I carry IWB with a double reload on my belt, and most days wear a large, three pouch carpenters type tool belt. The belt goes at or just under the top of my pants, so thats not an issue. It does go over my untucked shirt in the summer, which does tend to slow access a little, but its still a lot faster than trying to get to something in my pockets, which is about impossible with the belt on.
Ankle carry isnt a good idea for construction, at least it never worked to well for me. Its hard on you and the gun, which is in a bad place. It will quickly be full of dust and dirt, and beat up on anything you bang into while climbing around. Water/mud is also an issue. You also have to constantly check to make sure its still there, as the retaining straps on my holsters were always knocked off at least once during the day.
Shoulder holsters can work in colder weather, but if you move around a lot or swing a hammer or something similar, they will beat you up and like the ankle holster, you need to constantly check its secure.
IWB, even with the belt over it is still probably your best bet. Its not the most comfortable, but it is the most concealable for a medium to full sized pistol.