Hi all! If have been gathering quite of bit if information oo this great forum. I am currently redoing the extra garage at my house. It is 14'-6" W X 23'-6" D X 8'-6" H (340 SF).
Sounds like a somewhat oversize one-car garage. Your biggest problem will be the relatively low ceiling height; but that can be worked around.
Walls and Ceiling will be OSB painted flat white.
This is a near-trivial point; but I would go with AT LEAST semi-gloss, if not gloss. Flat paint will attract dirt a LOT faster (and retain it more tenaciously). This will not only eventually look bad; it will also degrade your overall lighting efficiency.
I plan on using (12) 4' 2-bulb T8 fixtures with 32W 6500K lights to light this garage (768W and approx 62,000 lumens total). I plan on doing mainly automotive work and want it to be bright. Think this will be enough?
Layout and light DISTRIBUTION trumps raw lumens every time. But that said, here is the math:
F32T8 tubes usually have nominal "initial lumens" ratings of about 2,800 each; so 24 of them will yield a total of approximately 67,200 source lumens, presuming "fresh" tubes (5-10% less than that for aged tubes). You will also lose some fraction of this (probably about 20-30%; you can use an online lighting calculator for a closer estimate, but it's not really necessary) by the time the light travels down to "working height", and due to reflective losses. So all in all, let's say about 48,000 USABLE lumens.
Now,
IF that light is distributed perfectly evenly over the entire garage area, that would mean about 140 lumens/ft.^2. That is well above the oft-cited "rule of thumb" recommendation of 100 lumens/ft.^2 at working height, for a "serious" workshop/garage; but that doesn't necessarily mean you'd have "too much" light. (Far from it, in fact.)
As alluded to above, the key is the actual LAYOUT of these lights, vis-a-vis the work you will be doing in that area. Secondarily, you also want to implement your switching so that you can maintain reasonably even coverage (particularly in critical areas) while NOT having to run all the lights, all the time, even when you do not need such intense illumination.
I cannot seem to figure out the best way to lay out the lights. There will not be much storage in this garage so all of it can be considered work area.
Given the relatively generous dimensions of that space (compared to "normal" one-car garages), this should be somewhat easier than would usually be the case.
I'd probably start with some more-or-less contiguous runs down each side of the garage, perhaps two or three feet off the walls. That's close enough to take advantage of whatever reflectivity the walls can provide, yet far enough away to still do a decent job of illuminating whatever might be ON those walls (even if that's just some pegboard or SlatWall). These runs should extend to within about three feet of the end walls (a little closer won't hurt anything). I'm also presuming that the overhead door is NOT so wide as to block any of these when open.
Across the back of the space, I'd put another similar run, again perhaps three feet or so off the wall.
Next, I'd fill in the largely empty middle of that "U-shape" ring of lights with some additional shorter runs, as needed to maintain passably even illumination throughout the space. But be aware that these are probably the LEAST important fixtures in the entire lot, as they will mostly either illuminate the roof of whatever vehicle is parked there (as opposed to the areas you are really working in) and/or be blocked by the overhead door (when open).
Finally, I'd finish it off with a good hand-held trouble light on a retractable cord reel, mounted somewhere near the centerline (but probably more toward the back of the space, so you can still easily reach it when there is a car/truck parked in there).
I am planning on doing a uniform layout of the lighting.
Not entirely sure what you mean by this. But if you are referring to the simplistic "rank & file" lighting schemes so often suggested by typical "lighting calculators", that would near-certainly be a mistake.
Does anyone have any rough guidelines on how far apart the fixtures can be and still provide complete coverage?
Depends on the direction you're talking about. Think about the radiation pattern of a linear fluorescent tube for a moment: In theory, it is a near-perfect cylinder, with all the light emanating radially from the axis of the tube, and virtually none emanating from the ends. In practice, and as typically "modified" by the fixtures they're installed in and/or the nearby reflective surfaces, the reality is somewhat closer to a "bloated doughnut". But the fundamental point remains: The fixture-fixture spacing can (and should) be MUCH greater going "athwartships", than in the end-to-end direction. Note that this is also where that low-ish ceiling comes into play; the lower the installed height of the fixtures, the closer they must be spaced to maintain acceptably even illumination at working height.
Also any suggestions on how far they should be from the walls? Basically I am trying to determine if it would be best to run the lights in rows parallel or perpendicular to the depth of the garage.
As mentioned above, why arbitrarily limit yourself to one or the other?
