Why Is My Composite Decking Cracking?
Composite decks have become popular due to their outstanding durability and low maintenance. Modern and stylish, composite decking can add more beauty and functionality to your outdoor space. But in actual daily use, some people still experience problems with composite deck board cracking and warping. Many homeowners want to ask, why is my composite decking cracking?
Although composite decking has good durability and resistance, some factors can still lead to damage. In this article, we’ll take a closer look at why your composite decking is cracking. And offer some insights and options on preventing cracking in your deck.
Table of Contents
Understanding Composite Decking
Composite decking board is a new type of deck made from a blend of wood fibers and recycled plastic. The unique design provides a more durable deck material with outstanding performance. The mix of plastic and wood fibers gives the deck the advantage of being moisture, rot, and insect-resistant. It is therefore highly resistant to extreme environments and weather. In addition to outstanding performance, composite decks are available in a wide variety of looks and finishes. The durability and variety of looks make it an ideal choice for outdoor spaces.
Learn More: What is Composite Decking?
More Durable & Waterproof Composite Decking CPD-05
EVODEK unique two-tone art color technology gives you a stunning natural wood look so you can enjoy the great outdoors.
Common Causes of Decking Cracks
While designed for long life, composite decking can crack due to environmental stress, installation mistakes, or material limits. Here are the most common causes:
| Cause | Description | Risk Factors |
|---|---|---|
| Thermal Expansion | Material movement with temperature changes | Extreme climates; direct sun |
| Improper Installation | Inadequate gaps or supports | DIY errors; non-compliant fasteners |
| Moisture | Swelling from poor drainage | Humid areas; no ventilation |
| Weight/Impact | Surface damage from heavy loads | Heavy furniture; high traffic |
| Material Quality | Inferior composition | Budget brands; uncapped boards |
Thermal Expansion and Contraction
Composite materials expand in the heat and shrink in the cold. If not properly installed, this movement can create stress and lead to cracks. In areas with temperature swings over 30°C, this is a bigger issue. Prolonged sun exposure can also cause uneven heating, which worsens warping and cracking.
Improper Installation
Improper installation can lead to cracking and damage to composite decking. For example, improperly spaced decking may not contract and expand properly, leading to cracking. Inadequate support structures or improper fastening may also result in uneven stresses on the decking. Leading to severe damage and cracking.
Learn More: How to Install Composite Decking?
Moisture
Composite deck boards are well protected from moisture. But constant exposure to moisture or prolonged exposure to water can also cause the deck to swell and warp. This is especially true for uncapped or low-quality boards. Poor ventilation under the deck traps humidity, causing boards to expand and crack.
Learn More: Is Composite Decking Water-resistant?
Excessive Weight or Impact
Overweight or impact can cause cracking and damage to composite decks. Excessively heavy furniture or frequent moving of furniture may cause wear and scratches on the deck. Heavy objects dropped on the deck may cause damage to the overall structure. Sagging can also happen if the support joists are too far apart (ideally, no more than 16 inches on center).
Material Quality
While the impact of this factor is not significant, the material quality of the composite material does affect the performance of the deck. Different materials and compositions have different resistances and properties. Generally speaking, high-quality, name-brand decks offer greater performance and longevity. But of course, their price tag increases as well. Homeowners need to carefully consider the process of choosing a composite decking brand.
How to Prevent Cracks in Composite Decks
Prevention starts with good choices during selection, installation, and upkeep. Here are the key steps:
Proper Installation
Always follow the manufacturer’s guidelines. Use the recommended fasteners, like hidden clips or stainless-steel screws. Maintain the right gaps based on the temperature when you install—wider gaps in cold weather allow for expansion. Make sure joists are level and spaced correctly (12-16 inches apart). If you are not experienced, hire a certified installer.
Learn More: Composite Decking Hidden Fasteners vs. Screws
Adequate Ventilation and Drainage
Proper air circulation and drainage are essential to maintaining the life and performance of your composite deck. Leave at least 35mm of clearance under the deck for air to flow freely. Install drip edges or gutters to direct water away from the deck. This prevents water from pooling, which causes swelling.
Choose Quality Materials
As we mentioned above, the materials used in the manufacture of composite decks also affect their performance. Many manufacturers are not technically sophisticated and use inferior materials in the manufacturing process, resulting in poor-quality composite decks on the market. Check ratings for fade, stain, and scratch resistance to ensure the deck will last.
