Deck Framing: Complete Guide

Building a deck is a rewarding way for a DIYer to expand their outdoor living space and enjoyment. Once you decide on the type of deck, you’re ready to get started. Not sure where or how to begin deck framing? Don’t sweat it; we’re here to help.

Start with a design and develop a plan. Review the types of materials required and generate a material list for price comparison and purchasing. Check local building codes and any HOA requirements and get a permit if necessary. Follow safe building practices, have a supply of bandaids on hand, and enjoy the experience.

In this guide, we’ll discuss the overall guidelines for framing a deck and identify the materials you’ll need. We’ll also explain the differences when framing for wood or composite decking. Plus, we’ll examine how a ground-level or floating deck differs from a raised or attached deck. Our aim is to provide a general understanding of deck framing so you’re better prepared for your project.

Overall Guidelines for Framing a Deck

Once you’ve determined the type of deck you want, you’ll need to draw out the framing elements. The drawings will help you generate a materials list and to get any required permits. Our guide will help you identify the steps and materials to plan and build a safe deck for you, your family, and your friends to enjoy for many years.

One reference we use when planning a deck is Section R507 of the 2021 International Residential Building Code (IRC). It’s the foundation of many local codes, so it’s a great resource when planning a code-compliant deck – it’s online, up-to-date, and free.

Deck Building Permits

Most municipalities, States, and Provinces have building or safety codes that address outdoor decks. Depending on the size and distance off the ground, a building permit may not be required, however, the construction of the deck still needs to meet codes. A code-compliant deck means your deck meets the minimal building and safety requirements for where it is built.

Check online or visit your local building department and find out what their requirements are for a deck. If you’re planning the deck for a cabin in a different jurisdiction than the one in which you live, check the codes for where the cabin is as there may be differences. Local requirements often address snow loads, wind forces, soil conditions, and seismic issues that need to be considered in the deck design.

Most jurisdictions require a building permit if the deck is more than 24” to 30” above grade, greater than 100 to 200 square feet in area, serves an exit door, or is attached to a building. However, it varies so check before building. Building without a permit can result in fines and having to remove the deck and can cause issues when selling your house.

To apply for a building permit, you’ll need to complete the application. Most applications require two sets of construction drawings and a site plan. If a contractor is going to be building the deck, a copy of their license is often required. Some jurisdictions have an application fee that is deducted from the permit cost, others just have a permit fee.

In most locations, even if a permit isn’t required, having the building department check out your plans will help keep the deck code and safety compliant. They’ll let you know if the support posts, footings, and joists are adequate and properly spaced for the loads it will experience.

They’ll also identify and often explain how blocking, railings, and stairs should be attached and what type of fasteners to use for different components. It’s a good double-check and can be educational too.

If a permit is required, the cost commonly is based on square footage or the value it may add to the house or property, or both. If a permit isn’t required, the structure still needs to be code and safety compliant.

Many local codes are based on the 2012 or 2015 IRC, so building to the 2018 or 2021 IRC standards is better. Remember, the code is like the minimum passing grade, building above the code often means a stronger, safer, and more durable deck frame.

Pro Note: Whether a permit is needed or not, use hot-dipped galvanized or stainless-steel fasteners and brackets to avoid corrosion due to the chemicals in pressure-treated wood.

Deck Size and Design

Deck size and design often depend on personal preference, ability, and aesthetics. Two common rules of thumb are 20% of the adjacent building’s square footage or smaller and that no deck section is larger than the biggest room in the house. However, if you’re considering a wraparound deck or one that runs the full length of your home, the square footage may exceed both rules. Another consideration is sloped vs flat ground.

Use 1/4″ grid paper to draw out your deck idea. Begin by outlining the side or sides of the house it will attach to or be adjacent to. Consider one or more furniture layouts, BBQ and hot tub placements if applicable, and possible flow patterns to stairs and furniture.

You want to be able to move freely and be able to add or move furniture too. A 6’ or 8’ deep deck usually is cramped if the furniture is facing each other, while 10’ to 12’ or deeper allows movement between them. Decks more than 12’ deep, however, may require extra support, so greater costs.

A good practice is to drive stakes in where you want the deck corners to be and connect them with a string line. If the ground is flattish, lay out your furniture idea to see if it works. If you need a more concrete reference, use 2×4 or 2×6 planks to mark the deck boundaries. Adjust the string or boards until the shape and size work for you.

The height of the deck above grade level is another factor of deck design. Access from the house may be level, one 3” to 7” step down, or several steps depending on aesthetics, door threshold elevation, and possible vistas.

