Why Do Composite Decking Boards Warp?
However, many users find that composite decking can warp under certain conditions. Improper installation, exposure to excessive heat or humidity, and the use of substandard materials can all cause composite decking to warp. Specifically, composite deck warping is typically caused by improper joist spacing and uneven expansion and contraction of the boards.
This article explores the underlying causes of composite decking warping. You’ll learn how to prevent and repair warping issues. Create a sturdy, level outdoor living space.
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Table of Contents
Causes of Composite Deck Warping
Composite wood decking is manufactured by combining wood fibers with plastic polymers. It fixes the problems that solid wood has by itself. However, improper installation or use can also cause warping. Here are the main reasons why composite decks warp.
Thermal Expansion
Every material has a physical trait called thermal expansion, and composite decking is no different. Composite decking soaks up heat and grows when it’s exposed to high temperatures. The boards get longer and wider as they spread.
If there aren’t enough expansion gaps between the boards when they are put together, the boards that are growing will push against each other. In the end, this makes the boards bend up or down, which is called warping.
Humid Environments
Although composite deck materials possess some water resistance, they are not entirely unaffected. Prolonged or excessive exposure to moisture can still cause absorption and expansion. For instance, poor surface drainage prevents rainwater and dew from draining quickly. This moisture accumulates on the deck surface and may gradually seep into microscopic pores.
Furthermore, drainage beneath the deck is even more critical. When draining isn’t good enough, water builds up for a long time. This makes the boards expand and twist in an uneven way. What’s worse is that a damp environment not only damages the decking but also eats away at the framing underneath. When the framing is rotting or warped, it can’t hold the decking boards evenly. The decks will sag and warp because of this.
Improper Installation
The installation process is pivotal to composite wood decking performance. The vast majority of warping issues stem from substandard installation practices. For example:
- Insufficient Spacing: This is the most common and critical installation error. Inadequate spacing causes excessive compression during thermal expansion, leading to warping.
- Excessive Joist Spacing: Joists form the deck’s structural framework. The girder spacing must not exceed the maximum value specified by the manufacturer. Excessive spacing will cause the middle section of the deck plate to sag under load. Long-term sagging stress turns into warping distortion over time.
- Improper Fastening: Using incorrect fasteners or improper installation methods can also cause warping. For instance, using standard screws instead of specialized corrosion-resistant composite deck screws. Some hidden clip systems, if installed incorrectly, similarly restrict thermal expansion and contraction.
- Lack of Drainage Slope: Composite deck boards should be installed with a slight drainage slope. This ensures water flows quickly toward gutters or edges rather than pooling.
Quality Variations in Composite Decking
Not all composite decking is created equal. Its resistance to warping is directly tied to material quality. Lower-cost products may utilize weaker wood fibers and recycled plastics. The additives in their formulations are often inferior. Because of these things, the boards are less dense, have a less rigid structure, and are more likely to bend.
High-quality composite wood decking typically features higher density and more advanced manufacturing techniques. For example, EVODEK capped composite decking incorporates a rigid polymer shell around its core layer. This provides superior UV resistance and lower water absorption. It maintains excellent dimensional stability, offering more effective resistance to warping issues.
Structural and Load-Bearing Concerns
Composite wood decking has a limited design load capacity. Damage to deck structures can also be caused by uneven weight distribution. For example, a lot of people leave heavy things like plants or hot tubs on small parts of their deck for long periods of time. This puts constant pressure on the decking and joists below, which causes them to change shape.
Also, if the joists that hold up the structure aren’t strong enough, they could bend over time, which would cause the decks above to warp too.
How to Prevent Composite Deck Warping
Understanding the causes of warping allows you to implement preventive measures. For example:
Invest in Premium Materials
This is the most critical step when selecting composite decking. Choose high-quality composite decking brands like Trex or EVODEK. While the initial cost is higher, these products offer superior durability and stability. This will save you from costly repairs and replacements down the line. It’s important to pay close attention to important product specs like how well it resists UV light, slips, and water.
Follow The Steps for Professional Installation
Positioning tools from the maker should be used. Make sure that there is the right amount of space between boards and between boards and walls. Strictly adhere to the installation manual when building the deck frame. Verify joist spacing, dimensions, and levelness. When installing joists, wrap the surface of the framing lumber with waterproof tape.