Avoid Overweight
Focus on the weight of the deck surface and avoid placing heavy objects in the same area. Distribute heavy items or heavy furniture evenly on the deck, or consider using furniture pads and protectors. Excess weight can have a severe impact on composite decking, leading to damage to the overall structure.
Regular Maintenance
Clean your deck quarterly with mild soap and a soft brush. Inspect it for early signs of damage and fix any issues quickly. Avoid using harsh chemicals or pressure washers set above 1,500 PSI.
How to Repair Damaged Composite Decking
If cracks appear, assess and repair them promptly to prevent them from worsening. Minor DIY fixes, like filling small cracks, might cost $50-$100. Professionally replacing boards can cost $10-$50 per square foot, with an average repair cost of around $1,465.
Assessing the damage
Thoroughly assess the extent of cracking in the composite deck before proceeding with the repair. Distinguish between minor cracks and severe cracking that affects integrity. Evaluating the damage will help determine the appropriate repair method to extend the deck’s life and performance. For severe damage, it is best to consult a professional.
Prepare the proper tools and materials
To repair cracked composite decking, you need to prepare the right tools and materials.
- Safety gear: gloves, safety goggles, and a dust mask.
- Vacuum cleaner and soft brush: for cleaning debris and dirt from cracks.
- Professional composite decking cleaner: for de-staining the deck surface.
- Putty knife: for applying filler and sealant.
- Composite deck filler: Please choose a professional composite material filler.
- Sandpaper: Sandpaper is mainly used to sand the repaired area.
Clean the Area
Before you begin repairing the crack, use a vacuum cleaner and a soft brush to remove debris from the crack. Wash the surface as directed by the manufacturer and let it dry completely, which may take up to 24 hours.
Applying the filler
Once the surface has been thoroughly cleaned, it’s time to apply a professional filler for deck restoration. Please follow the steps strictly for restoration and operation.
- Read the use and instructions of the filler. Make sure that the composite decking repair can be done correctly.
- Use a putty knife to apply the filler into the gap until it is filled. Make sure the filled area is flush with the surrounding surface.
- Smooth the filler completely to keep the decking surface level.
- Follow the instructions and recommendations for the filler. Allow enough time for the filler to set and harden.
Sanding the filled area
Sand the filler area to repair the appearance of the filled area further, if desired. Once the filler is completely dry, use sandpaper to lightly sand the repair area. Remember to sand in the direction of the grain of the composite decking to avoid damage to the deck surface. Next, clean the sanded area thoroughly to remove dust and debris.
Severe damage
For more serious damage or damage that affects the overall structural integrity, consider replacing the decking. Minor damage can be repaired using the methods described above. While severe damage will require complete replacement. Replace severely damaged decks promptly to ensure overall safety and integrity.
Summarizing
Composite decking material offers great durability, but it’s important to understand the causes of cracking, like thermal changes and installation errors. By using quality materials, ensuring proper installation, and performing routine care, you can minimize these risks. This will help you enjoy a beautiful and functional outdoor space for decades. If problems continue, a professional assessment can ensure your deck remains safe and valuable.
Frequently Asked Questions
Does composite decking crack in extreme heat or cold?
Modern high-quality composite decking, especially capped variants, is quite resistant to cracking just from temperature changes. It changes size with temperature changes, but if you place it correctly with the right spaces, it won’t build up stress. Cracking normally only happens when there isn’t enough space between the pieces in hot weather (which causes compression) or when there isn’t enough air flow in cold, humid weather (which keeps moisture within).
Is cracking covered under warranty?
Most well-known brands offer limited guarantees of 25 to 50 years that cover faults in the manufacturing process, fading, staining, and cracking caused by material failure. But most warranties don’t cover cracks that happen because of bad installation, not enough space, too much weight, bad drainage, or changes made by the homeowner. Always read the warranty terms for your specific product and keep track of when you installed it.
Can I prevent cracking without replacing the entire deck?
Yes, in most cases. Focus on:
- Ensuring proper ventilation (at least 35mm under-deck clearance).
- Improving drainage to avoid water pooling.
- Distributing weight evenly and using furniture pads.
- Regular inspections and cleaning to catch early signs.
If cracks are minor and isolated, use color-matched composite filler as described in the repair section. For widespread issues, consult a professional to check the substructure before considering partial or full replacement.
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