Attach posts to plinth

[T-G-B]

What type of screw should be used to fasten impregnated posts in concrete piers?
All the existing posts set up with us are attached with bolts and nuts in the pier. It's hard to determine the surface treatment of these bolts. The posts are painted and not impregnated.
Today I have driven many miles, visited four hardware stores, and searched for such hot-dip galvanized bolts. They are nowhere to be found except at one store where they cost 40 SEK each. We're talking a price per kilo that's higher than for fillet steak and hot-dip galvanized is certainly not an exclusive material. Moreover, there is more metal in the pier that costs less.
Do regular galvanized ones work, or do they rust away in a few years?
Or do you have to use French screws, they seem to be available hot-dip galvanized everywhere.

 

[larsbj]

Biltema has some stainless ones. And Swedol also has surface treatment for outdoor use.

 

[T-G-B]

Biltema's stainless is slightly cheaper than the construction company's hot-dip galvanized. However, it is still 3-4 times more expensive than regular galvanized.
How long does an electroplated 10 mm bolt last outdoors, and can it be replaced? If it rusts within a year, it becomes uneconomical.

 

[larsbj]

Biltema's stainless steel is slightly cheaper than the construction company's hot-dip galvanized. However, it is still 3-4 times more expensive than regular galvanized.
How long does an electrogalvanized 10 mm bolt last outdoors and can it be replaced? If it rusts in a year, it becomes uneconomical.

Slightly cheaper? There's a difference between 40 kr and Biltema's stainless 12 kr.

It depends on what you mean by lasting, they might start rusting in 1-5 years but they will probably last your lifetime.

 

[Swamp]

Yes, they look nice for three to four years but probably won't rust apart in 25.

 

[T-G-B]

Okay, is it something that significantly affects durability? A bit of surface rust is no problem. It should be easier to replace the bolts than to replace the foundation bracket if it rusts. 25 years sounds like an okay time. Regarding the price comparison with Biltema, I calculated the entire package, needing five packages of bolts and three packages of nuts. Strange that the numbers in the packages aren't the same.

 

[Swamp]

I have only opinions and beliefs of 25 years, but after 5 years outside but under a roof, my electro-galvanized Biltema carriage bolts have only become a little dull.

 

[pelpet]

A regular hot-dip galvanized French screw should work fine, right?

 

[T-G-B]

French screws seem to be at normal prices, but they are too long. The posts are 70 mm, so you must have short screws, otherwise they'll collide in the middle? Or should you attach the post with only one screw on each side?

 

[JOW]

Too long?
There are many different dimensions and lengths of French wood screws.

 

[Swamp]

I usually screw in my nåra degrees at an angle so they don't collide.

 

[corre]

Common electro-galvanized carriage bolt, M10. Will last longer than the deck.
If you definitely know you will need to loosen the bolts, you can apply bitumen compound on the ends.

 

[Krejtos]

Recommend French wood screw for optimal results.

 

[corre]

Recommend French wood screws for optimal results.

They are far from being recommended today. There are better options that hold better. Carriage bolts as I suggested or screws like Essve Cut or similar.

https://www.essve.se/essvese/sv/pro...xkantshuvud-87502-46/träskruv-hex-corrseal-46
https://www.heco.se/sortiment/trainfastningar/traskruv-sexkant/traskruv-hexagon-protect-4.html