Does anyone know where to find span or load charts for hardwoods such as Ipe (Brazillian Walnut) and Tigerwood? My husband and I are building a home in which we want to place on open stair using two steel stringers and Tigerwood or Ipe treads. I know we need to use boards thicker than 1" to span between the two supporting brackets, a distance of about 34", but how much thicker I cannot seem to find anywhere! Any help would be appreciated. (and yes, we know we have to have something going across the opening to make it smaller than 4" wide!) Thanks!!!!

i would call a stair manufacturing company, it may be difficult to source the lumber you need due to the thickness and length and specie required. My stair company quit making ipe treads all together because they are very difficult to glue up properly and have stay together long term.