Sub floors & preparing for your new aquarium

[Frankie]

Hello everyone.
Over the years of keeping fresh and salt water aquariums, I have seen theres a question as to weather the aquariums we want in our home will be ok on the flooring we have there.
I have helped a lot of people in the past in the chat rooms with this question and a few here in this forum. Once people found out that I did hard wood flooring for a living it was always the big question, "How do i protect my wood floors and are they strong enough?"
Again I found myself recently in debate over weather plywood is safe under an aquarium. I think there is legitimate reason for concern of long term settling of large aquariums and floor structure. I want to share my professional thoughts on it and hope that others will join in also with there experience and expertize on the subject.
I will answer questions on structure, how to protect your flooring and safety.
I will bring personal experiences to the table of floors and sub floors I have seen and repaired over the last 15 years in the field. One of which was a 35 year old lfs I rebuilt in NY with over 5000 gallons of water along just one wall over a basement and a 600 gallon aquarium in the center. Some of you might remember that from the chat room 3 years ago.
I look forward to your questions and answers. Were all here to learn, thats why we come here. I hope I am able to help in this area to those of you who can use my expertize.

[Woodstock]

Great topic Frankie!! karma to you

This is the exact reason I did not upgrade to a 6' tank (which would have been located in our den that has wood flooring). I was afraid of floods and wood degradation so I kept my upgrade located on 4' of space that is on vinyl flooring.

A few of my concerns then were:

• If a flood does occur, how would I clean/dry under the stand?
• What type of damage would a flood do if the water was cleaned/dried from the floor within a few hours?
• How much damage would saltwater spillage (normal tiny drips and spills) do to the wood floors?
• If there were no floods, would the weight of the tank damage the floors?
• Is there any type of tray or protective substance that could be placed between the floor and the stand?

[BigAl07]

Excellent job Frankie!! I'm anxious to follow along and take part in this series.

I would like to see a discussion on each of the following topics:

1) wicking moisture from a masonry substrate

2) compression thoughts (which we are already "into")

3)structural intergrity (non-masonry floor)

4) Long Term moisture exposure and resutls

Most of my concerns have to do with the subfloor rather than the actual flooring itself. Compromising of the subfloor has much more dire effects than simply problems with the top layer (hardwood, carpet, vinyl etc).

I have some experience related to this field. I don't install or repair floors but I do work in the design/engineering aspect of construction and have seen more weight related problems and rebuilds than I care to admit. Now I admit I have only seen ONE such problem that was aquarium related but have seen a couple of small hot tub and fireplace related failures. Each one was directly connected to poor design/construction and or inferior materials.

When you have this much time and money invested in a tank this is no time to take any shortcuts. If you're in a hurry you're only going to suffer over and over again.

When you take the thread that Frankie and I started this discussion on My 120 to 300 upgrade...it begins!
you'll see that I somewhat duplicated something that he suggested. I mentioned treated wood in contact with the masonry slab in which a 300g tank was being installed due to the fact that all concrete will not only wick moisture from the ground (it's a building code that ANY wood in direct contact with the ground or masony units MUST be treated when building a new home so why wouldn't you use treated when building your new stand) but it will also give off the moisture from within itself for many years to come. Concrete is not FULLY cured for upwards of 50 years even though after about 5-10 it's 95+% cured. My thought is that a person should NOT use treated plywood in such an instance because the variations within the plywood could lead to uneven compression along the sub-frame of the stand and in a rare case could put stress into the tank where stress is not intended or designed for. Unless you order VERY high grade treated plywood it is rated C-D which is less than appearance grade (A-A, A-B or Select for cabinets). It will have randomly scattered "football plugs" (this is where knot holes and imperfections were removed by a machine and the resulting holes are plugged with indeed football shaped plugs). These plugs are usually a much denser (harder) material to compensate for lack of integrity of the material around it due to interruption in grain. What this boils down to is that the PLUG is harder and doesn't compress at the same rate as the rest of the plywood. Given that most stands are designed to carry the FULL weight of the tank and everything else along the perimeter you can see that the weight concentration is very HIGH along this area. If you happen to have a plug right in the middle of a span and no others, you have a high potential for uneven compression. The middle could stay high with the ends dipping ever so slightly. You have now introduced a high stress point right in the middle of your tank along that axis. See where this is going?

