Inspecting Decks
This section deals with the details of a deck inspection that may be performed during an inspection of the exterior.
At the end of this section, you should be able to:
· know how to inspect a deck; and
· list some common concerns related to a deck structure.
More than 2 million decks are built and replaced each year in North America. It’s estimated that of the 45 million existing decks, only 40% are completely safe.
Because decks appear to be simple to build, many people do not realize that decks are, in fact, structures that need to be designed to adequately resist certain stresses. Like any other house or building, a deck must be designed to support the weight of people, snow loads, and objects. A deck must be able to resist lateral and uplift loads that can act on the deck as a result of wind or seismic activity. Deck stairs must be safe and handrails graspable. And, finally, deck rails should be safe for children by having proper infill spacing.
A deck failure is any failure of a deck that could lead to injury, including rail failure, or total deck collapse. There is no international system that tracks deck failures, and each is treated as an isolated event, rather than a systemic problem. Very few municipalities perform investigations into the cause of a failure, and the media are sometimes more concerned with injuries rather than the causes of deckcollapses. Rail failure occurs much more frequently than total deck collapses; however, because rail failures are less dramatic than total collapses and normally don’t result in death, injuries from rail failures are rarely reported.
Here are some interesting facts about deck failure:
· More decks collapse in the summer than during all the other seasons combined.
· Almost every deck collapse occurred while the decks were occupied or under a heavy snow load.
· There is no correlation between deck failure and whether the deck was built with or without a building permit.
· There is no correlation between deck failure and whether the deck was built by a homeowner or a professional contractor.
· There is a slight correlation between deck failure and the age of the deck.
· About 90% of deck collapses occurred as the result of the separation of the deck from the house via the deck ledger board, allowing the deck to swing away from the house. It is very rare for deck floor joists to break mid-span.
· Many more injuries are the result of rail failure, rather than complete deck collapse.
· Deck stairs are notorious for lacking graspable handrails.
· Many do-it-yourself homeowners, and even contractors, don’t believe that rail infill spacing codes apply to decks.
This section does not address specific building codes, balconies, lumber species, grade marks, decks made of plastics or composites, mold, or wood-destroying insects. This section focuses on single-level residential and commercial wood decks. Recommendations found within this section exceed the requirements of both the Residential Standards of Practice and the International Standards of Practice for Inspecting Commercial Properties.
A proper deck inspection relies heavily on the professional judgments of the inspector. The following information will help improve the accuracy of those judgments.
Required Deck Inspection Tools:
· flashlight;
· measuring tape;
· ladder;
· level;
· plumb bob;
· probing tool; and
· hammer.
Optional Inspection Tools:
· moisture meter;
· magnet; and
· calculator.
Deck Loads
A deck inspection should progress in much the same order as deck construction. Inspectors should start at the bottom. If a deck is deemed unsafe from underneath, the inspector should not walk out onto the deck to inspect decking, handrails, etc. The inspector should stop and report the safety issues.
The image above depicts an evenly distributed deck load. Building codes require decks to be designed to carry a uniformly distributed load over the entire deck. If evenly distributed, half of the load is carried by the deck-to-house connection, and the other half is carried by the posts.
The image above depicts a likely deck load distribution. People tend to gather near the railings of a deck, and so more load is likely carried by the posts.
Hot tubs filled with water and people are heavy and can weigh a couple of tons. Most decks are designed for loads of 40 to 60 pounds per square foot. Hot tubs require framing that can support more than 100 pounds per square foot.
Footings and Posts
Required footing depths vary based on local building codes. The depth is normally below the frostline or 12 inches (where frostlines are not applicable).
On steep properties, the slope of the ground around the footing could affect the footing’s stability. The “7-Foot Rule” states that there should be a least 7 feet between the bottom of a footing and daylight.
Posts in contact with soil should be pressure-treated and oriented so the cut end is above grade.
The footing near the home may not be on undisturbed soil. Some codes consider soil to be undisturbed if it hasn’t been disturbed in more than five years. It may be difficult to find undisturbed soil near the foundation of a new home.
Posts can lift out of pre-cast concrete piers, and piers can slide. Posts should be connected to their footings so that the posts don’t lift or slip off.
Lawn sprinkler systems that regularly keep the deck wet contribute to decay of wooden components. Downspouts should not discharge near deck posts. Puddles contribute to post decay. Wood can decay and degrade over time with exposure to the elements. Decay is a problem that worsens with time. Wooden members within the deck frame that have decayed may no longer be able to perform the function for which they were installed. Paint can hide decay from an inspector and so should be noted in the report.
The “pick test” uses an ice pick, awl or screwdriver to penetrate the wood surface. After penetrating the wood, the tool is leveraged to pry up a splinter parallel to the grain and away from the surface. The appearance and sound of the action is used to detect decay. The inspector should first try the pick test in an area where the wood is known to be sound to determine a control for the rest of the inspection. Decayed wood will break directly over the tool with very few splinters and less or almost no audible noise, compared to sound wood. The pick test cannot detect decay far from the surface of the wood.
