Wood-framed deck: how tall is too tall?

[Ben29]

I have a wood-framed deck that is 4'-4" wide and is attached to the house via a ledger on one side. The top of the deck is 17'-9" above the ground elevation and the architect is suggesting 8x8 posts. See image below. The prescriptive design for post heights for decks only goes up to 14ft, and this just doesn't feel right the way they have it drawn. I could lower the braces, but then the braced would obstruct the window view. I'm not sure whey they couldn't just cantilever the floor joists to create this deck since it is only 4'-4" wide. Thoughts?

 

[KootK]

Just an incidental observation on the stair's impact on deck stability.

 

[Ron247]

Now that phamEng mentions it, I don't know anyone over 10 years old that could fit in that stair based on what it appears to be in size.

 

[r13]

Is 17'-9" post without intermediate braces a normal way of wood construction?

 

[phamENG]

r13 - I wouldn't call it "normal" but I have seen it before. I looked at a "fire escape" that was falling apart a couple months ago. 26' 8"x8" timber columns. There was a lower platform at about 5' above grade, but its effectiveness as a brace point was pretty questionable.

 

[jayrod12]

Normal is a relative term. If they don't need to contribute anything laterally, then why not?

Like Pham, it's not common, but I've seen it. I've even specified it on occasion, but they get unbearably large quickly to meet the slenderness requirements. And at those unbraced lengths have only minimal axial capacity.

 

[JStructsteel]

Each 8x8 post is carrying 600lbs max? I think easily a engineered design will work. A few diagonals on the underside of the deck joist and you have a design.