Nandina is extremely flexible in its site conditions. Will grow well in anything from full sun to almost full shade but coloring will be lacking the more shade it receives.

I'd have more concerns about winter hardiness....it will be marginal in your zone. You can expect some leaf drop at temps around 10-15F and stem dieback at around 0F. Below zero survival is questionable. The arborvitae would be a much safer bet.

remind us where you are with a little more specificity ...

it really boils down to how close to the foundation you mean ... and how dark it really is ... it is very hard to not make wild generalizations when discussing what shade means ... it can be anywhere from a dark grotto ... to a place where its rather bright.. even if the sun is not direct ...

one way to try to figure it out.. is what is growing there now ... e.g. if grass already wont grow there.. its pretty dark .... not much is going to thrive .....a pic might show us something ....

also ... is it open sky above.. or is there tree shade making it even darker ...

the bottom line is usually to just try it.. and give it a year or 3 ... and then move it or get rid of it.. if its not performing to expectation ... only downside to that.. is if you insist on multiples to start.. then it might get to be an expensive experiment ...

ken

I also don't think the Nandina will be winter hardy in USDA 6b.

All the websites state that Nandina Domestica is hardy from zones 6-9. I can testify to the accuracy of this. Here in South Central KS (zone 6b) there are several specimens of the dwarf varieties of Nandina Domestica that are planted out in the open with no protection from the wind. They winter very well here as evergreen shrubs. They don't lose any leaves or suffer die back. They do turn very pretty shades of red, orange, and yellow; usually all on the same plant, throughout the winter months.

Ken, in answer to your questions, the plants would actually be right in front of a concrete porch that sticks out from my house about six feet. The concrete slab is about 18" high. It is not deep afternoon shade as the shade is cast by the house with no trees around to offer additional shade. Bermuda grass, chrysanthemums, and hydrangeas flourish there. Our biggest challenge in this part of the country is the drying wind, which we have all year long.

They winter very well here as evergreen shrubs

For how many years? And through what kind of cold?

USDA Hardiness Zone designations are often based on incorrect concepts of what the Zones mean - in this case the mistake could perfectly well be "Nandina dies at 0F so it's hardy to USDA 6b" because the average annual minimum temperature range given for 6b is -5 to 0F. With "all the websites" merely parroting the same erroneous conclusion.

I've seen more than one clone of Nandina freeze to the ground here in USDA 8, so I do have to wonder about no damage being usual in USDA 6.