I have questions on fire safety. I lost some close friends recently to a fire. I had never thought about it before.
>Is it firesafe?
>WikiHouse is not really any different from most kinds of 1-3 storey buildings with timber roof, floors, or internal walls, in that the building needs to be designed with adequate means of escape, and the chassis needs to be reasonably protected from catching fire. This can usually be achieved either with a plasterboard internal lining, by using a non-toxic fire protection coating, or by installing a basic sprinkler system.
>If you are building several adjacent houses, located close together in a row, you will usually need to use an external fire barrier material to prevent fire spreading from one building to the next.
https://www.wsj.com/articles/wooden-skyscrapers-are-on-the-r...
https://www.thinkwood.com/mass-timber
https://www.naturallywood.com/topics/mass-timber/
https://www.ijpr.org/housing/2022-09-04/oregons-mass-timber-...
And regarding fire retardation - Cross Laminated Timber Fire Testing from the Forest Products Laboratory and US Forest Service - https://youtu.be/HuVTCOmRGd0
As to the cost - https://www.fs.usda.gov/treesearch/pubs/62676
> Based on commercial construction cost data from the RSMeans database, a mass timber building design is estimated to have 26 percent higher front-end costs than its concrete alternative.
And from the paper:
> The resulting TLCCs of the two buildings under these scenarios are shown in Table 6 and Figure 5. From the results of these scenarios, it was found that the TLCC for the mass timber building would have a cost advantage with its longer life span (100 yr) than the concrete alternative (75 yr) when other factors are the same (see Scenario S0 and S4), and the higher front-end cost (value) showed an even greater advantage of 7.0 percent difference (Scenario S4). When the life spans of the two buildings were the same, the end-of-life cost or value of the mass timber building was not able to be offset by the higher front-end costs (see Scenario S1 [12%], S2 [6.7%], and S3 [5.9%]). In this case study, the two buildings were designed to be functionally equivalent. Thus, we assumed the same operational utility and maintenance during the building-use stage. No impact from these parts were considered in the TLCC calculations on the cost- performance for the comparison of the two buildings. But if there are energy savings discovered in the new mass timber buildings, the LCC analysis would reveal more cost benefits (Liang et al. 2019).
I can't find any sources that agree with your cost assessment... instead: https://www.bdcnetwork.com/5-myths-about-cross-laminated-tim...
> When considering the total in-place value of a CLT system, it is cost competitive to other plate building materials. But you also need to consider all the value added benefits:
> • More savings can be found in the reduced installation cost, usually 50% cheaper than installing other plate materials.
> • With an earlier project completion date, you are open for business sometimes months ahead of schedule.
> • The building structure will weigh less than half the weight of other construction types, so the foundation costs less money.
> • Job site safety is dramatically increased due to the prefabricated CLT panels and usually the only power tools are pneumatic drills.
> The intent of cross laminated timber is not to replace light-frame construction, but rather to offer a versatile, low-carbon, and cost-competitive wood-based solution that complements the existing light frame and heavy timber options while offering a suitable candidate for some applications that currently use concrete, masonry, and steel.
And the beam size gets into "don't design a concrete building and swap in mass timber". https://www.woodworks.org/resources/creating-efficient-struc...
Another aspect to the beams is that the structural elements are often left bare for aesthetics ( https://uploads.map-dynamics.com/0518_Structurlam-U.S.-Mass-... ).
Table 6 in https://www.structurlam.com/wp-content/uploads/2019/04/Struc... gets into the snow loads and I don't know enough engineering to be able to do a comparison between mass timber and other building approaches.
The main thing to consider is this isn't a "it costs 2x" or "it uses 2x more materials" because they are different materials with different designs. If comparisons are to be done, they should be done at the building level ("it cost X to make a N story building with M square feet per floor" and "building A had a sustainability rating of P while building B was rated at Q with a difference in cost of Z%").