Have to go parallel to floor joist need some advice on how to strengthen floor please

[detroit_fan]

I am putting in a 125 gallon tank. The only place for the tank is going parallel to the floor joists. I know that is not recomended, but it is the only place it will fit. The joists are 2x8, and span a total of about 30 feet. They are 16" apart. In the middle it is supported by boards and support collums(see pics) so it is split into 15 foot spans. My tank will be in the middle of the 15 foot span. I assume i could just put 1 or 2 support jacks in the middle of the 15 foot span, but that is in the middle of my basement workshop so i would like to hear is there is something more space friendly. Here are some pics.

Tank will sit mostly on the first joist, and hopefully also over some os the joist closest to the cold air return-



This is where the ends of the joists are supported-



This is the center support-

[detroit_fan]

Edit- span between foundation wall and center support is 12 feet, not 15

[Sk8r]

I had a pro come in to raise a sagging floor. He jacked the beam (you don't have to) and ran a matching beam on either side of it, putting as much of it into the socket/ledge of the wall. Then he flattened them, applied plenty of glue, glued the 2 beams one on a side of the original beam, then bored through in 3 places and ran a fat bolt with large washers through the 3 beams and tightened it down. That made the original beam nearly square, and capable of bearing the whole weight of the floor above. With the problem we had, a sag, he chose beams of reverse warp, so that they would add that warp (upward arch) opposed to the sag---not your problem, as I understand. But it held firm and solved the problem (which originated from a cut stringer board and the insertion of a concrete shower on the second floor; not my fault. )

[detroit_fan]

Here are some pics of the basment area directly underneath where the tank will go. In the pictres you can see some lights on the ceiling, the set closest to the camera is he area under where the tank will be. The distance between the tool box and the wall is 10 feet, i was thinking about running a steel beam under the joist(parallel) with a 4x4 at each end, so the 4x4's would have 10feet between them, would that work? Could ijsut sister a board n ach side of the joist in questionand that would be enough? The goal is not to have a post in the middle of that area.

[Kenmx10]

I would sister another joist (double up) the existing joists under tank area( Full Length). An nail it together w/2 or 3 nails every foot , the length of the joist. Then I would install blocking ( 13") between the joist to tie them together. This way if there is any up and down movement, it will be spread over the width of the tank and eliminate rocking.

I would also consider the joist in front of the tank where two or three people may be standing. 2x8 lumber 12' long is not very strong as far as deflection goes.

If you do this make sure the crown (slight curve in the lumber) is facing upward . When the load is in place, the wood will flatten out . If not it will not be as strong.

[HighlandReefer]

You can buy laminated beams cut to size & use them to double up with. Installing full length joists or laminated beams is easier said then done, especially with copper pipes & any electrical wires, telephone, etc that may be in the way.

Several of our local club members have gone through the same thing. One paid to have a structural engineer to evaluate and he recommend using laminated beams.

[Hamp]

I would sister another joist (double up) the existing joists under tank area( Full Length). An nail it together w/2 or 3 nails every foot , the length of the joist. Then I would install blocking ( 13") between the joist to tie them together. This way if there is any up and down movement, it will be spread over the width of the tank and eliminate rocking.

I would also consider the joist in front of the tank where two or three people may be standing. 2x8 lumber 12' long is not very strong as far as deflection goes.

If you do this make sure the crown (slight curve in the lumber) is facing upward . When the load is in place, the wood will flatten out . If not it will not be as strong.




I agree....maybe then drop a 4x4 centered under the doubled up floor joists that are centered under the tank if you want to be safe.

[TAB]

I'm a general contractor, I really doubt that sistering is enough*. A glue lam would do it, but I'm not sure you want to go thru that expense. Sistering and a post is your best bet(and cheapest)


* While sistering would hold the load, there would be a lot of deflection. which is not a good thing for you tank.

[detroit_fan]

Originally posted by TAB
I'm a general contractor, I really doubt that sistering is enough*. A glue lam would do it, but I'm not sure you want to go thru that expense. Sistering and a post is your best bet(and cheapest)


* While sistering would hold the load, there would be a lot of deflection. which is not a good thing for you tank.

Don't they make some sort of composite board that is a lot stronger than wood? Could I just double the joists with the composite material?

[TAB]

They do, 2 probs with it.

Its not legal anywhere that I know of in a residence.

it cost more then a steel beam.

[HighlandReefer]

The laminated beams are what you are probably referring to. They will cost anywhere from $80 - 120.00 each. You want to use the same height beam as your 2x8 joists. The thicker the beam the stronger they are and the more the cost.

Deflection of standard 2x8 lumber is the reason for using these laminated beams. From your pictures, you are going to have a problems getting full length joists of any type into place. Additional bridging will help to spread out the load, but using standard lumber, you will stand the chance of deflection as noted above.

