Deck Planning from the Ground Up

First things first, when it comes to planning a deck.

A nice outdoor living environment tops most homeowner wish lists, and constructing a deck is among the most popular ways to enhance the property. The design of a deck can vary from a small DIY-built structure to a professionally constructed multi-level entertainment space. When planning for construction, there is a lot to consider even when the project is relatively small.

Location, Location

Where to build your deck is often determined by limitations of the home’s construction, but there are factors to consider as you plan. Inspect the lay of the land and note the slope away from the house where natural drainage will apply. Check that the drainage or downspouts will take the water away from the house foundation and deck footings. Any problems should

be immediately rectified to preserve the integrity of the house foundation, whether you move forward with a deck or not. Also, locate and mark any outdoor utilities—electrical, gas or water—to avoid damage during construction. Call 811 to have underground utilities marked for free.

Sun exposure and the direction of prevailing winds are two other important issues. Decks exposed directly to the midday sun may not be ideal. The farther south you live, the more exposure to midday sunlight can damage the deck over time from UV rays as well as make time spent there less comfortable for the homeowner. For northern homes, an ideal deck location is southeast or southwest, which can take advantage of midday and evening sun to the west as a way to maximize the heat. In southern regions, a northeast or northwest location will minimize the extreme midday heat but still take advantage of the morning warmth and setting sunlight. In some cases, you can build a deck that wraps around the corner of a house as a compromise. If your deck can’t avoid direct sun exposure, consider incorporating an overhead trellis, awning or other roof structure to provide shade.

Don’t forget the prevailing winds if you live in a windy area. A strong wind can make time spent on the deck less enjoyable, and if you can’t avoid wind, then consider incorporating

a wind screen or railing that acts as a barrier.

Permits and regulations might also factor into the deck’s location, and this varies widely depending on where you live. In a small town in Alabama, a building permit to attach a deck to your home may only cost you $25. However, in a city like Chicago, a similar permit might cost thousands to procure. The project’s site location can affect those permitting costs too. For example, a permit to construct a deck attached to a home in an Illinois city might cost considerably more money than a permit to build a freestanding deck just a few feet away from the very same home. Do this research ahead of time, because it could affect your design decisions.

Red Tape

You’ll usually need to submit two copies of deck plans and drawings to your local Building Inspector Department along with your permit application. Applying for a permit can also

verify if there are any property easements and make sure the deck plan meets local

homeowners’ association (HOA) standards.

(In many subdivisions, HOA approval is required before obtaining permits from your building inspector.) In addition to local regulations, your deck plan will likely have to comply with the International Residential Code (IRC), which has been adopted by almost all US states and include guidelines such as Residential PSF Deck Requirements. (For a residential deck, the code requires it be designed to support a minimum 40-psf live load.)

Two approaches to deck plans:

Cost and Budget

In the recent pandemic years, the costs of building materials have fluctuated dramatically. Not only will the size of the deck impact the cost, but its design will affect the materials needed when you factor more intricate features such as multiple levels, stairs, built-in benches and railing systems. All decks higher than 30 inches above grade must have a guardrail at least 36 inches high, although some states and local codes require them to be as high as 42 inches. Factoring all this together, the average cost of building materials for a deck can range between $15 and $38 per square foot.

Decking calculators can help you estimate the materials required to build your deck and the associated costs. Simply plug in your desired dimensions to get estimates. Here’s a not-so-secret tip—Decks.com offers deck-building calculators that are free for anyone to use. Visit the site to take advantage of the following:

Deck Stairs Calculator: Use this to determine the rise and run of your stairs, dimensions, the angle of your staircase, length of stringers and more.

Decking Floor Estimator & Calculator: Find out how many deck boards you’ll need or how many screws and hidden fasteners. This calculator helps you find how much material you’ll need.

Cost of Building a Deck Calculator: The cost to build a deck depends on many factors such

as square footage, how elaborate the design is, and type of materials. Plug in your dimensions to get an estimate on the materials cost.

Although the calculators provide a rough estimate, these are free to access and should help homeowners formulate a construction budget. The Decks.com site even offers a free deck-designer tool that can produce a downloadable schematic plan, which you can take to your permitting authority.

Deck Ledger vs. Freestanding Construction

Most of today’s residential deck frames are built of pressure-treated lumber that is intended for ground contact. Decks are usually constructed in one of two ways. The first way is to support one side of the deck with piers, posts and beams while the opposite side is attached to the house using a ledger board.

The second method is to build a freestanding deck that is not attached to the house and is instead completely supported by piers, posts and beams.

When attaching a deck to a house, the house siding is often cut and removed, then a ledger board (usually a pressure-treated 2x8 or larger) is anchored to the house wall to support the joists and bolster the deck framing. The joists are then fastened to the face of the ledger with metal joist hangers.

Ledger-board spacers present a way to prevent rot at this crucial connection. These donut-shaped Deck2Wall spacers are designed to install around the bolts or structural screws between the house and the ledger board to provide an air gap. (Although stacked stainless steel washers can be used as an alternative, ledger-board spacers are easy to install and provide a larger bearing surface area.)

A ledger board will also need deck flashing, which serves as a moisture barrier to protect the house from any openings made while attaching the board. Proper flashing and ledger-board attachment is critical to building a structurally sound deck that will remain safe for years to come. Without secure attachment and moisture protection, rot can develop and weaken the leverage connection, which is a common cause of collapsed decks and can pose a dangerous hazard to anyone on it or nearby.

