the district is subject to review. In a Type 2 district, review applies to work visible from a public right-of-way.

That makes the location on the roof important. A low-profile skylight on a rear slope hidden by the house and trees may be outside review in a Type 2 district but inside it in a Type 1 district if neighbours can see it. A new dormer changes the roof shape, and the ordinance asks that roof shapes and materials on altered structures be visually compatible with the district.

Before we quote, we check with the Historic Preservation Officer whether your house is in a local district and which type, and we photograph the roof from the street and neighbouring views. If review is needed, we prepare drawings, product information and a written scope for your application, and we schedule the work after approval.

On the roofing side, these additions need careful detailing. Skylights in slate need copper curb flashing and soakers matched to the slate exposure. Dormers need step flashing woven into the courses and properly sized valleys. Mounting equipment on slate requires replacing slates around each attachment with flashed metal pieces so the anchors do not crack surrounding stone. Done right, the addition will not become the roof’s weak point. Done wrong, it is the first place a Princeton roof leaks.