One big challenge with scaling anything up (or down), is that not all properties or characteristics scale linearly.
Consider a trivial case: a small cube. If you double the size, you've quadrupled the surface area and octupled the weight.
If you take a desktop-sized 3d printer design, and just double the size, it will weigh 8 times as much. But all the bolts holding it together are only 4 times as strong. So weight-bearing bolts are effectively under twice the strain (per unit of cross-sectional area); the exact factor depends of lots of things (orientation, leverage, etc).
If you scale up by 10x, they'll potentially be under 10 times greater stress, and probably snap.
Many, many parts will have similar issues: Drive belts that are twice as wide and twice as thick will still have 1/2 the (relative) strength -- and stiffness for the motors to overcome.
The stepper motors have to move 8 times the weight, and you'll want them to move far, far faster. But steppers lose torque when you spin them faster.
My main printer is pretty much a MendelMax 2, but the Y axis is about 6 times bigger (X and Z are normal). On MM2 the whole build platform moves along Y -- on my printer it weighs far more than on a regular-size MM2 -- it's 6 times the mass just because of size, besides that it has to be much stiffer to avoid sagging over that distance. I went to a larger motor, but it could still barely move the axis. I eventually got it to move at pretty normal speed, but to print long objects it really should be 6 times faster or so.
That would require an amazing motor -- and really big electronics to drive it.
Another challenge is the printing material -- 20mm diameter PLA fiber would be really impressive, but a little hard to find, and a spool would be hard to lift. The power needed to melt it fast enough would be impressive, too. Bridge and house printers I've seen in reports, use pumped concrete through about a 100mm wide nozzle (I have no idea what the nozzle is made of, to stand up to the abrasion). See Watch this giant 3D printer build a house for some cool pictures and video.
Scaling up is a fascinating project -- but it's harder than it looks.