These days, most contractors prefer to use vinyl flashing to protect the wall behind the ledger, and Z-flashing should be installed over the ledger, running a couple inches up the wall behind the siding to shed water.

Z-flashing is named for its Z-shaped profile.

When mounting a ledger to the house band, 1/2-inch through-bolts or lag screws were

once the standard fastener. Today, 1/4-inch structural lag screws (aka Construction Screws) actually hold stronger and have greater shear resistance than lag screws—plus, there is no need to pre-drill pilot holes because they have self-drilling tips. To fasten the ledger into a

solid concrete wall requires 1/2-in. expansion anchors set into the wall at least 2-1/2 inches.

The Construction Screw from U2 fasteners has the finished appearance of a conventional round head, and is created to provide an extra-large bearing surface under the head.

Check with your local building department for specific guidance on fastener requirements

and flashing details. The ledger fasteners should generally be installed in a zigzag pattern to avoid splitting the board along the grain. Never install a ledger board with nails.

Some builders install the ledger first, then use it as the basic point of reference for determining footings, posts and all the framing. In areas with heavy snowfalls, it may be desirable to have the finished deck built 1-1/2 inches or so below the door sill.

Not all situations are suited for deck-ledger installation. You should avoid mounting a

ledger board to brick or stone veneer exteriors. Attaching a ledger to a hollow concrete block wall also presents problems and requires special epoxy-strengthened anchoring systems. In these situations, consider building a freestanding deck frame.

A ground-level deck is a variation on the freestanding concept where you can create a simple foundation by using concrete blocks to support the deck’s corners. Lay the deck beams on top of the blocks, making sure they’re elevated enough to allow for ventilation. Level the beams to serve as your ground-level deck frame on which to build your platform of joists and decking. (In general, if a deck is closer than 12 inches to the ground, the deck perimeter should be left open for easy airflow to reduce dampness which might otherwise lead to rot. The deck can also be built over gravel for better drainage.)

Attach angle brackets at the corners of a ground-level deck where the joists and beams meet to provide additional support and maintain squareness as you work.

All decks higher than 30 inches above grade must have a guardrail at least 36 inches high. One of the most secure methods to attach guardrail posts is to fasten the full 4x4 inside the rim joist and adjacent to a deck joist, using through-bolts and washers or structural screws long enough to bridge the full post. Install blocking for added rim strength and to stiffen the guard rails. All guardrails must be built strong enough to withstand 200 lbs. of force anywhere along the top of the rail.

A variety of styles can be used for the railing sections between the posts, but the overarching rule prohibits any openings larger than 4 inches. This rule is to prevent small children from slipping their heads through the railing. (Exception: Stair rails may allow a 6-in. space for the triangle formed by the stair tread.)

Install blocking or bridging between joists at mid-span to reduce bounce. Install the blocking flush with the top of the deck frame and stagger the material to provide space for nailing the ends.

SIDE NOTE 1:

Smart Moves for Treated Wood

Although steel framing is an option, the vast majority of decks built in the USA are framed with pressure-treated lumber. It’s important to use treated wood rated for Ground Contact, which has a higher level of preservative treatment than lumber rated for Above Ground use. (A label affixed to the end of each piece of lumber specifies the use.) Its treatment level makes it better able to withstand long-term contact with soil, but also makes it the best choice for above-ground framing in critical applications such as ledger boards and support posts.

Even with chemical treatment, however, framing lumber can be damaged over time from prolonged exposure to the outdoor elements. You or your contractor can reduce such problems in the following ways.

Brush a wood preservative onto all saw cuts and into drill holes during construction. Anywhere a blade or bit penetrates the board, the interior wood-grain is exposed to water and potential rot. Also apply preservative on areas such as knots and defects where moisture can collect.

By using Outlast Q8 Log Oil (containing .675% oxine copper) to coat cuts in treated lumber, you can build and stain the project on the same day with no wait time.

Use corrosion-resistant fasteners. When nailing or screwing near the edge or end of a board, first drill pilot holes to help minimize splitting.

Apply flashing tape to the tops of joists and beams. These flat horizontal surfaces can trap moisture, but the rubberized adhesive tape will easily shed water.

Consider installing the deck boards with a hidden fastener system. Fastening the decking from the top creates an entry point for moisture on the surface where standing water can penetrate over time. Hidden fastener systems, however, attach deck boards to the joists from the sides or even the bottoms the boards, which means the fastener holes are less susceptible to water pooling from rainfall.

Finally, protect the deck with a weather-resistant finish. Any exposed wood, pressure treated or not, needs to be protected from the elements. Apply a high-quality clear coating or semi-transparent stain that contains a water repellent to help minimize the effects of the wood’s moisture-absorption cycles. For maximum protection, the stain/sealer product should be applied soon after construction when the treated wood has completely dried.

SIDE NOTE 2

Lateral Load Connector Device

One of the more significant code updates for a ledger-supported deck requires the builder to install a positive connection to the house wall to resist lateral loads. This may now be a requirement in your area. Lateral loads can result from earthquakes or from people moving around on the deck, and in severe cases, these forces can cause the ledger board to rip away from the house wall and collapse.

The easiest way to meet the code requirement is to install four hold-down connectors. You will need to pre-drill and attach these L-shaped metal brackets with a 3/8-in. diameter lag screw that penetrates at least 3-inches into the center of the house wall’s top plate, studs or header. Each connector bracket is then screwed to the bottom of the deck joist. Simpson Strong-tie offers the DTT1Z deck tension tie as a solution. Consult local codes to see if a lateral load connection is required, and always follow the manufacturer’s instructions when installing deck hardware.