@Mirikon
I just double checked my books you're right, still a short duration but different to what I thought. I'll have to take another look at it.
@Glonthein
They're weird to me too the spell description is 50 cubic meters per magic rating but I couldn't find an average office building in cubic meters only in square feet so I had to try and convert to work out the mages needed. The google entry I found said average office building = 14,900 square feet no mention of heigth/width/etc. Your calculation was mostly right but the spell is meters not feet which I'm not used to feet either which didn't 't help my conversions. Anyway 2 mages with magic 6 could cover 600 cubic meters. Problem is (for me anyway) trying to convert cubic meters to an actual personal idea of what it covers. Which is why I have a VERY strong suspicion I messed up those calculations earlier since I don't think that program I found is converting properly or at least representatively.
Lets take say a room 3 high by 3 wide by 3 long average square bedroom, that gives you 3 * 3 * 3 = 27 cubic meters. Less than 1 magic rating so easy to do. Now I can't exactly go measuring office buildings so I'll try guesstimating again with my apartment building. Looking at the contract of sales its roughly 50m by 31m by 8 stories and google agrees with you that 3m is average ceiling height for residential (mixed use 3.5 and office buildings are 3.9 interstingly enough). So that gives me . . .
50 * 31 * 3 = 4,650 Cubic Meters (not counting underground parking basements).
4650 / 50 = 93 (you could just multiply length by height here but not all buildings are this convenient).
So to ward just one floor of my apartment building you'd need mages with a total magic value of 93. To ward the entire building you'd need 93 * 8 = 744 magic rating.
Assuming an average magic ranking of 3 that is 744 / 3 = 248 mages, assuming an average value of 6 its still 124 mages.
Sooo . . . painful and not really easy to arrange even for megacorps I hink which is annoying as ritual magic should be good for that kind of thing. Get a group together and the results should be far beyond a normal mage, maybe if it was multiplicative one mage = 6, two mages = 6 * 6 = 36 or magic rating * magic rating / number of participants? Not for all spells obviously just a modfication on wards e.g. two mages with magic 6 can ward an area of ((6 * 6) / 2) * 50 = 900 cubic meters. Still not enough to cover a floor of my building or even much better than (6 + 6) * 50 = 600. However the more mages you can put on the spell the more effective the results will be.
So normal wards formula
Mage with magic rating 3 is 3 * 50 = 150 cubic meters.
Mage with magic rating 6 is 6 * 50 = 300 cubic meters.
Two mages with magic rating 3 is (3 + 3) * 50 = 300 cubic meters.
One mage with magic rating 3 and one with magic rating 6 is (6 + 3) * 50 = 450 cubic meters.
Two mages with magic rating 6 is (6 + 6) * 50 = 600 cubic meters.
Four mages with magic rating 3 is (3 + 3 + 3 + 3) * 50 = 600 cubic meters.
Four mages with magic rating 6 is (6 + 6 + 6 + 6) * 50 = 1,200 cubic meters.
Now with my revised formula.
Mage with magic rating 3 is 3 * 50 = 150 cubic meters.
Mage with magic rating 6 is 6 * 50 = 300 cubic meters.
Two mages with magic rating 3 is (3 * 3) * 50 = 225 cubic meters.
One mage with magic rating 3 and one with magic rating 6 is ((6 * 3) / 2) * 50 = 450
Two mages with magic rating 6 is ((6 * 6) / 2) * 50 = 900 cubic meters.
Four mages with magic rating 3 is ((3 * 3 * 3 *3) / 4) * 50 = 1,012.5 cubic meters.
Four mages with magic rating 6 is ((6 * 6 * 6 * 6) / 4) * 50 = 16,200 cubic meters.
So interestingly 1 mage is the same, at lower levels of power/participants my formula gives a worse result but if you can put multiple mages and especially multiple powerful mages the results increase exponentially. My apartment building is (4,650 *
37,200 cubic meters. So to ward that size an area you need 744 magic rating which under the current formula means a LOT of mages even if they're extremely powerful but under mine and assuming lets say an initiated leader of 6 + participants at 3. . . .
Normal Formula
(744 - 6) / 3 = 246 or 247 mages ritual casting for 6 hours (force 6 ward) to ward my apartment building (a fairly standard 8 story building).
My Formula (I just kept multipying and dividing till I got over the 744 combined magic rating needed).
(6 * 3 * 3 * 3 * 3 * 3 * 3 * 3) / 8 = 1640.25.
So 8 mages ritual casting for 6 hours to ward an area equal to 82,012.5 cubic meters or more than twice the estimated size of my building could easily cover the basements as well and part of the surrouding terrain. If you only use 7 (624.8 and lots of numbers) you can ward an area equal to 31,242.85 cubic meters nearly all the residential floors. If you drop the ritual leader to 3 magic as well that will give you a combined value of 820.125 capable of warding an area of 41,006.25 cubic meters all the residential floors and some of the basement/balconies.
I rather like that since 7-8 mages of varying power being needed to ward an 8 story apartment block rather than nearly 300 seems a lot better number and when you consider there are far, far larger buildings to ward? Lets try an office block of say the same width/length as my building but 15 stories tall that's . . .
50 * 31 * 3.9 * 15 = 90,675 cubic meters.
Which isn't even if the full extent of what we have out there with 20-30 story buildings being common and then there's the shadowrun acrologies. Of course there is always going to be outliers Harlequin is something like 32 magic so he alone could ward an area of (32 * 50) 1,600 cubic meters and with 2 assistants of 3 magic could hit 1,900 (normal formula) or 4,800 (my formula and roughly the size of a floor or my building).