Deck Construction Overview
Decks are a common feature on many houses. Whether serving as an essential egress point, or added as bonus square footage, decks can often become one of the most popular places in the home to spend time. This is why it is so essential to make sure your deck was built properly. The last thing you want to be doing while entertaining company is worrying if the components of your deck were properly constructed.
Here, we will break down each component of a deck, and describe the various methods and materials commonly used to build a safe, reliable deck.
Silver Maple Home Inspections not only inspects hundreds of decks each year, but I’ve also built many decks throughout the Hudson Valley using a variety of approved methods.
Footings
Let’s start from the ground up. The footings of a deck act as a solid, water resistant base for which a deck can be built up from. Think of them as your deck foundation. Proper footings keep the deck posts and framing above the ground level to prevent rot, help pin the deck down to resist uplift, and evenly distribute the weight of the deck onto the ground. Beyond this, footings help protect a deck from frost heaving. Frost protection is important so that the structure does not move with the movement of the ground during seasonal freeze and thaw cycles.
To that point, each area of the United States has different frost depth levels. These different levels are spelled out in the NYS 2020 Residential/Building Codes. In the Hudson Valley of New York, these levels are typically 42 or 48 inches of depth. Refer to your local building code official to find out what the frost depth is in your area before planning a build.
Now that we know why footings are a vital part of deck construction, let's look at the different types of footings typically implemented in deck builds.
Concrete
Concrete footings, or piers, are the most typical footing found in deck construction. Concrete is often poured into a tube known as a “sono-tube” which is a specific diameter specified to support the given weight of the deck to be constructed.
Most often these are 12-14 inches in diameter, but can be larger depending on the proposed deck. Oftentimes a bell shaped footing is used at the bottom of the sono-tube. This further helps distribute the deck load to the soil below.
Many footings require rebar reinforcement to be placed in the concrete. This helps strengthen the concrete footing, providing for better stability and longevity.
If you are unsure of the size of footing you may need for your project, consult with a certified design professional; aka an engineer or architect.
To hold the post or framing of the deck to the footing specialized metal brackets are typically utilized. These are set into the wet concrete for best adherence to the footing. These also provide a few inches of height for the framing to keep it off the ground.
Helical Piers or Screw Piles
These types of piers have been coming back in popularity lately, even though they have been implemented since the 1800’s. These are made from galvanized steel and are equipped with a screw shaped flange. As the name indicates, these are screwed into the ground with a machine. The pier does not just go beyond the frost depth, but also has to register enough torque to indicate that the soil bearing capacity is sufficient.
This can potentially equate to several feet below frost depth to reach bearing capacity. This is dependent on the type of soil being drilled into. If rocky soil is present, the footing may have to be repositioned. If bedrock is encountered, there may be some pre-drilling involved, which can increase the cost of installation.
These piers are faster to install than concrete footings, and require less labor. They also cause less ground disturbance to the work site. These screw piles require specialty equipment to install, and typically require a professional service to do so.
Photo and video link provided by:
TECHNO METAL POST HUDSON VALLEY
706 State Route 44 55 Highland, NY 12528
TEL.: 845 249-6757
info.hudsonvalley@technometalpost.com
Direct Burial Posts
Some contractors and homeowners opt to directly bury the deck posts into the ground beyond the frost depth. Oftentimes these posts are set on a small cylinder of concrete to level the post. This can be an acceptable construction method, however certain rules should be adhered to. First and foremost, the lumber must be rated for ground contact. There are different types of pressure treated lumber on the market, and some of it is not intended to be sitting on or below the earth's surface. Secondly, these deck posts may need better draining soils around the post in order to allow the post to not become saturated. While this method has been used for many years and some contractors will swear by it, it is widely accepted that the other two methods above yield better results in terms of water and pest protection as well as stability and longevity.
Framing
Next we will discuss the common methods used to construct the deck framing. The framing is a system of structural supports which form the “skeleton” of the deck. This is most often pressure treated lumber, but other materials can be used, such as steel and hardwood lumber. There are many different elements to the framing of a deck. Each has its role in providing a key structural component, and like any system, one component is only as good as its counterparts.
Posts
Again, let's start from the ground up. The posts are the vertical framing members which support the deck from the footings. Think of them as the “legs” of the deck.The dimension of the post will be determined by the height of the deck and the proposed load to be carried. A 6x6 inch post is typical in most applications. The posts should be rated to handle the compression of the loads above. These should be properly anchored to the footings and well attached to the framing.
