No rooms are more used-and-abused-than kitchens and bathrooms. Their floors carry the heaviest traffic; their cabinets are attacked by heat, moisture, acids and alkalies; thier walls are splashed by cleaning aents and grease, and drenched by water and steam. The rigors of this environment must be taken into account in all aspects of renovating these rooms, or building new ones, for such conditions affect every step of the work from planning to carpentry, plumbing and electrical installations. But the major consideration is the surface-floors, walls and countertops. In kitchens and bathrooms their coverings are special. They have to be. A large selection of materials is now available to protect and beautify the exposed surfaces of these difficult rooms. A choice among the materials depends partly on economics and partly on esthetics. Replace old countertop or sink or build a new kitchen from scratch.