Rafters and floor joists should be installed with the:

When it comes to the installation of rafters and floor joists, having the crown facing upwards is critical for several reasons. The crown of lumber is the natural arch that is often present in a board or beam due to the growth pattern of the wood. By orienting the crown upwards, you take advantage of the natural strength of the wood. This positioning helps to minimize the risk of sagging over time under load, ensuring a more level and stable structure.

When rafters and joists are installed with the crown up, they can better support the weight of the roof or flooring. If the crown were to be positioned downwards, the wood may warp or bend under the weight, leading to uneven surfaces and potential structural failure. Additionally, having the crown up allows for better drainage in roofing applications, reducing the likelihood of water pooling and causing damage.

Moreover, installing rafters and joists with the crown up is consistent with standard building practices and codes, which aim to ensure the long-term durability and safety of constructions. This attention to detail plays an essential role in the overall performance and integrity of a building structure.