FairFAR.org

Please note that we’ve updated our calculator to reflect the latest draft ordinance language.

We’ve just completed our online calculator for the proposed new FAR and building coverage standards.  Please give it a whirl, though we recognize that determining the actual figures that go in the different boxes is beginning to resemble doing your own taxes!

But remember, the online calculator doesn’t try to model the effects of the new bulk plane ordinance on your home, and that may immediately put many existing homes in violation of the new standards.  Frankly, only an architect and land surveyor could model the effects of that part of the ordinance with any certainty.

The formulas we use come straight from the proposed draft ordinance language in the 26/30 June 2009 staff memo, attachment A.  We observed that there are numerous other formulas scattered throughout the various attachments to the current staff memo, and we suspect there are some errors in those tables, but that is the current proposal and we’ve implemented it faithfully.

One of the more interesting findings that we observed in building the online calculator was that even modest homes can easily run afoul of the new building coverage standard.  Try the default figures to see an illustration of how it can catch even small homes.

If you’d like to check our mathematics and logic for accuracy (hey, it was just written by a couple of guys with PhD’s who write software for a living), here is the relevant part of our source code.

function calculate() {
global $lotsf, $maxsf, $maxBC;
if ($_POST['zd'] != "RMX1") {
# RL-1 formulas from attachment a
# FAR rules
if ($lotsf<6000) { $maxsf = $lotsf*0.5; }
elseif ($lotsf<14501) { $maxsf = $lotsf*0.174+1902; }
elseif ($lotsf<20501) { $maxsf = $lotsf*0.1+2975; }
else { $maxsf = $lotsf*0.25; }

# BC rules
if ($lotsf<6000) { $maxBC = $lotsf*0.35; }

elseif ($lotsf<9501) { $maxBC = $lotsf*0.1+1400; }
elseif ($lotsf<15001) { $maxBC = $lotsf*0.1+1500; }
else { $maxBC = $lotsf*0.2; }

} else {

# RMX1 formula from attachment a
# FAR rules
if ($lotsf<4000) { $maxsf = $lotsf*0.74; }
elseif ($lotsf<5000) { $maxsf = $lotsf*0.2+2150; }
elseif ($lotsf<6500) { $maxsf = $lotsf*0.2+2320; }
elseif ($lotsf<10001) { $maxsf = $lotsf*0.195+2450; }
else { $maxsf = $lotsf*0.42; }

# BC rules
if ($lotsf<4000) { $maxBC = $lotsf*0.5; }
elseif ($lotsf<7001) { $maxBC = $lotsf*0.165+1320; }
elseif ($lotsf<9001) { $maxBC = $lotsf*0.165+1300; }
elseif ($lotsf<10001) { $maxBC = $lotsf*0.16+1300; }
else { $maxBC = $lotsf*0.25; }
}
}
$lotsf=$_POST['lot_sf'];
$present_maxsf = .8*$lotsf;
$adjsf=$_POST['house_sf']+$_POST['basement_sf']+$_POST['detached_sf'];
$adjbc=$_POST['footprint_sf']+$_POST['detached_bc']+$_POST['covered_sf'];
//show what no basement at all would calculate as
$minadjsf = $_POST['house_sf']+$_POST['detached_sf'];

calculate();

$newFAR = $maxsf/$lotsf;
$newBCpct = $maxBC/$lotsf*100;
$currFAR = $adjsf/$lotsf;
$mincurrFAR = $minadjsf/$lotsf;
$currBCpct = $adjbc/$lotsf*100;
$curr_expsf = $present_maxsf-$maxsf;
$curr_expPCT = (1-$maxsf/$present_maxsf)*100;
$prop_expsf = $maxsf-$adjsf;
$exceedsf = $adjsf-$maxsf;
$exceedBC = $adjbc-$maxBC;