Strengthen floor for aquariums

I am in the process of buying a new home and want to get a 360 gallon aquarium. The Home is a 1 level on a crawl space. In addition to this aquarium we will have a 120 gallon, an 80 gallon, and a 10 gallon. We will use a 55 gallon sump with the 360. I would guess that with water, stands, rocks, etc. total weight for the aquariums would be about 7000 lbs.

I have not had a chance to get below the house too see the joists and such. I am not familiar with how the whole flooring works, though I have learned quite a bit over the last week of researching, so I don't know what to look for exactly when I do get to take a look, I am hoping that I can check it out this weekend.

I am looking for any advice on what to check while I am below the house, and then what would be some good options to reinforce the floor to hold the weight. I am planning on putting all the tanks in the same room, except maybe the 10 gallon, so I will only have to worry about reinforcing the floors for the one room.

Thank you for any help.

Hopefully you have a high crawl space. Because your going to have to be digging some footers.

The highest my span calculator goes to is 100 psf. (pounds per square foot) so if you think your tanks will weigh 7000 lbs then 100psf would a 7X10 area.

using 100psf with 2x8 floor joists your max span is 8'6
2X10 will be 10'4

this is the distance between your main beams

Im thinking your closer to 150 psf.

My guess would put you at 6' and 8'

If your tanks are in one area you can probably get away with one more support beam directly under the tanks. Double up on 2X12 for your main beam. I like to sandwich plywood in between to help limit deflection.

guyod said:

Hopefully you have a high crawl space. Because your going to have to be digging some footers.

The highest my span calculator goes to is 100 psf. (pounds per square foot) so if you think your tanks will weigh 7000 lbs then 100psf would a 7X10 area.

using 100psf with 2x8 floor joists your max span is 8'6
2X10 will be 10'4

this is the distance between your main beams

Im thinking your closer to 150 psf.

My guess would put you at 6' and 8'

If your tanks are in one area you can probably get away with one more support beam directly under the tanks. Double up on 2X12 for your main beam. I like to sandwich plywood in between to help limit deflection.

Click to expand...

You touched on this but my vote would be to install support columns to footers under the tanks since the load is fairly concentrated. How the columns connect to the floor joists would depend on how much room you have. If you have the room, a 8" or 10" steel beam running perpendicular to the joists supported by these column would be best.

Well, first see what you have under your crawl space. Then think.
8.8 x 360 = 3168 lbs of water. + about 360 of gravel. + stand. If the stand is 200 lbs you still are a far cry from 7000. Your at 3728 lbs.
So take this into consideration when reinforcing the floor. You may not have to do much but you won't know until you get under to see what the construction of the floor is. "Much" is a relative term...............

JFI: I used to design and install high end reefs as well as just a few, big, almost totally sustainable fresh waters systems. This was a few years ago so I may be a bit rusty but I still remember a lot.

Now your tank. It's length is important to how the weight is distributed.
Is the tank custom made? Is it 4' long, 6' long or is it 8'?
Is your sump going to be under tank or in another room/ closet? your sump could be 40' away if need be. The water doesn't care where it flows from.
Let me leave this for now. Get back to us.

I like your idea...a BIG tank is so much easier to maintain.

Thanks for the responses, they have been very helpful.

What should I use for support columns? 4x4s, 6x6s, something else?

Adk- I will be adding the 360 to an existing 120 and 80. I think 7000lbs may be a bit high, but better to over shoot than under. I am planning on having the sump under the tank. The tank will be 8x3x2.

The 120 is a 4x2x2 and the 80 is 4'x18"x22" (LxWxH).

Any other tips or suggestions would be appreciated.

With out seeing your crawl space we cant tell you exactly what to do.

For support columns it depends on how much height you have.

Steel Screw jacks are the easiest thing to use. they are 2 steel poles that fit into each other. there is holes in them and you use a steel bolt through the holes to achieve your correct height then there is a big bolt up top that you screw up to get nice a snug against your beam. i think they start at 3 feet

if you need less than 3 feet then use cinder blocks to build up to your correct height. use 2 blocks side by side and alternate the seam with each coarse. you can get away with using just one chimey block put you should choke the hole up. when you get to the top you can use half blocks or bricks to get as close as you can. to be done right it should all be mortared in place. to get the main beam snug against the floor joists you can use scrap boards and shims i like to use cedar shingles because of there extra width.

i like to sit the ends on the block foundation. you will have to chip out the block to do that.

I dont see why you have to go the whole width of the house. You can probably get away with having your beam only about 2 feet longer than the fish room. if the beam is under 20 feet 3 supporting points should be fine.

Footers should be 3 feet deep to get below the frost level but since this under your house and should not freeze at all and since this just extra support. 18'' to 24'' should be fine depending on the hardness of the ground. it should be 2 feet wide.

I was bored and did some calculations based on craigs weight and your dimensions.

Tank----Water weight---Extras--Total---SF---pfs
360------3168----------560-----3728---24---155
120------1056----------175-----1231---8----153
80 -------704----------100------804----6----134
TOTALS------------------------5765 lb--38sf

As you can see all the tanks have very high PSF. So because of weight distribution they all weigh very close. A floor is normally build to only hold 40 to 50 PSF.

As far as craig's suggestion of columns connected directly to 1 or 2 floor joists. well I don't think he realized the tanks would span so many joists. I don't see it working.

