Replacing a roof you share with a neighbor

In Mercer County, a large share of houses share a roof edge with the house next door: rowhouses across Trenton, twins in West Trenton and elsewhere in Ewing, and townhomes in Hamilton, Lawrence and Robbinsville. Replacing your part of a shared roof raises questions a detached house never does.

The joint is the job

Where two roofs meet, water has to cross from one owner's roof to the other's, or be stopped at a parapet. On a replacement, the roofer has to:

• Tie new underlayment and roofing into the neighbor's existing roof, or turn it up a party-wall parapet
• Flash that joint so water cannot run between the two roofs
• Avoid damaging the neighbor's roof while working along the edge

Ask the roofer to explain exactly how they will handle the joint on your house.

Doing it together

If the neighbor's roof is also near the end, replacing both at once has real advantages:

1. One continuous roof with no seam between old and new
2. A single setup for the dumpster, ladders and street access
3. Matching materials and colors from the start
4. One crew responsible for the whole roof

Each owner still signs their own contract, with a registered contractor, and each contract should describe that owner's section of the work.

Permits for attached houses. New Jersey's re-roofing permit exemption covers detached one- and two-family houses. Twins, rowhouses and townhomes are attached, so check with your municipal construction office. See New Jersey roof permits.

Townhome associations

In many townhome communities the roof belongs to the association, not the owner. Read your association documents before calling a roofer; the board may already have a replacement plan.