Beams
The beams are the horizontal framing members which carry the deck floor framing, and are attached to the posts. These are often double or tripled framing members in order to support the significant load they are carrying over a span. The distance between the posts will often determine the size and design of the beam.
Joists
The joists are the framing members which the finish decking is attached to. These carry the span from the beam to the house ledger board and provide the structure which will support the deck boards. The spacing and size of the joists is again based on the distance between the beams or ledger to beam span.
Rim Joist
The rim joist is the cap at the end of the joists in order to hold them in place at the appropriate span and help prevent twisting or movement of the joist floor framing.
Ledger Board
The Ledger is the deck component where the majority of deck failures take place. Therefore it is critical that the ledger is installed properly.
This is the framing which is attached to the main structure and should be sufficiently bolted to framing members of the house. This will carry the weight of the deck joists via mechanical attachment. The ledger must be properly flashed using metal or other approved impermeable material so that water does not get between the framing and exterior wall. Improper flashing may cause the bolt attachments to disintegrate and cause structural failure.
Sway Braces or Hold-down Tension Devices
Tension devices are a relatively recent addition to deck building practices. These devices became part of building codes around 2007 but may have not been fully adopted into your local jurisdiction until later. Therefore they may or may not be present on your deck depending on the build type, structural design, and date when the deck was constructed. These fastening devices connect the ledger board to the interior framing of the building and are important for handling lateral forces and decreasing the risk of separation from the structure.
Posts, Guards and Balusters
The posts and guards are the structure which is used as fall protection and supports the top railing. These must be sufficiently attached to the framing to support lateral force and weight. There are specific guidelines as to the height and spacing of guards/balusters in order to assure safety (see graphic above).
Other Framing Methods Used
While this article is not technically exhaustive into all possible deck builds, here are a few other common methods of deck framing which are often seen in New York State.
Cantilevered Joist Framing
Cantilevered framing describes the method used when the floor framing from inside the building is over extended to the deck joists on the exterior of the building. A formula is used to determine the ratio of the overhang beyond the exterior wall for adequate structural support. This method does away with the need for a ledger board and ledger attachment to the structure. It may also not require posts or footings depending on the size of the deck and proposed load calculations for the deck.
Free Standing/Unattached Decks
A deck may not be reliant on the ledger board to support the joists if it has a set of footings and posts near the structure. This essentially creates a deck which is self supporting and may be minimally attached to the building. The joists then span a beam-to-beam construction, rather than beam-to-ledger.
Decking
Finally the reason all of the above is so important, the decking. Choosing the right decking will factor into the durability, longevity and aesthetic appeal of your deck.
Deck boards can be made out of a variety of materials.
There are many lumber varieties which are commonly used. Wood decks require maintenance such as staining or sealing. These wood decks can last 15-20 years depending on the variety of wood used.
-Pressure Treated Lumber: This may be the most economical option and can be custom stained to produce a wide variety of colors and looks.
-Exotic Hardwoods: This option may increase your initial cost, but may hold up better in the exterior conditions over time. These are more dense than pressure treated lumber and often resistant to rot and insect infestation.
These wood varieties include Ipe, Mahogany, Garapa, Cumaru, and Tigerwood.
-Composite Decking has become a popular option for a largely maintenance-free decking material. There are many different companies and varieties of composite decking. It comes in a multitude of colors and finishes.
Composite decking is made when raw materials, mostly wood and plastics, are melted together and extruded into the deck board shape. These composite materials have an advertised life span of 25-30 years.
Summary
I hope you have found this overview of deck construction informative and helpful. There are many options when it comes to deck construction. It is important to fully understand the proper theory and methods used to construct a deck. Unless a homeowner has an extensive construction background, deck construction is best left up to a qualified contractor. Silver Maple Home Inspections LLC, of the Hudson Valley New York, has inspected hundreds of decks. Whether during construction phases or as a part of a certified Home Inspection, we always report and advise on the proper practices for deck construction. If you are looking to purchase a home in New York, or would like a detailed report on your deck construction, call or email
Silver Maple Home Inspections LLC.
845-594-3211
silvermapleinspections@gmail.com
*Disclaimer* This article is in no way meant to be instructions for deck construction. Silver Maple Home Inspections LLC does not take any responsibility for the reader’s interpretation or implementation of the information presented in this article. All construction should be performed by qualified professionals.*
