ᐅ Timber House: Wood Cladding vs. Rendered Facade (Wood Fiber Insulation Panels)

Good morning everyone,

Yesterday we met with the first company concerning our house planning.

It will be a timber frame house.

The company offers two types of exterior finishes: wood cladding (available in several versions) or a rendered facade.

The (standard, not premium) wood cladding costs about €40 more per square meter (approximately $43 per square foot). This results in an additional cost of around €7,000 for our currently very rough planned house.

We are generally more inclined towards an untreated wood cladding instead of a rendered facade. For the following reasons:
- We like the appearance.
- With a good roof overhang, I won’t need to do any maintenance on the facade for about 60 years, so it will almost outlast me. (We don’t mind the natural aging look)
- It is the most natural (ecological) material (German larch).

Now we are reconsidering if this is the right decision. Here are some points to consider:

- How maintenance-intensive is the rendered facade? It uses reinforcing mesh. Can I expect that other than repainting every 10 to 15 years (which we would do ourselves), there is no other work needed? Or is cracking a likely issue? I can’t judge the use of render on wood fiberboard panels.
- We often hear about algae growth on facades of well-insulated houses. Does this typically only affect houses insulated with synthetic materials, or also the type of house we plan? Only mineral-based paint (preferably KEIM or Sto) would be used.
- How much more ecological is the wood cladding really? The material is natural, but the amount needed is noticeably higher than for a rendered facade.

Perhaps someone can share some suggestions or explain their own choice and the reasons behind it.

We do not necessarily want a wood facade, but we find it more attractive and see advantages in the aspects important to us (appearance, ecology, low or no maintenance). The question is whether all these points hold true in reality.

We have also considered a mixed solution: wood cladding under the roof eaves and a rendered facade on the ground floor. Are there any disadvantages to this approach?

I look forward to your replies.

Best regards,
Specki

We chose a pre-weathered wood cladding for our timber frame (see profile picture). Here is our decision process, which might be helpful:

The base insulation board from our supplier is made of polystyrene (Styrofoam). Although the board is much thinner than the polystyrene blocks commonly used on many houses today, we did not want that on our house. Additionally, there are plenty of biocides in the coating to prevent algae growth. So, essentially, we stayed with wood (unfortunately only spruce, rhombus profile). We had seen attractive wood facades in Austria and southern Germany, so we were open to the idea. Solid paint finishes eventually require repainting and hide the wood grain completely, while untreated wood shows very uneven color variations (especially under larger roof overhangs, which my wife doesn’t like). That led us to choose pre-weathering. This finish also contains biocides, but I was not aware of that at the time.

If I had worked with an architect and had complete freedom of choice, I would have chosen real Siberian larch wood and a different pre-weathering glaze (probably water-gray, as the color tone we selected is a bit too dark and uniform for my taste). If I could decide again, I would also have a partial facade in render (plaster) visualized—render on the lower part and wood on the upper part—because I have since seen some attractive variations, and it would have added some visual relief to the two-story building with a gable roof, regardless of the insulation board.

Ecology is a challenging topic for me in a resource-intensive project like house construction. We did make some environmentally motivated decisions (no pellet heating, no fireplace, no polystyrene...), but for the house facade, appearance and practicality were the main priorities.

Thank you for sharing your experience.

Ecology and practicality (ease of maintenance and durability) are our top priorities in this case.

In terms of appearance, we do prefer wood slightly over plastered surfaces, but we are flexible there. That’s why we place strong emphasis on the other two points. For example, if I have to repaint a plaster facade every 10 years, deal with algae growth, and completely renew the plaster after 20-30 years, that wouldn’t be our favorite option. However, if repainting is only needed every 15 years and the plaster lasts for 50-60 years otherwise, then that would be acceptable.

And yes, I fear the question, “which facade is more ecological?” is probably difficult to answer. But maybe someone has some insights on that. We are not interested in “greenwashing.” So just having a wooden facade to make it look ecological... that’s not practical.

Looking forward to more suggestions and comments.

Best regards,
Specki

What is the location of the house? Right next to a forest? In that case, I would be cautious with plaster, as a lot of debris blows onto it and it gets dirty faster. In a typical residential area, plaster is completely unproblematic. After 10 years, nobody usually repaints; 15 years is more realistic, sometimes even longer.

Algae problems are not related to plaster; you get the same issue on brick facades (it’s just much less noticeable). For algae growth, it doesn’t matter whether the insulation is made of aerated concrete, polystyrene, wood, or mineral wool—the effect is the same: it insulates, with no direct contact to the outside air. In my opinion, this is generally a highly overrated issue. I don’t know of any house in this region that has algae problems, regardless of whether it has plaster or brick, polystyrene or mineral wool insulation. Of course, you can find some examples on the internet (but what can’t you find examples for...), but that’s mainly from a small group of insulation conspiracy theorists.

In the end, I would choose whatever you like better visually. Weathered façades tend to be quite polarizing—you either like them or you don’t.

As mentioned, we are visually leaning towards a wooden facade. However, it is not really worth an additional $7,000 to us.
We could just as well live with a rendered facade.

So far, the wooden facade had the advantages:
- No maintenance required and more durable compared to a rendered facade
- More environmentally friendly

Now we want to verify these two advantages a bit more to see if we might be on the "wrong track" with wood.
Once we have that information, we can decide if the extra cost is worth it for us.

Perhaps as an additional note: When we discussed the type of wooden facade we wanted and how to treat it, we spent a lot of time browsing through the professional blogs of the Swiss timber builders Renggli, as they provide extensive photographic material showing weathering over certain time periods (larch wood after 1, 3, 9, and 10 years), along with many other well-founded pieces of information.

For completely naturally weathered facades, I was concerned that poorly exposed sections might turn entirely or patchily black, while areas under the eaves, for example, would hardly change.