The Basics of Building a Curved Deck

Elaborate deck designs are becoming more popular, and any home in America is enhanced by the value and beauty of a curved deck. This deck design requires specialized plans, including distinct framing, and railing systems suited for this shape. But the additional work may not be worth the investment. Understanding how this gorgeous style of deck comes together will help you decide whether to include it in your outdoor living space.

Ring Joist Concerns

Some deck builders design a curved deck with overhanging deck boards cut to form an arched shape (as this picture shows), but this type of deck design will not work in many climates. Deck board end cuts must be supported to avoid cupping and warping that occurs in seasonal changes. A ring joist is the key component in this framing design.

Ring joists combine with the ledger board to form the frame around your deck boards. Posts and beams create the support underneath, and can be built using standard dimensional lumber. Square framing supports any shape of decking; an arched ring joist is used to create the curvy shape we want.

One of two construction methods can be used to create an arched ring joist. Choose the method that best suits your project and budget:

  • laminated ring joist - using strips treated plywood, wet down to increase flexibility, the contractor will bend two to three strips and laminate them together using heavy adhesive (often marine grade works well) and durable fasteners. Once dried and fastened to the deck framing and blocking, this structure provides an incredibly solid frame for joists and deck boards.
  • Kerf cut dimensional lumber - some contractors prefer to create a ring joist using treated or cedar wood scored at regular intervals along the back. With these type of shallow cuts applied, 2x6, 2x8 or 2x10 lumber can be bent into a fairly large arch. The lumber is then attached to standard joists, cut to fit within the arch and secured to the ledger board using joist hangers.

The Ideal Structure

Both of these construction methods allow for a solid structure, but the installation must be precise. If scoring is too deep, the stability of your framing will be suspect, and if an inferior adhesive is used to laminate plywood the ring joist will quickly deteriorate.

The size or severity of the arch can also create challenges. Remember that your posts or deck piers must be set fairly close to the edge of your framing or ring joist. Cantilevers can be installed to provide support for overhanging sections, but a solid frame requires posts or piers. When the arch is very pronounced, extra posts and/or cantilever designs are required.

Blocking is required to support the deck board as well, and needs to be secured to the ring joists and standard joists. This is generally made from 2x8 or 2x6, depending on the height of your deck. Remember that the curved shape requires extra blocking and precise cuts in order to provide a solid surface above, as opposed to squared shapes, which are the most efficient in terms of framing and installation.

Curved Railing Concerns

If your curved deck design requires railing, the construction may also present challenges. Standard wood pickets can be secured to the curved ring joist, resulting in a flowing line of railing, however the top rail or handrail must follow the same line.

For gentle curves with a shallow arch, consider cutting the arch out of a larger piece of dimensional lumber, such as 2x12. If the ring joist curves to a degree beyond that, you may need to laminate wider pieces together to form the curved top rail. Kerf cutting will not work for this application, since the back side of the top rail will be visible from your deck. The laminating technique may work, but the plywood will need to be covered for aesthetic purposes.

Steel or metal provides another option for curved railings. Fabricators can create a curved railing from given specifications. Provided this railing is painted or powder coated, a metal railing will last for years with minimal maintenance. Ensure that all posts, capping and mounts are made to the same quality, and use durable stainless steel fasteners to install this style of railing.

Premium Costs

Homeowners can expect to pay a premium cost for curved decks, based on the additional materials and installation required. That extra cost could be used to add other features, making your deck larger, more

functional or fancier. Think about which features will provide the greatest value for your investment; if a curved shape is desired, be prepared to pay for the design.

Composite decking provides excellent performance with very low maintenance levels. It can also work very well on a curved deck design, covering a laminated ring joist and other framing components. Thin fascia boards work well to trim the deck framing and wrap wood posts, but this premium product comes with a higher price tag as well. Cedar is also a good choice for curved decks, and costs only a little more than treated lumber.

Curved deck designs provide an upscale finish in your outdoor living space. If you are willing to invest the premium costs and have a contractor that can handle the framing issues, installing a curved deck is fairly straightforward. Arched accents can transform a standard deck design into something spectacular, but other deck features can achieve the same effect without the same design concerns. Talk to your decking contractor about the best options for your home and living space.

Posted by: diana
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