Shingle maker CertainTeed Corp., of Valley Forge, announced an indefinite shutdown of its Meridian, Miss., ceiling tile plant and the lay off of 90 workers there.

The company says the layoffs will come in 60 days. It announced the shut down yesterday.

Plant manager Kyle Watts says the economic downturn and sluggish commercial building business prompted the decision.

Watts says production will continue until mid-August and then be consolidated with a sister plant in Michigan. He says 15 employees will remain for distribution and sales.

CertainTeed produces ceiling tiles and acoustical wall panels used in residential and commercial construction.

CertainTeed also operates ceiling tile plants in L'Anse, Michigan and Plymouth, Wis., as well as a ceiling tile grid production facility in Ellenton, Fla.