In “Elves of Evermeet”, how does the “construction” spell work?

Question

This is in the 2nd edition book: Elves of Evermeet. On page 65 there is the description for a spell: Construction.

Construction (Alteration)
Range: Touch
Component: V,S,M
Duration: Permanent
Casting Time: Special
Area of Effect: Special
Saving Throw: None

The buildings and structures of Evermeet are constructed using this spell. With it, natural materials such as stone, crystal, and wood can be transformed into sculptures, shelters, buildings, or even great palaces.

The building material must maintain contact with the earth at all times and still be in contact at the end of the spell. The material being effected must be within a radius equal to 10 feet times the level of the caster.

The caster can create any object with a volume equal to 1,000 cubic feet (10x10x10 feet) per level. Each 1,000 cubic feet so created takes one entire day. Once created, the object can be added to at the same rate (1,000 cubic feet per day) for as long as the caster wishes.

The DM should work with the player to deter- mine the exact nature of the object or structure created. It can be subdivided with rooms, walls, hallways, or chambers as the caster wishes, but the creation of complex areas such as vaulted ceilings, columns, or galleries will add to the overall construction time. Once construction is complete, the structure is permanent and needs no further magical enhancement or maintenance.

Buildings constructed using this technique will maintain the appearance and texture of the substance they were created from.

These structures are also much stronger than those constructed using non-magical tech- niques. If besieged or attacked, they receive a +5 bonus to all saving throws (DMG, Chapter 9).

I have several questions relating to the spell:

1. How much stuff is created in a day? Is it 1000 cubic feet/level, or 1000 cubic/feet? Once constructed, it says you can add 1000 more per day, how does this work?
2. How is volume calculated? (I apologize for the math that follows) Imagine you have a house, that’s essentially a cube (30ft side) with a triangular prism on top (=the roof), for which the triangle base is isosceles with a height of 10ft. Let’s say that the walls/roof are 1ft thick. The insides of the cube and prism are empty. That’s about 6x900 cubic feet for the cube’s walls, and 2x541 cubic feet for the prism (we’ll assume the bottom of prism=top of cube). This amounts to about 6500 cubic feet of materials. However, if we take the whole structure, and dip it into a mega-bathtub (à la Archimedes), it would displace 31500 cubic feet. So which volume is correct? One interpretation would take nearly 5x the time to build.
3. Casting time? Must you be present and actively participating in the days-long construction process, or can you magically design the whole structure ahead of time, cast it once (in which case, how long is the casting?), and then let it grow according to your vision? Could you use multiple spell slots to build multiple buildings simultaneously?
4. Can you re-cast this spell on a building created using this? Since the building is living stone/wood..., and thus an extension of the earth, I would say “yes”. This would allow the creation of large palaces given enough time. (which we know, in canon, happened)

Conclusion: My aim is to decide how long it would take for a single caster (of 20th level) to build a town: comprised of many smaller houses, and a few massive ones. For that I must have answers to a bunch of questions. Can you have multiple constructions going on at once? For building a palace, the archimedes style volume could be huge, so is it only the volume of the materials that counts?

Answer 1

1. How much stuff is created in a day? Is it 1000 cubic feet/level, or 1000 cubic/feet? Once constructed, it says you can add 1000 more per day, how does this work?

The way I read this: A 20th level caster could continually add 1,000 cubic feet of material to the structure every day and only have to recast this spell every 20 days to keep construction going.

Said another way, cast it at 20th level and get 20 days of construction.

2. How is volume calculated? (I apologize for the math that follows) Imagine you have a house, that’s essentially a cube (30ft side) with a triangular prism on top (=the roof), for which the triangle base is isosceles with a height of 10ft. Let’s say that the walls/roof are 1ft thick. The insides of the cube and prism are empty. That’s about 6x900 cubic feet for the cube’s walls, and 2x541 cubic feet for the prism (we’ll assume the bottom of prism=top of cube). This amounts to about 6500 cubic feet of materials. However, if we take the whole structure, and dip it into a mega-bathtub (à la Archimedes), it would displace 31500 cubic feet. So which volume is correct? One interpretation would take nearly 5x the time to build.

Given that the spell says "The material being effected must be within a radius equal to 10 feet times the level of the caster." It's pretty clear that the 1000 cubic foot per day volume is the displacement volume not the size-of-box-it-would-fit-in volume.

As for how to calculate this?

The DM should work with the player to deter- mine the exact nature of the object or structure created.

A little web research can be a powerful thing:

The precise amount of lumber required to build a wood-framed house varies slightly across the nation, but a good average would be 6.3 board feet for the structural framing materials in every square foot of house.

homepreservationmanual.com - how-many-trees-to-build-a-house

A board foot is 1”x12”x12”. A cubic foot is 12”x12”x12”. So a cubic foot is 12 board feet. Since the average per square foot is 6.3 board feet you get about 2 square foot of house per cubic foot of material. But that just gets you the wood frame.

Real world houses aren't just made of wood. There's drywall, brick, cement, and more. None of which are available to you. Hope you like wood paneling. So I'd guess most DM's would be happy to say that:

one cubic foot of material is one construction spell house square foot.

As long as you're reasonable with how high you make the ceiling.

This means you could comfortably crank out one 30x30 one story house every day.

3. Casting time? Must you be present and actively participating in the days-long construction process, or can you magically design the whole structure ahead of time, cast it once (in which case, how long is the casting?), and then let it grow according to your vision? Could you use multiple spell slots to build multiple buildings simultaneously?

This doesn't leave you casting for 20 days. You planted a building and are watching it grow.

4. Can you re-cast this spell on a building created using this? Since the building is living stone/wood..., and thus an extension of the earth, I would say “yes”. This would allow the creation of large palaces given enough time. (which we know, in canon, happened)

"Once created, the object can be added to at the same rate (1,000 cubic feet per day) for as long as the caster wishes."

This is true up until the days per level limit has been exceeded at which point it will need to be recast.

"The caster can create any object with a volume equal to 1,000 cubic feet (10x10x10 feet) per level."

If it wasn't for the level limit this spell would never end. Recasting doesn't start over from scratch. It does give you a chance to recenter the 10 foot per level radius.

The spell doesn't say anything about concentration being required or not. Seems excessive to expect a wizard to focus on this for 24 hours per day. But keep in mind this is elvin magic and elves don't require sleep.