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, railing 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 posts. 6x6 (or larger) pressure treated posts are used in modern decks to transfer at least half of the deck load to earth; some areas still permit 4"x4" posts for decks close to grade but this is now rare. 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 8.2 lbs.
The deck’s hardware, framing, and footings must form a continuous load path into the ground to provide a strong reliable deck. The wooden support posts can be cemented into the ground (considered a poor quality install) or a metal bracket is used (see below photo). The bracket has its bottom portion cemented into the cement footing and the bottom of each post is secured into the top of the bracket. The metal bracket method is considered the best of the two options. Keeping the wood away from the cement/ground helps prevent future rot even when pressure-treated lumber is used. A rotted support post can compromise the rest of the deck. The concrete footer should continue underground below the frost line, typically at least 36" in south central PA. Without digging (which home inspectors don’t do), the depth of the footer is most often unknown. Lumber that enters the ground should 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 posts 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 which often leads to rot.
The photo below shows a metal bracket secured into the concrete post (below it) and secured to the wooden deck support post (above it). The wood post and the ground/earth do not 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 or lag screws. Years ago, carriage bolts were allowed at the ledger board but are no longer permitted at this important connection.
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. Also, the interior side of the deck connection hardware is most often not visible due to either basement insulation and/or a basement ceiling; insulation nor ceilings (fixed or dropdown) are disturbed to perform a home inspection.
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 provide little support. If a home has brick, stone, or stucco, these materials likely need to be removed in the area where the deck will connect to the home 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 wood structure. There is one new exception to the above. Simpson StrongTie has recently come out with the BVLZ (Brick Veneer Ledger Connector) fastener system that is designed to be used to secure a deck ledger through veneer to the home's structure. If present, however, a home inspector would likely have no way of confirming that these connectors were properly installed.
The above photo shows a partially loose deck ledger board; a gap of approx. 1/2"
was noted either due to improper or inadequate lag bolting.
Deck collapse due to ledger board failure
Also, decks may not have their ledger boards connected to a cantilevered floor system (see the photo below). A cantilevered floor system is a bump out (can be a trapezoid, a square, or a rectangle) of a window or door that protrudes out beyond the home's foundation wall. The deck's connection to the home must exist over the home's foundation wall so that the weight of the deck is transferred to the foundation directly below where the joists terminate. This type of connection could possibly fail and allow the deck's ledger board to separate from the home. One exception exists in this situation - if the deck's floor joist don't stop at the ledger but instead continue through the cantilever and terminate above the home's foundation (inside the home), this is permitted. This setup would be visible from under the deck as the floor joists would not stop at the ledger board. In some cases, where a cantilevered floor joists is somewhat narrow, a doubled or tripled header may be a possible way around a cantilevered floor.
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 posts situated adjacent to the home's foundation. Flashing isn’t needed and therefore water penetration into the home where the deck and home come together is likely a non-issue related to the deck. Since a free-standing deck has to fully support itself independently, additional angled structural bracing is required for this type of deck structure.
Lateral Load Connectors (a hold-down tension device) are also standard practice for modern decks. Decks must be designed for vertical and lateral loads. 2 lateral load connectors should be installed; the interior ends of these connectors are secured inside the home and the outer ends are secured to deck floor joists (within 2' of either side of the deck). The 2 ends of the connector are attached with a threaded rod which passes through the ledger board.
To connect the rest of the deck’s various structural components (posts, 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 zinc/galvanized (Z) or stainless steel (SS) 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 posts 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/screws 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 above photo shows a similar setup.. 2x8 beams rest on a 6x6 post and only a few nails and gravity keeps these connections together. A small earthquake or ground erosion causing the posts to move could allow the deck to slip off the posts and lead to deck failure. This deck was on a 2 year old home; not sure how it passed the township's code inspection.
A proper connection of the deck floor joists, posts, and beams would include proper metal hardware (hangers, brackets, seismic straps, and bolts). The tops of the posts should be notched to allow the beams to sit within the notch (with the post supporting the beams from underneath) and then laterally through-bolted (with 2 bolts each) to secure the beams and posts together. Below shows a good example of this setup on a deck being built. Some areas permit carriage bolts to be used at these post/beam connections although bolts are generally the standard method.
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 or membrane; aluminum is generally no longer as a deck flashing material used due to corrosion due to steel nails and the preservatives used in modern lumber. In many cases, the flashing on older decks is totally missing or, even if it is installed, is often insufficient and barely functional and very likely barely 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 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. Nails or screws inserted into the end-grain of lumber will often fail in short order. Over time, the nails will come loose and the rim joist and floor joists will separate (notice the gap in the 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; it
is also only end nailed through the rim joist.
