- Chassis
- The steel frame beneath a manufactured home, made of long beams and cross members, that carries the floor and is the part supported by piers and anchored to the ground. Its spans between supports are the reason pier spacing matters.
- Marriage line
- The seam where two sections of a multi-section home are joined, running along the floor, walls and roof. It must be closed with gaskets, fasteners and sealing at each level so no air, water or pests get through.
- Pier
- A vertical support, often concrete block, steel or a prefabricated unit, that carries the chassis load to a footing. Height, width, cap material and spacing all follow limits, and tall or narrow piers need extra bracing.
- Footing pad
- The base under a pier that spreads its load over enough soil. Its area comes from dividing load by allowable soil pressure, and it may be concrete or a listed pad of another material.
- Presumptive soil bearing
- A tabulated soil pressure, assigned by soil classification when no engineering report is available, used to size footings. Poor soils such as soft clay carry far less than gravel or rock, so footings grow accordingly.
- Ground anchor
- A device driven or set in the soil, connected by a strap or cable to the chassis, to resist wind uplift and sliding. Its holding power depends on soil type, so the anchor must match conditions at the site.
- Tie-down strap
- A steel strap that connects the chassis or frame to the ground anchor, tightened to keep the home from lifting or shifting. Strap angle, spacing and corrosion protection are checked, and slack straps do not perform.
- Perimeter skirting
- Panels that enclose the gap under the home, from its underside down to the soil. Beyond looks, it keeps out animals and weather, and it must include required ventilation and an access opening to the crawlspace.
- Crawlspace ventilation
- Openings in the skirting or foundation that let air through the space under the home to carry away moisture. The required vent area is based on floor area, and vents must be spread so air crosses the whole space.
- Ground vapor retarder
- A sheet of plastic spread on the soil below a home to hold back moisture evaporating from the ground. Overlapping seams and sealing at piers and walls keeps it working and reduces rot, mold and corrosion.
- Lot drain inlet
- The fitting at the site where the home's drain connector joins the sewer or septic line. Its location, height and fit matter because the connector must slope down to it without sags.
- Drain connector
- The pipe or flexible assembly installed on site that links the home's waste outlet to the lot inlet. It needs support, continuous slope, tight joints and must not be a substitute for the home's own traps and vents.
- Water service outlet
- The supply point at the lot where the home's water line connects, typically with a shutoff and protection from freezing. The installer's connection must be tight and kept clear of damage and contamination.
- Backflow preventer
- A device that stops used or contaminated water from flowing backward into the supply line. Where cross-connection is possible, such as hose bibs, the device protects the public water system and the home.
- Gas shutoff valve
- A manual valve on the supply piping near the home, used to cut off fuel quickly. It must be accessible and of the right type, and the installer closes it when leak testing or servicing.
- Air test
- A leak test in which the piping is filled with compressed air to a set pressure and watched for a drop over time. It checks new gas connections before fuel is introduced, and no gas is released until it passes.
- Site plan
- A scaled drawing of the lot showing property lines, the home's location, setbacks, utilities and access. It is the drawing that accompanies a permit application for utility connections on private property.
- Wood-to-ground clearance
- The minimum gap between untreated structural wood and the soil, meant to prevent decay and termites. It shapes pier height, posts, stairs and landings, and shows up in foundation and accessory questions.
- Axle and wheel removal
- Taking off the transport running gear, hitch and tongue once the home is set on its supports, so they are not left as a permanent base. Planning for where they go, and for lifting safely, is part of preparing for transport and set-up.
