Many homes have decks attached to them for entertaining and for relaxing under the stars, but most home owners do not regularly inspect their decks. Each year, people are injured or killed due to faulty construction or the lack of needed regular maintenance of decks. According to statistics, there are over 40 million decks in the US; many of these are over 20 years old. In addition, many of those decks were constructed prior to 2009, before true deck codes existed. Since the year 2000, the number of injuries and deaths related to deck failures has been increasing according to the North American Deck and Railing Association (NADRA). The typical life expectancy of a wood deck is approximately 15~20 years assuming regular maintenance. Nothing lasts forever, and any wooden structure exposed to the elements 24/7 will require regular maintenance and inspection to ensure safe usage and long life.
According to the Consumer Product Safety Commission (CPSC), 224,000 people were injured nationally due to a deck or porch between 2003 and 2007. Of those injuries, 33,000 were a result of a structural failure or collapse.
Many home owners assume their deck was built 'to code' and everything is working as it should. Prior to 2004, however, the Commonwealth of PA had no statewide building code. This means that contractors and builders could construct a deck in any way they wanted with no set safety standards. Over the years, I've inspected thousands of homes with decks and many of these decks are not either constructed or maintained properly. This can lead to an increased injury hazard down the road.
As part of a home inspection, the inspector should inspect the deck for stability, check the railing size, spacings, and strength (rigidity), hardware type and condition, water damage, and staircase issues. Keep in mind, however, that a home inspection is not a code compliance inspection; a well-qualified home inspector, however, uses the various codes in place as guidance for what is considered 'standard practice'.
Starting at the ground, look at the size, number, and condition of the support columns or piers. 4x4 and 6x6 pressure treated lumber is used in most modern decks to secure the deck to the ground. Anything less than 4x4 posts probably won’t be able to properly support the deck and its occupants. I’ve inspected a few decks more than a few feet above ground that were only supported with 3x3 posts at the corners which are considered inadequate to support the weight of a deck. Decks should typically be designed for at least a 40 pound per square foot load. If a hot tub will be added, for example, the deck’s structure will need to be beefed up to safely carry the extra load of the hot tub and the water in the hot tub. This may mean larger or more numerous joists, extra bracing and/or support columns, etc. Remember that a gallon of water weighs 8 lbs.
The deck’s hardware and footings must form a continuous load path into the ground to provide a strong reliable deck. The wooden support columns or piers can be cemented into the ground or a metal bracket can connect the concrete pier to the bottom of the wooden columns. Keeping the wood and cement/ground away from each other can help prevent future rot. A rotted support pier can compromise the rest of the deck. The concrete pier should continue underground below the frost line, typically at least 3’ in south central PA. Without digging (which home inspectors don’t do), the depth of the pier (concrete or wood) underground is most often unknown. Lumber that enters the ground must be rated for ground contact and properly preserved (including adding preservative onsite to the exposed interior grain once the lumber is cut).
Check the wooden columns and joists for excessive cracks or rusting/deterioration of the metal hardware used to hold the components together. Most older decks have the wooden support posts simply installed into the ground.
The photo below shows a metal bracket secured into the concrete pier (below it) and secured to the wooden deck support column (above it). The wood pier and the earth do not ever make direct contact.
Also, the home’s downspouts, sump pump, and the grading under the deck should drain away from the deck to help minimize the chances of wood rot as well as insect or rodents being attracted to the area around the deck.
Fasteners and Ledger Boards
Most decks are attached to a home and many of the decks that I inspect lack proper fasteners or hardware. Older decks routinely had their ledger boards only nailed to the home. Nails are not designed for shearing loads and may allow a ledger board come loose from the home over time. The ledger board is the deck component that the floor joists connect to adjacent to the home; this ledger board then also must be structurally connected into the home's structure. Modern standards require a proper and durable connection between the home and the deck, such as using lag bolts, carriage bolts, and/or threaded rods with proper washers and nuts. With a proper connection, the deck partially relies on the home for support. An improper connection can allow the deck to fall off the home which will likely injure (or possibly kill) whomever is standing on the deck at the time. If your deck’s ledger board is only nailed to the home, a qualified deck contractor can often retrofit the ledger board's connection method to better secure the deck to the home. For decks that are close to grade or have screening/lattice around them, inspecting the ledger board connection can be next to impossible due to clearance issues.
