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Views: 0 Author: Site Editor Publish Time: 2025-09-05 Origin: Site
Wood plastic composite (WPC) decking has become a go to choice for homeowners, architects, and contractors in recent years. Why’s that? It’s got a nice look and feels natural when you walk on it. Unlike regular lumber, it doesn’t need constant upkeep like sanding, staining, or sealing. Also, it’s promoted as earth friendly because it combines recycled wood bits with plastics. So, you get a great blend of benefits: it’s good for the environment, looks attractive, and takes little effort to maintain.
But here comes the real world question: If WPC decking is so reliable, why do we still hear about cases of decks cracking, sometimes even during the warranty period? The short answer: there are a few root causes, and they fall into two big categories product quality issues and improper installation plus some smaller contributing factors. Let’s break them down.
Not all WPC decks are created equal. If the ratio of wood powder to plastic resin is off, the material can become brittle. For example, using too much filler and not enough glue like stuff leads to weak areas in the deck. Some companies might also use cheaper recycled plastics with bits of junk in them. These small imperfections aren’t always obvious right away. But when stress or weather hits, they turn into spots where cracks start.
WPC decking, like most composite materials, expands in heat and contracts in cold. If the formula doesn’t account for this, the deck ends up pushing against fasteners or neighboring decks. Imagine a 4 meter deck on a hot summer day it can expand several millimeters. Without the right design tolerance, that pressure has only one way out: cracking.
Sometimes the weakness isn’t in the raw ingredients but in the profile itself. Hollow core decks, if designed with thin walls or poorly distributed internal ribs, concentrate stress in small areas. That’s where you’ll often see a hairline crack spreading. It doesn’t mean hollow WPC is bad by default just that poor plate design shortens lifespan.
Even the strongest deck will crack if it isn’t supported properly. A deck frame with joists spaced too far apart can cause “deflection” the deck bends under foot traffic. Over time, this repeated bending introduces cracks at the weakest points.
Fasteners are a bigger deal than most people think. If installers use the wrong clips, or forget to tighten them consistently, the deck decks shift unevenly. Uneven stress leads to cracks. MexyTech actually developed a patented Dental Part Technology fastening system that not only grips the deck firmly but also leaves just enough clearance for expansion. This simple detail can save you from annoying cracks.
Leaving expansion gaps isn’t optional it’s essential. If decks are installed edge to edge with no space, summer heat will make them swell until they push against each other. The result is splitting at the edges or around screws. A 5–8 mm gap may look like a small detail, but it’s really a safety margin.
Cracks don’t always come from manufacturing or installation mistakes. Sometimes it’s the way the deck is used.
Prolonged overload: Putting heavy machinery on one section can exceed design load.
Impact with sharp or heavy objects: Dropping a steel tool can create invisible micro cracks. Later, with temperature cycling, those cracks spread until they’re visible.
Improper cleaning methods: A high pressure water jet aimed at seams might look effective, but it can drive water deep inside and weaken the bond over time.
At the end of the day, most cases of WPC deck cracking boil down to two things:
Material quality: weak raw material ratios or insufficient thermal expansion resistance.
Improper installation: poor foundation leveling, no ventilation, missing gap spacing, or the wrong fasteners.
Choose a high quality manufacturer: Look for certifications and anti crack warranty terms. A trusted brand with a history of R&D and patents is less likely to cut corners.
Adhere to installation guidelines:
Foundation must be flat and stable.
Leave proper expansion joints (5–8 mm).
Use smart fasteners like MexyTech’s Dental Part Technology clips for both grip and breathing room.
MexyTech, after years of study and earning several patents, makes wood plastic composite decking, fencing, and outdoor wall panels built to last. They don’t just sell decks. They also offer clear setup instructions. This helps folks cut down on upkeep hassles and keeps cracks at bay.
Q1: What are the main causes of WPC deck cracking during the warranty period?
The biggest reasons are poor material quality and installation issues. Problems like thermal expansion stress, weak support, or lack of ventilation can all lead to cracks.
Q2: Can installation mistakes really cause cracks in WPC decking?
Yes. If there’s no expansion clearance or the wrong clips are used, decks can push against each other as they expand. This is one of the most common causes of early cracking.
Q3: How does ventilation affect WPC decking performance?
Without proper ventilation under the deck, moisture builds up. Trapped humidity accelerates swelling and weakens the composite material, making cracks more likely.MexyTech's 2nd Co-extrusion WPC Decking uses Surlyn plastic on the outer layer, which wraps the core material on all four sides, providing protection against oil, acid, insects, wear and UV rays, and is superior to the first generation in terms of moisture resistance.
Q4: What role does material quality play in preventing cracks?
High quality decks use balanced raw material ratios and tested designs to handle expansion and contraction. Low grade decks often fail under seasonal changes.
Q5: How can I avoid cracking problems when building a new WPC deck?
Choose a reliable manufacturer like MexyTech, check for warranty coverage, and follow proper installation methods: stable foundations, expansion gaps, and correct fasteners.
