I just did maths for fun, and if my calcs are correct, a chest with a volume of 6.75 cubic yards, is equivalent to around 5.16m3.
Since charcoal weights (aprox) 208 kg/m3, that means a little more than a ton...
So, with 12 uses each day, thats 61.93m3 each day... thats translated into nearly 13 tons of charcoal each day.
Maybe... maybe we went overboard xD
On the bright side... we can fuel every hearth in Laimunt Valley xD
We can cover your lab in charcoal if you want xD
I'm considering alternatives to the mundane construction of my laboratory using ritual spells.
Between using wood or stone, I am inclined to use stone, since it is a much more resistant material and in which termites will not appear 
Also, using a "living tree" would require more magnitudes to make the same building (and so, a higher vis cost, and Alba prefers to actually invest into learn others Arts than make something more costly).
Therefore, I decide on using the tried and trusted CrTe combination ^^
I've been looking to other similar CrTe building spells to understand a little more how it should be done. That means Conjuring the Mystic Tower (ArM 5, pg. 153) and Creation of the Walls of Simple Cottages (TME, pg. 61) and all the variations of this last one.
Understanding that the Complexity part its a little more subjective, I though into making a proposal so we can discuss it before Alba can work towards it. So I don't end with wrong expectations due to oversights or bad calculations.
This would be my proposal and my explanation, so we have something to work with. But first, the building size:
Doing some rough calculations, Alba's sanctum would measure around 600-650 m3. That translates into 880-990 paces3 (understanding pace as yard). In other words: +3 size (to reach 1000 paces3 for the spell).
So, the result would be (if i'm not missing anything): Base 3 + 1 Touch + 3 Size
Now, with the +X Complexity.
The Cottage spells have a +1 due to making several buildings in chain, and the advanced ones have another +1 to make doors, pivots, plumbing, sewage... Also, they have the possibility to add +1 to make diversify the buildings.
Conjuring the Mystic Tower doesn't have a lot of explanations... it has a +3 and you need to imagine why. I understand that making a 100 feet height monster (20 of those being the foundation) would need a +1 for complexity due to the design in itself to sustain the tower. Also, its not directly explained, but i understand that this tower could have chimneys and similar types of "plumbing", so i understand that another +1 could come from this. The last +1 would come from the fact that the tower itself is customizable.
Following this line of thought (it may be wrong), in my case i think that a +1 its needed due to being an intricate design (its not a tower, but it has arches, dome, etc). Also, it would be interesting to be able to use the same spell to make buildings with customizable layout (increasing the usefulness of the spell), so another +1 for customizable would be needed.
So, if my understanding is correct, the spell would end being CrTe 25 (Base 3 + 1 Touch + 3 Size + 2 Complexity).
It's also interesting to think about other limits from the spell. I already mentioned things like no plumbing, no chimneys, no stone doors with pivots, no building chains... but others could be max 2 stories high, max X paces wide or things like that.
Let the discussion begin xD
PS: maybe there is a better place to post this? I feel like its not completely Character Creation even when its Alba related... maybe we need some thread for spell/object design discussion?
This is a fine place to discuss it, as this is a project that Alba is contemplating. If rou feel this might be more of a covenant project, then Covenant Discussions (OOC) would also be suitable.
Aside from the exact dimensions (see later), the calculation of the magnitudes seems fine. Note that with 1 magnitude for complexity (the other one being for flexibility) you should end up with a fairly plain construction -- no carving or decoration of any kind -- because all the complexity goes into the layout. That's where the 3rd complexity magnitude of Conjuring the Mystic Tower goes to.
As for the dimensions, the basic Individual ia 1 cubic pace, 0.75 cubic meter or 9 cubic feet (the unit of measurement which is more useful for a lab design). So adding +3 Size would give you up to 9000 cubic feet.
Now, since you want a domed ceiling for the hawthorn, as well as a gallery above it (I can't find the drawing you posted), I'm guessing you need at least 20 feet in height. That would only leave you with a 450 square feet for your lab, which on the small side. Looks like you may need another magnitude for Size...
The here seems ok for now 
Idk... if decorations would be added, then those spells wouldn't need Finesse rolls to know the quality of those decorations? 
About the dimensions:
I don't follow the logic here I re-did some maths and i'm probably missing something here, because the Size seems correct... ^^!
I took the building volume from the AutoCAD design that i did (very roughly, ignoring windows, doors, railing...). Btw, funny fact: i forgot to add the 206 cubic meters of the dome into the final value, so if would be around 600-650 cubic meters, not 400-450 cubic meters as i said (i've changed that into the previous post to avoid misunderstandings).