Now this only really affects plywood that's on a hardened substrate that does NOT allow for sagging! If this same set up is placed on a truss/floor joist system the entire floor is actually designed to sag and give under normal weight loads and carry these loads to either a perimeter or intermediate point and then down into the foundation. In most instances you can't see or feel this sag (at least we HOPE you can't) but it's there and designed in. This is defined as an L/# (called L over..). This is actually calculated into the floor system and if your contractor/designer knows your going to be adding something massive in a certain area or room it's as simple as increased the l/# value to compensate for it.

Hope this doesn't cause more confusion than it helps!

Allen

[Woodstock]

Ouch!! I need more coffee! LOL~
Thanks Allen

[BigAl07]

Yikes! sorry about that.... that's the EXACT opposite of what I was striving for... arrgggg!! I'll try to sit down and re-think it and try to come up with something less geeky!!! Maybe later this evening or tonight!!

Allen

[Woodstock]

I get most of it Allen I did learn that concrete wicks moisture up from the ground. I didn't know that... now I know why the paint cans in the garage have rust on the bottom!

[Dentoid]

I'm no expert in this field, but when I was growing up we had 2 king sized water beds on the second floor of our house (yes-we were hippies). There was some concern about the weight and damage to the subfloor, but we were told that the weight would be distributed over the the base of the beds and that the trusses were designed to compensate for sag. We never had any problems. Somehow this relates, but I can't tell you why. Al? Frankie?

[BigAl07]

Originally Posted by Dentoid

I'm no expert in this field, but when I was growing up we had 2 king sized water beds on the second floor of our house (yes-we were hippies). There was some concern about the weight and damage to the subfloor, but we were told that the weight would be distributed over the the base of the beds and that the trusses were designed to compensate for sag. We never had any problems. Somehow this relates, but I can't tell you why. Al? Frankie?

Yes it relates! Water is water! For the most part a floor system is designed to carry a LOT more load than what we put on it. Here is how one of my professors described it.." The floor is designed to carry all of your normal furniture, all of your family, and ALL of your freinds at any given time. This way when you have that HUGE cook-out and everyone you know is there and it starts raining, when they all come running inside you're covered. Now if they all go upstairs and stand in ONE small area you have problems because that's a concentrated load that we have NOT accounted for."

A waterbed is much more spread out over a larger area than most of our tanks are. The "footprint" of the tank is a direct factor in how much load is going into an area in PSI! I've only had one water bed and when I took it down to get rid of it I noticed that it had support in several areas under it. Where as our tanks are usually supported around the perimeter of the stand only. The actual "Structure" of the floor is designed to carry a lot of weight short term and a fair amount long term. It's like you can stand on your head short term and the concentrated weight isn't bad but you can't stand it for long because it's a concentrated load and your head isn't designed for it. Now you take your same bodyweight and apply it over your feet. You can tolerate this loading long term because it's not nearly as concentrated AND it's been designed for my our Great Engineer Above!!

Yes all concrete will literally PULL water from the ground and slowly apply it to whatever is placed on the concrete. A common test to see how much moisture is "wicking" apply some clear plastic to a room in your basement. Make sure it's taped around the perimeter so the water doesn't just evaporate out. Check it every day at different times and you'll see water gathering on the plastic from underneath.

Hopefully this helps some more. I'd hate to muddy already cloudy waters!!

Allen

[kimoy]

great info.

i have a couple Q's myself.

i have a new construction house(1 yr old) with solid wood trusses(not the fabricated one which some contructors are using) and my tank(it's a 120 gal, 48X24, with a total weight of +-11000 lbs) is at the corner of a room by the outside wall. will i have any problem or weight issues? do i need to reinforce my floor.

thank you kim

[Woodstock]

I look forward to the answer. My 120 is also on a 'load bearing' wall and in a corner...

[BigAl07]

will i have any problem or weight issues? do i need to reinforce my floor.

Without sticking My neck out there... I would say NO! From a technical stand point the closer to the load bearing support (wall, beam, post) the less "sag" you'll have. I did see one 180 that was placed away from a wall and apparently the floor system was weak (slightly older home) and there was enough sag/droop to where if she filled the tank to it's full level by looking at the back of the tank it would run out the front. It was sagging maybe 5/16" of an inch over just a 2' span. But that was an older home and a LOT has changed in building and design. People have more and heavier stuff and we have a much better understanding of weight, how it travels and how to get it safely down into the ground.