Some hobbyists have bolted on plate steel to the joists, which would work. This would be alot of work and expense over using laminated beams.

[TAB]

I was speaking of "plastic" lumber. its being used a lot now it things like short span bridges where wood would have been used in the past( mainly bike/ pesd) The prob with it is when it burns it gives off toxic smoke.

glue lams would be fine, but *** I said get up there in pricy fast.

It actually looks like he has lots of room to work down there, atleast compared to most. I see np with him getting joists in there.

[detroit_fan]

Ok, so triple the 3 joists with regular 2x8's and I should be ok? I only need to go from the foundation wall to the center support with my sister joists, correct?

[TAB]

yes, but even tripled you may have alot of deflection. with 3 its not longer nails, its bolts.

[HighlandReefer]

Structural engineers recommend using 1/2" bolts spaced about 1' or so apart installed in a diamond pattern when creating beams out of joists. You should have at least 1.5" of the installed joists on the foundation wall and the center partiton wall. You only have about 16" to work with when you try to install the joists and may have to get by with 1" of puchase. If the water pipes in the picture are where you want to install the joists, they will have to go probably.

[Kenmx10]

In International framing code for residential construction is , Live load is 40 pounds per SQ foot. If you have a tank 5' long x 32" wide , spread over 3 joist , your live load (Load or weight added to structure ) capacity would be about 600 pounds. Double the joist and you have 1200 ponds. Triple joist= 1800. The weight of 125 Gallons of water would be 1043 pounds.

That is the capacity of the wood alone. Adding bolts doesnt increase to the load bearing capacity of the lumber. It only secures the two joist together so they cant move independently from each other. Also the more holes you drill in the lumber, the weaker the structure becomes. So, Nails work fine for this and are alot cheaper and easier to install.

You can order Engineered lumber(LVL- Laminated veneer Lumber) to carry heavier loads. But it will cost more, and isnt really necessary. A 2x8 12' might cost you $10.

Also , each end of joist should rest on supporting wood or metal support by 1.5 inches or greater. If either end is not supported (only nailed to sistered joist), The the wood member adds no usable bearing capacity.

[Kenmx10]

Some hobbyists have bolted on plate steel to the joists, which would work. This would be alot of work and expense over using laminated beams. [/B][/QUOTE]

Bolting steel on to the Lumber will only add more weight to the Live load capacity, and reduce how much weight you could add to the floor system. It would have to span the full length of the joist and rest on the structural members on each end to add any load bearing capacity.

In that case a full length metal I-beam could be used.

[sbin]

Good building supply yards usaully stock steel-flitch plate that is used between two pieces of dimensional lumber to reinforce long unsupported headers.A 6" x 1/4" plate might be able to be slid into place and then sandwiched between another 2x8 drilled and lag bolted.The plate would carry way more load than your tank.
If you can not find steel there are galvinized metal plate that are stamped so triangle pieces of metal protrude in both direction.Using these fasteners in conjunction with a good contruction adhesive between sistered joists increase the strength greatly, poor mans gluelam.
I just setup a 125g over a joist that is hanging blocked on one end, nailed to a piece of wood between to adjoin joists.Reinforcing the area wasn't expensive or difficult set the tank up empty with a level and when full it did not deviate from level.

[buck50bmg]

Put a floor jack under it. Also run your wires correctly, through holes in the joist. What happens when you hit that 12-2 with a board or worse yet a metal part.... need to portect the wiring. And not even one staple...... Its in the NEC for a reason. Wire ties are a no no.

Also running coax thru a cold air return "can" be done, but you need to seal the hole around the wire to prevent a path for fire to travel.

[el aguila]

In the past I was a commercial GC. I really liked LVLs for strength. They were cheaper for me than using steel plates sandwiched between dimensional framing lumber because of the labor factor.

Many places that sell LVLs also have someone on staff who knows enough engineering to look up the sizing that you would need for your span.

I would highly encourage you to either use LVLs or steel plate sandwiched between 2 2x8s held together with bolts. Just price both and go with whichever is the best value.

I have 2x10 floor joist with a 190G tank running parallel, and I used 2 14" LVLs that I had left over from a job with concrete post 4' apart. It is strong enough to hold a tank several times my 190, but hey we always want to go bigger.

[myaerica]

find out where your tank is going to sit and put 2 2x6 bearing walls under each side of the tank. make sure studs line tite under floor joist. I have done this for people with much largertanks than125.

[myaerica]

I just re read your post if tank sits parallel and doesent land on joist put your2 2x6 bearing walls right up to the plywood under tank. studs 12 inches on center shold be plenty.