Cubic paces is the only important measure here because the building plan that i did is already for a sanctum with a +2 Size lab inside (the interior lab height would be 36 feet, btw). And with +3 Size the spell can do a building with 1000 cubic paces of building material (nearly 765 cubic meters).
So the full building should be able to be done with that size already. Maybe? What i'm missing? (Its very typical from me to miss some key number xD)
Edit: I will link here the proposal for reference: Table Talk (OOC) - #952 by Gaxxian
That's were the discrepency is. The size of an object is not based on the volume of its materials (a common mistake IMHO), but rather on its actual outside dimensions.
So if you create a building that is 10 x 10 x 3 paces, its size does not change depending on how thick its walls are, it is simply 300 cubic paces.
EDIT: Looking at the drawing of Alba's proposed lab, looks to me like the whole building would be roughly 20 x 20 x 10 paces in size, or 4000 cubic paces. That would require 4 magnitudes for Size.
From what i saw, thats not how it works
Conjuring the Mystic Tower size: 100 feet height x 30 feet diameter = 282743 cubic feet = 10471,45 cubic paces (and thats understanding that the tower is a cilinder, if it has a square base would be even bigger).
Only taking into account external dimensions, it would need +5 size. The spell uses +4.
Creation of the Walls of Simple Cottages size: 30 feet lenght x 15 feet wide x 6 feet height = 2700 cubic feet = 100 cubic paces (x5 buildings) = 500 cubic paces
Only taking into account external dimensions, it would need +3 size. The spell uses +2.
The second spell its specially clear about the building volume and sizes. Explains perfectly how the +2 Size is used in the spell, detailing even the thickness of the walls (and the advanced version, how many inches the roof and floor has).
A little less, I believe? 1 cubic pace = (1 pace)^3 ~= (0.75m)^3 ~= 0.42 m^3.
Agreed. The math for Creo spells is usually consistent in using mass/volume of the created matter, not of the end object.
Targets and Sizes box, p. 113:
This depends on the mass of the target, so a five level boost to a Corpus spell would allow the magus to affect a giant up to fifteen feet tall, not sixty feet tall.
But also:
This rule should not be applied with absolute mathematical precision. A rough guess by the storyguide is fine, as long as the troupe agrees.
Going in another direction with the spell design: A "Small Mystic Tower" would be at most 10ft high (decreasing by 10 in one dimension). Since Alba's lab is larger than that, but smaller than a Mystic Tower, I think that stopping at +3 is going to be quite at the limit (the Tower is smaller than what it could be given the +4 mags, so I think +3 is still enough, but anything bigger an she would need that extra mag). Since the lab is not as complex as a Tower however, +2 for Complexity seem reasonable to me.
But I also think that at this level of complexity no detailed carvings or decorations are possible (and even with +3 mag for complexity I understand they would require a Finesse roll anyway).
Conjuring the Mystic Tower is indeed 100 feet high by 30 feet in diameter. That is 33 paces high by 10 paces in diameter. The volume of a cylinder is: Pi (3,14) x Diameter (10) x Height (33) = 1036 cubic paces.
That is almost exactly 1000 times the base individual for Terram, so +3 Size is pretty much on the nose.
IMNSHO, Transforming Mythic Europe is a book about pushing the boundaries. Even twist them so far beyond what I consider reasonable that you have mush. The spell Creation of the Walls of Simple Cottages goes to some length about calculating the volume of the walls forming the cottage. Essentially, it is using Wall of Protecting Stone as a base for the object being created, instead of Conjuring the Mystic Tower.
It does not create a complete building -- the spell's description specifically says there is no roof, shutters nor portals, so that it can say it's just creating a wall in a particular consifugration. Furthermore, the spell goes on to create a group of such cottage by keeping a narrow link of stone between them to maintain a single "individual". Bleh!
Yeah, but CtMT has +4 mag.
If we assume a wall thickness of around 2 paces (a rough guestimate powered by Google) that's about 2.000 cubic paces for the outer wall. Plus 150 cubic paces for each floor and inner walls (again a rough guestimate) and assuming 9 floors, this is close to 3500 cubic ft, requiring +4 mags for size instead of +3.
To me it really does not make sense to make it based on the volume of the shape created, instead of the amount of matter. The baseline creates matter in standard shape. The purpose of the extra mags for complexity is exactly to reshape this matter in a more complex form, no?
But well. In the end we are discussing a difference of 1 mag on the spell. It isn't nothing, but it isnt' unsurmontable either.
