The wood foundation must be design for each house. The lumber is treated to fdn .60 standards and is grade stamp too. Wood foundation are design to outlast the home above with over 60 year in testing of treated wood. We have a design web site called www.woodbasement.com Material and hot design information is there. I have 20 years or service in designs for pwf foundations. Need help call us 810-232-5099 Thanks Roscoe Clark Designer.