Although deck inspections are visual-only inspections, inspectors may want to dig down around posts and perform pick tests just below grade level to look for decay.
Tall, 4×4 posts twist under load, and 4×4 posts, even when treated, decay below grade too quickly. In all but the lowest of decks, deck posts should be at least 6×6, and be no higher than 12 feet; 14 feet is acceptable if cross-bracing is used.
Decks higher than 3 feet above grade that do not have diagonal decking should have diagonal bracing across the bottoms of the joists to keep the decking square. A deck that is not held square could permit the outer posts to lean to the right or left and parallel to the ledger board, and thus twist the ledger away from the home or building.
Girders and Beams
The image above depicts the minimum distance of untreated support members from grade. Untreated joists should be at least 18 inches away from the ground. Girders should be 12 inches away from the ground. However, in many situations, exceptions are made where the elevation of the home does not provide for these minimum distances and the climate is very dry.
Ledger Connection
The most common causes of deck collapse are ledgers that pull away from the band joists of homes and buildings.
The two most common ways to correctly attach a ledger to a structure are with lag screws or through-bolts. The installation of through-bolts requires access to the back-side of the rim joist, which, in some cases, is not possible without significant removal of drywall within the structure.
Most building codes state that, where positive connections to the primary building structure cannot be verified during inspection, decks shall be self-supporting (freestanding).
Determining the exact required spacing for the ledger fasteners is based on many factors, including:
· joist length;
· type of fastener;
· diameter of fastener;
· sheathing thickness;
· the use of stacked washers;
· wood species;
· moisture content of the wood;
· integrity of the band joist; and
· deck loads…
…and so is beyond the scope of a visual inspection. However, the number of ledger fasteners required is primarily determined by the length of the joists. The ledger-fastener spacing formula provides inspectors with this rule-of-thumb:
On-center spacing of ledger fasteners in inches = 100 ÷ joist length in feet.
A deck with substantially fewer ledger fasteners than that recommended by our formula may be unsafe.
The image above shows the minimum distance of fasteners to the edges and ends of a ledger board. Lag screws or bolts should be staggered vertically, placed at least 2 inches from the bottom or top, and 5 inches from the ends of the ledger board. Some codes permit the lag screws or bolts to be as close as 2 inches from the ends of the ledger board; however, avoiding the very ends of the ledger boards minimizes splitting from load stress.
Through-bolts should be a minimum of ½-inch in diameter and have washers at the bolt head and nut. Lag screws should also be a minimum of ½-inch in diameter and have washers. Expansion and adhesive anchors should also have washers.
Deck ledgers should be comprised of pressure-treated wood that is at least 2×8.
Ledger Board and Band Joist Contact
The image above depicts washers being used as spacers between the ledger board and band joist, which is incorrect.
In some cases, the ledger board and band joist are intentionally kept separated by a stack of washers on the lag screws or bolts to allow water to run between the two boards. In other cases, there is insulation between the two boards. Even worse is when the siding or exterior finish system was not removed prior to the installation of the ledger board. Situations where the ledger board and band joist are not in direct contact significantly reduce the strength of the ledger connection to the structure and are not recommended, unless the two members are sandwiching structural sheathing.
The image above depicts a ledger board and band joist sandwiching the structural sheathing. This is a correct installation.
All through-bolts should have washers at the bolt head and nut.
The image above depicts a hold-down tension device. The 2007 IRC Supplement requires hold-down tension devices at no fewer than two locations per deck.
Codes in some areas outright forbid attaching a ledger board to an open-web floor truss.
The image above depicts a ledger board attached to a concrete wall. Caulking rather than flashing is used.
The image above depicts a ledger board attached to hollow masonry. When the ledger is attached to a hollow masonry wall, the cell should be grouted.
The image above depicts a ledger board improperly supported by brick veneer. Ledger boards should not be supported by stone or brick veneer.
Ledger boards should not be attached directly (surface-mounted) to stucco or EIFS, either. Stucco and EIFS have to be cut back so that ledger boards can be attached directly to band joists. However, cut-back stucco and EIFS are difficult to flash and weather-proof.
Ledger Board Flashing
The image above depicts both over and under ledger board flashing. The ledger board should always be flashed even when the home or building has a protective roof overhang.
Aluminum flashing is commonly available but should not be used. Its contact with pressure-treated wood or galvanized fasteners can lead to rapid corrosion of the aluminum.
The image above depicts a deck ledger attached to an overhang. Decks should not be attached to overhangs.
The image above depicts proper framing around chimneys or bay windows that are up to 6 feet wide. Framing around chimneys and bay windows that are more than 6 feet wide require additional posts.
Cracks
As wood ages, it is common for cracks to develop. Large cracks (longer than the depth of the member) or excessive cracking overall can weaken deck framing. Toe-nailed connections are always at risk for splitting. Splitting of lumber near connections should be noted by the inspector.
Connectors and Fasteners
The inspector should note missing connectors or fasteners. All lag screws and bolts should have washers.
