Remedy for a dangerous deck
Howdy. I was visiting a man’s getaway cabin and when I looked at his cantilevered deck, I heard in the back of my mind: “Danger Will Robinson!”
Images included for clarity.
1. 4ft Cantilever with 2×8.
2. Only two of the 6 structural 4×6 posts in ground.
1. Deck is off of steep embankment and hangs about 9ft over the water.
2. It has 8ea 4×6 posts, of which only 6 are holding up beams and other two are just attached to outside joists.
3. Off the 8 posts only 2 are in the ground and these are immersed in permanently soaked soil as they are just a couple feet from lake and the 4″ side of post is taking all the lateral for the entire deck, aside from friction that the walkway onto deck and other posts provide (next to nothing).
4. The other 6 posts are setting on top of the ground on different items (soil, rock, or block with no attachments.
5. The deck is 16ft x16ft with 2×8″ joists 12″ on center on top of 2-2×12 beams 12ft apart and supported by three posts 8ft O.C.
6. The deck has a 4ft cantilever.
7. ? The outside 2×8 joists have a 2×12 immediately under them, so they are esentially 2×20 outside joists. The 2×8 header joist at the cantilever end has another 2×8 immediately under it making it a 2×16 in essence.
1. 2×8 joists 12″ O.C. spanning 12ft provides a wopping 100 PSF.
2. 2-2×12 beams supported every 8ft is within acceptable limits for a deck (not 100psf) but they are just walking on it, not putting a jacuzzi.
1. Cantilever limit should be 20″ for 2×8, not 48″
2. The two 4×6 posts providing 3.5″ of lateral support looks like a nightmare happening free standing about 6-7 ft out of ground and the additional fact it is several years old.
I warned him that it is unsafe. If that thing were to fail, it could go down, into the water, and really harm someone weather elderly, young, or rendered incapacitated from the impact with debris or entangled in the mess.
He is planning to have 20 family members out there next week for Thanksgiving and wanted me to see what I can do to render it SAFE. If that thing went into the water with half his guests on there, it would surprise me if it did not end in at least one fatality.
I am unsure what to do?
1. Cross brace the 4×6’s and add some sort of earth anchor out of concrete and galvanized attachment or one of those galvanized screws that go into the earth and some steel cable to keep the deck from moving laterally toward the water/downhill side.
2. Lift the deck and put in new posts embedded into the ground, or on sono tubed concrete, and add cross brace, and eliminate the cantilever problem somehow, set deck back onto new structural supports.
3. demolition and start over.
What do you think of idea number 1?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part