Galvanized Studs for Outdoor Kitchen

AikiPapi

Hi, All.

Continuing to enjoy reading in this forum and learning a lot along the way.

Quick question about which type of galvanized stel studs to use in framing an outdoor kitchen (in NJ). I'm not quite a DIY guy yet so I have a contractor doing most of this, but I've certainly learned a lot of the right questions to ask here.

I notice that he's using G40 galvanized studs (25 gauge, I think) where typically the higher levels of galvanization (G60 and up) seem recomended for exterior walls in general construction. Is this something I should be concerned about?

Thank in advance for any insights!

Bud Cline

The G40 will likely out live us all. But, what are the studs being covered with? If cement board is being used the gauge should be about 18. Twenty-five gauge won't always take a screw if it is in cement board without stripping out the stud and leaving the screw head standing proud.

AikiPapi

Thanks for the reassurance, Bud. That frees my mind up to obsess on other details of the build (follow-up posts coming soon to a chatroom board near you!).

concretemasonry

You will always have to confront the classic problem of corrosion to the studs when a self tapping screw or drilled thing penetrates a steel stud (creating a moisture path to the steel stud by cutting into the galvanizing) while in a moist environment. - I have seen this many times on commercial buildings where moisture gets into the area behind the exterior finish.

AikiPapi

Sounds like I'm probably going to be dealing with the same primary issue at the points of penetration regardless of the level of galvanization. I suppose I can live with that better than knowing I've made a key structural mistake.

Hope I understood you correctly - and thank you!

Bud Cline

Very true - good point.

You could always waterproof the wall to mitigate moisture migration into the structure.

You didn't answer my question about how the wall was to be prepared beyond the studs. Would be nice to know.

AikiPapi

Oops - sorry. Cement board (Hardibacker) is being installed over the galvanized frame. I honestly don't remember the gauge of the studs so I could be off with that but it does look to be going well from that standpoint. I'm just trying to figure out what's reasonable to question up front as opposed to dealing with avoidable consequences a few years from now. Access to the inside of the island seems pretty good so I suppose my best bet to defend against rust & corrosion might simply be to inspect the inner frame annually and keep a rust protectant spray handy.

Still trying to find that balance between due dilligence and driving our contractor off the job!

AikiPapi

I was also a bit concerned about the studs that were in direct contact with the stone patio (those that aren't shimmed) and the corrosion and rust that might ensue. The patio does drain well so I don't foresee them actually sitting in water too often and from what I understand there would need to be another metal and an electrolyte (water?) involved to spawn true galvanic corrosion. Trying to talk myself out of sweating this detail I suppose.

Bud Cline

I think you are over-analyzing the benefits of the galvanized studs. The studs will be fine, it is the cut edges of the metal studs and the fastener penetrations that will rust and corrode first. The stud construction could be built on a redwood (or treated) bottom plate to protect any oxidation from staining the stone.

You should investigate the use of Hardibacker. Hardibacker (tile-backer panels) ARE NOT rated for outdoor use. Don't know why because Hardi also produces a great siding material that is. I am told that the formulas are different even tho the products appear to be the same.

The walls could also be waterproofed with a liquid waterproofing material. Laticrete's Product 9235 qualifies for this. There are others but they all may not be rated for exterior use. Bed and tape the seams using ceramic tile thinset and alkali-resistant tape, then waterproof the seams and the entire board surface as well. Sorta like building a tile shower.

AikiPapi

Thanks again, Bud. I'll try to shift my attention to some more practical concerns (like fasteners, etc.) as you suggest.