how do i measure floor deflection/sag aroun my tank?

[kevensquint]

As you know I just filled my 125 on the strongest floor in my apt. perp. to the joists and along a main wall. As it is, the stand sits on a sheet of 5/8" ply with shimms under it to level out the whole set-up. My floor is uneven so I had to shimm an inch under the ply at one end of the tank. Before filling, the tank was perfectly level all around, after filling (3 days ago) its still exactly level. So, what do I watch out for in the months to come to see if the floor is losing the weight battle? I thought if the floor sagged the tank would fall out of level or cracks may appear in the walls near the tank. Any advice?

[kevensquint]

where are all the contractors?

[bklynmet]

Deflection (aka sag) occurs when a structural member is loaded and it's delfection is a direct function of how much load it sees. More load = more dflection and vice-versa. Deflection also occurs due to member creep. Creep is a phenomenon where a structural member undergoes strain under a contant load

If you are going to get any deflection now - after the tank has been filled - it is going to be the result of creep. Quantifying creep for wood is rather complex because of the variables - wood joist species, moisture content of wood, ambient temperature and humidity, loading pattern, span, geometric properties of the joist, TIME and some other factors.

Short story - if you put the tank by the wall where the joists are supported, then you'll get virtually no noticeable creep. However, if it's midspan for the joists, you'll get some creep occuring over a few years time frame - realm of 1/4 to 3/4 depending on how long the joist span is based on your 125g.

As far as wall cracks - I would not anticipate seeing any unless the wall serves to restrain the joist rotation - unlikely for wood construction.

[Zan]

I'm in the same situation, but I have a 180g tank + 110g sump. I've had it setup for a little over a yr w/ no noticeable problems.

[AcroSteve]

Good info there, bklynmet.

I have a 110 freshwater that was level when I set it up. And over about a year, one end settled nearly an inch and then stoped. I have not doen anything to fix it, but I did have to install some shims when I 1st set it up.

[joelowrider]

got to love slab floors

[kalare]

If you put anything near a wall, I wouldn't forsee any deflections...if your house is newer. If it's old, that's a different story, many old houses have undersized joists and members (not for normal use, but for code). Still though, I can't see where anything under 200g would be a big deal. Just don't put big tanks in the middle of rooms unless you know what you're dealing with :)