Any strcutral engineers/home builders out there? Question about reinforcing a floor

[EmilyMarie85]

I'll save you the gory details, but turns out, I need to reinforce my floor. I live in a house with a crawlspace and have a 6' aquarium running parallel with joists, sitting up against the exterior wall. One of the joists sagged, causing a ply board piece to crack. I was able to get the joist reinforced with 2 4X4 supports sitting on 12X12X6 concrete pads with a 2X6 block:



My question is directed at that piece of ply board. It doesn't appear to be broken in 1/2, just cracked. I would rather reinforce that ply board from the crawl space than tear the carpet up, the padding up, and replace the piece that is damaged. This is the crack:




On to my question: can I put 2(?) 2X12(?)s between the joists, butting them up right against the bottom of the sub floor and attach them to the joists with brackets to reinforce the ply board? Will that be sufficient? Or do I have to tear up the floor?



Edit to title: *structural .... sorry. It was a long freaking weekend....

 

[skjl47]

Hello; A repair from below seems worth trying as along with the flooring, the aquarium will have to be taken down. You made a good start.

A potential issue, to me, is that the flooring and floor joist are of engineered material, not dimensional lumber. While the engineered material is reported to be superior in some ways, I am not sure how effective the single joist will continue to be as it must have been stressed or how to attach the 2x12's to that type joist.

Were the joists dimensional lumber I would suggest sistering in additional joists and adding perpendicular bracing and attaching them with metal joist hangers. Some such system may be available for the engineered joists, so check about.

My initial thought is to pour a couple or few of additional footings directly under the cracked section, which I guess is where the front edge of the aquarium rests. I would then likely place a sheet of 3/4 inch plywood to the bottom of the existing cracked floor. I would then consider blocking this plywood sheet up from below with perhaps some dimensional lumber along the line of the crack and catch the weight on additional piers of 4x4's much as you have already done. I considered this approach as you essentially now have a large portion of the weight resting on the one, potentially weakened, joist. Spreading the load to adjacent joists as you mentioned may help some, but I feel that some solid structure directly under the load would make me rest easier. One other thing to consider would be the use of the metal poles with a screw jack at one end could be used and may well be easier and quicker to set up. (lolly poles??)
Some of what you will actually be able to do will depend on the work space available in the crawl space. Having worked in crawl spaces, I do not envy you the task.

While it has often been questioned on this forum, your photos do give proof that aquariums can be heavy enough to do serious damage to flooring. The house must be fairly modern as structurial joists appear to be used.

Good luck

 

[skjl47]

Hello; Let me add that this is likely a situation where someone with specific knowledge should look at the structure. The pictures give a limited scope of what is in play and there may be other things to consider with the overall structure. Perhaps a good contractor could take a look and offer suggestions. A structural engineer may not be too expensive for a basic inspection.

I recall from the physical science classes I taught that dimensional wood would often bow/deflect a great deal before failure. We would test materials to destruction. Hang weight at the center of a length of wood and it will deflect as additional weight is added. The longer the wood, the more it deflects and it takes less weight to reach eventual destruction. With enginered structures where we would glue pieces into some form, there would often be less deflection for the same lengths and weights. However with some of our engineered forms the failure would be much more sudden, often without much deflection. That said I am not familiar with commercial engineered floor joists and particle boards, so I can not reliably relate what the differences may be.

It may be a good idea to get someone to take a look at the total situation.

One other thought is to get rid of the aquarium or at least empty it for a time until some resolution to the issue is achieved.

Good luck

 

[Robulus153]

Any update? I'm trying to figure out how to make a 200 gal tank work in my new house.

 

[skjl47]

Any update? I'm trying to figure out how to make a 200 gal tank work in my new house.

Hello; So far you and I are the only members to respond. The OP has not followed up so we do not have any information as to an outcome.

Perhaps you can describe the particular situation of your new house in a new thread? It may be that others will be willing to give pointers.

There has been a long running disagreement on the forum about floor capacities. Some, such as myself, take the view that a particular house/apartment needs to be checked out and the actual condition of the structure considered by someone with suitable knowledge or experience. Others nearly always post on such threads that they think all structures will hold big tanks, sight unseen. They usually say to go ahead with the big tanks, apparently based on a feeling of how all floors are supposed to be built to some very high standard.

The pictures of this particular thread should be enough to give anyone that has a large tank some pause.

 

[FishOnCampus]

I doubt that the integrity of that beam has been compromised due to a little sagging. I don't see anything wrong with it visually, asides from the fact that it's made of particle board.
As stated by skjl47, I'd screw a piece of plywood into the cracked area of the flooring because obviously, that's no good. You can put cross members in or install another support as you did before under the piece of ply.

 

[Phixer]

Excavate and install pier footings below frostline, bridge with steel H beams. There is more to it but the right way is often the most difficult.

 

[old_guy]

Your pictures scare me. Normally there is a substantial floor joist every 16 inches, covered by either 1xsomething boards or 3/4" or greater OSB or plywood. In your pictures there is the "beam" supporting an edge of the subfloor (the Oriented Strand Board - OSB), and what looks like a 2x4 joist holding up part of the subfloor.

Can you provide a sketch (from above, looking down) of what is holding up that floor?

Like Number 5 said, "Need Input".

 

[skjl47]

Your pictures scare me. Normally there is a substantial floor joist every 16 inches, covered by either 1xsomething boards or 3/4" or greater OSB or plywood. In your pictures there is the "beam" supporting an edge of the subfloor (the Oriented Strand Board - OSB), and what looks like a 2x4 joist holding up part of the subfloor.

Can you provide a sketch (from above, looking down) of what is holding up that floor?



Like Number 5 said, "Need Input".

Hello; Before purchasing my current house, I looked at a number of new built houses. I found in some of the newest used engineered trusses and joists on 24 inch centers in both the floors and roofs. I saw the OSB panels for floors and roof sheeting. I have been told that the newer OSB panels and engineered trusses can be stronger than they used to be. Some decades ago I did some flooring covering installation and it was common to have to replace what we then called particle board in kitchens, bathrooms and any where it got wet. I do not know from experience how the newer stuff holds up to being wet.

It is possible the cracked OSB panel in the OP's pictures is a subflloor with another layer of some sort on top. It can not be determined from the pictures. I am a believer in checking things out for myself. I crawled under many floors and got in many attics before deciding on my current place. I understand that it would be better if all structures were built to a high standard, but have not found this to be the case.

 

[old_guy]

24" works. Less margin, but generally fine. Are there joists under the OSB every 24"?. What size? The pics show only the joist you propped up and what appears to be a single 2x4. I cannot tell if there are any joists and, if so, what size they are or what the spacing is. Repairing from below should be fine, but there needs to be adequate support to start with.

Your repair to the joist is very good. If there is generally adequate support under the floor then the cracked OSB can be easily reinforced. It all depends on what is under there. Can you describe the existing floor framing?