Decking Glossary of Terms

ADA (Americans with Disabilities Act) Approved Railing: These ramps provide safe access to users with wheelchairs or walkers and are also helpful for people with strollers.

Balusters:  A vertical, vase-like posts or legs on the railing.

Beadboard Ceiling: A tongue and groove look for a portico, 3 season rooms, or farmer’s porch.

Beams or girders: Hefty framing members (usually 4x, 6x, or doubled or tripled 2x stock) attached horizontally to the posts to support the joists.

Bridging: Short pieces of lumber between joists that strengthen the framing. They are designed to prevent the joists from twisting.

Capillary Break: A hydrophobic material uses in the gap between parallel layers of siding and roofing.

Cascading Stairs: Otherwise known as wrap around stairs which are designed to flair out and increase in size towards the ground

Columns: PVC vertical pillars commonly used to support the roof of a farmer’s porch or portico.

Decking: 5/4” or 2” stock attached to the joists to form the deck floor.

Fascia: A board attached to the front of the 2x frame. Usually a white PVC or 1×8 or 1×12 decl color matching composite.

Footings: Concrete columns below grade that support the posts and, thus, the deck. On sites where the soil freezes and thaws, concrete is poured in an above-grade form and a cylindrical hole. Ask your building department for footing depths in your area.

Four Season Room: This may have walls or roof to floor windows. Instead of screens, this room is weather tight and is composed of windows so the space can be heated.

Fibrex Railing: Colored railing made of a composite of wood and plastic polymer with resistance to rot and insect damage, and a low rate of thermal expansion and contraction.

Framing: The process of creating connections between joists, beams, and support posts in order to build a code complaint deck structure.

Galvanized Nail: A nail with a protective zinc coating to steel or iron. However, when subjected to the elements, these nails tend to rust and leave orange/ yellow residue on white trim boards like decking fascia

Galvanized Steel – Steel that has been coated with zinc to improve its corrosion resistance. For use in marine construction projects, hot-dipped galvanizing (H.D.G.) is the process by which steel is coated. H.D.G. steel does offer good corrosion resistance in fresh water and slightly brackish water environments; however, it will eventually corrode if exposed to these harsh conditions.

Helical Piles: sometimes referred to as screw anchors, screwpiles are a steel screw-in piling and ground anchoring system used for foundations. They are manufactured using varying sizes of tubular hollow sections for the pile or anchors shaft to accommodate appropriate weight loads for the structure.

Hurricane Clips: Hardware pieces that connect the joists to cantilevered beams to reduce uplift forces caused by high winds.

Ice & Water Barrier: A self-adhered waterproofing material installed along eaves, valleys, side walls, and other sensitive areas to protect against ice damage and wind-driven rain.

Joists: Horizontal framing members (usually 2x stock) fastened on top of the beam or flush with the ledger to support the decking. A header is fastened to the ends of the deck?s interior joists. Rim joists or end joists are the outermost joists perpendicular to the ledger.

Joist hangers: Metal fasteners that allow you to fasten the joists in place without notching the ends of the board. A joist hanger secures a joist to a ledger or rim joist.

Lattice Styles: Used around the deck skit for storage or concealment. Commonly used in a diagonal pattern but more recently the vertical panel look is most popular.

Ledger: A board (usually 2x stock) attached to the house to support one side of the deck.

Lighting Options: There are many choices included but not limited to (post cap light, riser light, recessed deck light, and side post light). Transformers are required. Some lights are purely decorative while others serve function. Professional, warranted lights should be installer by your decking contractor for the safety of your deck, house, and family.

Light Gauge Steel (LGS): Steel framing for decks is a lightgauge steel that is similar to what is used for wall studs in commercial properties. It is a cold-formed steel made by passing steel sheets through a roller which folds the sheets into a U-shape which is uniform and straight, so pieces are simple to square and won’t twist, warp, rot, crack or burn like wood.

Lumber Size Tolerances: Moisture Content & Size Considerations

Because a waterborne preservative system is used, the moisture content and physical dimensions of Southern Pine lumber can vary after treatment. Wood swells in both thickness and width during treat- ment. For example, a 2×6 at 19% moisture content prior to treatment measures 1-1/2” x 5-1/2”. This measurement can increase as much as 1/8” to 1/4” directly after treatment, depending on the density of the wood.

Most treated Southern Pine is delivered to the supplier or job site in a wet condition, usually in excess of 25% moisture content. The actual size of this material (thickness and width) could vary depending on drying time after treatment and ambient temperatures.

Picture Frame: Pictureframing” refers to putting a border around the edge of a deck or porch. On a composite deck or porch, picture frames are constructed using square-edge boards and mitered corners to ensure a clean, finished look. Among the reasons to consider a picture frame: It heightens visual interest.

Piers: Precast concrete pyramids made to set on in-ground footings. Where frost heave is not a factor, piers set directly on the ground to support posts.

Platform/ Landing:  It says that there needs to be a landing at the bottom of the stairs that is at least as wide as the stairway and at least 3 ft. long from the nose of the bottom tread to the outside face.

Post anchors: Metal framing connectors that attach posts to piers or footings. They raise the base of the posts slightly above the top of the footing, protecting them from water damage.

Posts: Timbers (usually 4x or 6x) set vertically to support the deck framing. Posts are used on all but the shortest decks. The posts can be cut off below the deck surface, or they may rise above the surface to provide support for the railing. Posts may rest on top of concrete footings or they can be set plumb in the hole before the concrete is poured.