When you look under the house inspect the floor joists for termite and dry rot very closely. . hit the joists with a hammer and listen.. A sharp loud noise is good, a thud is not.. crawl spaces have a tendency to have high humidity leading to dry rot. under normal conditions these floor joists may still have a long life but not with lbs on them.

guyod, thanks for all the info, that will be very useful.

I went out to check the crawl space this afternoon, and there isn't a way in. I am unsure what the best way to make a way in, any tips on how to go about doing this.

Thanks for the help.

assuming there is a couple feet of exposed cinderblock walk the entire perimater of the house looking for any place that the cinder block is replaced another material. most of the time its a painted plywood. It may even be under a porch. the openning may of been sided over.
Every once in a while they are inside. which probably means its been covered up with flooring.. but check all the closet floors, utility room. i had to cut a whole in the floor once to get in. hope fully it doesnt come to that but do not buy the house if you can't get in there first.
I noticed you from utah and im pretty sure its dry there so that means you have less of a chance of dry rot.
how old is the house?

The house was built in 1890, with an addition put on in the '60s. The area in question is the addition. The seller has just put in new flooring and such, but also said that he was not aware of an entry way into the crawl space. I checked the closets and around the house and did not see anything.

It is pretty dry here, and dry rot is not a common problem, termites are really rare as well.

I am pretty sure I will have to cut my way in, any recommendations on how to do it?

Thank you for your help.

Welcome to TBBCs:
For my money, I would dig down to undisturbed earth to place a 2' wide X 8" thick footer and lay 8" concrete blocks around the peremiter of the room. If it is an interior room there is no fear of getting below the frost line. The foundation would support the walls around the room on half of it and a concrete floor on the inner half; with thoroughly compacted rock or sand filling the foundation to the bottom of the concrete. I would also run a #4 reinforcing bar each foot in both directions and suspend it in the center of the 4" height of concrete.
Now you have a commercial floor and you can load it any way you please.
Please let us know how you come out.
Glenn

Is there a basement to the original house? did you check in there?

If its from the 60's the subfloor is probably 1" X 3" tongue and groove. . so using a circular saw set the depth to 1 1/4 " cut the floor following a groove. cut only an inch once the saw deck hits the floor. then look to see that the blade went all the way through. if not set it a little deeper. Keep cutting short distances and keep looking for the floor joist. once you find it take a square and make a line directly over the middle of the stud 2 feet long. Flip the saw around and find your Floor joist on the other side and do the same thing. Once you cut the hole you can nail or screw a board to the back of the tongue and groove boards now you have a cover for your hole.
You probably will only have a 14" wide hole to crawl through

glennjanie- Thank you for the input. I am having a hard time visualizing what you are describing. Please correct any misinterpretations that I have.
I should dig the loose dirt around the perimeter of the room where I want to put the tanks and put a concrete footer in the trench I dug out. Then I put in concrete blocks to build a wall on top of the footer that I put in. After this I get lost. Do I replace the wood floors with a concrete one? Then fill in under the concrete floor with sand or crushed rock? Thank you for you help.

guyod- The original house does not have a basement, and I couldn't find a crawl space entrance in that part of the house either.
I am not sure what a groove in the floor would be, is it the joint between two of the wood slats, or something different?

Thank you.

Yup, if it is tongue and groove subflooring then there will be a groove at each joint (tongue and groove joint).

I got confussed with glennns suggestion too . But he did say that your footer doesnt have to be that deep which is good for you. I didnt want to be the one to say that. but you do want to dig til you get to some real compact dirt. beacause any compression of the ground will sag your floor. if you are able to get screw poles under new beam then can worrry a little less about that cause you can easily screw it back up as long as your notice it.

i think he is saying to pour a concrete slab to the top of the floor joist. That would be ideal but would cost thousands and would require taking up the subfloor of the room.

I'm wondering why not just put precast footings and screw jacks where the aquarium is going to be? It's not like he's going to be moving it around all the time. If the footprint of the aquarium is 2' x 8', and if it will sit perpendicular to the joists, that is 6 joists that need extra support. I'm assuming the aquarium sits on a base that is not on feet, so the weight is evenly spread out under it.

If it runs paralell to the joists, then only 2 or 3 will need extra support. Maybe do the same for the 120 gallon aquarium just to be on the safe side. The 80 gal. should be fine. Lot's of people have 80 gallon aquariums and they don't reinforce their floors.

As for access, cut a sqare hole in the floor in a closet and make a cover for it.

Ok, you have the foundation built up to the bottom of the floor joists under the walls. Now, remove the wood floor for the whole aquarium room, fill the foundation with sand or compacted stone, put a 6mil polyethelyne vapor barrier down, support the #4 reinforcing bars (they make steel chairs for this) one each foot in each direction (use tie wire on each intersection of the bars), place 4" of concrete for the floor making it level with the other floors, or leave 1/2" low for space to install quarry tile.
With this floor you can place any size aquarium anywhere you want it without fear of the floor sagging or falling through.
Glenn

OH! I would also put a drain in the center of the floor and pitch the floor 1" lower from each corner to the drain.
Glenn

precast footings might work if he has solid ground,

I dont see how you can support 8 or 9 floor joist without a beam.

That a great idea glenn but thats not a diy job. and sounds about a $10K job.