Deck Construction
Until about fifteen years ago, decks were considered structures that anyone could build, and just about anyone built them. Investigations of deck failures, and research into deck construction practices, have shown that decks are more complicated than people realized. As a result, building codes (since 2012) have mandated stricter standards for building decks, and many building departments are enforcing these stricter standards. Deck inspections often reveal failures to comply with modern deck construction standards. Such compliance failures are common with older decks but can also occur with recently built decks. Some of these compliance failures involve safety issues. Building codes do not require that existing decks be brought up to current standards, however, when safety is involved, homeowners would be wise to address safety issues regardless of whether or not doing so is required. The service life of deck components ranges between ten years (or less) for decks located on the ocean to thirty years for decks in a dry environment. Twenty years is a good average to use in most environments.
What Is a Deck?
A deck is a structure generally made from wood that is usually located adjacent to the house. When most people think about a deck, they think about the structure located at the rear of the house. A deck can, however, be located anywhere on the property. A front porch may be a deck. A stairway and a landing serving a door may be a deck. If the structure is built like a deck, then it is a deck, regardless of where it is located and what it is called. If the structure is a deck, then the deck construction standards apply.
Decks Around Above-Ground Pools
Decks are sometimes built around permanent above-ground swimming pools to provide access to the pool, and to provide a place to relax at the water’s edge. These decks present some special challenges. Most local governments require an access barrier system around swimming pools to help keep children from entering the pool without supervision, and possibly drowning. If the deck around the pool is part of the access barrier system, it must comply with some special requirements. These requirements can include a specific height for the deck and guards, and self-closing and self-latching gates that allow access to the pool deck. Pool water contains chemicals that can deteriorate deck components. You should be careful when selecting and installing components for decks around pools. Consider stainless steel for hardware and fasteners and consult manufacturer’s instructions when selecting deck flooring (decking) to ensure that it is designed to resist deterioration by pool water chemicals.
Parts of a Deck
Decks can range from a simple, single-level rectangle to a complex multi-level structure with angles and rounded turns. Whether simple or complex, most decks consist of the same components. While all deck components are important for safety and longevity, some components are more important than others. The following list is in order from the most important to the least important from a safety perspective.
1. Flashing
Flashing is required between the deck and the house when the deck is attached to the house. Flashing helps keep water from entering between the deck and the house. Water can damage the important connection of the deck to the house, which can allow the deck to collapse when it pulls away from the house. Water can also create conditions for fungal (mold) growth.
2. Ledger Attachment
Most decks are attached to the house. The board that attaches the deck to the house is called the ledger board, or ledger. The ledger must be attached to the house using bolts or screws. Nails, by themselves, are not acceptable. The deck must also be secured to the house using connectors called lateral load connectors (tension ties). Failure to properly secure the deck to the house can allow the deck to collapse when it pulls away from the house.
3. Guards (Guardrails)
A deck that is more than thirty inches above the ground is required to have a guard around the perimeter to keep people from falling from the deck. Many deck injuries are caused when the deck guard fails and people who are leaning on the guard fall to the ground. Building codes have requirements about the force that a guard must resist, but the codes provide no guidance about how to build a guard to resist that force. As a result, very few guards comply with the code requirements. Building codes also have requirements for the height of deck guards above the deck flooring. A horizontal deck guard should be at least 36 inches tall, except in California where the minimum height is 42 inches.
4. Stairways and Handrails
A stairway is required if the deck is more than 7 ¾ inches above the ground. A handrail is required if the stairway has four or more risers (the vertical part of the stairway). Injuries involving stairways are common. This is especially true for exterior stairways because they are exposed to rain and snow. Special care should be used when building exterior stairways and handrails. Handrails and guards on the open sides of deck stairways should be at least 34 inches, and not more than 38 inches, above the leading edge of the stairway treads. Handrail shape requirements for all exterior stairways, including deck stairways, are the same as for interior stairways. A handrail made from a two-by-four or larger lumber is not a proper, or a safe, handrail.
