Deck Building Terminology
Aggregate: Sand, gravel, crushed stone or other material that is a main constituent of
Portland cement, concrete and aggregated gypsum plaster.
Anchor Bolt: Heavy, threaded bolt used to secure a post base to a concrete footer or a ledger to a concrete foundation wall.
Baluster: One of a series of vertical supports installed between guardrail posts. Maximum allowable distance between balusters is 4”.
Beam: A load bearing member spanning a distance between supports. Also called a “girder.”
Bearing Point: A point where a bearing or structural weight is concentrated and transferred to the foundation.
Blocking: Pieces of wood that are installed between joists to strengthen the deck and/or provide an additional surface for decking installation.
Building Codes: Regulations detailing accepted materials and building methods, usually adopted by city, county, or state building departments.
Butte Joint: The spot where the end of two deck boards meet. Vulnerable to rot since moisture becomes trapped under the surface.
Cantilever: A construction method that involves extending the joists beyond the support beam or the support beam beyond the posts.
Column: Vertical load bearing member (also called post).
Composite Decking: Decking that is manufactured from a combination of wood fiber and plastic, creating a “low‐maintenance” product. Cleaning is typically the only maintenance required. Warranties vary from ten years to limited lifetime warranties. Warranties cover manufacturing defects such as splitting, rotting, or delaminating.
Concentrated Load: The application of force on an isolated area.
Dead Load: The weight of the structure itself, which includes decking, support structure,
railings, and other permanent features (grilling stations, fire pits, hot tubs, etc).
Expansion and Contraction: All building materials expand and contract and thus must be accounted for. Low maintenance decking is no different, it expands during the warmer months and contacts in the colder months. This must be accounted for when installing decking (check with the manufactures installation recommendations).
Fascia: Wood or composite boards used to cover the face of a deck or patio cover structure. Fascia is also installed on stair risers.
Fasteners: Generic term for nails, bolts, screws and other connecting devices.
Flashing: Strip of metal or waterproof material used to make joints waterproof primarily the ledger
board that is attached to your home .
Footing: Also referred to as a “pier”. This is the foundation of the deck, consisting of
concrete on which the deck‐supporting posts will rest. In Minnesota, footings must
have a minimum depth of 48” this may vary from city to city. Their width is determined by several factors including spans and loads.
Grade: A designation given to lumber indicating the amount of flaws and knots typically found in the wood. Example: construction common (aka con‐common) is a grade of redwood containing sapwood; construction‐heart (con‐heart) contains virtually no knots or blemishes.
Girder: A load bearing member spanning a distance between supports. Also called a beam.
Guardrail: A protective railing required when decks are 30” or more off the ground. Residential guardrails must have a minimum height of 36”.
Handrail: A narrow rail for grasping with the hand as support. Required with 3 or more steps and can be in addition to a guardrail.
Hidden Fastener: A small fastener used to install decking to the joists, eliminating surface penetration like traditional deck screws.
Hurricane Clip: Metal straps that are nailed and secure the joists to a beam or rafters to a beam.
Joist Hanger: A manufactured galvanized metal piece that attaches the joists to the ledger and beam.
Joist: Joists are the main horizontal framing members that support the deck. Joists are supported by the ledger and/or beams.
Kiln Dried: Lumber that has been dried and seasoned with carefully controlled heat in a kiln. Minimizes shrinking, warping, and sap.
Ledger: Part of the decks frame that is attached to the house, providing support for joists.
Linear Feet: The total length of a building material. For example, if you had two decks boards that were each twelve feet in length, you would have twenty‐four lineal feet.
Live Load: Part of the total load on structural members that is not a permanent part of the
structure. Live loads may be variable, as in the case of loads contributed by occupancy (people), wind, and snow loads.
Low‐Voltage Lighting: A 12‐volt lighting system that uses a transformer to reduce the current from 110 volts. Low voltage lights, also available with LED bulbs, are routinely installed on deck posts, step risers, and in landscapes.
Nominal Dimensions: Term indicating that the full measurement is not used; usually slightly less than the full net measurement, as with 2″ x 4″ studs that have an actual size when dry of 1.5″ x 3.5”.
On Center: A method of measuring distance between two structural members, such as joists, where you measure from the center of one member to the center of the other. The distance between the center of deck joists is usually 12” or 16”.
Patio Cover: A solid roof typically installed over a deck or patio, providing protection from the weather. Pergola: A shade structure that is typically installed over a deck or patio. Pergolas are usually made of
wood.
Picture Frame Border: The method of installing at least one deck board around the perimeter of a deck.
Post: The vertical structural element that rests on the footing and supports the beam, also called a column.
Post Base: A small piece of metal hardware connecting the bottom of a post to the concrete footer. PVC Decking: Manufactured decking that is made of PVC (Poly Vinyl Chloride).
Rafter: That member forming the slanting frame of a roof or top chord of a truss.
Rise: The vertical distance from one stair tread to another.
Riser: The vertical piece between two stairs treads.
Run: The distance from the back of a step to the nose of the step.
Soffit: Undersurface of a projection or opening; bottom of a cornice between the fascia board and the outside of the building; underside of a stair, floor or lintel.
Span: The distance between supports.
Square Feet: Computed by multiplying the width x length. For instance, a deck that measures 10’ x 12’
is 120 square feet in size.
Stringer: A support for steps, typically a 2×12” that is notched for stair treads.
Tongue & groove: Joint where the projection or “tongue” of one member engages the mating groove of the adjacent member to minimize relative deflection and air infiltration. Hardwood floors are an example of a tongue and groove application.
Top Cap: The top horizontal piece of a guardrail.
Tread: Horizontal plane or surface of a stair step.
Wind Load: The lateral pressure on a structure in pounds per square foot caused by the wind