How to Locate & Repair Wood Rot on Your Deck

If you notice a slow decline in the appearance of your exterior deck or porch, it’s time to figure out what is needed to shape things back up. What are the indicators and signs of deck wood rot? Knowing how to identify these potentially problematic areas is essential. We offer a few pointers so you know if your deck requires repair or replacement.

We identify five of the most common areas to inspect for damages. But first, you must understand a few basic structural terms! Continue reading and understand what needs to be done before an opportunistic deck builder convinces you to replace the entire deck when it’s not required.


Our Top-5 list will include structural explanations and visuals illustrating these areas and the technical names for structural and non-structural boards. But most critically, we will explain the difference between normal wood wear and total wood decay!

After reading this article, you will better understand your deck repair needs before calling a professional to do the work! Or, if the repairs are minor enough and you are handy, you may even be able to handle them on your own!

Deck Building Technical Terms

Here is an illustration to reference different areas of your deck. This photograph shows what joists, posts, railing, and decking terms mean and where to locate them.


Rotting Decking

Deck flooring covers almost the entire deck’s surface, and most areas are exposed to UV, rain, and other elements. Wood horizontal decking that is subject to standing water takes a beating. So, these areas are the most prone to failure. 

Rotting decking is easy to detect. The signs of wood rot include soft spots on the floor and wood decay. If you want to future-proof the decking on your deck, it’s best to use Timber Tech composite decking or premium ground contact number one grade lumber.

Loose & Damaged Handrails

Code requires handrails on stairs to be no wider than 3 1/2 inches, making rails easy to grab. While the smaller size may help ergonomically, 2×4s are less sturdy and weather-resistant.

However, the limitations of 2×4 handrails are not limited to stair rails. Horizontal rails are also affected. Since the code requires a 2×4 on stair rails, you can only use a 2×6 on horizontal rails for added strength and durability. 

Deck Step Damages

Treads and riser on the step must be flat and not flex or roll forward. Screws are best to prevent floor treads from becoming a loose tripping hazard. When the stringers on steps are jeopardized, the steps need rebuilding.

If a concrete pad does not support your deck steps but rests directly on the ground, inspect the stringers underneath the steps for excessive mildew growth and rot. Removing organic growth from wood will help with wood decay.

Rotted Ground Support Posts

Support posts are another area that fails over time. Most posts measure 6×6 for well-built decks or 4×4 on older builds. Both sizes are ground contact treated lumber but can decay prematurely if your deck posts are inside concrete footings or stay wet. As the ground gets wet, concrete absorbs and holds water, exposing the wood to moisture for an extensive amount of time. 

Ground contact has several use classifications. Common ground contact is rated for constant ground contact and occasional moisture. If the ground is constantly wet, your posts will rot unless you take care of the moisture issue or use a higher grade ground contact treated lumber.

Ground posts are best protected from moisture when raised off the ground using a concrete pier or block.

Damaged Floor Joist & Sub-Structure

Decks less than 3 ft off the ground are especially susceptible to premature wood rot. Since the floor and rim joists support deck flooring, replacing damaged joists is critical to the deck’s safety.

Installing a vapor barrier under the deck is best to prevent a ground-level deck from absorbing moisture. A plastic barrier will dry out faster than wet soil, keeping areas underneath the deck dry and limiting organic growth.

Deck usage should be limited, and no more than one person should be on the deck when floor joists are compromised. Reframe from using the deck if the beams are rotted or broken.

How to Address Wood Cracks

Structural rigidity is critical to any deck, porch, or structure and is useless if it can’t be weighted or doesn’t safely support foot traffic. When your deck shows slight wear or has a few boards starting to fail, it doesn’t mean it is a total loss! The floor and handrails can be removed and rebuilt if the substructure remains intact. But there is a distinguishable difference between normal wood wear and decay.

Normal wear includes changing wood color and splintering. Most wood sold is farm-raised and more subjected to splits and wood cracks. Minor cracks are normal and don’t jeopardize the strength. 

Removing Wood Rot & Mildew

Black or green wood discolorations indicate either mildew or decay. Follow the mold and mildewed areas when searching for wood rot. Wood containing mold and mildew growth rots faster than drier areas.

Mold can be treated with a pressure washer and bleach solution. We recommend removing all soft areas even if they don’t show total degradation. Wood rot will continue if not removed, causing further damages, leading to a rotted sub-structure, costing more to repair the deck.

Deck Building Best Practices

Use Carriage Bolts: In the ‘80s, there were cases where decks were collapsing by pulling away from the house. Today’s code requires lag bolts as a minimum fastener requirement, but carriage bolts are best to secure a deck to the house.

Use Deck Screws: Deck screws are also best practice for fastening deck planks and handrails. Nothing is worse than having nails back out, causing the deck floor to become uneven. 


Use Ground Contact Lumber: Ground contact lumber is exceptionally critical in how long your deck will last. Whether you want a composite or wood deck, always purchase premium materials. You will be surprised how much longer, thicker, and more heavily treated lumber will last. 

As a surprise to some, Home Depot has thicker deck lumber. Severed Weather floor planks are ground contact and measure 1 1/8 thick. They are slightly thicker 5/4 boards, unlike others that measure equal to or less than a solid inch. 

Build Stronger Handrails: Treated lumber is expensive, and for that reason, you don’t find 2×6s used for deck flooring like once before. But some may argue that a ground contact 2×6 will last just as long as a composite deck board. The only difference is the maintenance of having to stain it. 

How to Hiring Deck Repair Services

Now that you have enhanced your knowledge of deck building, what are your next steps? Here are steps to hiring a professional deck repair service.

  1. Before calling a deck builder or repair contractor, closely examine your deck. 
  2. Record measurements and take photos of what you find.
  3. Contact a professional, explain your concerns, and show them what you have found. 
  4. Ask for their professional opinion.
  5. See how it compares to your expectations.

Asking questions without making a contractor feel challenged or belittled always allows for healthy discourse. In doing so, you will learn and better understand the overall process. When you generally understand the process, you are equipped to make informed decisions confidently. 


Hopefully, your deck project won’t be as intimidating and overwhelming as you thought. You might even be able to salvage your old deck after all. 

Either way, a little knowledge and insight helps. Contact us anytime for further assistance for your Raleigh deck repair or replacement needs!

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