Ensure Proper Slope and Ventilation
Install with correct drainage slope. Maintain adequate ventilation space beneath the deck. Avoid enclosed designs to allow airflow for moisture dissipation.
Hire a Professional
If you want to build a deck that is big or complicated deck, you should definitely hire a professional. They understand different product characteristics and ensure code-compliant installation. Some manufacturers even require professional installation for warranty coverage.
Plan a Sensible Layout
If you can, use pergolas or awnings to provide some shade to places that get a lot of direct sunlight. This also helps mitigate thermal expansion caused by extreme heat. Additionally, avoid permanently fixing heavy objects in one spot. Rotate furniture placement to distribute weight evenly across the deck.
Regular Maintenance
Promptly remove fallen leaves, soil, and other debris. This prevents clogging of drainage gaps and water pooling on the surface. Regular cleaning with special cleaners and soft brushes. This will keep mold and stains from building up. Additionally, conduct a comprehensive deck inspection at least once annually. Check for loose screws, damaged boards, and signs of rot in the framing.
How to Repair Warped Composite Decking
If your decking has warped, don’t panic. Prompt repair can prevent the problem from worsening. Of course, before proceeding, you need to carefully assess and inspect the decking.
Assessing Warping Extent and Causes
First, find out if the warping is limited to a few boards or covers a bigger area. Widespread warping could mean that there are problems with the structure or the material. Isolated warping is usually caused by problems with the installation or localized flaws.
You need to carefully inspect whether the joists beneath the warped areas are secure and free from rot. Use a flashlight to examine the ventilation and moisture conditions beneath the deck.
Replacing Individual Warped Boards
For limited problems, swap out the warped boards. Make several cuts with a circular saw along the direction of the bent board, close to the joists. Make sure that the cuts only remove the deck board and don’t hurt the joists below.
Then, use a pry bar to carefully lift the cut board off the frame. Check the uncovered joist for damage and fix it first. Next, replace it with a new board matching the original deck’s brand, color, and specifications. Ensure the new board maintains the correct expansion gap from adjacent boards. Secure it firmly using corrosion-resistant fasteners.
Reinforcing the Substructure
If excessive joist spacing or frame sagging is detected, you can reinforce the structure beneath the deck. Add new joists in problem areas to reduce the original spacing. This provides more adequate support for the deck boards.
Seeking Professional Assistance and Warranty Claims
If there is major warping soon after installation, it’s probably a sign of a material defect. Talk about warranty claims with the deck maker right away, making sure to include proof of purchase and installation records. It is safer to hire a skilled contractor for repairs that are hard to do or when the cause is not clear.
Conclusion
Even though composite decking is a great material, it can still warp for a number of reasons. Understanding these points allows you to implement preventive measures during installation and maintenance.
Select the best composite decking material. Strictly adhere to scientifically sound installation guidelines. Your deck will provide decades of comfortable enjoyment. For more information on composite decking, contact the EVODEK service team. We are here to answer all your questions.
FAQ
How Long Does It Typically Take for Composite Decking to Start Warping?
There is no fixed timeframe for composite decking warping. It varies depending on the quality of the materials, how they are installed, the weather where they are, and how they are used and maintained. A high-quality, properly installed composite deck may remain flat and new for decades. Conversely, a defective deck may develop issues within one or two years.
Can Painting Composite Decking Prevent Warping?
No. Painting does not address the root causes of warping. It may also impede surface moisture evaporation, leading to peeling and flaking. Furthermore, most manufacturers will void the product warranty if this is done.
Which Material Offers Better Warp Resistance?
Aluminum decking ranks among the most dimensionally stable products available. It remains virtually unaffected by humidity and exhibits low thermal expansion. However, its cost typically far exceeds that of composite deck boards.
Can Cold Winter Weather Cause Composite Decking to Warp?
Warping directly caused by cold is rare. Composite deck materials contract in low temperatures. If installation gaps were perfectly sized for summer, they might appear too large in winter. But this usually doesn’t directly cause warping. You need to guard against moisture from prolonged snow accumulation in winter. This can increase the risk of warping.
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