Hope this helps!!

Allen

[Woodstock]

From: http://www.african-cichlid.com/Structure.htm

Residential Wood Framed Floors and Aquarium Weights

<BIG>One of the questions that is inevitably asked in every aquarium chat room, newsgroup and bulletin board is "just how large an aquarium can my floor support." Then the answers follow from people who usually use basically correct structural principles to come to often incorrect conclusions. Unfortunately, I then jump into the fray and try to explain in just a few words, what cannot possibly be explained in just a few words. So the result is that no one fully understands my explanation, since it seems contrary to his or her experience. So here is the long winded explanation from some one (me) that has been working as a structural engineer since 1976.</BIG>
<BIG>This is what the basic residential wood floor framing layout looks like: </BIG><BIG>http://www.hometips.com/hyhw/structure/116frame.html</BIG>
<BIG>An apartment building might or might not have similar framing. </BIG>
<BIG>First a few definitions:</BIG>

• • <SMALL><SMALL><SMALL><BIG><BIG><BIG>dead load</BIG></BIG></BIG><BIG><BIG><BIG>: This is the weight of everything that is permanent such as the floor joists, walls, piping, ductwork, floor tile, etc.</BIG></BIG></BIG></SMALL></SMALL></SMALL>
  • <SMALL><SMALL><SMALL><BIG><BIG><BIG>live load</BIG></BIG></BIG><BIG><BIG><BIG>: This is the weight of everything that you add to the house or apartment when you move in. Furniture, bookshelves, people, appliances, and of course, your computer and your aquarium(s).</BIG></BIG></BIG></SMALL></SMALL></SMALL>
  • <SMALL><SMALL><SMALL><BIG><BIG><BIG>safety factor</BIG></BIG></BIG><BIG><BIG><BIG>: Your floor was designed to support loads without collapsing using a "safety factor". The "safety factor" in most structures is usually somewhere between 1.5 and 2.0. So, if I tell you that your floor can "safely" support 1000 pounds then that also means that your floor might theoretically fail when it receives a load of 1500 to 2000 pounds.</BIG></BIG></BIG></SMALL></SMALL></SMALL>
  • <SMALL><SMALL><SMALL><BIG><BIG><BIG>bearing wall:</BIG></BIG></BIG><BIG><BIG><BIG> This is a wall in your house or apartment that was designed to support the weight of the floor, wall, ceiling or roof. (Most or all of the concrete or masonry block walls in your basement are bearing walls.)</BIG></BIG></BIG></SMALL></SMALL></SMALL>
  • <SMALL><SMALL><SMALL><BIG><BIG><BIG>partition wall:</BIG></BIG></BIG><BIG><BIG><BIG> This is a wall in your home that acts only to separate rooms. While it might be able to support some load, it was not designed as a part of the structural system that carries the weight </BIG></BIG></BIG></SMALL></SMALL></SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>of your floor or roof down to the foundation.</BIG></BIG></BIG></SMALL></SMALL></SMALL>
  • <SMALL><SMALL><SMALL><BIG><BIG><BIG>floor joists</BIG></BIG></BIG><BIG><BIG><BIG>: These are typically 2 x 8'</BIG></BIG></BIG><SUP><BIG><BIG><BIG>s</BIG></BIG></BIG></SUP><BIG><BIG><BIG> or 2 x 10'</BIG></BIG></BIG><SUP><BIG><BIG><BIG>s</BIG></BIG></BIG></SUP><BIG><BIG><BIG> at 16 inches on center that support your floor. Each end of the joists are supported by bearing walls or beams.</BIG></BIG></BIG></SMALL></SMALL></SMALL>
  • <SMALL><SMALL><SMALL><BIG><BIG><BIG>subfloor</BIG></BIG></BIG><BIG><BIG><BIG>: The sheet of wood (usually plywood) that is nailed to the top of the floor joists to form the floor itself before carpeting or tile etc.</BIG></BIG></BIG></SMALL></SMALL></SMALL>
  • <SMALL><SMALL><SMALL><BIG><BIG><BIG>beams</BIG></BIG></BIG><BIG><BIG><BIG>: The beams act to support the floor joists. These beams might be constructed of wide-flange steel beams (commonly and incorrectly called an I-beam) or they might be wood triple 2 x 10'</BIG></BIG></BIG><SUP><BIG><BIG><BIG>s</BIG></BIG></BIG></SUP><BIG><BIG><BIG>, etc.</BIG></BIG></BIG></SMALL></SMALL></SMALL>
  • <SMALL><SMALL><SMALL><BIG><BIG><BIG>column:</BIG></BIG></BIG><BIG><BIG><BIG> A vertical post that supports the floor beams. In a home this is usually a round hollow pipe.</BIG></BIG></BIG></SMALL></SMALL></SMALL>