Proper lag bolting of a deck ledger board
Also, brick, stone, and stucco are not permitted to be used to support a deck as these types of exterior cladding materials are not structural and may not support anything but their own weight. Hardware may not even pass through these materials to secure a deck's ledger board to a home. If a home has brick, stone, or stucco, these materials may be able to be removed, where applicable, and the ledger board can be installed where the former masonry existed so that the ledger board can be secured directly into the home's structure. With the latest changes to how decks must now be constructed, lateral load connectors (anchors) must also be used (typically one near either side of the deck) to secure the home and deck together.
Deck collapse due to ledger board failure
A free-standing deck is another option, especially if the home is brick, stone, or stucco. A free-standing deck is not structurally supported by the home but secured into the ground adjacent to the home with piers/posts. Flashing isn’t needed and therefore water penetration into the home where the deck and home come together is much less likely. Since a free-standing deck has to fully support itself independently, additional structural bracing is required for this type of deck structure.
To connect the rest of the deck’s various structural components (piers, girders, joists, etc.) together, proper metal hardware is a must to ensure strength and long life. Proper bolts and screws are preferred over nails when constructing the deck's structure, railings, and flooring, although nails are often used to connect certain deck components such as at hangers and brackets. Bolts and screws should provide longer lasting service at critical connections. Hot dipped galvanized or stainless hardware should be used, the latter is more expensive but is most often used on decks near the ocean due to salt water deterioration of fastener plating.
The photo above shows a tripled wooden girder under a deck that is merely sitting on top of wooden piers and the girder is only fastened to the piers using short pieces of 2x4 and 8 screws. This is an inadequate mechanical connection. There are no bolts to secure the deck’s structure together. Ideally, the piers should have had a pocket or notch cut in them to allow the girder to rest on the pier and allow bolts to secure everything together. This particular deck was relying on gravity and a handful of nails to stay in place. Settlement or erosion of the grounds around the deck or even seismic activity could also lead to a deck failure.
The location where the deck’s ledger board meets the home is a common location for water entry and rot. Flashing should be installed behind the ledger board to prevent a place for water to enter. The flashing can be metal (such as aluminum) or membrane. In many cases, the flashing on older decks is totally missing or, even if it is installed, is often insufficient and barely functional and visible. Adding flashing to an existing deck can be difficult if not impossible. Proper flashing should be visible below the ledger board and will stick out beyond any siding installed below the deck to shed water.
It is also best if the deck surface is a step down from the doorway’s threshold to help prevent water or snow from possibly backing up into the door opening. Rot is not uncommon at doors leading to a deck where the door and deck surface are at the same height. Modifying this after the deck is built is nearly impossible without major modifications or removal of the deck.
Joists and Hangers
The underside structure is critical in supporting a deck; it can be considered the bones of the deck’s body. While some older decks often have joist spacing of 24” on center, newer decks most often will have 12” or 16” floor joist spacing. Most composite decking manufacturers will also require 12” or 16” joist spacing. The floor joists are the on-end structural members that support the deck’s walking surface. Damaged or improperly sized or secured joists can cause the overall deck structure to weaken, therefore presenting a possible hazard of collapse. Often, older deck joists are only end nailed, meaning the ends of the joists are fastened using only nails through the deck’s outer rim joist. Over time, the nails will come loose and the rim joist and floor joists will separate (see photo below); deck collapse is soon likely.
The deck above had a good amount of racking when standing on it. Racking is horizontal movement and most often indicates a weak deck structure and may lead to failure. Once these nails continue to pull out, the deck’s structure is compromised and safety becomes a real concern as the deck may now pull apart and fall.
Notice the gap in the framing between this deck's corner post and the lateral framing.
Continued separation could lead to deck failure and possible injury.
