035. Design consideration: roof and facade

There are so many details of the house under consideration right now that it doesn't make sense to talk about them until we come to some sort of agreement. I'm going to try to write updates as we get close to decisions, to keep a record of the evolution of the process. First up, a discussion of the choice of roof and siding material.

The unusual angular shape of our house demands a smooth transition between the roof and the walls. Ideally, the cladding should be of the same material and this limits the choice to slate, metal or fiber-reinforced cement board[1]. Factor in the cost, and only the last option remains.

In Switzerland there is only one[2] supplier for this material: Eternit. Eternit cladding stock is composed (by volume) of 40% Portland cement, 11% limestone powder and similar, 2% reinforcing fibers such as PVOH[3], 5% process fibers, 12% water and 30% air in the form of pores. The precursor to this material used asbestos fiber, but since 1991 all Eternit products have been asbestos-free. For more information on asbestos cement, see the report at the link at footnote 2.

I haven't been able to find a good example of an unconventional house completely clad in Eternit boards in a way similar to what we're considering, so below are a couple of examples in slate where the roof-wall differences are eliminated. The details here are not important (for example, our house will definitely have gutters), the point is that the same material covers all the surfaces and the format of the tiles is uniform over the two building elements (roof and walls).

Figure 26. House in Wallis by Nunatak Sàrl Architects[4].

Figure 27. House in Basel by Luca Selva Architects[5].

---

[1] Faserzement in German, I'm not sure of the generally accepted English translation. Fiber cement board and fibrated concrete are some of the terms I've come across.

[2] An Austrian named Hatschek invented fiber cement (using asbestos) and patented it in 1901. He licensed the production method to only one manufacturer per country and it seems to remain that way. More information can be found in this report which deals with the asbestos aspect → The Tragedy of Asbestos

[3] PVOH is a synthetic polymer → Polyvinyl alcohol

[4] Details at ArchDaily → Zufferey House

[5] Details at ArchDaily → House in Lupsingen