[Woodstock]

From: http://www.african-cichlid.com/Structure.htm

<BIG><BIG><B><BIG>Wood Floor Design Loads</BIG></B></BIG></BIG>

<BIG>In the United States the minimum design floor live loads are stipulated in pounds per square foot (psf) by either state or local building codes. An example of typical design live loads might be 200 or 150 psf for a storage warehouse, 100 psf for a public meeting room, 50 psf for an office and 40 psf for a single family residence or apartment building. So, your home should be able to safely support a uniform live load of </BIG><BIG>at least</BIG><BIG> 40 psf. But keep in mind that this design live load is theoretically spread uniformly over the entire floor from wall to wall throughout your entire house. It is not a maximum load on any given area of the floor, it is just a theoretical average load that is used to design the floor for loads that are initially unknown. Some people find this confusing because in reality it is not the floor pressure (in psf) that matters at all, it is the floor load in pounds that really creates the stress in the primary structural framing members. </BIG>
<BIG></BIG>
<SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #1</BIG></BIG></BIG><BIG><BIG><BIG>: </BIG></BIG><BIG><B><BIG>"According to the building code my house can only support a maximum total load of 40 psf anywhere on the floor."</BIG></B></BIG><BIG><BIG> </BIG></BIG></BIG></SMALL></SMALL></SMALL>

• <BIG>No, the 40 psf is a theoretical uniform design live load over your </BIG><BIG>entire</BIG><BIG> floor. You might have a whole lot more than 40 psf directly under your aquarium, but that's okay because you didn't fill your entire room with aquariums either.</BIG>

<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #2</BIG></BIG></BIG><BIG><BIG><BIG>: </BIG></BIG><BIG><B><BIG>"So then, if I fill my entire room with aquariums that weigh more than 40 psf, my floor will collapse."</BIG></B></BIG><BIG><BIG> </BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>No it shouldn't. I said that the 40 psf was a </BIG></BIG><BIG><BIG>MINIMUM</BIG></BIG><BIG><BIG> design load and I also said that it is a </BIG></BIG><BIG><BIG>SAFE</BIG></BIG><BIG><BIG> load. That means that your floor could be (probably is) stronger than the 40 psf minimum in many places, and it also means that the full safety factor is still there to prevent a collapse</BIG><BIG>.</BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #3</BIG></BIG></BIG><BIG><BIG><BIG>: </BIG></BIG><BIG><B><BIG>"A structural engineer designed the floor structure in my home for a live load of 40 psf.</BIG></B><BIG>"</BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>No, probably not. First of all, your floor was probably never actually custom designed. What builder would ever want to pay a structural engineer to design something this repetitive and simple. All an experienced contractor has to know is that 2 x 8'</BIG></BIG></BIG><SUP><BIG><BIG><BIG><BIG><BIG>s</BIG></BIG></BIG></BIG></BIG></SUP><BIG><BIG><BIG> span ?? ft then he starts using 2 x 10'</BIG></BIG></BIG><SUP><BIG><BIG><BIG><BIG><BIG>s</BIG></BIG></BIG></BIG></BIG></SUP><BIG><BIG><BIG><BIG><BIG>.</BIG></BIG></BIG></BIG><BIG><BIG><BIG> </BIG></BIG></BIG><BIG><BIG> See</BIG></BIG><BIG><BIG><BIG> </BIG></BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL> http://www.mcvicker.com/resguide/page013b.htm (not my site!)

