Floor joist opinions

Thanks for the replies everyone.

Good read daplatapus, thanks.

I'm going to go to my local lumber yard and inquire about some 2x10 oak and see if they can calculate what load the joists will support. I'll chime back in with what I end up doing :)
 
2x10 oak? I know where I could find it, but then my brother has a saw mill too. I doubt you'll find that at the local lumber yard. Break the span up if you can, but stick with SYP, or LVL for any additional joists.
 
+1 on LVL or other engineered lumber. Better yet put the wall underneath and reduce the chance for deflection. Or get an engineer to tell you the same for a fee, and gain the peace of mind for your self. Many of us construction workers know from years of experience what works and what doesn't, but we could not prove it with calculations. Framers routinely build structures that support higher loads, and we build from engineered plans, so you generally learn what works for certain situations. If you have doubt, then get an engineer and sleep at night because that's what it comes down to.
 
jdargonaut said:
+1 on LVL or other engineered lumber. Better yet put the wall underneath and reduce the chance for deflection. Or get an engineer to tell you the same for a fee, and gain the peace of mind for your self. Many of us construction workers know from years of experience what works and what doesn't, but we could not prove it with calculations. Framers routinely build structures that support higher loads, and we build from engineered plans, so you generally learn what works for certain situations. If you have doubt, then get an engineer and sleep at night because that's what it comes down to.
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Yup. While I am not a carpenter I see and do a lot around them and go through a lot of prints.
Also engineers are sometimes engineer blind, they can't see past what the paper should be. For something that should be as simple as adding a wall under that part of the floor they will want an engineered beam spanning to two posts that are on newly poured footings....

The concrete floor isn't going anywhere, it's a small load and not really point loading it. You're not taking the full weight, you are only preventing the sag.
 
I'd like to hear more about yours or anybody's (1 hour) structural engineer visit. I'd suggest you ask for their recommendations in writing or keep shopping. I am having trouble getting those commitments in my area.

Keep us posted.
 
Reefocd said:
I'd like to hear more about yours or anybody's (1 hour) structural engineer visit. I'd suggest you ask for their recommendations in writing or keep shopping. I am having trouble getting those commitment in my area.

Keep us posted.
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I had an engineer come in to see about replacing the LVL beam and 2 posts with a single steel beam and no posts. He recommended a beam. I talked to a contact at a steel fab shop about how much the beam would cost. And he was asking what the beam was for, said it was 20 times what I needed. It was more what they would use for a freight train bridge, not to keep a house standing.

No engineer will sign off on a retrofit like that without serious investigation of what's really going on.


It's a house people, not a suspension bridge or space shuttle. They are very simple, you don't need to bring in engineers, what you are wanting has been done to death, a simple wall will support what's above it. The floor is already designed to hold more weight than the fish tank, jsut not in such a constant way, which is why the simple wall would keep the floor from bowing.
 
I had no problem getting a local engineer, specializing in residential, and familiar with the uniform 1956 construction in my hood (the infamous "Little Boxes" in the folk song of the 60s) for an hour with two Franklins who provided me with calcs of maximum load for the area I was using. However, I am sure I would have been much more costly had I asked him to review and sign off on a retrofit design.
 
sleepydoc said:
Rather than take the advice of people here on RC with unknown experience & qualifications, pay for a qualified structural engineer to evaluate the capacity of the joists. Most everyone here means well, but if they're wrong, they just log out and let you mop up the basement and rebuild your living room floor.
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When we built our house we had to have a structural engineer review are plans. The guy we used had all the credentials and certifications. He told us that our floor joists were oversized for the span,and to save some money we could use 2x10's instead of 2x12' well that was all fine and dandy until the tile in our kitchen started coming loose from the floor bouncing when our daughters ran across it. Engineers are alright but a lot of them have been taught to build strong but just strong enough. The one we used didn't know much about real world applications.
 
