Slate roof replacement

Slate roofs are part of the character of Princeton, of Lawrenceville's Main Street and of Trenton's older, larger houses. A good slate roof lasts for generations, which is why so many survive. When one does finally reach the end, replacing it is a project that deserves careful choices.

Is it really time?

Slate roofs often fail at their nails and flashing long before the stone wears out. Before deciding on replacement, ask the roofer for close-up photos. Signs the slate itself is finished:

• Slates flaking, splitting into layers or turning soft at the edges
• Widespread slipped or missing slates because the nails have corroded through
• Rotted decking under the slate from long-term leaks
• Years of tar and mismatched patches covering large areas

Small-scale reworking is outside what this phone line covers; the participating roofers handle full replacements.

Three ways to replace slate

1. New natural slate. Matches the original and lasts the longest, but needs an experienced slate crew and copper flashing throughout.
2. Synthetic slate. Composite tiles molded to look like slate. Much lighter and installed more like shingles. Products vary widely in how convincing they look.
3. Architectural shingles. The usual choice when slate is replaced on a house outside a historic district.

Changing from slate to a lighter material is never a structural problem. Going from asphalt to natural slate is different: it is several times heavier, so the framing needs checking first.

Historic districts

Princeton has a Historic Preservation Commission, and Lawrence Township's Main Street is a local historic district. In local districts, changing a roof's material usually needs approval before work begins. The Princeton and Lawrence pages have more.