Yes, DRYWALL is a Scrabble word!

Letter values in Scrabble US: D 2, R 1, Y 4, W 4, A 1, L 1, L 1.

Is it a valid word?

DRYWALL is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a wide flat board used to cover walls or partitions; made from plaster or wood pulp or other materials and used primarily to form the interior walls of houses

Also: dry wall.