I own an old house with a tin roof circa 1915. Recently the roof leaked and as a result stained and warped the ceiling board in the hallway.

The ceiling board was replaced in kind throughout the house when we purchased the property. The person performing the renovation (1983 timeframe) referred to the ceiling as “epson board and slat”. This ceiling board is a foot or more in width and cut to the appropriate length. Narrow slats are used between adjacent boards.

Is there such a product as epson board or like product as I am trying to replace? Of course, I may be misspelling it.