My "basic room size" has been 11x11 for a looong time, because that's what you get with enter, 2 shift-arrowkey presses to the other corner, enter. Fits eg. 9 farm plots at 3x3 (with seed stockpile in the # mark left between them), or workshops with a similar arrangement, or 3 workshops along a middle, with input+output stockpiles. Also can fit eg. a kennel (if I build one) and three 5x5 pastures for pigs, my breeder dogs and puppies and (insert other non-grazer, non-egglayer of choice here), or 4 5x5 farm plots (may be necessary now, since I modded crop growth times up quite a lot). Or a 3-wide corridor with 12 1x3 bedrooms (or 3-wide corridor with 6 3x3 bedrooms, or 4 3x3 bedrooms plus 3x3 bedroom/office/dining room apartment for nobles). Good barrack size too.
tl;dr: 11x11 is easier and faster to designate than 9x9, can do all 9x9 can and more.
On the other I'm trying to get a bit more variety into my designs, so it's not all 11x11 squares.
My current fort has the following around a central staircase:
- surface has walls, drawbridges, water moat, grazers outside fort, barracks, trade depot, beekeeping on roof above trade depot, trash, butcher, surface farms,archery barracks on roof above barracks, a walkway with fortifications on Z+1, will have a tower extending up from my main stairwell
- Z-1 has surface plant seed stockpile cellar, which also gives access to the basement of my walls, mainly has some levers to control draining/filling of my moats on both sides of the river (which my fort straddles). The river itself also has a drawbridge dam now
- 1 soil level just above aquifer: farms, butcher, XSocksX stockpiles, breeder dogs, pigs, poultry, kitchens, stills
- "main" floor: noble quarters, dining hall, hospital, childcare room
- main crafting level: room A: bone and similar, leather; B: Wood products, including ash/charcoal; C: Stonecrafters, masons, mechanic; D: temporary ore stockpile, will be something else later (gems?
- product stockpile level for the crafting level (logs, boulders, bones etc. are stored in the workshop rooms themselves, wood and stone with minecart quantum stockpilers, although with autochop the wood one wouldn't be absolutely necessary)
- Textiles, floorplan is 4 leaves. One "half" of each leaf is a source stockpile, the other half + usually the 1st half of the next leaf is a product stockpile and the source stockpile for the next leaf, 2 workshops along the middle of each leaf. Plants come in to the NW, get processed to thread stockpile, auto-weaved to cloth, dyed, and made into clothes. Minimal barrels/bins, for instant viewing of stocks levels in each portion. Auto-weave + workflow for unsuspending "process plants"(into thread) are great, too bad workflow doesn't understand dyeing.
- I think 5 floors of 3x3 bedrooms, from top to bottom 2 bedroom floors + bedroom lobby (all rooms are accessed via stairs) which also has my crypts off to the side + 3 more bedroom floors. Coffers/cabinets are/will be made of same material as the floor they're on (gabbro or orthoclase).
- Magma industries level is being cleared out at the moment.
- Magma plumbing. The magma will be in the shape of a rough ASCII-art dwarf face (eyes+beard+smiley mouth probably)!
- A couple of layers that have the jails (being furnished/water plumbing under construction), access area to 1st cavern, and will the top terminal for my automatic magma minecart route; dwarves will haul the magma minecarts from here, at least if it's only for workshops etc.
- lots of space down through cavern 2 down to cavern 3, still waiting on dwarves to dig drop chute for magma minecart route, haven't even designated impulse elevator back up yet
- at cavern 3/the magma sea, the magma minecart filling area is being cleared/engraved. I've dug out and am furnishing a barracks, all in blue since it's in a 10-tile diameter microcline pillar that runs through the 3rd cavern (about 20 tiles away from my main stairwell). The whole pillar may end up as a outpost tower, filled with barracks, ammo, booze, food, all the essentials to function as a "bug-out" location if need be. When I get around to it.
I built my bedrooms in ordinary stone, but my jails in marble. Heh.