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Deck Inspection Tips for a Safer Outdoor Living Space

November 19, 2020
Deck inspection tips by TimberTech

Routine deck inspection is necessary for every deck to ensure it is safe for you and your family. Inspections also minimize the risk of creeping mold and mildew damage so you can avoid a costly full-scale deck replacement down the road. 

Whether you have a traditional wood or composite deck, both decks use traditional lumber for their substructures. While composite deck boards are highly resilient, traditional wood is vulnerable to weathering and moisture damage. This vulnerability can cause structural damage that could make your deck unsafe. Routine deck inspections help you catch any problems early before they become more costly to repair.  

Depending on the type of deck you have, your deck inspection should include a substructure inspection and a surface inspection.  

Deck Inspection Best Practices 

For the substructure of a wood or composite deck >For the surface of a wood or composite deck >

How Often Should I Perform a Deck Inspection?

How to perform a deck inspection

The North American Deck and Railing Association (NADRA) recommends an annual deck inspection every May, just before the start of summer’s peak use. However, anytime is a good time for a deck inspection, especially if you haven’t performed one in more than a year, or if your deck has been facing winter weather. Older decks (10+ years) may also require more frequent inspections.  

Routine Deck Inspection Allows You to 

✓ Solve smaller, less expensive problems to keep your deck safe and beautiful. 

✓ Avoid making bigger, costlier changes like total replacements.  

✓ Have peace of mind knowing your deck is structurally sound for you and your family to enjoy.  

Tools You’ll Need for a Deck Inspection

Part of the best practices for any deck inspection – whether wood or composite – involves the use of the right tools. With the right tools, you can detect issues that may not be evident to the naked eye but could mean the difference between a safe and unsafe deck.

Deck inspection of substructure flashing deck joists

Tools to Inspect Your Deck

✓ Flashlight for better visibility, especially under your deck. 

✓ Safety glasses for eye protection from debris or dripping water. 

✓ Measuring tape to check joist spacing

✓ Ladder if your deck is raised or two-storied. 

✓ Level to check for slanting surfaces. 

✓ Probing tool (such as a screwdriver) to check for rot. 

✓ Hammer to check that blocking is secure and to hammer in any protruding nails. 

Deck Inspection Best Practices for Wood & Composite Decks’ Substructures

Deck Joist Substructure Top-Down View

The best practices for inspecting your deck’s substructure involve an inspection at the time of build and then again once the deck is built. Addressing issues at the time of build, when the full frame is visible, is critical for ensuring the substructure has no structural issues that could cause greater problems in the future.  

Once your deck is built, periodic inspections of the surface and any visible substructure will help you assess the health and safety of your deck over time.  

Checking Your Deck’s Substructure at Time of Build 

  • Check that your joists, beams, and blocking are in-plane, securely fastened, and correctly spaced.  
  • Examine the ledger board to make sure it is flush against your house, securely fastened with the appropriate fasteners and lag screws (heavy-duty screws often used to attach lumber that bears a load), and has the appropriate flashing installed. 

Checking Your Deck’s Substructure Once the Deck Is Built

Remember, unless you have a two-story deck, your deck joists will not be visible from the surface of your build, whether it’s a composite or wood deck. You will therefore need to check for substructure damage at the surface level.  

  • Check your support posts for signs of moisture damage, particularly where they meet the ground. 
  • Look for problems with your deck’s surface such as cracking, discoloration, or rusted nail heads to determine if there is damage in the substructure below.  

Common Deck Substructure Problems  

Deck substructures can be impacted by weathering, moisture, and wear and tear. Keep an eye out for these common problems in your deck inspection. 

Ledger Board Pulling Away from House 

90% of deck collapses occur because the ledger board pulled away from the house, making it the most common problem to look for. The ledger board is the piece of wood that runs parallel to your house and secures the deck to your house.  

Ledger Board & Flashing Deck Inspection

Signof a problem: 

  • Debris build-up between the ledger and your house, which indicates a gap and a lack of protection from flashing. 

Possible fixes: 

  • Remove any debris and tighten the lag screws to better secure the ledger board to your home.  

Rusted or Loose Screws, Nails, & Fasteners

Rusted or loose screws, nails, and fasteners in the deck’s surface could imply damage to the support joist underneath.  

A deck inspection can reveal rusted fasteners

Signs of a problem: 

  • Rusted screw heads and nail heads.  
  • Protruding nails. 
  • Loose screws or fasteners. 

Possible fixes: 

  • Replace rusted screws, nails, and fasteners. 
  • Tighten any loose fasteners or screws. 
  • Hammer in protruding nails. 


Rot is one of the most widespread problems for traditional wood.  

Deck inspection tips by TimberTech

Common areas affected by rot include the deck’s substructure such as the ledger board, joists, and the support posts, especially where they meet the ground. However, rot can also spread to your wood deck boards. 

TimberTech composite deck boards, on the other hand, protect against rot thanks to our proprietary synthetic capping.   

