I have heard that there is a database for estimating the root spread of a tree given its height and crown. I realise that this will be varied by obstacles to roots but it would be useful for me as an architect in assessing whether i need to consider a tree's welfare

Thank you

To my knowledge, there is no chart for estimating root spread. It is much too dependent on other environmental factors, including species, soil depth, texture and nutrient content, moisture availability, etc. Even plant stocking and shade can have an effect. Any chart would probably have to be developed on a local basis.

Within a given species, there are some genreralizations that can be made for root development, however.