Martin describes a top band aerial that can be made to fit into a small space that gives good ground wave for local contacts.
I must say from the start that this no DX aerial, but will enable you to get on the local top band net without the need to wind any coils or build an extensive earth mat. It should give you a stronger ground wave signal over a long wire for local working and is basically a vertical oblong loop that has been earthed at the far end. It is a grounded Marconi with a return wire back to the shack. The very rough diagram shows the conditions at my QTH. Nothing is set in stone and the dimensions are not critical. Just get up the biggest loop you can. It can be fed from top or bottom corner straight to an ATU. The tuning at my QTH is done with a bog standard MFJ tuner used on its wire setting and is very sharp. With seven watts from my AT5 on AM I am at least twenty over nine in the local area and well above the noise. Even if you think that you do not have enough room, I urge you to give it a go!