There is really not much of a relationship between the width of a tree and how far its roots might spread - probably a closer relationship between its mature height and root spread but even that is extremely variable, depending on soil conditions and moisture levels.

The good news is that if your foundation is structurally sound - no cracks, settling, crumbling, etc. - then the roots should not be a concern. They hit the solid surface and just change directions.

Note that even on this very narrow cultivar, you can often get branches that will extend beyond the 2-3' and be more horizontal than pendulous. I would allow a good 5' away from the house for planting, more if possible.

Thank you! I may have to go with someone else. I wanted to get within 2 feet of the foundation because of a pathway next to it.

The repeatedly promised 2-3 ft. wide is absurdly narrow for what probably isn't a dwarf cultivar at all. Another open and drooping form being called 'Van Den Akker' (Van Den Akker grew it as 'Pendula') was over 70 ft. tall at an office building near Seattle (USDA 8) some years ago. Unless your house is absolutely monumental such plants are much too much for foundation plantings.

Take a look at Taxus baccata (English or Irish) yew varieties like 'standishii' or 'Beanpole'. Both are very narrow and easily pruned to shape, unlike most conifers. If a yew ever gets too large, it can be hacked back to sticks and still regrow.

Thank you Michael. That is one that I was also considering after seeing it at the nursery.