Hello,
I've read a lot here but I'm not quite sure about mixing metal materials with each other and with pressure-treated wood, especially outdoors. No thread seems to reach a conclusion.
I'm building a deck and have decided to use joist hangers for the beams. Treatment class A and beams 45x195.
Biltema doesn't have joist hangers for 45x195 beams (if you want to be able to screw all the way up), so I found Joma's variant instead at Bauhaus and Hornbach. This is exactly the same product, and Bauhaus describes it material-wise as hot-dip galvanized sheet, while Hornbach states steel, zinc. Hornbach also mentions that this is only for indoor use. That's where it went wrong. Biltema and Bauhaus don't mention anything about the environment for the joist hangers. Is hot-dip galvanized and hot-dip zinc-coated the same thing, as I have thought?
https://www.bauhaus.se/balksko-joma-45x197mm-utatvanda-flikar#go-to-description
https://www.hornbach.se/shop/JOMA-Balksko-kombi-45-x-197-VFZ/5119901/artikel-detaljer.html
I was thinking of using anchor screws to attach beams to the joist hangers and joist hangers to the support beams. Electro-galvanized is not an option, I understand. Biltema sells C4 anchor screws where they mention surface material/coating but not the screw material. Can I use these?
https://www.biltema.se/bygg/fastelement/byggskruvar/ankarskruv-250-st-2000034545
Apparently, stainless steel A4 is best outdoors and also a bit more resilient to movements, but you should avoid it together with hot-dip galvanized joist hangers? Will there be galvanic currents resulting in rust on the joist hangers? Stainless steel joist hangers are not an option considering the price and the number needed.
Help! Which joist hangers together with which anchor screws? Are there joist hangers for outdoor use?
I've read a lot here but I'm not quite sure about mixing metal materials with each other and with pressure-treated wood, especially outdoors. No thread seems to reach a conclusion.
I'm building a deck and have decided to use joist hangers for the beams. Treatment class A and beams 45x195.
Biltema doesn't have joist hangers for 45x195 beams (if you want to be able to screw all the way up), so I found Joma's variant instead at Bauhaus and Hornbach. This is exactly the same product, and Bauhaus describes it material-wise as hot-dip galvanized sheet, while Hornbach states steel, zinc. Hornbach also mentions that this is only for indoor use. That's where it went wrong. Biltema and Bauhaus don't mention anything about the environment for the joist hangers. Is hot-dip galvanized and hot-dip zinc-coated the same thing, as I have thought?
https://www.bauhaus.se/balksko-joma-45x197mm-utatvanda-flikar#go-to-description
https://www.hornbach.se/shop/JOMA-Balksko-kombi-45-x-197-VFZ/5119901/artikel-detaljer.html
I was thinking of using anchor screws to attach beams to the joist hangers and joist hangers to the support beams. Electro-galvanized is not an option, I understand. Biltema sells C4 anchor screws where they mention surface material/coating but not the screw material. Can I use these?
https://www.biltema.se/bygg/fastelement/byggskruvar/ankarskruv-250-st-2000034545
Apparently, stainless steel A4 is best outdoors and also a bit more resilient to movements, but you should avoid it together with hot-dip galvanized joist hangers? Will there be galvanic currents resulting in rust on the joist hangers? Stainless steel joist hangers are not an option considering the price and the number needed.
Help! Which joist hangers together with which anchor screws? Are there joist hangers for outdoor use?
these are for outdoor use
https://www.woody.se/hus-bygg/bygg/...skor/balkskor-utatvanda-for-trabalk-45-mm-fzv
https://www.woody.se/hus-bygg/bygg/...skor/balkskor-utatvanda-for-trabalk-45-mm-fzv
Best answer
The best option is not to use joist hangers at all. If you need stainless steel joist hangers or similar fittings, you have to make them yourself from bent stainless flat steel. You can also paint them (the galvanized ones, that is). However, regular galvanized joist hangers are made of such thick material that they don't rust right away, even unpainted. Galvanized post bases last a long time even in corrosive environments.
When it comes to screws, it's a completely different story. Outdoors, only A4 (acid-resistant) is completely safe. In coastal areas, nothing else works in the long run, especially when it comes to decking screws. If you can use galvanized coach screws, which require fairly large holes in the fittings, you generally don't need stainless steel.
When it comes to screws, it's a completely different story. Outdoors, only A4 (acid-resistant) is completely safe. In coastal areas, nothing else works in the long run, especially when it comes to decking screws. If you can use galvanized coach screws, which require fairly large holes in the fittings, you generally don't need stainless steel.
Thank you for the thorough response, Justus.
Hangers it is, even though I know they have their weaknesses. It's just a small deck project, so if anything goes wrong, I can always fix it relatively easily.
The material thickness of hangers I find seems to be 2 mm hot-dip galvanized sheet. Do you consider this "thick" when you say it takes a long time to rust through?
I prefer to use A4 screws as I want durability, and the decking will definitely be screwed with this. Do you mean that it's no problem to use A4 anchor screws for hot-dip galvanized hangers? Now we're getting into mixing metal materials and beyond my knowledge...
For example: https://www.velltra.se/product/ankarskruv-a4-48x40-250st-
Hangers it is, even though I know they have their weaknesses. It's just a small deck project, so if anything goes wrong, I can always fix it relatively easily.
The material thickness of hangers I find seems to be 2 mm hot-dip galvanized sheet. Do you consider this "thick" when you say it takes a long time to rust through?
I prefer to use A4 screws as I want durability, and the decking will definitely be screwed with this. Do you mean that it's no problem to use A4 anchor screws for hot-dip galvanized hangers? Now we're getting into mixing metal materials and beyond my knowledge...
For example: https://www.velltra.se/product/ankarskruv-a4-48x40-250st-
Some rust spots will occur, but it will probably take time before it rusts completely. I think A4 screws can be used with most things without risk of galvanic corrosion. Velltra must be the cheapest in the country for screws...
Depending on the construction design, a deck board often ends up above the joist hanger. Since it is then situated "dry," neither the joist hanger's nor the screw's rust protection is heavily burdened, so a galvanized anchor screw would work fine as well.
I agree with @Maximarcus except on the last point. At least here in Blekinge's coastal area, where I live, it's not possible to use galvanized screws outdoors anywhere. At least not if you want to be able to unscrew them again. I guess the conditions are similar in large parts of Skåne. I don't think galvanized anchor screws exist. Before, before the advent of power drills, brass screws were the only screws used outdoors, except for galvanized lag screws. The problem is not new.
Thank you for your continued input.
I don't live by the sea, but here (in Skåne) it rains horizontally due to the constant strong wind over the fields. At least the deck gets the most sheltered spot on the property.
@justusandersson It's almost as if A4-class anchor screws don't exist either. I did find a few when I searched, but most aren't A4, just different surface treatments. Surprising.
I don't live by the sea, but here (in Skåne) it rains horizontally due to the constant strong wind over the fields. At least the deck gets the most sheltered spot on the property.
@justusandersson It's almost as if A4-class anchor screws don't exist either. I did find a few when I searched, but most aren't A4, just different surface treatments. Surprising.
It's probably not that surprising. Most of the use of ankarskruv occurs in internal building constructions, such as the fastening of roof trusses. Many building suppliers do not have A4 classified screws in stock, except for decking screws, because the demand is limited.