Yep. The Jerbiton in me also screams "begone, ugly and distasteful creation!" XD
Yes, it's been discussed before that Conjuring the Mystic Tower is inefficient in using its size magnitudes. It's just slightly above 1000 cubic paces, so it could have been optimized a bit and used only 3 magnitudes for size. But it's also a legacy spell, so I gues there was a decision to keep the dimensions of the tower the same, and round up the magnitudes for size.
As for using the size of the object vs the volume of the material, I think it's a very appropriately medieval way of thinking about the magical creation of objects. Otherwise you could create a very thin stone dome covering half of Mythic Europe with a single spell, not even a ritual one. What matter is the dimensions, not the volume of the materials. A ship is mostly empty space, yet it is big. Same with a house or a tower or a castle. It's a matter of how big rather than how heavy.
Well... as long as you can properly define the target's location, I don't see why you couldn't? Again, there are spells that work like that. But even if you could, would the dome sustain itself? Structurally speaking? Created objects are still subject to the laws of (medieval) physics. A "1 atom thick" dome (assuming magi could create something so thin) would just pulverize itselfon the next second, regardless of being ritual or not.
Anyway. Size based on dimensions then, not mass. Ok.
I assume it applies all the same for Creo, Rego, Perdo and Muto (Intellego is generally not bound by the target's size)?
Can you add this to the House Rules on the Notes and Claims thread (perhaps the relevant post should be renamed as "House Rules and Clarifications" or something alike?).
EDIT
Follow up question: the subject of CrHe spells was previously discussed on this very topic, with the final conclusion essentially amounting to "1 cubic pace of plant matter is not the same as 1 cubic pace of solid wood". How does this relates with the current subject? Because they do seem to be pointing in two different directions (in CrHe the amount of plant matter is the key point, but in CrTe the key is the volume occupied by the created object).
Done About the Ars Magica 5th Edition: The Heir of Laimunt Valley category - #4 by Arthur
Creating an Individual is based on its size. How many individuals are in a Group depends on the mass of the individuals.
I've used the "yard" pace (0.9m3). Idk which measures are we using at this point, tbh 
Sorry, but thats just splitting hairs and doesn't make any sense that the behavior changes depending on whether it is Group or not.
Choose one, so i can play knowing the rules, please.
At this point i'm feeling sad and frustrated to feel that i have no idea about what i can or cannot do, since seems that apparenlty will appear a new houserule at anything that i try to make (and always to make it harder).
I'm inadvertently turning Alba into an ubermunchkin that needs to be put in place at each step or something?
A pace is 0.91 meter. A cubic pace is 0.91 x 0.91 x 0.91 so 0.75 cubic meter. (Rafael was incorrect).
A pace is 3 feet. A cubic pace is 3 x 3 x 3 so 27 cubic feet.
Not trying to make it complicated, nor am I trying to lay down traps. Just explaining my understanding of how Individual and Group are described, along with the size variations.
The insert "Targets and Size" on ArM5 p.113 lay down the rules, but these were written with a living creature in mind, so it gives a slant on how the effect of size increments work. It leads to misunderstanding when that is translated into created objects that can have different shapes and density.
The base individual of each Form are described in terms of dimension, not mass. So when you add size magnitudes, you increase the dimensions (and thus the mass).
Group, on the other hand, is defined based on the multiple of the maximum mass of a base individual of that Form -- so that creating a Group of insects results in a swarm instead of just 10 insects.
It's not a really logical system, but it's what's there.
Herbam guideline: "A base Individual for Herbam is a plant roughly one pace in each direction."
Terram guideline: "The base Individual for Terram depends on the material involved. For sand, dirt, mud, clay, or similar substances, it is about ten cubic paces of stuff. For stone, it is a single cubic pace. ..."
Creating an Individual of charcoal would result in a big piece weighing about that same as a plant 1 pace in each direction. Which is about what, 5-10 kg? Group of Herbam would weigh about 50-100 kg of charcoal in whatever size you want. For comparison's sake, an 8 kg bag of charcoal is about 2 cubic feet. So a Group of charcoal pieces would be about 20-25 cubic feet.
Creating an Individual of stone would result in stone building about 1 cubic pace. Alba is designing a spell that will create a larger building, about 1000 cubic paces. So that would require 3 added magnitudes for size. BTW, the building she wants to create is about one-third of the total size of a Mystic Tower, which has 4 extra magnitudes for size.
Again, I'm not targeting you or Alba here. I don't feel like you are turning her into an ubermunchkin. I'm just correcting the math on how you are using the size for individuals and groups.
Ok, then i did my maths well.
When 1 volume = 1 mass, then 10 masses = 10 volumes. For practical uses in-game, its the same.
