Propagation tanks

[Aquattro]

I found this.....

TGI joists are made with wood on the top and bottom but have a composite material between the wood that allows them to be manufactured perfectly straight. Their design prevents warping, providing a consistently flat surface to which sub-floors and finished flooring are attached. When the floor joists are perfectly flat, and there are no gaps between the joists and the sub-flooring, the finished floors are sturdy and have no creaks.