Can treated lumber be used for floor joist?

Yes, treated lumber can be used for floor joists, particularly in areas where moisture exposure is a concern, such as basements or near ground level. However, it's important to ensure that the treated lumber is rated for structural use, as not all treated wood is suitable for load-bearing applications. Additionally, proper ventilation and moisture control should be considered to prevent potential issues with decay or insect damage. Always check local building codes for specific requirements.