Depending on how the deck was built, vital connections may have degraded over time due to various factors. Issues such as wobbly railings, loose stairs, and ledgers that appear to be pulling away from the adjacent structure are all causes for concern. The tightness of fasteners should be checked. If it is not possible to reach both sides of a bolt, it may be struck with a hammer. The ring will sound hollow with vibration if the fastener is loose. The ring will sound solid if the connection is tight. The hammer test is subjective, so the inspector should hammer-test bolts that can be confirmed as tight or loose, and compare the sounds of the rings to develop a control.
Corrosion of Connectors and Fasteners
All screws, bolts and nails should be hot-dipped galvanized, stainless steel, silicon bronze, copper, zinc-coated or corrosion-resistant. Metal connectors and fasteners can corrode over time, especially if a product with insufficient corrosion resistance was originally installed. Corrosion of a fastener affects both the fastener and the wood. As the fastener corrodes, it causes the wood around it to deteriorate. As the fastener becomes smaller, the void around it becomes larger. Inspectors normally do not remove fasteners to check their quality or size, but if the inspector removes a fastener, s/he should make sure that removal doesn’t result in a safety issue. Fasteners removed should be from areas that have the greatest exposure to weather. Some inspectors carry new fasteners to replace ones they remove at the inspection.
POSTS and RAILS
Missing Posts
You might find a guardrail improperly supported solely by balusters. Guardrails should be supported by posts every 6 feet.
The image above depicts a notched-deck guardrail post attachment. This common notched-type of attachment is permitted by most codes, but could become unsafe, especially as the deck ages. Because of leverage, a 200-pound force pushing the deck’s guardrail outward causes a 1,700-pound force at the upper bolt attaching the post. It is difficult to attach deck guardrail posts in a manner that is strong enough without using deck guardrail post brackets.
Notched Guardrail Post
The image above depicts a notched-deck guardrail post attachment. This notched-around-decking-type of attachment is permitted by most codes, but it could become unsafe, especially as the deck ages. Because of leverage, a 200-pound force pushing the deck’s guardrail outward causes a 1,700-pound force at the upper bolt attaching the post. It is difficult to attach deck guardrail posts in a manner that is strong enough without using deck guardrail post brackets.
The image above depicts a deck guardrail post properly attached with brackets. Because of leverage, a 200-pound force pushing the deck’s guardrail outward causes a 1,700-pound force at the upper bolt attaching the post. It is difficult to attach deck guardrail posts in a manner that is strong enough without using deck guardrail post brackets.
Level-Cut Post and Balusters
The end grain of vertical posts and balusters should not be cut level. The image above depicts a post and balusters properly cut at angles to shed water. The end grain of vertical posts and balusters should be cut at an angle.
Improper Guardrail Height
Most residential codes require the top of the guardrail to be at least 36 inches from the deck surface. Most commercial code height is 42 inches.
Infill should not permit a 4-inch sphere to pass through.
Ladder-type guardrail infill on high decks is prohibited by some local codes because they are easy for children to climb over.
STAIRS
Deck Stair Stringer
The image above depicts a deck stair stringer. Stair stringers shall be made of 2×12 lumber, at a minimum, and no less than 5 inches wide at any point.
Stair Stinger Span
Stringers should be no more than 36 inches apart.
Stair Ledger Strips
Where solid stringers are used, stair treads should be supported with ledger strips, mortised, or supported with metal brackets.
Open Stair Risers
Most deck stairs have open risers and are not safe for children. Risers may be open but should not allow the passage of a 4-inch-diameter sphere.
Uniform Riser Height
To minimize tripping, the maximum variation among riser heights (the difference between the tallest and shortest risers) should be no more than 3/8-inch.
DECK LIGHTING
Decks rarely have light sources that cover the entire stairway. Any unlit stairway is a safety issue.
STAIR HANDRAILS
Stairs with four or more risers should have a handrail on at least one side. According to the International Standards of Practice for Inspecting Commercial Properties, ramps longer than 6 feet should have handrails on both sides.
Handrail Height
The image above depicts proper stair handrail height. Handrail height should be between 34 and 38 inches measured vertically from the sloped plane adjoining the tread nosing.
The image above depicts a stair handrail that is not graspable. Many deck handrails improperly consist of 2×6 lumber or decking. Handrails should be graspable, continuous and smooth.
The next three images depict graspable handrails.
Graspable Handrail
The three images directly above depict graspable handrails. Many deck handrails improperly consist of 2×6 lumber or decking. Handrails should be graspable, continuous and smooth.
Stair handrails should have posts at least every 5 feet.
The image above depicts permitted spacing at stairs. Larger spacing presents a child-safety issue.
ELECTRICAL RECEPTACLES
As of 2008, the National Electric Code (NEC) requires at least one receptacle outlet on decks that are 20 square feet or larger.
The image above depicts a weatherproof receptacle cover. The deck receptacle should have a weatherproof cover.
DECK LOCATION
Decks should not be located where they might obstruct septic tank accesses, underground fuel storage tanks, well heads, or buried power lines.
