Hello Michelle, this is an excellent question with a complex answer :)
1) New construction, by design, usually has an understated monthly that has to be adjusted upward after the HOA is turned over from the builder to the residents. The low amount helps the builder sell them, and then the HOA of residents determines the real amount by the method shown below. If they do not do this within the first year or two, then there is sure to be a special assessment somewhere down the line.
Note that until recently, WA Law did not require part of this method, and recently changed the law to some extent, but expect to see the laws draw all HOAs toward better accuracy using the method below.
2) For an existing complex, once all units are sold, the monthly dues are calculated annually using this method.
a) Annual expenses divided by # of units or total square footage, equals Part 1 of monthly dues
b) A Reserve Study is done to determine the replacement cost of all "major components". Cost per item is divided by the life expectancy of each Major Component, and then divided by the number of units or total square footage and that equals Part 2 of the monthly dues
Monthly dues equals the total of Part 1 plus the total of Part 2 . A ballpark might be $150 a month for annual maintenance and $100 for reserves, equals $250 a month in annual dues.
Some that you see up at $375 are a result of the owners not changing the dues from the $.79 the builder placed, as soon as the HOA was turned over to the residents. The longer they wait to make that change, the higher the monthly will be, as they are playing "catch up". If they wait until something needs to be replaced, then there will be a large special assessment AND a dues increase, both.
>From a value perspective, people like the dues to be no higher than $299. When they see $300+, they want more amenities. It's psychological, of course, but many buyers will balk at $315 vs. $295. It's not about the twenty dollar difference. Seeing that $300 + just feels like "too much" and does impact property values.
For larger complexes with more amenities that are already $300 something...going to $405 is a killer. Same psychological reaction. Boards should always manage complexes to keep the number within the same first number as much as possible, knowing that going to $315 from $295 will impact property values.
Still, a special assessment can push values down much further than a higher monthly...so following the formula regarding Part 1 an Part 2 is the best method.
As to per unit or per sf, that will be determined in the CC&Rs. In my experience, properties in Downtown Bellevue and Downtown Seattle will be different than interior complexes. Many of the high rises with views have much larger units at the top, and the units vary in size dramatically as you approach the lowest of floors. That is why they use square footage. A complex in Kirkland on 7th Ave that have only 2 or 3 sizes of units, will likely have three fees that are "tied" to the size of the unit, but not specifically square footage driven.
The problem with being square footage driven is the "as built" does not come out exactly as planned for each unit. The HOA inherits a huge headache if they use square footage...so best to adjust dues by size of unit...but not pin it to specific square footage numbers. That becomes a nightmare.
The builder may say $.79 per square foot, but usually that says (approximate) and when implemented at closing, the dues are a set monthly and not a square footage quote.
If that confuses you more than it helps you :), please feel free to call me