Perfectly stated Stan. There is a lot to be said for real world experience, and unfortunately many engineers are lacking this. I have built more than a few homes that are engineered correctly, but are unable to be built in the real world. It would be great to get a engineers perspective on this topic. They are, as a whole, a very important resource for a builder to utilize, and there are many situations in which I would not feel comfortable without their consultation. Adding 270 gallons of saltwater + stand + sump in your situation is not one of them. Another option you could consider is call a couple of local reputable contractors for a free estimate, and get their advice on the situation.
 
stan zemanek said:
When we built our house we had to have a structural engineer review are plans. The guy we used had all the credentials and certifications. He told us that our floor joists were oversized for the span,and to save some money we could use 2x10's instead of 2x12' well that was all fine and dandy until the tile in our kitchen started coming loose from the floor bouncing when our daughters ran across it. Engineers are alright but a lot of them have been taught to build strong but just strong enough. The one we used didn't know much about real world applications.
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2x10s for residential floors are standard, and generally more than adequate. Was the proper cross bracing installed on yours? Did the builder use SYP, or a less substantial species? 2x10s over an appropriate span shouldn't feel springy if good construction practices were observed. As for tile popping, a number of factors could be responsible such as an inadequate subfloor, poor quality or non-modified thinset, sub par installation, etc...
 
As a tile guy I know that 2x10's are frequently inadequate due to the larger basement rooms (and so longer joist spans) that modern home buyers want. "Appropriate span" is the key.
FunnyguyMI, at 16' span, 2x10's, 16" oc, fir floor joists have a calculated deflection of L/269, which would deflect about 3/4" when you put a 300 lb weight mid span. That sucks. Definitely not good enough for any kind of tile at all. We call it a trampoline. :) You're putting 10 times that weight mid-span though. I would say that no reasonable amount of sistering is going to do the trick. You need a wall or beam down below perpendicular to the joist span. Do you have enough height downstairs to add a perpendicular beam about mid-span, so you can preserve the use of the large playroom?
One possible idea: if you added a structural closet at one end of the basement room to cut the span down from 16' to 13', you improve to deflection strength to L/458, or only 1/3" deflection for a 300 lb weight mid-span. That might be in the range of workable with a couple of basic sistered joists & blocking, but I would want an engineer to approve that one. Without an engineer, I think your only option is a perpendicular wall or heavy beam about mid-span.
 
Tom Hulse said:
Do you have enough height downstairs to add a perpendicular beam about mid-span, so you can preserve the use of the large playroom?
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This is a possibility.. I'm trying to avoid a 40" wall in the middle of the room. But, I might have enough height to add 3 2x10s as a beam perpendicular to the joists and have it run from one side of the room to the other. Would I be able to just put 2x4/6s bracing each end of that beam, without any support mid-way? That would prevent the 40" wall..
 
Oh, and I suggest if you go with a beam either use LVL beams from your local lumber yard...cheaper but heavier...or a steel beam. Both are MUCH stronger than a few 2 x whatevers.
 
My plan at this point is to add a beam mid-span to support the joists from sagging.

I'm planning on making the beam out of 2 2x10 or 2x12s with 1/2" plywood pieces sandwiched in between every 2' or so. I'm going to support the beam on both ends with 2 or 3 2x6s, and the 2x6s will be notched so that the beam sits in the 2x6s.

I can screw the outer 2x6s (those closest to the wall) on each end to studs to help stabilize it. But, I'm not sure what I should do to attach the joists to the beam. I was thinking maybe some 'L' brackets to give it some added side-to-side stability. Or, is there a better bracket or way to do this?

These pics kind of show what I'm thinking about doing..

photo1-1_zps52b76c43.jpg


photo2-1_zpsf783801d.jpg


And what the joists look like, if that helps at all.. The beam will run right along the 'X' cross bracing.

photo3_zps60bf6a74.jpg


photo4_zpsdb17f88a.jpg
 
To me this sounds like a great excuse to build a kick *** fish room under the tank! Put the walls strategically for support and voila....WIN WIN.
 
The beam is a good idea. I'm not sure spanning the entire basement will be that effective. it would be much better to use a short beam going out from the staircase wall to the third or fourth joist from that wall. As the beam gets a longer span it will tend to deflect in the middle, exactly where you need the support.

This could be a wall used to create a closet or the beginnings of a sump stand.

If you decide to do it as you have shown, consider LVL instead of regular 2x10/12. They are stronger and straighter.

I see mess777 and I are thinking about other 'fish ways' that space could be used instead of a dumbbell storage area! :)
 
Hey my first post lol, I ran into a similar problem with this when I was going to do a 240g build. The reason many say use a structural engineer is your not only having to figure out the load the floor is having set on it but also the loads that are transfered from the roof down and also the load of the aquarium is not dead weight its a moving weight and all that combination with improper support can lead to a very big mess or someone getting hurt.. I would recommend using a structural engineer for sure with this amount of weight. . Just my .02 hope it helps a little.
 
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