5. Framing
Framing includes components such as floor joists, joist hangers, deck flooring, and the nails and screws that hold everything together. Installation of framing components according to building code requirements and manufacturer’s instructions is important, but it is unusual that framing errors are the sole cause of deck injuries.
6. Posts and Footings
Like framing components, installation of deck posts and footings is important, but it is unusual that improper installation of these components is the sole cause of deck injuries.
Deck Flooring (Decking)
You may use many types of materials for deck flooring. Wood, such as 2x6 and 5/4x6, is the most common type of deck flooring. It can have a service life as long as the deck, if properly installed and maintained. Preservative-treated Southern Pine is a common wood species in many markets, especially in the Eastern United States. Other species (such as Redwood) are available. Other deck flooring materials include wood/plastic composite materials, plastic (such as PVC), and metal (such as aluminum). The primary advantage of these other deck flooring materials is low or no maintenance. The primary disadvantage is higher initial cost. These other flooring materials must be installed according to manufacturers’ instructions. Some of these materials have a limited span distance between supports, and some are not designed to be installed near the ground.
Deck Stability
The deck flooring is the most visible part of a deck, so some equate the condition of the deck flooring with the condition of the entire deck. While deck flooring is a structural component, the contribution of the deck flooring to overall deck structural stability is less significant compared to other structural components. It is important to understand, therefore, that placing a coat of stain on the deck flooring, or even replacing the deck flooring, will do little or nothing to improve the structural stability or safety of a deck.
Deck Codes and Standards
It is important to know that a deck built in compliance with the local building code may or may not be safe. There are many reasons why this is true including slow adoption of up-to-date building codes by local building departments and sporadic enforcement of building codes in some areas. In addition, building codes are a minimum standard. Building a deck beyond the minimum standard is recommended for both safety and longevity. The most complete resource for building a safe deck is DCA 6-15 published by the American Wood Council.
Deck Inspections
Experts advise that decks be inspected by a qualified professional. How often this occurs depends on the deck. Once a year is ideal for decks that are older than about ten years. Every two or three years may be acceptable for newer decks. While not a substitute for a professional inspection, here are some things you can look for that might help you determine if your deck presents a significant safety risk.
Deck ledger is attached to the house using only nails, or using only small screws, such as deck flooring screws. Guards move when you push on them. Stairs move or shake when you walk on them. Joist hangers, nails, or other metal hardware present significant visible red rust. Wood to which the deck ledger is attached in the house is soft when probed with a sharp object such as a screwdriver or presents water stains. The damage you can see from inside the basement or crawlspace may be worse where you can’t see it. Wood is soft when probed. This is especially common where posts are buried in soil.
DIY Deck?
Applying a wood preservative to a deck is a good do-it-yourself project. Be sure to use a high-quality product that is intended for decks, such as a semi-transparent exterior stain. Follow the manufacturer’s instructions involving surface preparation and application. Repairing a deck, especially if structural repairs are necessary, is usually best left to professionals. If you try, be sure to read and understand DCA 6-15, and to follow manufacturer’s instructions for any joist hangers, connectors, and screws or nails that you install. Building a deck is also usually best left to professionals. If the deck is not more than about three feet above the ground, and is a simple rectangle, then you might give it a try. You should have some experience building structures. Building a deck is not a project for a novice. Be sure to read and understand DCA 6-15, and to follow manufacturers’ instructions. Many jurisdictions require a building permit to build a deck, so be sure to contact your local building department to learn their permitting and inspection requirements. Decks can provide enjoyable and functional outdoor living space, but they require special attention in order to keep them functional, looking good, and safe. Selection of materials is important, especially in corrosive environments, such as near saltwater and where snow and deicing salts are encountered. Installation of materials is a major factor as well. You should install all materials in compliance with manufacturers’ instructions and best practices, such as those in DCA 6-15. Regular inspection and maintenance also make up for the longevity of your deck. Do all of these, and you should get many years of service from your deck.
