I don't normally prewash fabrics, but I would for a Cathedral Windows quilt. This is because a Cathedral Windows quilt is fabric only -- no batting. It might be a good idea to make a sample without prewashing and another sample with prewashing, just to see what the quilt looks like after washing. I don't think the "puckery" look I like in quilts made with batting would translate to a Cathedral Windows quilt.
Has anyone here made a Cathedral Windows quilt?