Signs of a problem: 

For wood and composite decks, check your deck’s ledger board, support posts, and joists (if visible), as well as your wood deck’s surface for the following: 

  • Soft spongy wood, a darkened color, or cracked appearance.  
  • Use a screwdriver to penetrate the wood and pry up a splinter parallel to the grain. If the wood breaks with no splintering, decay may be present. 

If you have a composite deck and your substructure is invisible, check for rusted screw or nail heads in your deck boards which could indicate rot in the substructure below.  

Possible fixes: 

  • Remove thumb-sized areas of rot from the ledger board, joists, or support posts with a chisel and treat the hole with a wood preservative to keep it from spreading. 
  • Severely rotted ledger boards, joists, and support posts should be replaced.  
  • Replace any rusted nails or screws. 

If you’ve chosen to invest in an enduringly beautiful TimberTech composite deck, you know the importance of durability and premium performance. Don’t let an irregular deck inspection schedule introduce substructure issues that could become costly and/or dangerous. 

Deck Inspection Best Practices for a Wood Deck Surface

Deck inspection best practices for a wood deck surface

Over time, traditional wood deck boards will fade and deteriorate and could require extensive repairs or even full replacement. Regular inspections can help you mitigate the damage and your repair costs.  

Inspecting Your Wood Deck’s Surface Once the Deck Is Built

Immediately after completing the build, your wood deck becomes vulnerable to the elements. Moisture and weathering will begin to take effect and could cause significant damage.  

  • Examine the deck boards for cracking, warping, splintering, and moisture damage. 
  • Check the railings for any loose posts or handrails.  

Common Wood Deck Surface Problems

Inspect a wood deck surface for mold and mildew

Mold & Mildew

Moisture in organic material is food for mold and mildew growth. Mold and mildew don’t only look unsightly but will also weaken your deck’s structural integrity if not addressed.  

Signs of a problem:  

  • A greenish tint. 
  • Black or white fuzzy areas. 

Possible fixes: 

  • Power-clean the area to remove mold and mildew, and then apply a waterproof seal or treatment. Power cleaner rental is expensive and time-consuming to use, and traditional wood deck stains can release Volatile Organic Compounds (VOCs) into the atmosphere.
  • Replace any boards heavily impacted by mold or mildew.
Inspect a wood deck surface for cracks and splintering

Cracking, Splintering, & Insect Damage

Cracking and splintering can be caused by simple wear and tear, but growing cracks in your boards could indicate serious structural damage. 

Signs of a problem: 

  • Watch any cracks and splintering closely for signs of growth.
  • Small holes in your deck boards are signs of insect damage.

Possible fixes: 

  • Replace deck boards that show significant cracking, splintering, or insect damage.
  • If the insect damage is minimal, treat your wood deck with an insect repellant. However, be aware that many insect repellants can ruin the stain of your wood, due to the use of potentially harmful chemicals, and so should be used with caution.
Inspect a wood deck for a loose railing

Loose Railings

Loose or unsteady wood railings are not only a nuisance they can be dangerous, especially if your deck is raised or two stories .Metal and composite railing lessens the risk of railing damage.

Signs of a problem: 

  • Railing that wobbles or leans when pressure is applied. 
  • Protruding nails or fasteners in the railing posts. 

Possible fixes:  

  • Tighten the screws or fasteners securing the railing.
  • Replace any damaged or rusted screws or fasteners.
  • Remove and replace any damaged, bowed, or warped rails.

While problems with your wood deck’s surface are unlikely to impact your deck’s structural integrity, they could still cause injury to you or your guests. In fact, more deck injuries are the result of railing failure than complete deck collapse. Routine inspections ensure you fix problems before they become a cause for injury. 

Deck Inspection Best Practices for a Composite Deck Surface

Deck inspection best practices for a composite deck surface

Composite deck boards do not require an exhaustive inspection like wood deck boards because TimberTech composite decking boasts mold-, mildew-, and moisture-resistant protective capping. 

That said, it’s still important to keep your deck looking its best.  

To Preserve the Aesthetics of Your Composite Deck 

  • Sweep up leaves, dirt, or debris. 
  • Wipe up standing water (water won’t permeate composite deck boards, so it can sit on your deck. However, for safety, it’s a good idea to wipe up water where people walk.) 
  • Periodically clean your deck with TimberTech® DeckCleaner™.  

Make Your Deck Inspection Easier With TimberTech Composite Decking

TimberTech composite decking is designed to last

Inspecting your deck regularly for these and other signs of damage is ideal for maintaining a safe outdoor living space. While wood decks will translate to regular maintenance costs that accumulate — especially if you don’t complete a regular deck inspection — a TimberTech deck protects against the weathering agents that eat away at wood. With a TimberTech composite deck, you’ll rest easy knowing your deck boards are built with advanced materials science

Contact a TimberTech-registered contractor today to talk about the benefits of composite decking vs wood or get a professional opinion about your existing composite deck’s substructure. 

Bring the Beauty of TimberTech to Your Backyard

Work with one of our registered contractors for a build that transforms your outdoor living space.

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