Hi Henryk, thank you for your question! All the exterior beams and rafters here are S4S (smooth on four sides) Douglas Fir. Cypress and cedar can also be great exterior woods. We often use Messmer's U.V. Plus Natural Wood Finish. They have some beautiful colors, we like "Driftwood Gray" but in this case we used "Natural". Let us know if you have further questions, we've been designing porches in Texas for nearly 50 years. Good luck with your project!