How to Inspect and Reinforce Decks

So many homeowners have wood decks and patios, which are older and could be less than structurally sound. Decks and wooden structures became very popular when the first pressure treated wood was introduced to the building industry. The processes of preserving wood and preventing rot and deterioration has advanced considerably, and the processes have become extremely efficient and safe. This has caused the explosion in wood decks and other structures, using this pressure treated wood. In addition the current introduction of synthetic products to add to the creativity of deck building has increased the popularity and the prevalence of wood structures with various elements of the deck made of synthetic material.

Due to this popularity, as well as the advancement of preservation techniques and synthetic products, decks are present on the majority of residential homes and rental units.

Although the majority of wooden deck structures are structurally sound, and will remain so for many years, there are structures in existence, which could be either unsafe or marginally safe. How can an individual homeowner determine the safety of their wooden deck structures?

  • Obviously the best and most productive method of determining if a structure is safe, and properly built, is to hire a professional structural engineer to evaluate the structure. These professionals are trained and educated in the various structural methods of deck support and will be able to evaluate your structure with a simple field visit. The downside of this structural review is both the time involved as well as the cost. Structural engineers are expensive and will not provide the physical means of correcting the issue, if they find a structural concern. The best that the homeowner can anticipate is a professional structural evaluation and report that you will be able to pass on to a contractor for repair. Obviously this is the most proficient method of structurally evaluating your deck; however, it will be the most expensive.


  • The second method of evaluating the deck is a self-inspection by you as the homeowner. What are the various aspects of this deck that you should review?


  • Any structure, is only as strong as the bottom most support of the structure. This means the footings or the foundation of the deck. Examine the footings that the deck rests on. This could include a round diameter concrete column that has been dug into the ground beneath the posts of the deck. These concrete columns should be deep enough to be below the frost depth of your location. The frost depth must be determined by the local code. For example the depth of the frost level in the northeast, is certainly deeper than the frost level in North Carolina. In some situations, the deck posts may not even sit on a footing or a foundation. They may actually bear on a flat piece of concrete or even directly on the ground. However the support of the deck is maintained at the ground level, the posts should be stable and without deterioration. The base that the post bears on, should not be broken or cracked, nor should there be any erosion of the earth away from the bottom of this support.
  • Traveling up the length of the post or support, the connections of the deck itself to the posts, should be reviewed and evaluated. This support should be stable and properly fastened. Check for loose screws, backed out nails or even missing nails. Although the current codes indicate the use of steel fasteners at all the interfaces of posts and floor joists or secondary supports, the use of simple toe nailing was a popular method of constructing decks, years ago. Each connection should be evaluated for stability, and for the proper number of connectors, nails, screws, lag bolts, etc. making up the connection.


  • The deck boards should be individually tested for flex, lack of deterioration and proper connection to the support joists, beams or whatever structure is supporting the actual decking. Again, depending upon the age of the deck, the required spacing of the support structure, under the actual decking could be as wide as 24 inches. If this is the case, the flexing of the deck boards could be too much, and additional intermediate supports may be necessary.


  • The most important element of any deck is the perimeter rails and stairs that lead up to the final elevation of the deck. The ability of the perimeter rails and the stairs to safely protect anyone on the deck is of ultimate importance. Current codes have increased the importance of ensuring that the perimeter rails are properly constructed. However, older decks may not have been built with the strict adherence of structural stability regarding the perimeter rails. The lateral stability of the rails is an important element that will ensure that the rail will not fail, if there is lateral pressure against the rail itself. Lateral means a sideways pressure. This would occur if an individual leaned against the rail or pushed against it. The rail must be adequately supported to restrict any lateral movement and any ability to fail, if occupants on the deck leaned or pushed against the rail.


  • The stairs or ramp, leading to the upper elevations of decks are as important, structurally, as the handrails that surround these elements. The higher above the ground the deck is the more dangerous the failure of any perimeter protection, the guardrails and handrails. A perimeter inspection of the deck is a good method of ensuring that all of the rails are adequately supported. It is very easy to determine if the rail is not supported properly, it will give with the lateral push or pressure. Stiffening this lateral movement is mandatory to ensure that there are no safety issues or compromises.


  • How to reinforce your deck if there is concern for its safety and stability?


Once again, as with the inspection, if you feel that your deck may have compromising safety issues, the best and most professional means of correction is to hire a contractor to review the deck and reinforce or rebuilt to ensure safety.

However, there are several means of performing a DIY type repair or correction, which would add to the margin of safety of your deck. Some of these suggestions are noted.

  • If there are areas that you feel have separated from the supporting structures, the simple introduction of additional nails or screws will add to the stability of this portion of the deck. Always remember that a screw or nail in shear, is much better than a fastener in tension. We have discussed this concept within this website; however the easiest way to identify the difference, is if you were to visually identify the pressure or force on the fastener, and if it is perpendicular to the fastener, then this connection is in shear. If the force is along the main axis of the fastener, or in a pull out situation, the fastener is in tension. Shear will require the fastener to actually break in failure; tension will simply pull the fastener out.


  • There are special brackets that are specifically engineered to provide proper support for the joints and sections of the deck. These special brackets, clips or reinforcement elements are normally made of galvanized metal and can be purchased at all local hardware stores, or any of your big box lumber yards. It is best to research the type of connection that you are trying to reinforce and use the recommended bracket. These brackets are normally applied with nails or screws and can be installed against the existing elements of the deck.
  • One of the most important aspects of proper deck support is the need to have enough posts transferring the load of occupants on the deck, to the ground or supporting structure of the deck. Most collapses of decks occur due to lack of enough posts or supports that transfer the load, from the deck to the ground. This type of situation can be modified by adding posts or additional supports. Do not be afraid, or timid to add a simple support under a deck member that may be flexing under load. This is important due to the fact that many collapses occur, due to lack of supports to the ground.


  • Span reduction is another method of strengthening your elevated deck. The longer the span between supports, the more the supported element will sag or flex. The identification of span is important to properly support all of the decking making up the surface of your deck. If it appears that the span is too long without support, introduce another floor joist to reduce the span. This can occur with a simple addition of a joist with the proper joist hangers at each end.

Decks and elevated patios are extremely popular, however can be dangerous if used without any type of knowledgeable inspection and maintenance. How many times does a collapse of an elevated deck or porch occur? We read every year of collapses that result in injury or death. It is very important that homeowners be aware of the potential safety issues of elevated decks and porches. They are a popular means of providing an entertainment are relaxation environment, however must be acknowledged as a potential safety hazard, if not properly constructed and maintained.