This deck floor joist has a large crack which should be promptly repaired.
This deck has joist hangers installed that are far too small for the size of the floor joists.
This deck's framing is simply end-nailed. This tends to cause the framing to separate over time and the deck is more likely to fail (causing injury to anyone on the deck at the time). Joist hangers (see photos below) should have been installed at perpendicular (and other) connections to ensure a reliable mechanical connection. Hangers are available in various sizes, finishes, and orientations depending of the design of the deck and its staircase and their proximity to salt water. If the deck is near the ocean, stainless steel hangers is normally the best choice since sea salt can damage other finishes are deck hardware.
Modern decks would use joist hangers to properly and securely attach the joists and other framing (ledger board and rim joists) together. Hangers can be added to older decks that have only end-nailed joists in most cases to shore up the structure. The photo below shows a properly installed joist hanger. Also, notice flashing installed behind the ledger board (visible above and below it).
Deck joists are most often 2x10 or 2x12 lumber depending upon the deck’s size and joist span. Joist hangers approved for the specific size of the joists should be used. Each hole in the joist hanger should be filled with a properly sized nail or screw. I've seen a few contractors use drywall screws to install joist hangers; not a good idea. This is really the only place that nails should be used when building a deck. Filling only some of the hanger nail holes may not provide a durable connection for years to come. Also, sometimes it may be difficult to tell, but joist hangers should not be bent, cut, or otherwise modified in the field. Various sized and orientated joist hangers exist for different applications. Modified joist hangers often indicate that the installer didn’t have the proper hanger on hand and simply 'field-modified' whatever he had on hand. This is a red flag indicating that other short cuts may have been made when building the deck and hidden hazards may exist. Also, the joist hanger’s flange should be flush with the lumber to which it is fastened.
This photo shows a rusted joist hanger that lacks nails at some of the holes. Per the joists' manufacturer, each of the hanger's holes are supposed to be filled with the proper type of nail. Also, once the joist hanger starts to rust, it likely needs to be replaced since it can fail.
Where deck floor joists bear upon (rest on) a cross beam(s) or girder, modern standards generally require proper hardware of these perpendicular connections in order to prevent possible uplift in the event of an earthquake, hurricane/strong winds, etc. Hurricane straps (also known as seismic straps) are the most common option to use. These straps come in a few different versions including a pocket type and a twisted tie variety (seen in the photo below). Some areas also allow nails to be driven at opposing angles to secure the joists and cross beams together. In most cases, hurricane straps can pretty easily be added to an existing deck for this extra needed support. Each place the perpendicular connection occurs (where every joist meets each beam/girder) should be properly secured.
Most decks have a staircase to a patio or the adjacent yard. Like interior staircases, modern building standards have specific requirements for height and width of staircases as well as their railings. Home inspectors are not performing code compliance inspections, however the well-qualified inspector should be familiar with the various codes used in his area. The staircase should be safe and easy to traverse. Many older deck staircases have cracked or improperly secured stringers (the underside framing that holds the staircase together), cracked treads (steps), or improperly-sized stair tread heights or depths. The cracked components can present an obvious hazard as they further weaken. An improper stair tread height or depth can be a trip hazard going up or coming down the staircase.
Staircases should be at least 36”wide. The riser height (the vertical distance from one step to the next) should not exceed 7 ¾” and the stair tread depth should be no shallower than 10”. The most common issue that I find while inspecting a deck staircase are risers that vary greatly in height or are well beyond the 7 ¾” standard. Modern standards require that stair tread heights can not vary more than 3/8” between the shortest and tallest. Anything more than that can present a trip hazard.
The top of this deck staircase (above photo) is pulling apart from the deck. As it continues to separate, it will likely soon fail and present an injury (or worse) hazard if someone happens to be walking on the staircase at the time.
The throat of a staircase stringer must be at least 5" deep based upon building standards. The 'throat' is the amount of wood remaining between the sawn kerf (the area cut out for the step) and the opposite side of the stringer. In the below above, the throat was only 3.5" deep. A small/shallow throat can lead to a cracked stringer and possibly a failure of the staircase over time.
