Yesterday’s inspection had a cantilever deck supported by steel “I-beams”. All of the information that I’ve found talks about dimensional lumber and formulas based on that for the amount of overhangs. The deck was 8’ 4" out from the house and was 34’ long.
There are 2 “I-beams” at the end and middle of the deck. A square steel beam runs the length of the deck and has a metal support post at the end of the deck where no beam is present.
Any information available on specs for this type of construction?
This should be an engineered system, thus I would refer to an Engineer for review of the plans, at a minimum! The seller should have a copy of the plans for this purpose.
I am assuming there was nothing visible within the home that you could inspect, such as dimensions, connections, fasteners, etc. all of which are crucial to a systems performance and longevity.
Not only the weight of a crowded deck comes into calculations. Add the roof structure above,
The deck is not supported/braced vertically as it should be.
I agree with both above. I also see a few other concerns with the deck and stairs such as missing railing, sidewall ledger attachment, corrosion etc. I would not say the beam/post system is inadequate but I would put it back on the seller to provide design plans or SE evaluation.
Thinking it was engineered originally with two or three support posts. I am an experienced mechanical engineer and that is how I would have designed it. Even with the cantilevered steel I-beams, the bending torque stresses involved are monstrous and the deck edge would deflect down under peak load as a result. I would be looking very carefully to see if there were any evidence in the driveway/walkway and at the underside of the deck that indicates posts were there that were later removed. If that is the case, the deck was structurally altered and needs correction (i.e. posts restored).
