I wonder how often this is said by "contractors" - "Really, is it so important to follow the manufacturer's instruction?"
Or, "I have been doing it this way for 20 years..."
The answer to the former is yes, and the answer to the latter is - SO WHAT!
On this new construction the manufacturers' stickers were present on most everything.
This is the sticker on the pull-down attic staircase.
This sticker is approximately 12"x12".
It is right in your face when the stairs are pulled down and hard to miss.
It has various installation instructions. Even diagrams!
Most notably, for the purposes of this post, it says this:
"Stair frame must be secured directly to ceiling joists on all four sides with 16D nails or 1/4" by 3" lag screws. Use of other fasteners such as finish nails, brads, staples, sheet rock or deck-type screws, can cause sudden, catastrophic failure and should not be used."
That is #3 on the list above. The manufacturer ranks it as pretty important! Properly installed this staircase is rated for 300 pounds, so the manufacturer thinks it is a good product.
A 16D nail is 3 1/2" in length. That is long enough to go through the stair frame, joist and even into a second joist beside, which is recommended at least at each end. The same strength would be achieved by lag screws.
There are even holes in metal brackets at each corner and the front to accept these nails and screws!
Imagine what I was thinking climbing up to see that this staircase had been installed with brads!
At least they used the very strong triple array! (I cough as I say that)
There was a gap all around of 1/2", except at the front where the stairs hinge. Even without the gap, brads are not strong enough to hold this ladder. In fact, they are SPECIFICALLY EXCLUDED from installation use.
The other thing in the right photo is the tip of a screw coming from the other side of the joist, and not touching the stair frame.
By anybody's definition, and certainly the manufacturer would agree, this is not a securely-installed ladder staircase.
IT IS DANGEROUS.
My recommendation: new construction needs an inspection just as does old! Maybe even more so because the house has never been lived in and nothing in the house has been tested. My biggest beef with modern construction can be described in one word:
The installation above is amateur, dangerous, unthinking, uncaring and decidedly UNPROFESSIONAL.