The addition of plastic trim at the oldest retail store on Martha’s Vineyard has officials in West Tisbury questioning whether they should allow new modern construction materials on historic buildings.

 The issue arose when Alley’s General Store, which dates back to 1858, put PVC on some of its windows and corner boards without approval of the town’s historic district commission. On Monday, the Vineyard Preservation Trust, which owns the building on State Road, asked for permission retroactively to put the plastic materials up.

The commission ended up giving its blessing to the trust, but historic commission members now feel they should come up with clear rules on how and where plastic siding such as PVC and AZEK can be used on historic buildings in the town’s historic district.

Commission member Mark Mazer said the issue is especially important to take up now, as these building materials become more prevalent and are sought to shore up old buildings.

“Let’s really put some thought into this and come up with a real guideline,” he said. “This is going to happen over and over again.”

Buildings in the historic district, which encompasses parts of State Road, Edgartown-West Tisbury Road, Music street and Old County Road, are supposed to replace “like with like,” said commission member Nancy Dole.

She was the lone vote against the trust’s application for Alley’s, saying she would have voted against the addition of PVC if the application had come in before the work was already done.

“You’d be piecemealing PVC with wood and they’d be right smack against each other,” said Ms. Dole. “No matter what you did, one piece would look like PVC and the other would look like wood.”

Trust executive director Nevette Previd said the plastic was added to prevent rot. She took the blame for the trim going in without alerting the commission, calling it a “rookie mistake.”

The commission asked that the trust paint the new plastic additions to make them look like wood.

Some members were uncomfortable with forcing Alley’s to go back to wood because the commission did allow town hall to have plastic trim.

The commission vowed to poll other towns on the Island and the mainland about what they do for PVC in their historic districts so the commission could set clear standards going forward.

“We really do need to have a uniform written opinion on [manufactured siding],” said commission member Carol Sarason. “Because if people see that the town hall has AZEK, everyone’s going to think they can have AZEK.”