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Build strong: Free standing decks

James Moylan

Friday, March 18, 2011

Decks fail for two reason: they are not flashed properly and they are not free standing. A freestanding deck is a separate structure that only attaches to the house superficially and to help with lateral movement. Free standing decks do no put any additional weight on the house. Builders for years have been trying to find ways to cut cost, and they do this while sacrificing the longevity and safety of their products. It is imperative to have a free standing structure for a variety of reasons.

Newly constructed single family homes typically no longer use solid 2×10 band boards, where the ledger is attached. Historically, it would be OK to bolt into the solid 2×10 beam that runs around the perimeter of house(if done correctly). Now, new home contractors are using engineered floor joists that deck ledgers cannot attach to and that will not stop a deck from pulling away from the house. A TGI floor joist is an engineered wood ‘I’ beam that has incredible vertical strength and resists warping and shrinking. However, engineered wood does not have much lateral strength and cannot take bolts very well.

In the mid-atlantic we are prone to severe weather that can result in a foot or two of snow per year. If a non-freestanding deck was not constructed correctly with the appropriate flashing and the correct attachment method to the house a heavy snow load can put the deck at risk of collapsing.

The sure fire way to avoid any problems in the future is to build a free standing deck. This simply means that the deck itself carries all the weight. To build a fee standing deck you need to add an additional beam within two feet of the house. There are ways to include the additional beam while not clogging up the under deck area. By using over sized beams we can minimize the amount of columns needed. Aloso, by using larger joists we can span larger spaces. If possible, we try to put the beam tight to the house in an attempt to maximize the under deck space for future use. For more information, or to see past free standing decks we have built, please visit www.DesignBuildersMD.com

*Band Board-outer most member of the flooring system.
The band board sits directly on the sill plate. Deck ledger attachment is made to this band board.

http://www.ilevel.com/floors/f_TJI_joists.aspx