I do my lifting at home and don't have a suitable bench. I'm currently using two ordinary monoblock chairs as my "bench" and I don't think I'm doing my bench presses right because my arms are supported by the chairs.
So my question is: can the overhead press replace the bench press in the Stronglifts 5x5 or Starting Strength program?
The bench press focuses on the pecs primarily (depending on the elbow position) and secondarily on the triceps and delts.
The over head press focuses on the delts and secondarily on the upper traps.
So - both exercises should be done - but probably not on the same day (depending on your specific program). To overcome the lack of a bench, you can do a floor press, as described here: http://www.weightliftingdiscussion.com/floorbarbellpress.html
either using dumbbells or a barbell. One issue with the floor press is that your arms do not go down far enough to work the bottom part of the press (off the chest) - but this may be a bit safer than trying to balance on chairs.
No, they can not.
First, they work different muscles.
Second, the overhead press is a part of Stronglifts already, and adding another session of it could prove detrimental to your recovery.
I'd try to find a better bench, and in the meantime work with weighted pushups or similar motions, which corresponds more closely to what the bench press does. Dips can also partly work the chest, if you have anywhere to do those (not between chairs, you need to be able to lean a bit forward to get the chest involved)
Doubling up on the overhead press doesn't sound like a good modification to StrongLifts to me. I'd opt for dips (if you have two chairs, or rings, or parallel bars) done with three sets of max reps like chin-ups, or one high-rep set of Hindu pushups. I would focus on maintaining a non-bench-press, non-overhead-press pushing movement. Personally I would not go for the floor press because it's a limited-range-of-motion movement.
If I did go for doubling up overhead press, I'd make the "overhead press as alternative to bench press" days into light overhead presses (70% or 80%) instead of full weight.
I would disagree with other comments on here and say YES you can; but only for a while. It is not absolutely necessary to work both pressing motions in all your training cycles. Of course you should "pay your dues" on both these exercises for a more balanced muscular development but there is nothing wrong at all with focusing or "specializing" in one of these movements for a while.
And in case you feel like you cannot do without a pump in the pecs then like others suggested dips, weighted pushups, or floor press should suffice. I should mention that you shouldn't feel discouraged from doing floor presses just because it is a partial movement. If you do floor presses with a pause at the bottom (don't bounce off your elbows), you would find that strength gains on it carries over pretty well to your regular bench.
Hope this helps.
The alternative to the bench press is the pushup. In addition to weight vests, bands, and/or chains for increased resistance, there is elevating your feet on a bench. The "functional strength people prefer the push up over the bench press because it requires the muscles that move and stabilize the scapula to work and of course the "core" gets a functional workout as well. Functional chest training is for pushing a car or an opponent and the pushup simulates that better than the bench press. If you get to one-armed pushups you also achieve the function of impressing the hell out of people (and you can do it anywhere there's a floor). Seriously, the pushup can be considered the real upper body pushing exercise.