All staircases (internal or external) need to have a proper hand railing if the staircase has more than 3 steps; the deck's walking surface counts as a step. The height of the staircase hand railing should be between 34”-38” above the stair tread’s nosing. The nosing is the portion of the stair tread that sticks out over the step below it (nominally about 1”). I often run across deck staircase hand railings that are much shorter than 34”. The lack of a hand railing at a proper height can allow someone to fall. The top surface of the hand railing should also be easily graspable.
Again, like many internal staircases, deck staircases typically have at least one open side. The open side can allow someone, such as a small child, to fall off the staircase below the railing. To prevent this hazard, components such as balusters or spindles are required. The spacing of these balusters or spindles should not exceed 4”.
Like the deck’s staircase, someone can easily fall off a deck that is elevated above the ground. Modern standards require guard railings on decks if the walking surface is 30" or more above grade. Older standards said this 30” height pertained to the ground immediately around the deck's perimeter, whereas newer standards extend this vertical measurement out 3’ horizontally from the deck’s perimeter. For example, a deck is built on the side of a hill and the vertical difference in height between the ground immediately around the deck and the deck’s surface is 25” (no railing would have been needed per the older standards). However, the ground running away from the deck extends down a hill. Extending 36” horizontally out from the deck, the difference in the above example in vertical height may be 40”. In this case, a guard railing is now required.
Guard railings (decks, porches, and interior guard railings) should be at least 36” vertically and should have no spacings within the railing or around it wider than 4”, like the staircase openings mentioned above. The 4" requirement is to help prevent small children from sticking their heads between balusters. Child #1 could have his head between wide balusters while child #2, goofing around, pushes child #1. This could cause child #1 to break his neck. This potential injury is the reason behind the 4" max. opening requirement in modern building standards.
Many older porches and decks have some sort of guard railing, but a considerable number of older porches and decks have only horizontal rails or have short railings. Having only horizontal components can allow a small child to climb them like a ladder and fall over the other side. The photo below shows a good example of this flaw. A short railing may allow an adult to fall over it backwards.
Guard railings will often come slightly loose over time. This may be the actual solid railing posts or the guard railing between the posts. As part of the home inspection, I check to make sure the guard railing doesn’t have excessive movement. Modern standards call for no more than 4” horizontal movement if 200 lbs. of pressure is applied to the guard railing. No home inspector is going to put 200 lbs. of pressure on the guard railing, however. A very slight amount of movement will be found in many deck’s guard railings over time, but a slightly loose (or very loose) guard railing will only loosen further in the future. Close attention is needed and repair is often recommended prior to the railing getting worse. A repair may often only entail some extra screws or bolts to better secure the guard railing and its posts to the deck.
The photo above shows a proper guard railing on a newly built deck with composite finishes and a wood structure.
A very basic thing that any home owner should do on a regular basis (monthly) is to simply stand at the center of the deck and try to cause the deck to wobble or rack simply by moving your body in the fashion of playing with a hula hoop. If you feel the deck’s structure move at all, this is an obvious indication that something is loose or improperly supported or bracketed. A qualified deck contractor should be called to make needed repairs at once.
The "Prescriptive Residential Wood Deck Construction Guide" (based upon the 2009 IRC) provides a considerable amount of information concerning how wood decks should be designed and constructed.
Watch this video to learn more about deck inspections:
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© 2014 Matthew Steger
Matthew Steger, owner/inspector of WIN Home Inspection, is a Certified Level 1 Infrared Thermographer, an ASHI Certified Inspector (ACI), an electrical engineer, and a US Dept. of Energy Home Energy Score Assessor. He can be reached at: 717-361-9467 or email@example.com.
WIN Home Inspection has provided a wide array of home inspection services in the Lancaster, PA area since 2002. This article was authored by Matthew Steger, ACI - owner of WIN Home Inspection in Lancaster, PA. No article, or portion thereof, may be reproduced or copied without prior written consent of Matthew Steger.