Mixing certain metals on my Tiny house build?
Hey everyone. I am in the middle of a THOW build out in the island of Hawaii. Tropical environment. Lots of salt and rain. This is my first build of this scale so I am hoping to get some answers to questions I have along the way.
We stared putting aluminum siding on the other day with stainless steel screws. There is a lot to consider out here in terms of metals and corrosion. Everyone uses stainless for exterior but I have been getting a lot info about not mixing stainless with aluminum. To further complicate things my house has a galvanic steel frame. Here is how my exterior sandwich is from outside to in starting with now the aluminum siding.
Aluminum siding (pictured) patina color.
Tyvek house wrap
15/32 sheathing
Galvanized steel frame
I was told to use stainless for fastening the aluminum siding to the house, so I used 1/2 inch stainless to try and minimize touching the galvanized steel. But now I am reading that aluminum and stainless will not work together? Pretty much all hardware out here that isnt stainless rusts like crazy. (The fasteners are under the lip of the siding but still will be affected by humidity and probably water no doubt. Furthermore I am reading now that stainless steel and galvanized steel are not compatible? My stainless steel 1/2 fasteners and galvanized steel are separated by the house wrap, sometimes window flashing tape and sheathing but since my sheathing is only 15/32 I am sure there are some places they will touch where studs and headers ect are..
I have installed 1/4 of the siding now, so I could take things down. My fear is getting corrosion especially in the frame of my house from all these potential reactions. Perhaps i am over thinking all this, but it seems like a pretty big issue to avoid. Also on a completely different side of the house I am hoping to use copper shingles for siding. I know I have to separate the copper and galvanized steel, which is done by my tyvek and sheathing, but I was hoping to fasten these two with stainless steel. again there would be points where the fasteners could touch both copper and galvanized steel (albeit seperated by my sandwich.) Could the stainless act as a bridge for corrosion of some kind? And could stainless be ok touching the galvanized when going through tyvek and sheathing since hopefully it will be dry?
Building in the tropics has its challenges! Any insights would be greatly appreciated.
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Replies
Do not listen to internet conversations about galvanic corrosion
consult building professionals with specific knowledge about your application
What I can tell you:
I have owned a car for 40 years that I replaced all the small screws holding lenses on with SS in 1984. Pot metal.
No problems
I drive in the rain, but not salt
I own a different car with an aluminum chassis and the brake master is held on with stainless hardware, factory.
If you are directly on the water, galvanic corrosion could be an issue.
Salt water, battery, bad.
Stainless and aluminum are on opposite ends of the galvanic table...BUT it is the direction that is important
Aluminum screws with stainless siding?
Bad
Stainless screws with aluminum siding?
Not so much
Your pictures did not show up, but I assume the galvanized framing is dry, so again, not really an issue
I recently replaced [8 years ag0] the ac condenser in the aluminum chassised car. It had rotted the [carbon steel]screws off in the previous 9 years. I replaced them with stainless that are perfect to this day
Real galvanic house building problem: copper and aluminum
Copper over aluminum exposed to water, boom, gone.
Z flashing on a water board trim, copper oil line run to Monitor heater, wherever it touched, gone. ACQ[copper] pressure treated, aluminum flashing, no more aluminum
Hey gusfhb,
Thanks a lot for your response. It helps clear the muddy waters/