Decks 24” to 30” above grade level and those attached to a house require a building permit, and may also decrease privacy from neighbors. Alternatively, high decks can improve access to views.

High decks require more support posts spaced closer together and with more bracing than those closer to grade level. It can also require more beams and larger dimension joists with narrower spacing between, thus increasing costs.

Additionally, decks more than 24” to 30” above grade require properly secured railings. However, too many steps down from the living area to the deck can decrease comfort and relaxation.

Materials

Once the size and design are decided upon, the next step is selecting material for the deck frame, post brackets, joist hangers, bolts, structural screws, and screws or nails. If the deck will be attached to the house, then support post footings need to reach below frost level.

The location and number of footings and posts, and their sizes depend on the loads they will bear, soil condition, elevation, and deck dimensions. All decks need to comply with the live loads (Section R301.5 – IRC 2021) or snow loads (Table R301.2 – IRC 2021), whichever is greater.

Footings support posts that are commonly 4×4 or 6×6 pressure-treated timber. The size and spacing depend upon the tributary area, loads, and wood species. Posts often fasten to a poured footing with a galvanized steel saddle bracket above ground level. They may be notched for beams or use connection brackets.

The lumber used for the deck framing should be pressure-treated No. 2 grade or better, or naturally resistant to termites and rot, such as cedar. There are other materials that can be used, but they need to be approved. Any timbers used in or near contact with the ground need to be labeled as such too.

A corrosion-resistant flashing is commonly used where a deck joins a structure, so add that to your material list and drawings. Many pros are using protective deck tape where wood rests on other wood support members or galvanized hangers.

The self-adhesive tape provides an anti-corrosive barrier to protect the wood from chemical and moisture damage. On double or triple-ply beams or joists, it also helps prevent moisture intrusion between the planks.

Decking, stairs, and railings may be pressure-treated lumber, cedar, Ipe, or another approved wood. If using plastic or composite decking, stair treads, railings, or guards, they must meet ASTM D7032 requirements and have a flame spread index of 200 or less.

The information is usually on the packaging or affixed label. All fasteners should be galvanized, stainless steel, or another approved material (Section R317.3 and Table R507.2.3 IRC 2021). Consider approved construction screws instead of lag screws, and use strong screws instead of nails.

Pro Note: If using treated lumber, remember to treat drilled holes, notches, and all cuts with a preservative.

Safety

Getting a building permit or approval means your deck meets code compliance, so the design is safe. Using appropriate materials will prolong the life span of the deck and your enjoyment of it.

When constructing your deck, remember to wear personal safety gear, such as ear and eye protection, and a respirator mask if needed. Gloves help prevent slivers and can improve grip. If using power tools, follow safe use practices.

How to Frame a Deck

Designing a deck requires a specialized knowledge base, so if you’re going to design and build your own, you may need to expand your knowledge base. A deck is only as strong as its weakest part, so skimping isn’t advisable.

Once you’ve identified the size and shape of the deck, you’ll need to lay out the decking arrangement as it typically runs perpendicular to the joists, which in turn are perpendicular to the beams. The footing and support post placements depend on the magnitude of the beam, length or span permissible for the joist timbers, and the loads.

Both beams and joists can also be cantilevered beyond their supports, so that’s something else to consider too.

Ledger Board

Decks are either free-standing or attached. Attached decks require a ledger board which must be of 2×8 or greater and of No.2 or better pressure-treated lumber. The ledger board should not be smaller in depth than the joists it will support.

The ledger typically has joist hangers spaced and attached prior to it being fastened to the house. The ledger supports one end of the joists and is fastened to the building using appropriate fasteners suitable for the structure.

Lag screws, bolts, or approved construction screws are commonly used to fasten the ledger in place. Subsection R507.9.1.3 and subsequent tables and subsections address fastener spacing and loads.

Posts

Support posts are commonly 4×4 or 6×6 pressure-treated timber depending on the tributary area, loads, height, and wood species (Table R507.4 IRC2021). They rest on footings that may be deck blocks or pads, poured concrete, or treated wood (Section R707.3 and Table R507.3.1 IRC 2021).

The posts often fasten to a poured footing with a galvanized steel saddle bracket above ground level. They may be notched for beams or use connection brackets.

Beams

Beams may be flush or dropped and can cantilever up to 25% of the typical beam span as in Figure R507.5.1(1&2). The span of deck beams depends on joist span, loads, wood species, and the magnitude of the lumber used to build the beam (Table R507.5 (1-4)).

Deck beams are commonly two or three-ply 2-by lumber between 8” and 12” in depth. The seams should be centered on support posts, and two rows of approved fasteners used to fasten the plies together.

