Anyone who complains about the weather in San Diego should be forced to move! It's been such an ideal place to build, very rarely anywhere near unbearable. There were a few week ends in May that the tiny house had to get through some rain. Not fun trying to tarp a tiny house alone when seeing the black clouds honing in. Just glad I only had to put up tarps a couple times.
Dupont Tyvek was used as the house wrap and fastened with 1" plastic round cap nails. All seams were tape by using Tyvek house wrap tape. The wrap was installed from the bottom to the top. The top piece overlapping the bottom piece prevents water from coming in contact with your sheathing. The same bottom to the top construction method was also used to install tar paper on the roof. I used #30 paper. I applied one layer of paper to the 9/12 pitch roof and 2 layers to the 4/12 pitch roof since it will have a greater tendency for water to soak in. The paper was fastened with 1" plastic round cap nails.