Unless you want to start calculatin the difference in mass between granite and limonite when you use a Terram spell. But only when its Group because... reasons.
Applying your logic here, i can asure you that i would have a lot more charcoal from a Group spell instead of less, since the mass from charcoal is lower than the mass from wood given the same volume.
The only way to avoid arbitrary and overcomplicated systems that changes in behavior depending of the Target type and that at the end serves no other purpose than add chaos and make everything harder, its understanding that 1 base volume = 1 base mass, always.
Also, Group just multiplies the base individual mass by 10, you can divide that number as you wish. I don't understand the insect reference here. I'm pretty sure than 10 size 0 animals have a volume (and mass) bigger than just 10 insects.
If that were the intention, the author would give us weights as base individual. Imo you are overthinking the author intentions.
You have Bridge of Wood and Wall of Living Wood. Both spells with individual where 1 pace of Herbam = 1 pace of solid wood. And also you have Fill the Capacious Silo, where 1 pace of Herbam = 1 pace of grain being a Group spell.
Also, funnily enough, you have spells like Conjuring the Mightly Barn, where you can create a 100x100x8 building (80k cubic paces using your logic) with a +2 Size (1000 cubic paces spell). Where do you place this spell with your ruling?
This also opens the door to a lot of questions in regards of when the volume stops being volume and starts being "occupied dimensions".
Btw:
Yes, the Mystic Tower could be designed to be a lot bigger (more than twice, for sure). Surely couldn't sustain its own weight if you go up (or would require more Complexity), but you have the possibility to make a version of the spell where the tower is wider.
As designed, the spell don't use the Size to its full potential.
I'm pretty sure that you are houseruling according to your personal interpretation instead of RAW (or even better, RAI).
I'm up for houseruling when it makes the game clearer or more balanced, or even when just catters the taste of player group, but this ruling comes by surprise and only adds complexity, subjectivity and a lil chaos too.
I agree, but let's be a bit clearer. 1 base volume = 1 base mass, so the mass of a T:Group spell can be up to 10 base masses.
It's an important distinction.
Might be. As I wrote on my previous post, a base individual of Herbam is a plant one pace across. Weight is unspecified, so we can argue about how much wood that represents. In my previous post I mentioned such a theorical plant would probably weigh about 5-10 kg. You could argue it could be more, and I might even agree with a greater weight.
The point is that the actual density of the charcoal doesn't really matter here. The important step is to establish how big a base individual of charcoal would be (and thus how much it would weight), then multiply that by 10 to get how much charcoal a Group represents. The relative density of charcoal vs wood doesn't really come into it. Just like the relative density of pine vs oak doesn't come into it.
I'll freely admit that I have a tendency to start from a lower amount when assessing if a specific item fits into the base individual of a Form. I'd rather take a conservative stance and adjust it upward, than accept something that's too high and either be stuck with it or have to retcon the result of previous decisions.
The insect reference was only a reminder that, although a single insect is still T:Ind (because an individual can be smaller that a base individual), the mass of a Group is assessed from the mass of a theorical base individual rather that that of a specific individual.
Bridge of Wood does indeed create a more solid object, covering 20 x 5 paces (and assumedly 1 pace in thickness). While certainly solid enough to support a creature up to Size +4 crossing it, it is not described as being a solid piece of wood. But it is true that it comes a lot closer to being solid volume than a regular plant. This is a good example to have me revise how much wood a base individual represents. I'd note that the volume described includes any void in the structure, so it's still not a solid chunk, but it is certainly more of a solid.
Wall of Living Wood is about the same as Bridge of Wood.
Conjuring the Mighty Barn is designed along the same lines as Creation of the Walls of Simple Cottages, using only the volume of the walls to calculate the size of a building. I consider it another example of the same form of misundertanding of how the size of an individual should be calculated. That spell would have to be revised before being used in this saga, to use +4 magnitudes for Size.
Common sense. If the object starts being enclosing enough to be described as a container or a building, then volume becomes a factor.
If you make a flat building then it's not a building/container. You may have a hard time floding the walls to assemble it if it's made of rock. 
About the building, as always it depends on its dimensions. Up to 100 cubic paces in occupied volume then it's 2 extra magnitudes for size, up to 1000 it's 3 extra mags, etc. Doesn't have to be exact to the fourth decimal (sloped or domed roof saves some volume), but it at least needs to be in the ball park.
We can all agree that CtMT could have been larger. As I mentioned, since it's a legacy spell it was probably decided to leave it as is.
