Moisture-proof layer of material installed on the ground to prevent moisture penetration from the ground due to capillary action. Also called damp course.
Damp course
Moisture-proof layer of material installed on the ground to prevent moisture penetration from the ground due to capillary action. Also called damp check.
Damper
A device that is located in ductwork to adjust air flow. This movable plate opens and closes to control airflow. Dampers are used effectively in zoning to regulate airflow to certain rooms. There are basically two types of dampers - Manual and motorized. A manual damper generally consists of a sheet metal (or similar material) flap, shaped to fit the inside of a round or rectangular duct. By rotating a handle located outside of the duct a technician can adjust air flow to match the needs of a particular area or room. A motorized damper is generally used in a zoned system to automatically deliver conditioned air to specific rooms or zones.
Damping off
A fungus, usually affecting seedlings and causes the stem to rot off at soil level. The result of soil borne diseases and over watering. Sterilized potting soil and careful sanitation practices usually prevent this.
Dampproofing
(1) Waterproofing treatment available as a coating or addition to concrete or mortar for use with masonry. (2) To prevent moisture penetration by capillary action in masonry. (3) To make moisture resistant.
Danish oil
Used as a wood finish to preserve wood and to impart a sheen, this blend of drying oil and plastic in a vehicle such as mineral spirits is also sometimes used to stain wood. Also called Antique Oil.
Darby
Used to smooth and level wet concrete this straight wooden board is about four inches wide and three to eight feet long.
Dark-dependent seeds
Seeds that germinate only in darkness.
Darrius (wind) machine
A type of vertical-axis wind machine that has long, thin blades in the shape of loops connected to the top and bottom of the axle; often called an "eggbeater windmill.".
Database
Large collection of information in a computer, organized so that it can be updated, expanded and easily accessible for use.
