After having built a small tower and airlock entryway out of nothing but raw clay (a Level 6 aquifer meant it took a while to get through for actual stone) I have a few important lessons about building above ground:
1) Plan before you build. Use one of the DF planning programs, an excel sheet with square cells, or even some graph paper to sketch out what you want to do. Planning out your build will save a lot of time having to build and deconstruct stuff in order to get it all right since you can't build walls on constructed floors. Keep in mind that you also can't build walls or floors diagonally, so any place where you have walls in a + configuration, you'll have to build a floor adjacent to the center, build the center tile, and then remove that piece of floor. Anywhere else can be accounted for by strategic building.
1a) Remembering to leave spaces for doors saves a lot of time.
![Roll Eyes ::)](http://97.107.128.126/smf/Smileys/aaron/rolleyes.gif)
(built a large portion of a kitchen floor and forgot to leave space so dwarves could actually get into the rooms, luckily a stranded dwarf reminded me that I was being dumb)
1b) Related to that dwarves build stupid, so make sure to plan things so dwarves can't strand themselves and die.
1c) Even
with good planning, dwarves will trap themselves and try to starve to death. It's a good idea to sweep your project every so often for stupid dwarves that are stuck.
2) Put a stockpile near your construction and set it to only accept whatever material you're building with. Even better if you assign it wheelbarrows and link it to a primary collection site. In my case, I was collecting raw clay 4 Zs below the surface construction, where it was piled on my general stone stockpile. I created a stockpile at the construction site and then set it to take from links only and linked it to the first pile. I assigned 3 wheelbarrows to this construction pile. In this way, only hauling enabled dwarves brought my clay to the construction site with wheelbarrows, which saves a LOT of time. It'll also make that material tend to show up first on your construction list, which saves time hunting for it when you want to build (Or you can use DFhack which brings the last used building material to the top of the list, which is very handy).
2a) Turn off hauling on all your masons. If you forget to do that, building takes a lot longer.
2b) More masons = faster building, even if they aren't very skilled. When using raw clay or raw stone, 80% of your build time will be hauling, so adding more unskilled masons cuts time dramatically. Even when using blocks, unskilled labor is extremely helpful. There is no impact of mason skill on the quality wall or floor construction, it only effects how quickly the wall/floor is made. Toggle some of your spare gunts to masonry while constructing large above-ground projects and then toggle them back after you're done. You may also want to limit your masonry shops to a certain level of skill, just to prevent these unskilled masons from wasting time and resources if you need to build something during your project.
3) Be mindful of any future need for expansion. It's better to build too big and have a little wasted room than to have to restructure everything later. Also, make sure your top floor has a ceiling. Trust me on that one.
4) While you can replace the materials that you use for constructing walls and floors at a later date, it takes a LONG time to do this, much longer than the original build. If you can wait for your ideal building material, do so. Deconstructing and reconstructing a tile takes about 5-10x the amount of time than just building it right the first time.
5) If you're looking for a good building material to boost room value, I highly recommend
billion as a building material. It has a rather good value at x6 and, with some strategic stockpiling, can be created in large quantities with otherwise cheap and easily acquired tetrahedrite. Once you've got access to iron or better, tetrahedrite becomes largely expendable, so is perfect to turning into billion bars.
6) Clay, glass, and wood can, depending on your embark site, be readily available and easily renewable, so they make good candidates for building utility walls that aren't otherwise needed for building room value (althoug glass is fairly valuable as a building material). In fact, if you're trying to control the value of your fort to avoid undue fun, wood or clay can make a great building material at the beginning. However, unless blocked by an aquifer, you'll typically have so much random stone laying around that it's not really an issue to just build with non-economic stone.
6b) On that note, be mindful of flux. Flux layer stone will be toggled for general construction at embark and will produce blocks that are worth twice as much as normal blocks, building value at twice the rate. And, flux is better used in making steel anyway. It's a good idea to check for that and toggle off any flux from general stone use before going crazy building rock blocks. Once you turn a rock into a pile of blocks, you can't turn it back to useful rock.
Hopefully that helps some. I hit most of those pitfalls and learned some of those tips when building my "mud" tower. Which I eventually renovated into a stone tower at the cost of much time and
expendable dwarf labor.