How to add structural support under this joist?

[mikedodge]

I happen to disagree but great thing about Internet its all free advice and everybody is entitled to their opinion. Here's a illustration of what I'm referring to.

I figured that's what you were doing, 2x4 on its side doesn't do much, it might if it was glued but if it helps that much on solid wood joists it would be a lot more common to see. He also doesn't have much room to do much in there or get much ofba span up.

The post he's added is adequate. Adding a second one would be better then one. It's better to support it but people regularely have heavy furniture, wall units and book shelves full of books, pool table, etc. In their houses without a second thought.

 

[cgrutt]

I figured that's what you were doing, 2x4 on its side doesn't do much, it might if it was glued but if it helps that much on solid wood joists it would be a lot more common to see.

The post he's added is adequate. Adding a second one would be better then one. It's better to support it but people regularely have heavy furniture, wall units and book shelves full of books, pool table, etc. In their houses without a second thought.

Again all free opinions OP can do as he pleases. I hear you but the difference here, I think, is we're talking about a 125 gallon aquarium which may have another 20 - 30 gal sump underneath. If floor settles, even just a little, the aquarium can break or leak. Leaving aside the potential water damage failure can cause him to lose potentially thousands in marine life (not sure what he's planning but potentially including fish, invertebrates and corals) and hundreds of hours of prep and tank cycling. He only is supporting this on basically one joist (aside from foundation) in a 100 year-old house with sagging floors. The post as he has shown it isn't even centered on joist which can cause joist to twist and potentially fail with additional weight. I'm just trying to recommend things that will make it as strong and resilient as possible. I did say to glue and screw the 2x4 at least twice. Again, just trying to help.

 

[mikedodge]

Again all free opinions OP can do as he pleases. I hear you but the difference here, I think, is we're talking about a 125 gallon aquarium which may have another 20 - 30 gal sump underneath. If floor settles, even just a little, the aquarium can break or leak. Leaving aside the potential water damage failure can cause him to lose potentially thousands in marine life (not sure what he's planning but potentially including fish, invertebrates and corals) and hundreds of hours of prep and tank cycling. He only is supporting this on basically one joist (aside from foundation) in a 100 year-old house with sagging floors. The post as he has shown it isn't even centered on joist which can cause joist to twist and potentially fail with additional weight. I'm just trying to recommend things that will make it as strong and resilient as possible. I did say to glue and screw the 2x4 at least twice. Again, just trying to help.

The base it sits on was designed to hold an aquarium and should be solid enough to not twist. The aquarium itself should be made strong enough to not come apart with slight movement. If either can't do their job that's a whole other problem. The floor boards spread the load beyond the one joist and the floor would be supported ontop the foundation wall so that's also helping things. The post might not be perfectly centered on the joist but he's pretty close to it, with the jack rod still on it. If it's really a concern he could do like I said in an earlier post and get a second post to have one below either end of the aquarium.
The way that nearby wall is constructed looks like it was also meant to be structural so that's another thing going for that spot.

 

[cgrutt]

The base it sits on was designed to hold an aquarium and should be solid enough to not twist. The aquarium itself should be made strong enough to not come apart with slight movement. If either can't do their job that's a whole other problem. The floor boards spread the load beyond the one joist and the floor would be supported ontop the foundation wall so that's also helping things. The post might not be perfectly centered on the joist but he's pretty close to it, with the jack rod still on it. If it's really a concern he could do like I said in an earlier post and get a second post to have one below either end of the aquarium.
The way that nearby wall is constructed looks like it was also meant to be structural so that's another thing going for that spot.

Yep I don't disagree with any of that and if you read my posts I basically said all the points about flooring, foundation, etc. Only thing Im saying differently is adding a 2x4 on bottom of joist could help stiffen joist and spread load. I've been extremely interested in aquariums for about 40 years and have read a ton about them and tank failures can and do happen almost always due to stress and imbalances in the foundation, which includes both frame/cabinet and flooring. Anyway this is become more burdensome that its worth I'm done. Good luck OP hope it all works out great.

 

[cmandp]

Ideally for me I'd want to adding blocking 16-24" on center from the joist in question to the next joist to the left and right. Then I'd put a column to halve the span on the 3 joists.

