Help Calculating Floor Area Ratio

[DerekRobertson]

I am currently creating map of floor area ratio of each parcel of land in an area. Floor area ratio is the total floor area of the buildings on a lot divided by the total area of the lot of land they're on. I've used building height to estimate the number of floors and then multiplied that number by the area of the building footprint. the problem I am running in to is that there is often more than one building one a given lot and I can't find a way to group them and add their total floor areas before dividing by the area of the lot.

I have tried using intersect, spatial join and merge tools all with no success. Is there a simple way to do this that I have missed.

[DerekRobertson]

In case anyone sees this and has the same question I talked to some GIS specialists at school they helped me figure it out.

You have to convert the buildings to points then use spatial join. Within spatial join the target is the new building point layer. The I had to right click on the total floor area value I was suing and set its join rule to sum. I also deleted all the other irrelevant fields to ensure they did not spawn repeats of the parcels as was the problem I had before.