I am building a facade, vertical tongue-and-groove paneling against horizontal nailing battens and ventilation battens behind to achieve the correct air gap. On the long sides of the house, one can simply leave a gap at the eaves and add an extra insect net (in addition to what might be installed against the roof's air gap), but how is it usually done on the gables? I've never seen anyone leave a gap/opening at the top there. Do you just ignore it? The air gap's function is to dry out any built-in moisture, but how effective is it if it's sealed at the top? It should be similar to creating a ventilated parallel roof without having ridge ventilation.
Or is it just that because the wood facade is more moisture-permeable, it's expected to ventilate through it?
Or is it just that because the wood facade is more moisture-permeable, it's expected to ventilate through it?
No one has any thoughts on this? One more thing I'm pondering in the same area is insect netting. On the gables, we install drip flashing at about 3m height to avoid having to splice the vertical paneling. Should insect netting be placed under the drip flashing and a rodent barrier behind the paneling on the top side?
I haven't really considered this question closely, but when I think about it, I can't recall ever noting that there is an air gap between the facade panel of the gable and the roof. However, I think the question is entirely justified if the panel is supposed to function as a pressure-equalizing layer. In that case, leaving a small gap open towards the roof would be advisable. It might work similarly to a shadow gap indoors. Alternatively, you could place a molding between the facade and the roof, but with a gap of course. I think this latter option is worse as it's likely more noticeable that it doesn't fit tightly against the roof or wall.
For question 2, I unequivocally answer yes. If there are gaps or openings where insects and rodents can get in, they should be secured.
For question 2, I unequivocally answer yes. If there are gaps or openings where insects and rodents can get in, they should be secured.
Thanks for the reply @Oldboy. Most of the wall automatically gets an opening at the top due to the drip edge. But placing an insect net there becomes a bit tricky. The drip edge is on a 45x120. Maybe I can attach the net between that and the outside of the nail battens. That would seal towards the wall anyway, even if there is a small space under the drip edge, as the battens are a few centimeters away. But better than nothing.
But how to make a neat gap towards the roof with some opening becomes more complicated. I was thinking of setting a trim like 45x45 or a little smaller... just setting it a bit lower with an insect net inside should do the trick.
But surely every house builder with wooden facades has dealt with this. Is there something obvious I'm missing?
But how to make a neat gap towards the roof with some opening becomes more complicated. I was thinking of setting a trim like 45x45 or a little smaller... just setting it a bit lower with an insect net inside should do the trick.
But surely every house builder with wooden facades has dealt with this. Is there something obvious I'm missing?
Long ago, the façade was probably never intended as a pressure-equalizing layer with an air gap behind it, but it was more or less applied directly (log houses). Then it has always been necessary to have nailing battens to attach the panel to houses without a log frame. Facade paneling was probably never an external shell/facade long ago, (before saws came that made thinner planks and boards affordable, mainly in the 1800s(?)), but was added gradually as the old façade deteriorated. The idea of a pressure-equalizing layer is probably quite new. I imagine it has come with the extremely airtight houses that we have been building over the past 25 years or so. Before then, a little drafty air in windy weather was probably not considered a significant problem.
Furthermore, ordinary wooden facades with cover strips/cover boards are not excessively tight at all the joints/overlaps, or for that matter at the end junctions against the plinth and roof. So they have "breathed" regardless. With tongued and grooved boards, the façade is probably a notch tighter, and then perhaps the air gaps are more important.
Furthermore, ordinary wooden facades with cover strips/cover boards are not excessively tight at all the joints/overlaps, or for that matter at the end junctions against the plinth and roof. So they have "breathed" regardless. With tongued and grooved boards, the façade is probably a notch tighter, and then perhaps the air gaps are more important.
I have thought a bit more and read a bit more, and I can come to a conclusion and answer my own question. The main purpose of constructing the facade in this way is to allow water penetrating behind the panel to be evacuated. This is preferably done downward with the help of gravity. The main purpose is perhaps not to create airflow behind the panel, so therefore an upper opening is not something to focus on. This is my conclusion.
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· Västernorrland
· 12 026 posts
The reason for having an air gap is that nowadays we have dense facade paints. Otherwise, it wouldn't work. In the past, and with timber for that matter, diffusion-open paints were used even on facades. Then you can have panel tight against the back if you want.
I'm also contemplating this issue with the air gap on the gable sides. Building an Attefall house. The front and back are not a problem just as TS writes. But what do you do on the short sides/gables? Do you skip the opening at the top?