<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #4</BIG></BIG></BIG><BIG><BIG><BIG>: </BIG></BIG><BIG><B><BIG>"A building inspector inspected my house or reviews calculations to make sure that homes can safely support a minimum design live load of 40 psf."</BIG></B></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Maybe, but in many locations the building code is only concerned with public</BIG></BIG><B><BIG><BIG><BIG><BIG> </BIG></BIG></BIG></BIG></B><BIG><BIG>buildings. How strong you build your own private residence is of little concern to them. Of course, they still want their cash for the building permit.</BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

<SMALL></SMALL>
<SMALL><SMALL><SMALL><BIG><BIG><BIG>So now we know that your floor can safely support no more than a uniform 40 psf live load, right? Wrong! If you go into the basement and look up you will probably see that the exact same floor joist size (and 16 inch spacing) was used throughout your entire house. So 2 x 10'</BIG></BIG></BIG><SUP><BIG><BIG><BIG>s</BIG></BIG></BIG></SUP><BIG><BIG><BIG> spanning 8 feet in your kitchen are a whole lot stronger than the 2 x 10'</BIG></BIG></BIG><SUP><BIG><BIG><BIG>s</BIG></BIG></BIG></SUP><BIG><BIG><BIG> spanning 15 feet in your living room.</BIG></BIG></BIG></SMALL></SMALL></SMALL>
<BIG></BIG>
<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #5:</BIG></BIG></BIG><BIG><BIG><BIG> </BIG></BIG><BIG><B><BIG>"If the floor in my kitchen can support the 500 lb refrigerator then the floor in my living room should be able to support my 500 lb aquarium."</BIG></B></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <BIG>This isn't necessarily good logic. Do the floor joists span exactly the same distance in both rooms? Do the other items in the rest of both rooms have the same weight? Is your refrigerator and aquarium the same shape so that this same weight is distributed over the same number of floor joists?</BIG>

<BIG></BIG>
<BIG>The reason that there is a rather large safety factor built into the floor design is to take care of as many unknowns and imperfections as possible. Did the plumber cut a notch in the bottom of your floor joists for his piping? Is there any insect damage or maybe a little dry rot? Is there a split or knot in the wood in a zone of high stress? No one wants to have to replace their floor because it is not in perfect condition. So if your aquarium loads your floor over the </BIG><BIG>safe</BIG><BIG> load limit, you might not be in danger of collapsing the floor, you might just have less safety factor than recommended. If you're stretching the load limits of your floor structure, then be absolutely sure that your floor structure has no imperfections.</BIG>
<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #6:</BIG></BIG></BIG><BIG><BIG><BIG><BIG><BIG> </BIG></BIG>"I put that huge aquarium on the floor and nothing bad happened therefore the floor is safe."</BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <BIG>If you choose to think of "not collapsing" as safe you are certainly free to do so. But if you have a safety factor of only 1.05 in your floor structure, you probably don't know it, and there is not a structural engineer in the land that would tell you that it is "safe."</BIG>

[Woodstock]

From: http://www.african-cichlid.com/Structure.htm

<BIG><BIG><B><BIG>Wood Floor Design Loads</BIG></B></BIG></BIG>

<BIG>In the United States the minimum design floor live loads are stipulated in pounds per square foot (psf) by either state or local building codes. An example of typical design live loads might be 200 or 150 psf for a storage warehouse, 100 psf for a public meeting room, 50 psf for an office and 40 psf for a single family residence or apartment building. So, your home should be able to safely support a uniform live load of </BIG><BIG>at least</BIG><BIG> 40 psf. But keep in mind that this design live load is theoretically spread uniformly over the entire floor from wall to wall throughout your entire house. It is not a maximum load on any given area of the floor, it is just a theoretical average load that is used to design the floor for loads that are initially unknown. Some people find this confusing because in reality it is not the floor pressure (in psf) that matters at all, it is the floor load in pounds that really creates the stress in the primary structural framing members. </BIG>
<BIG></BIG>
<SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #1</BIG></BIG></BIG><BIG><BIG><BIG>: </BIG></BIG><BIG><B><BIG>"According to the building code my house can only support a maximum total load of 40 psf anywhere on the floor."</BIG></B></BIG><BIG><BIG> </BIG></BIG></BIG></SMALL></SMALL></SMALL>

