I'm doing an earthquake retrofit on my house. I've read that you should use stainless steel instead of hot-dipped galvanized for any fasteners in redwood (and pressure treated lumber, too). How important is this? It's a pain to source the stainless steel fasteners... Are they going to be less structurally sound? I obviously don't care about anything cosmetic under the house. The redwood is decades old at this point.
Primary reason for using stainless fasteners are:
- they are corrosion resistant
- the have good strength/structural integrity
- they are reasonably inexpensive
- they are aesthetically appealing compared to others
- they are ROHS compliant
Anyway, the most important thing to note is that galvanized steel is significantly weaker than stainless steel. The corrosion protection is also less durable than stainless.
You can easily find galvanized fasteners that are rated for contact with all woods, including redwood, cedar, and pressure treated - see, for example, Simpson Strong Tie products.
Stainless is generally more reliably corrosion resistant since it's not a coating, all of the material is corrosion resistant, and stainless steel is generally much stronger, and much more expensive - but stainless fasteners are not hard to find, any local or online industrial supply or building supply can source them.
Galvanized is fine in a desert -dry. I have about 40 " of rain a year and galvanized is gone in about 8 years and then underlying steel fasteners are gone in about 15 years in a deck and 20 years in siding. Stainless deck screws are marked "316" , probably true and they are cold worked to almost as high a strength as deck screws ( which are heat-treated). I have found SS deck screws to require proper clearance and pilot holes to avoid twisting off ; maybe something to do with cold work rather than quench and temper for strength. The SS will not take the abuse of steel deck screws. At 20 years my galvanized joist hangers are rusting away/ falling off, corrosion depends mostly on how wet the location.