Choice of solution for "continuous" 45x45 in balcony railing

[Andreas_87]

I have previously built a deck where I used aluminum posts from Wernamo Design with a continuous 45x45.

I now intend to demolish my balcony railing and want to build in a similar design, but these posts are too weak for the balcony.
The balcony already has embedded mounting brackets and my current solution idea is 90x90 laminated timber where I route 25 mm deep vertical grooves for 45x45 placement. In front of this, I will put a 45 rule, also with routed grooves.
At the bottom, a 45x170 to cover the unattractive concrete balcony edge.

What I am considering is the risk of moisture in the routed grooves, is this a poor construction design in that regard?
Are there smarter ways to solve this?

 

[Nissegandhi]

There will be a lot of milling that requires great precision, and since you are milling across the grain direction, you will have plenty of places where moisture can seep in.

 

[Unikt namn]

Have you considered just angle-screwing cut slats between the posts?

 

[Andreas_87]

It involves a lot of milling requiring great precision, and since you're milling across the grain direction, you'll have numerous spots where moisture can be absorbed.

Yes, the milling will be work, but I can handle that; it can be fun to be meticulous sometimes.
Yes, I thought about the moisture but not the grain direction, it feels like it will be a bad solution which I was afraid of.

 

[Andreas_87]

Have you considered just using angled screws to attach cut slats between the posts?

Yes, I've considered it, but I'm worried it might be difficult to get the slats straight with such short pieces? Also, the attachment to the posts might not look so nice, but maybe you could rout a groove along the entire side of the post to make it look better.

 

[Unikt namn]

I have considered it, but I'm worried it might be difficult to keep the slats straight with such short pieces.
Then the fastening to the posts might not look as nice, but you could perhaps rout a groove along the side of the post to improve the appearance.

I imagine short slats are easier to keep straight than long ones.

Since wood is more variable than aluminum, any inconsistencies will be more noticeable.
Picture from my balcony, but I don't notice the seam when I see it, and it's even painted white.

Even if you rout a hole, there's a risk you won't have a perfect fit across all seasons.