 

[billconner]

Hmm this could possibly work. The layers would then look something like (from top down):
joist -> new 2x4 (or whatever) block -> jack post top support
i think the additional layer, while helpful with spacing issues, could just introduce another point for failure.

A 2x4 anchored to a 2x10 with some 6" timber loks is not going to be the least unstable.

 

[billconner]

There's no need for that unless it looks like the post is starting to dig into the bottom of the joist. The 2x4 wouldn't add any strength.

I didn't suggest it for strength, just as a means to set the top of post away from wires and ducts so it's easier to adjust.

 

[TRWham]

There's no need for that unless it looks like the post is starting to dig into the bottom of the joist. The 2x4 wouldn't add any strength.

No, it will add some strength, but it will add significant stiffness, which is what we really need in this case. A properly fastened 2x4 along the bottom of a joist is the same as a flange on a beam, and would stiffen a 2x10 joist versus bending by about 50%, and add lateral stiffness to the joist as well. That lateral stiffness is needed in a case like this where a beam is supported at a point along its length to prevent buckling the web. Some additional stiffening along the side at the bearing point would also be helpful to resist rotation.

 

[CraigStu]

Maybe I am wrong but I don't think that the top plate needs to rotate to do an adjustment of the post.

 

[mike93lx]

Maybe I am wrong but I don't think that the top plate needs to rotate to do an adjustment of the post.

I think the rotation comment is in regards to the beam twisting, not the column plate

 

[TRWham]

I think the rotation comment is in regards to the beam twisting, not the column plate

Correct

 

[CraigStu]

Ahh, thanks, I was misunderstanding.

 

[orioncyg]

Hi all. A couple of follow up questions as I just got back into town last week and have been working on setting up the aquarium.
I added a 2' x 4' plywood (3/4" thick) piece under the jack post to help distribute the load.

As for the aquarium + stand, I had to shim the bottom of the stand along the 6' front edge. There was about a 1/4" drop from the back to the front due to uneven floors. I used a composite shim for this. I also shimmed the sides to compensate.

Note the bottom surface of the stand is flat. There's no rim or leg, etc.
I'm a bit unclear on if the entire bottom surface of the stand is exerting a uniform load on the floor, or if it's primarily the perimeter of the bottom surface that's exerting most/all of that load on the floor? Let's assume a flat level floor for ease of discussion since the shimming likely changes the answer. If the load is uniform, then I think having the shims will cause the non-uniformity, since there's now triangular air gaps between the floor and bottom of the stand at the end of the shim.

 

[Burt Shaver]

Would have to see how the stand is constructed to know if the entire bottom of the stand is supporting weight or if it’s just the perimeter of the stand. If I had to guess I would say it’s the entire bottom since it’s quite heavy. Made of press board?

 

[orioncyg]

Oh sorry I thought I had pasted the aquarium here before but I did not. It's this one from petsmart: link


I'm not 100% sure what the material is. In the Q&A section (where the manufacturer answers many of the questions) and reviews, it seems the stand is made of some combination of plywood and pdf.

 

[duneslider]

I happen to disagree but great thing about Internet its all free advice and everybody is entitled to their opinion. Here's a illustration of what I'm referring to.

Just to add to this, this absolutely works and is a great way to stiffen a floor. I got a detail like this from an engineer a long time ago. The detail we were given was that the 2x4 had to be glued and clamped (screwed). We were using it to stiffen floors that didn't meet spec to install stone flooring, this got it stiff enough to work.

This would NOT make a floor stiffer than adding additional posts and shortening the span but not everyone can/wants to add additional posts.

 

[cgrutt]

Just to add to this, this absolutely works and is a great way to stiffen a floor. I got a detail like this from an engineer a long time ago. The detail we were given was that the 2x4 had to be glued and clamped (screwed). We were using it to stiffen floors that didn't meet spec to install stone flooring, this got it stiff enough to work.

This would NOT make a floor stiffer than adding additional posts and shortening the span but not everyone can/wants to add additional posts.

I actually suggested all of that, glue, screw and add a post to concrete. Seems OP added post and a piece of plywood. Hope post is on the beam and not just unsupported section of plywood.