Joists

Joists are the framework to which the deck boards and railing posts are usually attached. They fasten to the ledger and beams to form a level or near-level base. Joists are commonly spaced 12”, 16”, or 24” on center and may be cantilevered up to 1/4 of their span depending on wood species, dimensions, spacing, and loads.

Joists must be supported by a joist hanger and/or have at least 1-1/2” at the end resting on the beam. Section R507.6 is a good reference, as are Tables R507.5 (1-5), Table R507.6, and Table R507.7. Select planks that are straight and have a slight crown so they will flatten with the weight of decking and other loads. Prior to fastening the joists to the beam, it’s a good idea to square the framing.

Since you’ll want the deck square with the house, use the ledger as the base to form a right-angle triangle with the outside joists. The Pythagorean theorem is helpful but stick to multiples of 3, 4, and 5. Measure 3 feet in from the inside of where the last joist attaches to the ledger and put a mark on the ledger.

Measure 4 feet out along the outer joist from where the end of the joist meets the ledger and make a mark. The diagonal distance between the two marks should be 5 feet. If it isn’t, move the free end of the joist in or out until it is, and fasten it in place. Then adjust the placement of the other joists based on the required spacing.

Blocking

Blocking is used to prevent joists from twisting under load. They should be the full depth of the joist, so are often cut from joist lumber. Blocking is paced every 8 feet or less along the span of the joists. The blocking is also helpful for supporting railing posts too.

Rim Joist

The rim joist typically closes the open ends of the joists and helps them maintain their spacing. It also helps prevent the joists from twisting under loads. They may be secured to the joist ends with joist hangers or approved fasteners, and are usually the same dimension as the joists. The rim joist isn’t usually load-bearing but can provide support to railing posts.

Railing

Railings are also referred to as guards as their purpose is to prevent falls. They can be mounted to the top of the deck, to the rim and band joists, or through the deck surface to the joists and blocking underneath. Railings may be made of wood, metal, glass, plastic, or a combination of materials.

If the ground 36” horizontally out from the edge of the deck is 24” to 30” (depending on local codes) below the deck’s surface, then it must have a railing. Railings should be 36” to 42” tall depending on the deck’s distance from the ground and where you live.

It must be able to withstand 200 pounds of outward force at the top and have no openings large enough for a 4” diameter ball to pass through. Sections R507.10, R301.5, and R312 of the 2021 IRC address guard requirements.

Stairs

Decks raised above the ground typically require stairs to provide access to the ground or into the house. The location of the stairs should be determined prior to building as there may be additional structural requirements. Such as anchoring points, railing support post spacing needs, and blocking supports.

It’s a good idea to consider traffic flow between the house and the ground or other decks. All stairs need to comply with Section R311.7 and its subsections. The width of the stairway, rise and run of the treads, hand railing height, baluster spacing, and landings are all addressed, as are ramp alternatives.

Composite Decking Framing

There are many different types of composite decking available and most manufacturers provide installation instructions with their products or online. One important factor is that you need to identify the type of decking when applying for a permit.

Composite decking is heavier than wood so the posts and framing may need adjustment. Plus, most composite boards are more flexible than solid wood, so joist spacing may need to be adjusted. Additionally, due to their flexibility, they also show elevation deviations between joists, so joists may need to be hand or power planed to ensure they are all even.

Some products are non-capped and others require caps to hide hollow cores. Many have sculpted bottoms to reduce weight and material too, so you may want to consider how to structure the deck or decking to hide or mask decking ends. The decking also typically needs to be fastened to joists with special screws, nails, or clips that may require special tools.

Ground Level (Floating) Deck Framing

 

Ground-level, floating, or grade-level decks are typically constructed so the bottom of the deck frame is 6” or less above the ground. The framework may even be below grade level in an excavated hollow. However, the deck surface may be as high as 24” to 30” above the surrounding grade level, depending on local codes.

Most ground-level decks are free-standing, so aren’t attached to a structure, and seem to float above the ground. Footings are often deck blocks or pads, and wood for beams and joists should be pressure-treated ground contact or near-ground-rated lumber. All organic material should be removed from where the deck will sit, and where possible, airflow under the deck encouraged to decrease moisture damage and rot.

Ground-level decks are close to the ground and don’t usually require a railing or guard. However, if the ground 36” horizontally out from the deck surface drops sharply away so the elevation is 24” or greater, railings will be necessary.

Additionally, floating decks usually don’t require a building permit or stairs either. If the ground slopes, consider building a stepped deck with each component being ground level.