Pressure Treated Wood : Pressure-treated wood has been around for nearly 70 years and is softwood lumber, typically southern yellow pine, that’s been chemically treated to resist rot, decay and termites. The boards are carted into giant pressurized tanks where chemical preservatives are forced deep into the wood’s fibers.

However, it’s important to note that not all treated wood is created equal. The level of rot resistance is directly related to the amount of chemical preservatives in the wood and the chemicals used.

Pressure Treated Wood Grades:

  1. Premium – Highest grade for ¾ radius edge decking. 
  2. Select – The highest grade available, contains very few detects. It must meet a minimum 1/12-grain slope and have all knots sound encased. It has a high consistency and the appearance is very good. 
  3. Number 1- Will contain no splits larger than the width of the board. Knots may not be larger than 2 ¾”. One hole is permitted every 3 ft. Mid-range grade for 5/4 decking. 
  4. Number 2 – Grain slope must meet minimum 1/8 grain slope. Boards will contain no splits larger than 1.5 times width of board. Knots may not be larger than 3 ½”. One hole is permitted every 2 ft. Wane corners. 
  5. Number 3 – The lowest-quality grade. Not suitable for deck construction.

Pressure Treated Wood Types: 

1) Above Ground

Wood treated for Above Ground is intended for parts of your project that meets all of the following criteria:

  • is not on or in contact with the ground and
  • is expected to readily dry out between times it gets wet and
  • not located in tropical areas
  • outdoor furniture, such as Adirondack chairs and picnic tables used on a deck or other well-drained surface

2) Fresh Water Splash

    • The exposure to fresh water, either through immersion or splash, will dictate the required preservative system.

 3) Ground Contact

Wood treated for Above Ground is intended for parts of your project that meets all of the following criteria:

  • in the ground or in contact with the ground
  • in contact with debris, leaves or vegetation
  • exposed to daily wetting from sprinklers or other sources of moisture
  • in contact with old wood that may be partially decayed
  • posts supporting decks and fences (in ground or concrete)
  • all posts when secured by elevated post bases to concrete piers
  • all joists and beams when critical and difficult to replace
  • stair stringers that sit on the ground or on concrete on the ground
  • low retaining walls, planter boxes, and understructure for walkways
  • material installed over water if it will be regularly wetted by waves and wakes
  • less than 6” above ground and supported by permeable building materials

4) Heavy Duty Ground Contact

  • Posts supporting houses, garages, sunrooms, barns, or other permanent structures (in ground, concrete, or fresh water)

5) Marine Grade/Full Immersion

  • submersed in fresh water or salt water
  • fresh water or salt water splash

6) Saltwater Splash

  • The exposure to salt water, either through immersion or splash, will dictate the required preservative system – Micronized Copper Azole (MCA) or Chromated Copper Arsenate (CCA) 

Rails: Horizontal components of railings that provide a safety barrier and handhold for stairs or along the sides of the deck.

Railing: The assembly made of rails, rail posts, cap rails, and balusters or spindles. The balusters, the smallest vertical components, are positioned to fill the space between the top and bottom rails and between rail posts. Maximum baluster spacing for child safety is 4″.

Risers: Boards covering the vertical spaces between stairway treads. Although shown in the drawing, risers are often omitted on deck steps and other exterior steps.

Salt water splash zone – That portion of a marine structure located above mean high, but is still subject to frequent wetting from wave action and/or wind-blown water (salt water splash). The conditions in this zone of exposure support intermittent degradation by marine organisms. Corrosion of metal fasteners in this zone is also usually severe. Members in the salt water splash zone typical include: piling, walers, framing, stringers, and cross-bracing.

Stainless Steel – An alloy that contains chromium, nickel, and/or manganese. Stainless steel has very good corrosion resistance properties due to the high levels of chromium and nickel/manganese. The two most common alloys of stainless steel used in marine construction are Type 304 and Type 316. Both are used in marine construction for hardware, straps, plates, ties, bolts, nuts, washers, and screws. However, 316 stain- less steel provides the best corrosion resistance in salt water.

Stringers: Long, diagonal framing parts (usually 2x12s) that support stair treads. The stair treads are attached to the stringers.

Three Season Room: Also known as a screen porch or screen room. Instead of walls, screens run from roof to floor.

Trex Elevations (LGS): Is the premier LGS framing system using an unparalleled three layers of protection surround a carbon steel core, ensuring each critical joist, beam and ledger connection holds up to the elements for decades, with a 25-Year Limited Residential Warranty to prove it. Elevations is the ONLY one code-listed for exterior use, supported by the CCRR0186 code compliance research report.

Trex Protect: A non-skid, self-adhesive deck flashing tape that is designed to shield the tops of joists, rim joists, beams and ledger board from moisture that can lead to the development of rot and wood decay and the loosening of deck screws and fasteners.

Trex RainEscapes: An under-deck drainage system that uses a network of troughs and gutters to keep rain, spills and snowmelt from dripping through elevated deck boards creating a dry space below the deck.

Versetta Stone:  A panelized stone that comes in a variety of styles and colors. It is a common decorative upgrade to the traditional diagonal lattice.

Water Table: An architectural feature that consists of a projecting course that deflects water running down the face of a building away from lower courses or the foundation. These are primarily made of PVC and can also be purely decorative.

Wood preservative – A chemical formulation that is forced deep into the wood fibers, typically through the process of placing lumber inside a pressurized chamber and introducing the chemical and pulling a vacuum. Commonly used formulations for preservative treatment of Southern Pine products, as discussed in this guide, include: Chromated Copper Arsenate (CCA), Copper Azole (CA), and Alkaline Copper Quaternary (ACQ). Designers should check with local suppliers for the latest ap- proved wood preservatives in the project area. 

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