Stud finder that will work thru gypcrete?

Hi,
Does anybody know of a stud finder that will look thru gypcrete? I want to figure out which way the joists are running in my 3rd story condo but I think my my sub floor is covered in gypcrete.
Thanks, Ryan
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Almost always, the same direction as the ceiling joists in the same room. Usually, the same direction as the roof slopes, and from the centerline of the building to the outside edge, centerline being along the long direction.
Why does the direction of the floor joists matter?
aem sends....
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Thanks for the advice.
I have a strange hobby. I collect and restore old arcade games.. that weigh in at an average of about 275lbs each and have a foot print of about 2'wide x 3'deep each. I have a spare 10' x 11' bed room (in a third floor condo) and I am trying to figure out if the room can handle the weight of 9 games. I will have the games positioned around the edge of the room so.. I figure that if the joists are going 'with' the games I will probably have at beast 2 joists supporting 4 games and of the joists are going 'against' the games I will probably have about 2 joists supporting 2 games which might be better.
If anybody more familiar with construction loads can give me some advice that would be great. I think current building code in WA is a minimum of 30lbs per square foot live load but I have received so much input on the issue (negative and positive) that I am a little confused at the moment. I know people do heavy fish tanks, water beads, grand pianos, weight machines, etc, etc but I might be talking about a little more weight than most of those.
Thanks, Ryan www.ryansarcade.com
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On 29 Mar 2006 08:54:01 -0800, snipped-for-privacy@ryansarcade.com wrote:

30 PSF live load is the minumum for a upper story (bedroom) in most codes. A building that was purpose-built as a multi-family is probably designed to 40 PSF, or possibly 50 PSF.
At 30 PSF, the room will theoretically hold 10' x 11' x 30 psf 300 pounds, which works out to 12 machines, 11 machines and 1 person, or 9 machines and a
Even at the 30 PSF that's supposed to be an average, so if you don't put down a solid row of the ALONG the joists you should be ok. And the failure more will be sagging, bouncy floors, and cracking in the plaster/drywall of the ceiling below long before an actual failure is likely.
If you know which way the floor joists go, and where a load- bearing (generally exterior) wall is, then lay a pair of 2x6s across the ends of the joists to spread the load a bit, and then line the machines up on those, and you should be fine. If the games have ballast in them, you might remove or reduce that and store the ballast somewhere else.
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Thanks Goedjn, your reply helps me a great deal.
The condo below me has an identical floor plan. Does this mean that all of the walls in my room are load bearing? Also, I looked at the roof over the room (it has a separate roof orientation from the rest of the building) and it slopes along the 11' side of the game room so I am guessing that the joists are lined up parallel to the 11' side. All but one of the games are going to be positioned along the 11' sides of the room as well.
So I will basically have three games lined up against one 11' wall along two joists (approx 825lbs) and five games lined up against the other 11' wall over two joists (approx 1375lbs). I will also have one game centered up against one of the 10' walls (approx 300lbs). Make sense? I am not sure how the 30PSF averaging works. Can the weight be anywhere in the room or does is need to be evenly spread out? In other words.. does the floor act as a single structure or do I need to be concerned about weight on individual joists? Having games in the center of the room would not really be feasible.
Thanks again, Ryan
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On 29 Mar 2006 12:27:44 -0800, snipped-for-privacy@ryansarcade.com wrote:

If you assume that the joists are 16" on-center, and that the floor is designed to support 30 PSF, then each joist is sized to support (30/12)*16@ Pounds/LINEAR foot. If they're running the short way in a 10x11 room, then that's 400 pounds/joist, or 800 pounds for a pair of them. This assumes an even distribution, which you don't have. For point-loads, you have to either do math (which I don't know how to describe), or make sure that most of your load is closer to the support walls than to the middle of the span.
I'd say that the five games along one pair of joists is more than you probably want. Do you have to arrange the machines so that they're all lined up on the same pair(s) of joists, or can you go along the other wall(s)? How do you know which way the joists are going, anyway?
(It's getting near time to draw a diagram of the room, and post it somewhere.)
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OK, I will try to wip out the AutoCAD tonight and make a simple drawing. As far as the joist direction goes, I was following the logic from the second post 'Usually, the same direction as the roof slopes'. I think the plan now is to get a good stud finder and figure out which direction the ceiling joists are going. Hopefully the floor joists are going in the same direction as the ceiling joists.
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I wasn't able to get a drawing done tonight but I did take a closer look and, based on dryer vents on the front of the building, it looks like my joists are running perpendicular to the games which is great. So basically it's a 10' x 11' room with the joists running parallel to the 10' wall and the games lined up along the 11' walls (3 on one side and 5 on the other side). I think I am pretty safe because of the perpendicular joists but any more input would be fantastic. I will still try to post a diagram tomorrow.
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