Which type of slat for trellis?

[Tovin]

I am going to build a trellis that will be 1.8 m high and 4 meters long. The posts will be 70x70 and placed 2 meters apart. Between them, I am planning on horizontal slats with a width of 45mm.

The question is whether I should use 22x45, 28x45, or 45x45 slats? I don't want them to twist after a year.

 

[Joacimz]

I have installed 45x45 on my trellis. Like you have, I planned for about 2 m between the posts. Now I have 90x90 posts with a vertical 45 onto which I have screwed the horizontal 45 slats. Not only did I achieve a smooth appearance, but it was also difficult to get 4 m 45x45 that were straight enough to look nice.

 

[andersda]

I would have taken the cheapest one if the local Kulturråd hadn't had objections...

 

[Tovin]

I would have taken the cheapest one if the local Kulturrådet hadn't had objections...

Do you mean that there won't be any difference in torsion in the above dimensions?

 

[nodden]

Thinner than 45x45 with a center-to-center distance of two meters will definitely twist and bend. If you want a thinner dimension than 45x45, you should reduce the center-to-center distance of the posts.

 

[andersda]

First and foremost, I am stingy.

And yes, I think the difference is small.

 

[justusandersson]

The deflection due to self-weight is entirely comparable among the three dimensions, 22x45, 28x45, and 45x45. The truly decisive factor is the wood quality. 22x45 and 28x45 from decking boards and 45x45 as pre-cut battens all maintain a very low wood quality, making the material less suitable for the purpose. I would look for a board (45x145 or wider) of C 24 grade that was truly straight-grained and dense. Then I would cut the slats with a plunge saw and guide rail. I believe 28x45 is an optimal size considering the available fastening material, but all dimensions are probably sufficient.

 

[Tovin]

Thank you for your suggestions.
If you place a vertical rib between the posts, which is not anchored in the ground, but only used to screw the ribs into, would that make a difference?

 

[justusandersson]

Yes, marginally for the worse, as it increases the load on the ribs.

 

[Tovin]

Yes, marginally for the worse, since it increases the load on the ribs.

Ok, I understand. The other posts are cast in the ground. But if I let the standing ribs rest on paving stones instead. Would that prevent twisting more?

 

[Tovin]

I have used 45x45 on my trellis. I have about 2 m between the posts as you have planned. Now I have 90x90 posts with a standing 45 which I have screwed the horizontal 45 slats into. Partly I got a smooth look and then it was difficult to get 4 m 45x45 that were straight enough for it to look nice.

The standing slats aren't visible in the picture, right?

 

[Joacimz]

The vertical slats aren't visible in the picture, right?

I don't have any vertical slats, only horizontal ones. If you're going to have both vertical and horizontal slats, you might want to reduce the thickness of the slats.

 

[Tovin]

[image] I don't have any vertical slats, only horizontal ones. If you're going to have both vertical and horizontal, you can probably decrease the thickness of the slats somewhat.

Ah ok. I thought you had a vertical slat between the 90 posts to reduce the cc measurement.

 

[Hallb]

[image] I don't have any vertical slats, only horizontal ones. If you're planning to have both vertical and horizontal, you might be able to use thinner slats.

Hi Joacimz

Your dialogue here is helping me with a similar project right now
How have the slats held up over the years? I'm also planning to use 45*45 with about 2m.
It looks like there might be shorter distances between the posts than 2m in your picture, but maybe that's just an illusion.
Thanks!