Pull together two decking boards 28mm

[AG A]

As mentioned, buy or borrow a number of clamps. Then apply wood glue (for outdoor use) between the boards, and tighten with the clamps. Screw with strong wood screws, with slightly larger heads.

 

[Derbyboy]

Is this a wood glue?

https://sanojtape.se/products/casco-cascol-tralim-utomhus-outdoor

 

[TheImprovisor]

Curious question: What is the reason you want double boards? Isn't one enough?

 

[Derbyboy]

Good question!

1) avoids screw heads on the top side
2) becomes stiffer - hopefully avoids "sag" between the posts
3) Becomes more grip-friendly because the lower is split to 105-110mm
4) Visually more appealing than 1 piece of 45mm
5) I usually complicate things
I have probably thought wrong but oh well

 

[Grannens Häck]

Have you considered something like carriage bolt with a dome nut or something similar? It sticks out but is rounded.

 

[AG A]

Is this an assembly adhesive?

[link]

No, that is regular wood glue, for outdoor use.

 

[TheImprovisor]

Good question!

1) avoids screw heads on the top side
2) becomes stiffer - hopefully avoids "sagging" between posts
3) Becomes more grippable since the lower part is split to 105-110mm
4) Visually more appealing than 1 piece of 45mm
I have probably thought wrong but oh well

Point two is good.
Point one I don't understand. Don't you attach the handrail from the side?
Point three: Personally, I appreciate a handrail that can be grasped around, not just over.
Point four: That is also an aspect to consider.

 

[MathiasS]

construction adhesive (for outdoor use)

Will it really work on pressure-treated lumber that might not be dry yet?

 

[Derbyboy]

No, that's regular wood glue, for outdoor use.

Construction adhesive = assembly adhesive?

I have previously used PU glue to screw glue studs outdoors

 

[Derbyboy]

Point two is good.
Point one I don't understand. Don't you pull the handrail from the side?
Point three: Personally, I appreciate a handrail that you can grasp around, not just over.
Point four: That is also an aspect to consider.

Difficult to achieve a handrail that you can hold around, it would have to be like a pipe then...

If I only have a handrail, it’s impossible to avoid screw holes from above.

I have a distance of 153 cm between two posts. There's a risk that a plank/handrail will start sagging between the posts after a while/year.

 

[Derbyboy]

Have you considered something like a carriage bolt with a dome nut or something similar? It sticks out but is rounded.

I don't think it will be visually appealing, plus I would need a lot of carriage nuts

A bit too punky!

 

[TheImprovisor]

Difficult to get a handrail that you can grip around, it would have to be like a pipe then.....

If I only have a top rail/handrail, I can't avoid screw holes from above.

I have a distance of 153 cm between two posts at the longest. There's a risk that a plank/handrail might start sagging between the posts after some time/year.

Aha. You are going to place the handrail on top of the posts, not on the side?

 

[Derbyboy]

Yes exactly, doesn't one usually do that?

 

[TheImprovisor]

Well, exactly, doesn't one usually do that?

Yes, it is probably customary, but since the boards you are going to use are quite wide, I assumed you would screw them into the posts from the side (see image for example)
and therefore drew strange conclusions. My bad.

 

[Grannens Häck]

I don't think it will be visually appealing, plus I would need a lot of vagnsmuttar

It's a bit too punk!

I probably don't understand at all how you intend to mount it, you're not supposed to screw from above, right?