Verifying square footage and how not to waste $400

BEWARE OF THE TRAPEZOID!

When we bought our house the lot was advertised as 8514 sq ft.  At the bottom of the brochure, in tiny eight point font was the disclaimer: Information deemed reliable but not guaranteed.  These six little words are a get-out-of-jail free card for the seller in case any of the data is inaccurate (which it often is).  We had two conflicting reports on the lot size:

Santa Clara County assessor records: 8514 sq ft
City of Palo Alto parcel report: 8383 sq ft

The reason square footage matters is because the city uses lot size to determine the maximum allowable floor area of your house.  The footprint of your house is also bound by setbacks which mandate the distance the house must be from the edges of your lot.

Palo Alto Allowable Floor Area Ratio*:
45% of the first 5000 sq ft plus
30% of the balance of the lot
Standard front & rear setbacks: 20 ft
Standard side setbacks: 6 ft 

This maximum allowable floor area includes the square footage of the garage, so if you want a two-car garage, you have to subtract 400 sq ft from the total.  (However, when you go to sell your house, the garage is technically not supposed to be counted as part of your livable square footage).

Here are the two calculations for our allowable floor area:
8514 lot = (0.45 x 5000) + (0.30 x 3514) = 3304.2 - 400 garage = 2904 sq ft house
8383 lot = (0.45 x 5000) + (0.30 x 3383) = 3264.9 - 400 garage = 2865 sq ft house

We decided that 40 additional square feet was material to us, so I started looking for ways to verify the lot size.  Apparently, inaccuracies are common when land parcels are irregularly shaped like ours.  I was told that in order to change the official records, the city requires a report by a licensed land surveyor and was referred to a civil engineer who works in Palo Alto.

Our $400 big fat yellow sheet of nothing.

In retrospect, this is probably where I should have slowed down and done a bit more research.  But no, I was on a mission to get my precious, precious square footage so I didn't ask questions, I simply sought an expert to fix the problem and the civil engineer seemed to fit the bill.  I explained to him the situation and the conflicting reports.  A jolly yet garrulous fellow, he rambled on for a while then offered to do an area survey for $300-$350.  Not really knowing what I was signing up for, but wanting it to be done already, I said go for it.  A few days later I received a bill for $400 along with a hand-typed document on yellow bonded paper with green letterhead certifying that our property is 8,383 square feet.  Wha wha.

Feeling certifiably stupid, I decided to learn more about what you can do to avoid paying $400 for big fat sheet of nothing.  Here are my recommendations:

1.  Gather all public records for the property
You can access Santa Clara County property records and parcel maps online.  The county's parcel map doesn't have square footage but it does show the dimensions which you can compare against city records.  Palo Alto allows you to request a parcel report online.  The Palo Alto report includes the lot and house square footage as well as details on what you're allowed to build on the property (maximum floor size, height allowances, setback information, etc).  I would do this before making an offer on a property to ensure that there are no surprises.  By comparing the records, you might find the source of any errors.

2.  Talk to the city planners
Visit the building department to get as much information on the property as possible.  Ask for any background on how the square footage was calculated and their confidence level in it (it's quite possible that the city or a previous owner has already done an official survey).  Gathering this information is free and it gives you a chance to get to know your city planners.

3.  Call the county assessor
Call the county assessor's office and ask to speak with the assessor assigned to your property.  Ours was very friendly and helped me understand the tax implications of remodeling vs. building a new house.  He also explained that property tax is calculated based on the market value of a parcel, not the square footage, so their records are often just rough approximations.  In our case, they likely took the average length and multiplied it by the average width to come up with 8514 sq ft--not exactly precise, but close enough.  When I told him we calculated it at 8383 sq ft he agreed that it sounded correct and made an update to the county's record.  Unfortunately errors of less than 1000 sq ft do not lead to a property tax adjustment, so we didn't really gain anything here.

4.  Get a topographic survey done first
The city of Palo Alto requires a property survey performed by a licensed land surveyor for new homes or any construction done near setback lines.   The surveyor goes onsite and records property lines,  placement of the fences, trees and easements, so you will get actual measurements of your usable lot.  Since it's required, you might as well get it done before ordering a square footage calculation.    It turns out Alan's yellow paper certification was simply a calculation based on the lot measurements from a publicly available sub-division map.  Had I realized this at the time, I would've ordered a topographic survey then hired my husband to do step #5.  [Update: No need to hire husband.  The topographic survey includes a lot area calculation. Skip to step #5 only if you don't plan on ordering a topo survey.  Click here for a referral to a great Bay Area land surveyor.]

5.  Do your own rough estimate
Once you have accurate measurements for the property, brush up on your geometry skills and do your own estimate.  Divide the property into rough triangles and squares and calculate the total area this way (or bake cookies for someone who will).  If your calculation comes close to what the city has, skip the yellow certificate step and save yourself $400.  If it's significantly more than what the city records have, it probably now makes sense to shell out for an official report.

Bonus tip:  If you do decide to hire someone, get a project quote in writing.  The yellow certificate cost $400 as opposed to the anticipated $300-$350 because the civil engineer and I had differing recollections of what we agreed on.  In the end, I chalked it up to a fifty dollar dummy tax and a lesson on what to look for when hiring contractors (more on this later).

Update: Out of curiosity, I just had the husband do a rough estimate.  He came up with 8165 sq ft confirming that I shouldn't have ordered the yellow certificate.  Now I'm out $400 *and* a plate of cookies.

* Addendum: You can find the full specification for allowable home square footage in the Palo Alto Zoning Ordinance Technical Manual for Single-Family Residential Zones:  
1. FLOOR AREA RATIO (FAR) Existing Regulation(s): The total gross floor area on a single family lot shall not exceed 45% of the first 5,000 square feet of lot area plus 30% of lot area over 5,000 square feet.  The total gross floor area for the principal structure on an R-1 lot cannot exceed 6,000 square feet.  Included in the FAR calculation are all floors of the main residence, stairs at all levels, covered parking, accessory buildings of more than 120 square feet, and attached or detached exterior spaces more than 50% enclosed  and covered (e.g. enclosed porches).  Floor area is not counted for basements where the first finished floor is no more than 3 feet above grade.  Additional floor area is also counted for tall building volumes, as follows:
• A second floor equivalent area is added to the total floor area where the distance from the first floor level to the top of the roof directly above is 17’ or greater.
• A third floor equivalent area (third floor equivalency) is added to the total floor area where the distance from the first floor level to the top of the roof directly above is 26’ or greater; however, up to 200 SF of third floor equivalent area is exempt.
"Gross floor area" (18.04.030) (65) (A) means the total area of all floors of a building measured to the outside surfaces of exterior walls.