CAINHOY — Buildings, like people, have a lifespan, but unlike people, they sometimes don't have a birthday.

This spring, students with the joint College of Charleston-Clemson University historic preservation and community planning program, delved into the walls, floors and foundations of the St. Thomas and St. Denis church here to try to answer a seemingly simple question:

When was it built? The project began when program director Robert Russell realized the building may be significantly older than the “1819” date above its front door.

Russell's hunch stemmed from new research showing its current dimensions were nearly identical to those recorded for the original church built by the colonists in 1708 — one that later burned, at least partly, in an 1815 fire.

How much of the original building survived? And is that enough to argue that its date should be earlier?

The students did find soft, early bricks on the eastern wall — opposite the current front door — that date to the early 18th century, as well as some floor beams scarred, but not really harmed by fire.

They also found some early brick below ground along the southern facade.

Complicating the picture is that the building not only has surviving 18th century fabric but later was altered perhaps before 1720 and then rebuilt in 1819, remodeled in 1859 and again in the 1930s. Its two side entrances and porticoes were removed and converted into a wall and a window.

So coming up with an exact date for the church is tricky, if not impossible —an invitation to argument. (Preservationists sometimes describe this ambiguity — one that's been described for two millennia, beginning with Plutarch — with this riddle: If your grandfather's axe has had its handle replaced a few times and its head replaced once, is it still your grandfather's axe?

“The real story turns out to be more complex than the standard story,” Russell says. “We certainly have found enough information to make the people in charge of the church very pleased.”

The students' findings will help the society and others in charge of the church move forward with more confidence.

The Society of St. Thomas and St. Denis 1706 holds services there at least three times a year and is beginning to plan for the building's repair — particularly as the Charleston metro area grows in this direction.

Society president Vic Brandt says the students' work is “fascinating” and shows any future work there should be done “with the highest quality of craftsmanship.”

It ought to be noted that while St. Thomas and St. Denis has been largely unused recently, its beauty has not been unappreciated.

A virtual copy of the church has been built in a Mount Pleasant office park off Coleman Boulevard, near the Ravenel Bridge.

The secular Tidewater Chapel and Reception Hall has walls that are 18 inches thick and was built in 2005 by contractor Scott Dow, and the SGM Architects Inc. and investors who figured many would want to use it for weddings, memorial services, funerals, etc., says manager Lin Lewis. It's even open for self-guided tours Monday through Friday.

And unlike its historical predecessor, the Tidewater version has something that its historical predecessor does not:

An undisputed birthday. Reach Robert Behre at 937-5771.