If you're still finding yourself awkwardly jammed in a corner with 10mm, then you need the bigger, heavier, more expensive, and optically superior Sigma 8-16mm. Breaking my Sigma 10-20mm when a sudden fierce gust of wind toppled my tripod gave me the excuse to upgrsde and i love the 8-16mm. Those extra 2mm get you a lot of extra width.
It sounds as though you're doing RE photography. While the extra wide angle of view will reduce your contortions it does so at the expense of a wider angle view, with the concomitant problems of more exaggerated "wide angle distortion" as the perfectly natural rectilinear wide angle perspective projection (which you'd equally get from a pinhole camera, it's just optical geometry, not "distortion") is often called. I note that most of the authoritative RE photographers who publish advice, articles, etc., think that going wider than 12mm on crop or 15mm on FF is both aesthetically bad and can lead to complaints of misrepresenting the size of small rooms.
As it happens I don't agree. I shoot a lot urban cityscapes, often in narrow old streets, and sometimes wish I had a little more than 8mm (on my crop frame). Not nearly as often, however, as I used to find myself jammed against the stop of 10mm and trying to find somewhere I could step a little further back, even though I do have a fully articulated live LCD for those awardly jammed in a corner shots. I once seriously considered doing local part time RE work to support my expensive hobby, and think a fully articulated LCD or remote live view on a smartphone essential for awkward interior spaces.