[kctess5]

Reminds me of when a family friend of mine (a professor of civil engineering) built his own barn on his property. He got permits and did everything the ordained way, but still got hassled over tons of details. The inspector almost couldn't grasp the idea that the tens of thousands of stainless steel screws he had bought and used significantly exceeded the specs of the nails required by code. He did manage to persevere eventually.

[cma]

Not sure if this was the issue, but some grades of stainless steel screws can't be used with treated lumber because of an increased corrosion risk. The rule might have been in to simplify inspections.

[rsync]

"Not sure if this was the issue, but some grades of stainless steel screws can't be used with treated lumber because of an increased corrosion risk."

If it's actually stainless, that is an approved connector for treated lumber. It's more expensive than galvanized, but much more resistant.[1]

It's plain old steel - untreated - that has very bad galvanic corrosion properties inside of treated lumber.

[1] http://www.finehomebuilding.com/2012/09/06/whats-the-differe...

[cma]

"All stainless steels may not be acceptable for use with preservative treated wood. Testing has shown that Types 304, 305 and 316 stainless steels perform very well with woods that may have excess surface chemicals. Type 316 stainless steel contains slightly more nickel than other grades, plus 2-3% molybdenum, giving it better corrosion resistance in high chloride environments prone to cause pitting such as environments exposed to sea water."

https://www.strongtie.com/products/product-use-information/c...

[stuckagain]

Also screws have poor toughness compared to nails, and should never be used for framing.

Just because it looks strong doesn't mean it is strong.

[scaryspooky]

Nails have higher shear strength and screws have higher tensile strength. That's the reason nails are used for framing and those nails are typically covered in a heat activated cement to prevent pull out.

[Frondo]

My aunt's also a civil engineer, and she has a much more mundane explanation for why nails are OK and screws are not: if you use nails, someone's already calculated how many you need to ensure the structure isn't going to fall down. The strength of the nails has been calculated, their material properties are known, etc. The engineering work has been done.

If you use screws, you could have an engineer sign off on that structure (and then the inspector would let it pass), but the engineer would need to:

1) Find a data sheet on the screws you're using,

2) Do the calculations to show that you're using enough of them, and in the right places, to ensure the structure will stay standing,

3) Be willing to then sign off on the structure.

Depending on the screw, that data sheet may or may not exist.

I'm surprised your family friend didn't know this, or left that detail out of the story. Maybe he worked in another branch of civil engineering (sidewalks, sewer, etc) from structural engineering?

tl;dr: If you can pay an engineer to do the calcs (and sign off on it) to show that your screw-based structure will stay standing, the inspector won't be any problem.