Although a CMA is not as detailed as an Appraisal, we use similar methods to determine the worth:
The biggest difference is that with an Appraisal, they use 3-4 Comp's and detail the differences,
and with a CMA we try to match the differences, (3 bedroom, 2 bath, 1450-1650 sqft, single story, pool, within 1 mile...) and we will use as many as 40-50 SOLD houses to show the Median, the Average and the $$/sqft.
If you haven't seen an Appraisal, this is how that works:
Visualize a series of COLUMNS, probably 4 or 5;
The First Column is the SUBJECT HOUSE and the others are COMP's.
Down the page we list FEATURES or FACTORS; such as # Bedrooms, # Baths, House Sqft, Lot Sqft, Fireplace, Pool, Roof, Garage, Fencing. Got it?
Now, in each box created, there will be a VALUE: Lets say the subject house is 915 sqft it would get --- or 0. And the first Comp house has 2500 sqft, it might get -100,000; which means that the house is WORTH $100,000 more because of the square-footage. (It is a negative number because the Selling price of that Comp house was approximately $100,000 more BECAUSE of the square footage and we have to deduct that $100,000 to bring them to equity.) Got it?
Now, lets say that the Subject house has $5,000 worth of new fencing and the Comp house has 25 year old OK fencing.: Then the SUBJECT house would get +5,000 and the Comp. house would get --- or 0.
When you go down the page, and enter everything, you get total Comparative Values on the two houses, which allows for the DIFFERENCES.
The two houses DO NOT have to be literally COMPARABLE, they MAKE then comparable with the VALUES.
So the house next door is larger, so what? They made up for that with the values.
Now, if you understand what I just did, then you will understand why;
1.) Two Appraisals can come so close together, and,
2.) Why the Bank will not listen to you about the results.
and in fact I will give you a third;
3.) If you hire your own Appraiser, he will end up with about the same numbers!
Also, please do not compare/equate the ASSESSMENT with the APPRAISAL: The ASSESSMENT is based on the LAST SELLING PRICE OF THE PROPERTY which might be last year. five years ago, or thirty years ago.
I hope I've helped.
Good luck and may God bless