How do carpenters calculate which exterior panel width to use?

[larsbj]

I don't know, haven't thought that far, the thoughts about it:

Slamfärg:
+ price.
- easily rubs off
- short time until you have to repaint again.

The villa a few meters away is painted with Alcro so maybe I'll use that for the cottage too to make them match each other.

Slamfärg lasts about 15 years and that's not so short considering how little work it is to paint and repaint with slamfärg compared to other paint.

 

[Mikael_L]

If you are using "slamfärg," the air gap is not as critical. It can work just fine without one, as the paint does not block the boards from drying out. (However, you should obviously have sufficient protective eaves then, as it's not a smart choice for houses without eaves).

With a modern water-based plastic paint system, I believe the air gap becomes really important because it's mainly from the backside that the panel gets to dry.

 

[Yrrol]

If I choose modern color and the air gap becomes important, how big does it need to be then?

 

[Mikael_L]

25mm.

Honestly, I can't really say any specific measurement. But I know that the air gap is usually the same as the nail battens - in most constructions - nail battens which tend to be something like 25x50, 28x70, roughly. So about a 25mm air gap seems to work, but I can't say how bad it gets with less, or how much better it gets with more air gap.

edit: It also depends on the climate of the location, how exposed the wall is, and possibly on the wall construction.

 

[Yrrol]

Since Alcro bestå requires a primer first, it will be extra expensive, but they said it provides a more breathable panel. It's silly to take a chance in that sense, but ah, I'll have to think about it a bit.