Hi Loreta, it really depends on the material and how often it gets replaced during the lifetime of the building. While it’s possible to model salvaged materials, for items that usually get replaced a few times over the LCA study (i.e. wall/floor tiles), it can be difficult to ensure that the items will be replaced with salvaged materials again. So the benefit associated with that salvaged material is very small in comparison with the rest of the building impacts and essentially pointless to model for the amount of benefit it brings. For timber flooring which can and usually lasts the life-time of the building, we have a recycled timber floorboard template that you may use.
So my advice would be that if you are to use salvaged materials, go for items that form the structural or permanent construction of the building such as structural timber, steel beams and bricks.