composite decking on a solid substrate
scooney801
| Posted in Construction Techniques on
This is my first post to “Breaktime”, I enjoy reading the threads in the magazine.
I am planning to replace an existing cedar deck with composite decking. I’d like to make a portion of area below the deck reasonably (not absolutely) water tight. I am thinking of using PT plywood as an underlayment and am wondering if it is okay to apply composite decking on a solid substrate. The young lad at the counter of my local supply house could not give me a straight answer. I plan a slight pitch to the deck, 1/2″ to 3/4″ in 8′ and the gaps will run with the water. This is a well shaded area in summer months.
Replies
Scooney,
Check the Timbertech website (http://www.timbertech.com) they make a below deck drainage system.
Don
Some timbertech can be used close to the ground others need a minimum of 12" air below it or it will warp. Check the web sites of the various manufacturers. Personally I wouldn't put PT ply under any surface except maybe indoor outdoor carpet. Breathing helps keep the material dry which helps it last longer. Maybe plywood, then stringers then composition flooring. But you'd have to check with the manufactuer. The stuff is so new no one seems to know for sure, but I do know some ventilation under neith is essential to long life - just like good underwear.
Yes, it's generally acceptable to install composite decking on a solid substrate, such as pressure-treated (PT) plywood, especially if you're aiming to create a reasonably water-tight area underneath the deck. Here are some considerations to keep in mind:
Substrate Stability: Ensure that the PT plywood is securely fastened to the deck framing and provides a stable, level surface for the composite decking to be installed on. Properly spacing the joists and using appropriate fasteners will help maintain structural integrity.
Moisture Management: While composite decking is resistant to moisture and rot, it's essential to provide adequate ventilation and drainage to prevent water from accumulating underneath the deck. Your plan to create a slight pitch and orient the gaps to run with the water is a good approach to facilitate drainage.
Composite Decking Compatibility: Check the manufacturer's guidelines and recommendations for installing composite decking over a solid substrate. Some composite decking products may have specific requirements or limitations regarding installation methods and substrate materials.
Ventilation: Ensure there's sufficient ventilation underneath the deck to allow air circulation, which can help prevent moisture buildup and promote the longevity of both the composite decking and the underlying substrate.
Shaded Area Considerations: Since the area beneath the deck is well-shaded, it may be more prone to moisture retention and slower drying times. Regular maintenance, such as cleaning debris and ensuring proper drainage, will help mitigate potential issues.
Overall, using PT plywood as an underlayment for composite decking can be a suitable approach, especially when aiming to create a water-tight or semi-water-tight space underneath the deck. Just make sure to follow best practices for installation and consider factors such as ventilation, drainage, and manufacturer recommendations to ensure a successful and long-lasting deck project.
https://deckitinc.com/decking/
Using PT plywood as an underlayment for composite decking is a common practice and can provide a solid substrate for your new deck. As long as the plywood is properly installed and the deck has a slight pitch to allow for water drainage, you should be good to go. Make sure to follow manufacturer guidelines for installation and enjoy your revamped deck in the shaded summer months!