Hub and Spigot Piping 
Also called bell and spigot piping this gravity-rated vent and drain or pressure piping, has a bell-shaped section at one end with a straight section at the other. The straight part fits into the bell-shaped end as pipe is being installed. 

Hub Stake 
Small stake, which is driven into the ground when used to mark a point. 

HUD (U.S. Department of Housing and Urban Development) 
Federal agency overseeing the Federal Housing Administration and other housing and community development programs. 

HUD-1 Uniform Settlement Statement 
Closing statement that outlines all closing costs on any real estate transaction or refinancing. 

Hue 
A particular shade or tint of a color. 

Hugger 
Ceiling fan that uses little vertical space and is usually used in homes with low ceilings. 

Humboldt Undercut 
Method of cutting down large trees, which makes use of the way the tree leans naturally. A horizontal face cut goes about a quarter of the way through the trunk, with an upward angled cut just below, intersecting the face cut, making the tree becomes unbalanced when this piece of wood is removed. Another horizontal cut is made on the opposite side of the trunk slightly higher than the face cut. When a wedge is inserted into the back cut, the tree falls forward because it goes past its center of gravity. 

Humidifier 
Device that heats and vaporizes water for the purpose of adding moisture to the air, making it comfortable to breath. 

Humidity 
The amount or degree of moisture in the air. Dampness. 

Humidity, Relative 
Ratio of moisture in the air to the highest level of moisture content possible in the air at the same pressure-temperature conditions. 

Humidity, Specific 
Weight of moisture per unit weight of dry air. 

Hundred Percent Location 
Particular spot in an urban area where land value and rents are the highest; the "best" location.

Hundredweight 
American - 100 pounds, British - 112 pounds. 

HVAC 
Acronym that refers to the climate control system, which governs heating, ventilation and air conditioning. 

Hydrant 
Standpipe for fighting fires, with connections for hoses and a valve to regulate the flow of water, which it obtains from a fire main or other water source. 

Hydrated Lime 
A quicklime, the normal addition to mortar on a job site, which has been treated with water and processed for use. 

Hydration 
Chemical process joining water with cement and aggregate to form concrete or water and cement to form mortar. 

Hydraulic 
1. Machine operated by the force and movement of liquid; when a liquid is forced through an opening, tube, etc. 
2. Setting or hardening of cement or mortar under water. 

Hydraulic Cement 
Cement, which will harden even when near running water, because it is formulated to repair cracks and holes in cement where water is actively leaking. 

Hydraulic Control 
Machinery operating with a fluid pressure system. 

Hydraulic Jack 
Jack, consisting of a large piston in a cylinder and a small piston in a cylinder, both enclosed in a system which contains noncompression fluid, to operate by hydraulic pressure. 

Hydraulic Lime (hydrated lime) 
Lime that hardens in water. 

Hydraulic Pressure 
The pressure that exists in a system containing noncompressible fluid. 

Hydraulic Shoring 
Shoring accomplished by use of shoring shoes, which are placed against the sides of an excavation site and held in place by hydraulic jacks, which are on the sides of the shoring shoes. 

Hydrocarbon 
Substance composed of hydrogen and a carbon source such as gasoline, plastics, kerosene or other petroleum products. Benzene and methane are examples of hydrocarbons. 

Hydronic 
System of forced hot water. 

Hydropower 
Hydroelectric power; power that is generated by the flow of water. 

Hydrostatic Design Basis 
Measurement of long-term hoop stress, which is the item's resistance to pressure from the inside, rating of plastic pipe, at a specified temperature in pounds per square inch. The force is exerted outward on an article, which has a circular cross section, like a pipe. 

Hydrostatic Test 
Test using noncompressible liquid under pressure. Test pressure is equal to or greater than the maximum operating pressure that will be utilized when in use, depending on specifications of requirements. Codes often require that a hydrostatic test be done at 1 ½ times the normal operating pressure of the particular system, to guarantee that the system is leak-tight and safe. While some systems are only tested before the first operation, systems such as steam boilers are tested periodically to guarantee that no deterioration has occurred during use. 

Hydrous 
Containing water; water of crystallization or hydration, as certain minerals and chemical compounds. 

Hygroscopic 
1. Attracting or absorbing moisture from the air. 
2. Changed or altered by the absorption of water. 

Hypothecate 
To pledge real estate as security for a loan without having to give up its possession.