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. As mentioned above, 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 as well as its staircase and their proximity to salt water. If the deck is near the ocean, stainless steel hangers should be used since sea salt can damage the deck hardware's zinc finish.
This deck is missing some very important components.. nails. The installer left
nearly all of the joist hangers completely empty. Each joist hanger on this deck
had only a single screw (improper fastener) installed and that was it.
Modern decks 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. Joist hangers may be up-sized 1 joist size; in other words, for a 2x10 joist, hangers for 2x10s or 2x12s may 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. Little of the fastener used at the joist hangers are visible so, in some cases, it can be difficult (or sometimes totally impossible) for the inspector to determine what fastener was used. Screws may be used but they must be approved by the joist hanger manufacturer; again, the inspector may not be able to confirm what was used.
Joist hangers are really the only place that nails should be used when building a deck. Filling only some of the hanger nail holes will likely 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. Generally, joist hangers may not be modified in the field without written permission from the hanger's manufacturer. A modified hanger 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 a joist hanger or its fasteners (nails) starts to rust, replacement is needed.
Instead of joist hangers at the ledger/floor joist connections, some areas still allow 2x2" nailer strips for the joists to sit on at the house side. Seeing this design is rare since it has been proven to have a short life span since, as weight is applied to the deck on the house side, the nailed can split over time allowing the joists to slide off.
Where deck floor joists bear upon (rest on) a cross beam(s) or girder, modern standards require proper hardware at 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). Many areas also allow nails (2) to be driven at opposing angles to secure the joists and cross beams together. In most cases, hurricane straps can be easily 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.
Seismic straps are installed at each joist/beam connection. Their location can alternate
sides of the beam which explains why you can only see a strap at every other joist in the above photo.
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. Stair stringers may be solid or cut; a solid stringer has no wood cut out of it and the treads (steps) are secured to the stringer using blocks, for example. A cut stringer has the zig-zag cut pattern for each tread to sit on the stringer. Solid stringers are generally stronger since they have no wood removed.
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 which is also not found on many railings. A rounded (1 1/2" diameter) or 2x2" square top to the railing is optimal.
Also, some older deck staircases were only secured to the deck by using a dropped header. This means, a piece of wood was fastened below the deck's rim board and then the deck staircase's stringers are connected to this piece of wood. This type of design is prone to fail and is not permitted as a deck/staircase connection.
This deck staircase's stringers are only end-nailed and
lack hangers where the stringers connect to the deck.
Simpson StrongTie makes all sorts of angled hangers including
some for this specific application.
Like some internal staircases, deck staircases sometimes have one open side or simply a hand railing. The open side can allow someone, such as a small child, to fall off the staircase below the railing. To prevent this hazard, a proper stair guard railing should be installed. The top of the stair railing should be 34"~38" above the stair nosing and have interior openings (such as between the balusters) no wider than 4 3/8". The space between the stair railing and the stair treads below should not allow a sphere wider than 6" diameter to pass through. Also, support posts should exist every 6' measured laterally in order to support a longer staircase and railing.
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 or have baluster spaces of 5" or 6". 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 encourage an adult to sit on the railing and possibly 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 coming loose. 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. A support post, for example, should exist at least every 6' along the run of the railing otherwise a long railing could have considerable movement even if properly secured only on its ends. The center support post(s) will help make the overall guard railing more rigid. 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 sometimes only require adding bolts to better secure the guard railing and its posts to the deck structure.
The photo above shows a proper guard railing on a newly built deck with composite finishes (flooring and railing) and a wood structure.
A very basic thing that any home owner should do on a regular basis (monthly) is to simply stand at various areas 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" also known as DCA-6 (based upon the 2015 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 (note - the video was based off an earlier version of the IRC when carriage bolts were still permitted at ledger boards):
You can find our full service list under the Services tab at the top of our website: https://elizabethtown.wini.com
© 2020 Matthew Steger. Originally written in 2014; updated in 2020 to meet more recent deck standards.
Matthew Steger, owner/inspector of WIN Home Inspection, is a Certified Level 1 Infrared Thermographer, an ASHI Certified Inspector (ACI), and an electrical engineer. He also earned the "ASHI Deck Inspection Specialist" certification. He can be reached at: 717-361-9467 or firstname.lastname@example.org.
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.