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How to Combat Ponding on Your Plastic Deck

By admin - Last updated: Monday, December 5, 2011 - Save & Share - Leave a Comment

Ponding water on a deck can be a homeowner’s worst nightmare.  Water that remains on a deck 48 hours or more indicates not enough slope or that sagging or settlement of the deck’s structure has occurred.  But with proper design, installation and regular inspection, you can prevent ponding conditions before they develop into extensive and costly situations.

Deck Drops

Deck Drops by kevinmarsh, on Flickr

For decades, construction litigation experts have testified both against and in defense of architects who have designed decks without slope, arguing whether or not a deck is a “roof.”  California Building Standards Code states that “Balconies, landings, exterior stairways, occupied roofs and similar surfaces exposed to the weather and sealed underneath shall be waterproofed and sloped a minimum of 1/4 unit vertical in 12 units horizontal (2% slope) for drainage.”  In other words, a one inch drop in slope per four feet of travel is standard (1/4” per foot fall).  Water sheets, flows from a horizontal surface, at no less than a 1% slope or 1/8 unit vertical in 12 units horizontal.  Therefore, slopes between 1% and 2% are acceptable.  Wood products will warp and cup, so the closer you can come to the 2% slope, the better.  This is one reason why vinyl, composite and plastic lumber is a popular choice among regular deck users as these materials are resistant to cracking and warping.  Whether you use these materials or traditional wood, building code compliance is imperative.

Immediate repair of loose concrete foots, splintered and cracked support posts and sagging boards is critical.  Sagging or splitting deck boards can trip visitors or collapse under their weight.  We’ve listed some methods that provide a permanent fix and others that will suffice temporarily until you can make more thorough repairs.

  • Use Strong Fasteners.  If your deck is leaning or pulling away from your home, the safest and fastest way to shore it up is with appropriately sized bolts.  Decks attached to home exteriors with nails, despite length, ultimately pull away, increasing the risk of collapse.  Hammer in any pulled away nails and add new bolts around the original fasteners.  Reinforce joists and support posts that have begun to detach with bolts as well.
  • Concrete Footings.  When concrete footings are cracked and damaged, a deck’s support posts can shift and lead to leaning or sagging.  Damaged concrete footers should be removed and replaced.  Pouring more concrete on top of a bad footer is not the answer as the cracks will quickly spread to the new material.  In this case, jacking up the deck is necessary so that you can break up the old concrete with a sledge hammer before pouring fresh concrete.
  • Combat Shifting and Sagging.  Your deck may be shifting and sagging because its foundation is supported with blocks that sit on the ground rather than posts and poured concrete.  You can repair stable and intact decks with shims.  Use a house jack to lift the shifting and sagging deck areas before installing weight bearing plastic lumber or pressure-treated wood boards between the deck and foundation blocks.  In some cases, jacking the posts off the piers and cutting one and one-half inches off the bottom of the posts will solve the problem immediately.
  • Joists.  Rotted and splintered deck joists can cause persons serious injury and in some cases death if a section drops out beneath them.  Only shore up a damaged joist if rot is limited and surrounding joists are in good condition.  Use 2x4s to support the joist, installing lumber splints on both sides of the joist’s rotted or cracked section to secure it, using the same lumber for the splint used for the original joist.

By following these guidelines and local building codes, you’ll safely enjoy your plastic deck this season and for years to come.

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