• <BIG>No, the 40 psf is a theoretical uniform design live load over your </BIG><BIG>entire</BIG><BIG> floor. You might have a whole lot more than 40 psf directly under your aquarium, but that's okay because you didn't fill your entire room with aquariums either.</BIG>

<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #2</BIG></BIG></BIG><BIG><BIG><BIG>: </BIG></BIG><BIG><B><BIG>"So then, if I fill my entire room with aquariums that weigh more than 40 psf, my floor will collapse."</BIG></B></BIG><BIG><BIG> </BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>No it shouldn't. I said that the 40 psf was a </BIG></BIG><BIG><BIG>MINIMUM</BIG></BIG><BIG><BIG> design load and I also said that it is a </BIG></BIG><BIG><BIG>SAFE</BIG></BIG><BIG><BIG> load. That means that your floor could be (probably is) stronger than the 40 psf minimum in many places, and it also means that the full safety factor is still there to prevent a collapse</BIG><BIG>.</BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #3</BIG></BIG></BIG><BIG><BIG><BIG>: </BIG></BIG><BIG><B><BIG>"A structural engineer designed the floor structure in my home for a live load of 40 psf.</BIG></B><BIG>"</BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>No, probably not. First of all, your floor was probably never actually custom designed. What builder would ever want to pay a structural engineer to design something this repetitive and simple. All an experienced contractor has to know is that 2 x 8'</BIG></BIG></BIG><SUP><BIG><BIG><BIG><BIG><BIG>s</BIG></BIG></BIG></BIG></BIG></SUP><BIG><BIG><BIG> span ?? ft then he starts using 2 x 10'</BIG></BIG></BIG><SUP><BIG><BIG><BIG><BIG><BIG>s</BIG></BIG></BIG></BIG></BIG></SUP><BIG><BIG><BIG><BIG><BIG>.</BIG></BIG></BIG></BIG><BIG><BIG><BIG> </BIG></BIG></BIG><BIG><BIG> See</BIG></BIG><BIG><BIG><BIG> </BIG></BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL> http://www.mcvicker.com/resguide/page013b.htm (not my site!)

<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #4</BIG></BIG></BIG><BIG><BIG><BIG>: </BIG></BIG><BIG><B><BIG>"A building inspector inspected my house or reviews calculations to make sure that homes can safely support a minimum design live load of 40 psf."</BIG></B></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Maybe, but in many locations the building code is only concerned with public</BIG></BIG><B><BIG><BIG><BIG><BIG> </BIG></BIG></BIG></BIG></B><BIG><BIG>buildings. How strong you build your own private residence is of little concern to them. Of course, they still want their cash for the building permit.</BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

<SMALL></SMALL>
<SMALL><SMALL><SMALL><BIG><BIG><BIG>So now we know that your floor can safely support no more than a uniform 40 psf live load, right? Wrong! If you go into the basement and look up you will probably see that the exact same floor joist size (and 16 inch spacing) was used throughout your entire house. So 2 x 10'</BIG></BIG></BIG><SUP><BIG><BIG><BIG>s</BIG></BIG></BIG></SUP><BIG><BIG><BIG> spanning 8 feet in your kitchen are a whole lot stronger than the 2 x 10'</BIG></BIG></BIG><SUP><BIG><BIG><BIG>s</BIG></BIG></BIG></SUP><BIG><BIG><BIG> spanning 15 feet in your living room.</BIG></BIG></BIG></SMALL></SMALL></SMALL>
<BIG></BIG>
<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #5:</BIG></BIG></BIG><BIG><BIG><BIG> </BIG></BIG><BIG><B><BIG>"If the floor in my kitchen can support the 500 lb refrigerator then the floor in my living room should be able to support my 500 lb aquarium."</BIG></B></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <BIG>This isn't necessarily good logic. Do the floor joists span exactly the same distance in both rooms? Do the other items in the rest of both rooms have the same weight? Is your refrigerator and aquarium the same shape so that this same weight is distributed over the same number of floor joists?</BIG>

