Seattle Custom Home builder - cantilever decks

Whether you are a Seattle custom home builder or a Seattle home owner, cantilever deck construction is like anything else.  It can be done correctly and be trouble free for years with periodic maintenance.  When a cantilever deck is built with shoddy construction practices the problems can become significant due to the structure extending inside the living space.  There are three problems this Seattle custom home builder runs into a lot in repairing cantilever decks that are in a state of failure.  Lack of maintenance , poor waterproofing, undersized joists and too little back span.
All buildings require maintenance to keep them functional.  Cantilever decks are no exception and should be inspected and cared for often as any problems that arise can work their way inside the building multiplying the cost and inconvenience of repair. Garden debris (leaves, pine needles, etc) should never be allowed to build up on the deck surface.  Allowing organic debris to build up invites, dry rot and pests that can compromise the structure.  Caulk joints, flashings, and membranes that are used to separate the exterior portion of the deck from the interior structure should be inspected and maintained regularly.  Builders with experience working in the wet Seattle climate generally have the experience to limit maintenance needs.
Probably the most damage we Seattle custom home builders see arise from poor waterproofing in cantilever deck construction is lack of slope away from the building.  With a waterproof walking surface on a deck the deck should slope away from the building at least 1/8″ per foot and ideally 1/4″ per foot.  With an open joint decking the slope is less important but the joist should still slope away from the building somewhat.  Lack of proper metal flashing elements is another big contributor to failure in a cantilever deck construction.  Since the joists of the deck are integral to the ceiling and floor of the building, protecting the area where the joists exit the building with proper waterproofing techniques is important.  Any Seattle custom home builder should be paying close attention to this.
Another problem I have seen in repairing cantilever deck construction is the under sizing of the joists and too little back span.  Having undersized joist leads to a soft and squishy deck that will move to much when in use.  Having the structure move and bounce works on the joints and creates construction problems over time.  Even when the lumber is sized correctly the system will not function correctly without the right back span.  The rule of thumb is the back span should be 2.5 x the length of the over hanging deck surface.  For example a 4 ft deck would need a 10 foot back span which would require 14′ joists.
If construction defects are present in your cantilever deck construction, taking measures to repair the deck sooner rather than later will avoid may more potential headaches.  In some of the repair projects the damage was so severe that the cantilever system was completely removed and post and beam deck structures installed.