The usual; I live in condo community with strict HOA rules; antennas outside of my unit is out of the question. Fortunately, I have access to the attic and the roof is asphalt shingles, i.e. its RF transparent. Unfortunately, the attic is very small, about 20x25ft (6.1x7.5 meters).

I installed Arrow Antenna's J-pole for 146/440 MHz there:

It works ok with my VHF/UHF zoo, but I wanted a HF antenna.
My attic is not the best place to work in Miami heat, plus its low, basically a crawlspace for the most part. Nevertheless, I installed a dipole cut roughly to resonate on 40m but because it is folded in M-shape, it does not resonate on that frequency, but can be used with a tuner as multiband doublet antenna. For the construction I used 14 gauge isolated wire, Radioshack-style standoffs, zip-ties to keep it off the beams, and 450 Ohm ladder line cable from HAM Radio Outlet with model 1110w, 1:1 current-type QRP balun in the shack. I have no plans to upgrade the power of my rig above its 100W rating so this balun from Balun Designs rated for 300W should do just fine. I call the antenna "Cobra" because...look:
"Cobra" resonates on number of frequencies, none of them usable but 10 and 15m (28 and 21 MHz), so the antenna tuner is the must:
I tame my "Cobra" with both manual antenna tuner (MFJ 949C) and automatic tuner (LDZ IT-100). Automatic tuner is more convenient and can be used remotely, but manual sometimes provides the closest match. With this antenna, I made number of contact across the US, Canada, Caribbean and South America, and recently had few QSO with Europe (Spain, Slovenia). It plays ok on 10, 15, 20 and 40 meters. That said, its a compromise antenna and while my Icom is happily putting almost all its watts into the antenna at the SWR close to 1:1-1.5, it is not nearly as good as elevated full size dipole. Still, its my best antenna to the date and gets me back to the hobby with my very limited resources.