But it's essentially demonstrating my point about volume of the object vs volume of the materials. If we were to calculate only the walls, floors and such of the tower, it would clearly be below the treshold for requiring 4 extra magnitudes. With those magnitudes, you can have an individual of up to 10,000 cubic paces of rock.
The tower's dimensions are 10 paces in diameter by 33 paces high, so roughly 2,600 cubic paces. So clearly above 1,000 but below 10,000. With the same magnitude it could have been three times its current volume (so either twice as wide with the same height, or 50% bigger in both height and width). If someone wants to do that, than he should invent a new version of the spell.
I'm not convinced I am houseruling anything here. It's my understanding of both RAW and RAI. I can't control other people interpretation, either, so I'm sorry that comes as a surprise.
I'm all for clarifying my interpretation of the rules in the House Rules section. Even adjusting my understanding. But you must convince me that I'm incorrect in my understanding in the first place.
I'm sorry @Arthur, I've already shown you different spells from different books that explicitly doesn't support your way of thinking, but you are brushing under the rug each and anything that contradicts your interpretation.
Idk if i could find more, but i dont want to lose my time anymore. After all, if you think that your interpretation it's more RAW and RAI that the one followed by the authors though several books, then there is nothing that i can tell or show to convince you otherwise.
On the other hand, I'm unable to see any direct reference of your interpretation at the core book, where is it? Its in some errata? Into another book?
I've mentioned the primary counter-example of Conjuring the Mystic Tower many times. The box on Targets and Sizes on ArM5 p.113 is also my primary reference, as well as the definitions of the base individual for each Form.
Another counter-example would be Conjuring the House of God (A&A 133), which requires 6 extra magnitudes of size for creating a church that is 19,000 suqare feet and up to 140 feet high (2,66 million cubic feet, or 100,000 cubic paces).
Looking at Herbam, Conjuration of the Seaworthy Cog also creates a container based on its full volume. The average cog is about 20 paces long by 6 paces wide. Assuming it is about as high as wide (if we disregard its mast), that's 720 cubic paces and the spell uses 3 extra magnitudes for size.
It's difficult to find examples from other Techniques, since those will use the Structure target for buildings and large objects. And since most animals and human-shaped beings aren't containers, that rules them out.
At this point I don't think arguing anymore is going to be helpful? While I do understand your point I don't fully agree with it, Arthur... but it's a mater of 1 mag of difference, so it shouldn't be worth it to to spend much more time on it anyway?
(Well, there's a matter of principles also, but still.)
Hey, at least expectations were clarified?
Apparently a bad example due to being exceptionally underperforming spell. But it cannot really drop a point in Size or the tower size should shrink too.
Again, doesn't mention anything. Or at least i don't understand anything at all like you. There is a line that helps to make a different idea? I read about mass in there, yet interior empty space and air doesn't add mass into a Creo Terram or Herbam creation.
Yep, an underperforming spell. Yet taking into account the foundations and all the interior walls, surely couldn't work with less Size either.
You literally took the smallest possible average cog as example:
Yet again, you can make that the spell create less volume than the max, so that doesnt really proves nothing.
I don't think so either, and this will be my last post writing about this.
Well, to be honest, that mag of difference is also the difference between Alba being able to do the spell in a few seasons, or not at all. But even then, thats not really the problem, no, since i counted on the possibility that people wanted to increase the Complexity.
What i never expected was a new ruling which also contradicted the previous nerf to Herbam (with which, although i still do not agree, i was able to accept it because, at least, it followed a consistent logic).
Yeah, well, if we continue down the path of interpreting the rules in such a draconian way, i would like to point out that since the fire flames in itself have no mass (at least, from a Medieval perspective), regardless of Ignem's base individual, all Group spells from Ignem wouldn't see their size increased to be able to affect multiple targets unless you also pay at least a +1 in Size.
The existing spells? I would handwave it as being legacy or just plain special discoveries (maybe through experimentation) that cannot be reproduced directly by players.
If you mean about this specific spell, now i know that i will not able to make it, so yes.
But if you mean for the future in general, then not at all, to be honest.
We have a ruling that allows you to have a spell with which you can create a cubic wooden bin measuring 1 meter on a side (slightly bigger than a pace)... but only when the opening faces to empty space. If with that spell you try to create that same bin facing down to the ground then, since its now an enclosed space and thus a "container", suddenly now the spell fails.
If you need an actual example of this problem in action: Character Creation for Gaxxian (OOC) - #87 by Gaxxian When I designed it, i mentioned about using it on cabinets. The spell was accepted at that time, but today a +1 Size would be required to be able to move cabinets. So, if something can be done or not it depends on the day.