<BIG></BIG>
<BIG>The reason that there is a rather large safety factor built into the floor design is to take care of as many unknowns and imperfections as possible. Did the plumber cut a notch in the bottom of your floor joists for his piping? Is there any insect damage or maybe a little dry rot? Is there a split or knot in the wood in a zone of high stress? No one wants to have to replace their floor because it is not in perfect condition. So if your aquarium loads your floor over the </BIG><BIG>safe</BIG><BIG> load limit, you might not be in danger of collapsing the floor, you might just have less safety factor than recommended. If you're stretching the load limits of your floor structure, then be absolutely sure that your floor structure has no imperfections.</BIG>
<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #6:</BIG></BIG></BIG><BIG><BIG><BIG><BIG><BIG> </BIG></BIG>"I put that huge aquarium on the floor and nothing bad happened therefore the floor is safe."</BIG></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <BIG>If you choose to think of "not collapsing" as safe you are certainly free to do so. But if you have a safety factor of only 1.05 in your floor structure, you probably don't know it, and there is not a structural engineer in the land that would tell you that it is "safe."</BIG>

[Woodstock]

From: http://www.african-cichlid.com/Structure.htm

<BIG><BIG><B><BIG>Where to put the Aquarium</BIG></B></BIG></BIG>

<BIG>So I just spent my last dollar on a mega-gallon aquarium and don't know where I can safely put it. I think that everyone knows the best place .... directly on a concrete slab-on-grade floor. The weight is carried directly from the aquarium to the concrete to the ground below and it will take a whole lot of weight to give you any problems. My first house was a split level home where the lower level of the house was a slab-on-grade. I could have had my dream aquarium right there in the family room.</BIG>
<BIG>Okay, so you can't put the aquarium on a concrete slab because you don't want to put your aquarium in the basement. Well now the best location is directly over top of a bearing wall or a column. Unfortunately, that might not be possible either, because there are often bearing walls supporting the second floor over top of the bearing walls and beams supporting the first floor.</BIG>
<BIG>Go into your basement and look up at the floor joists. Wherever the joists span the shortest distance will be the room with the strongest floor framing and wherever the joists span the greatest distance will be the weakest room in the house. (Assuming identical size joists) So the next best location is in the room that has the strongest floor.</BIG>
<BIG>Unfortunately, the strongest room is often also the smallest room and you might not want to put your aquarium in the kitchen. So, the best practical position is often as close to a bearing wall or column as possible and oriented perpendicular to the floor joists. That way the aquarium weight is distributed to as many floor joists as possible. And the closer to the wall the aquarium can be positioned the more total weight in pounds the floor joists can support. An aquarium stand with a continuous runner at the bottom will distribute the weight a lot better than a stand with just four legs.</BIG>
<BIG>Myth #7:</BIG><BIG><BIG> </BIG></BIG><BIG>"My aquarium is on a metal stand with 4 legs so all I have to do is put a sheet of plywood under the legs to distribute the load to more floor joists."</BIG>

• <BIG>That will help some, but not very much at all. A sheet of plywood laid flat is not very stiff so it will bend and not distribute the load to more floor joists very effectively.</BIG>

<BIG>Just keep in mind that if your aquarium is in the living room then the columns and walls supporting your living room floor are below you in the basement. Some of the walls in your living room might be partition walls and not bearing walls at all. It is important to distinguish which is a bearing wall and which is a partition wall. A structural engineer can often figure this out even when the floor structure is covered by the ceiling but maybe you can not. Most homes are rectangular with bearing walls in the front of the house, the back of the house and a central support system of walls or beams through the middle of the house parallel to the other bearing walls. In an apartment building it is often the opposite. The bearing walls are often the walls separating your apartment from your neighbors apartment.</BIG>
<BIG>And that leaves the worst possible position for an aquarium which is parallel to the joists in the mid span of the joists in the room with the longest joist span. There are probably several partition walls that run parallel to the floor joists in the house so don't assume that just because the aquarium is up against the wall that it is necessarily near a bearing wall or column.</BIG>
<SMALL><SMALL><SMALL><SMALL><BIG><BIG><BIG>Myth #8</BIG></BIG></BIG><BIG><BIG><BIG>: </BIG></BIG><BIG><B><BIG>"Why all this worry about weight? I am a 200 lb man and I can fill my bath tub with water and get in the tub without crashing through the floor."</BIG></B></BIG></BIG></SMALL></SMALL></SMALL></SMALL>

• <BIG>Well, the builder knew where he was going to put the bath tub so he put extra floor joists there to take care of the higher loads.</BIG>