Are you looking for guidelines, or measurements?
For guidelines...
The bunker "bar-bells" look like trapezoids x 6 for the outer bulbs, then two more with cut-outs along the inner edges. If you leave "tabs" on the lower edges of the trapezoids, you could glue them together beneath the floor, so they aren't seen.
The walkways between are inverted trapezoids. The upper edge will determine the length of the piece, and by adjusting the angle / height of the trapezoid, you can make it match the angles of the outer bells. Or not, depending on what you're in the mood for.
Once the outer walls are built, you could measure down "1 1/4 inches" from the top edges of the walls, and then draw lines around and measure them to create a floor that will fit exactly where you want it to. Make sure to put tabs on so you can glue them to the walls! To support the floors, you could make prisms [or cylinders, if you're fancy!] and glue them standing beneath the floors at reasonable intervals. That way, if someone puts their giant walker or MC on top, the floor doesn't tear away from the walls.
It is tough to make stairs "in scale" for 40k. A "floor" of height should usually be about 3". That works well with visuals, and the game mechanics too. I took a quick count, and the floors in my house have about 12 stairs between them. That would make each stair about 1/4 of an inch tall, and maybe 1/4 to 3/8 long... which is probably quite tricky with cardboard.
I prefer Styrofoam, but that's just me. It's easier to sculpt and make minor adjustments to it. I find it also lasts longer, if you're tossing the stuff into boxes for storage. Instead of prisms beneath the floors, you could just use chunks of foam, instead. Otherwise, you could use bamboo "food skewers" between two runners of cardboard. If you paint [drybrush] the tops a lighter colour, it gives the illusion of stairs, if you aren't super concerned with 100% realism. It certainly conveys the idea of stairs for gaming purposes.
To the buildings, I'd suggest using more "ruins" than "intact" buildings. They're more fun to play on, because you can move models around inside them. Intact buildings are basically boxes, with extra bits glued to the outside for windows and doors. As long as you stick to about 3" per floor, you're in good shape. A cluster of 3 small buildings about 3 to 4 inches square makes for a good "piece". A single 6 x 6 to 9 x 9 is a good sized piece. Larger buildings tend to dominate boards, and can start to contain multiple objectives during setup... which can be good and bad.
Due to true LOS, ruins with lots of windows don't block much LOS, unless you add a fair bit of walls / junk inside of the outer edges. Ruins without many windows don't offer much in the way of "firing points", for lack of a better term. A nice balance can be "floor and a half" ruins, with few windows on the ground floor. These tend to be able to block LOS at ground level, while providing ample cover and firing points on the first floor. Some people play that you can only move into buildings if there's an opening in the wall, so including a few "cracks" on the ground floor can provide canny players with a means to shoot "through" a building, and still allow infantry to enter from a point other than a door or window. Your group may not worry about that, but my LGW does. *shrug*
Ruins are pretty easy to make. Take cardboard strips about 22" long [plus a tab!], and 6" high. Cut a jagged edge along the top, leaving some tall sections, trying to average it at about 4.25 inches tall, no lower than 3" . That gives you some spots you probably can't shoot from, and a few spots that won't provide a "ruins" save on top. Try to make your leading edge the same height as your ending edge. Fold the cardboard at 5", 11", and 17" to make a 5" x 6" building. It's a good idea to cut a rectangular hole for a door, and maybe add a window or three... they should be fairly small. Alternatively, you could cut large cracks in the walls, but you'll probably want to use a base if you do that, for support. Doing that makes moving models on the lower floor easier.
Now take a 5 x 6 piece of cardboard, and cut away some of the center of it, and perhaps a bit of the edges. Especially from the outer edges if you've put big cracks in the ruin! That will be the upper floor of the building. Glue it inside the box you just made, 3" up from the "ground". If you have some small blocks you can add, beneath the floor and along the wall to support the floor, that's a good idea.
Spray with stone-textured spray paint and allow to dry. Tah-daaah! 30 minute ruins!
Post Merge: July 18, 2013, 01:50:19 PM
In the future, please use the modify button. Double posting is against the forum rules, and for that reason, the system merged your posts.
Oh yeah, the walls!
Very simple walls can be made with 6" sections of 1 1/4 tall cardboard, and some round wooden dowel. Cut the dowel to whatever height looks good to you. Attach the cardboard to the dowel. Tape works, or if you have thick cardboard and time on your hands, you can groove the dowel and slot the cardboard inside. Add a bit of glue before slotting, and you're laughing. Make a few sections with dowel on both ends, and a few with dowel on only one end of the cardboard. That way, when you link them together, you get a "seamless" look.
I made some with square blocks of Styrofoam, but I wish I'd used round pieces. With the square "ends" they look kind of odd if you don't put them together at right angles. With round blocks, a person could connect the pieces at any angle, and they'd look good.
It's a cheap way to build an ADL as well, though getting the exact lengths of wall pieces might be easier said than done...