Structural Engineering | architectural ??'s re: floor reinforcement

[sugartooth]

Hello,
I would like to see if there are any of you who have gone to structural engineers and architects to assess the integrity of your floor? I'm upgrading and very concerned, but how do you know if the person you are dealing with really knows how to crunch the numbers for your tank?

What kinds of questions should I be asking besides asking for references?

Also, if you have had the assessment done, what is fair hourly compensation? I ask because the quote I got was a lot higher than I thought it would be.

How much did you pay (ballpark figure) to have a structural engineer?

Thank you very much in advance and would welcome all thoughts and advice.

 

[sugartooth]

By the way, it's just the layout, numbers, and design. The assessment does not include contractors and labor.

 

[OCRick]

I would definitely make sure he is a Registered Professional Engineer in your State and has the proper liability insurance. Also, make sure he signs/seals any calculations and plans he provides you. This will help to prove his competency and protect you legally if something goes wrong.

 

[bbrantley]

I used a structural engineer to design (and validate, in some places) the reinforcements needed in my house to support Bertha. The tank is on the second floor of our house and the total room load needed to be close to 20,000 pounds.

OCRick is right -- you need an engineer who will deliver stamped plans, and you want someone who's been in the business a while or is part of a decent-sized organization. This gives you recourse down the road if something were to go wrong, and in some jurisdictions makes your building permit actually legal.

The good thing about most of these kind of static load analyses is that they're pretty cut and dry with normal residential materials, and on top of that it's not usually much more expensive to just overbuild a little more and get some extra safety factor. For example, in my case, we needed to add a steel support right in the middle of a downstairs wall plus connect that to a new concrete footing in the foundation. We also had to weld some extra steel beam to a few cross members as well. Once you're going to tear open the walls, ceiling, and floor and make a big mess, sticking in something a little beefier is often a small marginal cost.

My engineering analysis cost about $1,700, including two walk-throughs and a small series of iterations on the drawings. I saved a little because I could provide the original AutoCAD drawings for the house for him to start off of. I bet it took him a total of 12 or 15 hours, max. The actual construction costs ended up close to $25k, so this was a small, easily justifiable expense in the grand scheme.

You asked about questions you should be asking... I'm not sure what to say here. I think you should rely on licensing, references, and project history more than any specific technical Q's whose answers may well be out of a lay person's depth anyway.

Good luck!

 

[nauticac4]

The biggest things have been said.
1.Make sure they have their license.
2.Make sure you get a stamped load rating and if needed plans to reinforce the floor. This will give you something to fall back on in the event of a failure.
3.Be as upfront as possible about size, gallons, ect and dont be afraid to tell them that you don't know.

The firms I have been with and used charge anywhere from a flat fee of $500 to load rate a floor up to a couple grand if there is plans and drawings involved.

Call around too and ask about rates or see if you can get someone to give you a flat fee or not to exceed price for their work. Pickings are slim right now you might find someone to help for a little less if you beat the bushes so to speak.

 

[sugartooth]

Thank you all very much for the information and advice. This is extremely helpful for me that you all point me in the right direction.
Also, it's comforting to know the price range. What I was quoted was not that far off with what's been said here. It is only one place that I found on chance.

There are also quite a few very good points made here, and thank you all very much for bringing them up.

Now, another question. What sort of things do I watch out for? For instance, keywords that some companies may use that would mislead you. Or perhaps things that might be mentioned that I should do, but absolutely do not need to have.
For example, when you take your car in to get a tune-up and they come back and try to up-sell you on other things that are 'wrong' with the car.
Is there any of that?

 

[GSMguy]

Upgrading? How much bigger than the tank you just finished?

 

[bbrantley]

<a href=showthread.php?s=&postid=15470728#post15470728 target=_blank>Originally posted</a> by sugartooth
Now, another question. What sort of things do I watch out for? For instance, keywords that some companies may use that would mislead you. Or perhaps things that might be mentioned that I should do, but absolutely do not need to have.
For example, when you take your car in to get a tune-up and they come back and try to up-sell you on other things that are 'wrong' with the car.
Is there any of that?

I could be wrong, and my sample size is small, but I think structural engineering is much different than car repair.

Part of the reason is that, unless you go to an all-in-one firm, the engineer does not have a financial interest in having you do more work than is necessary. They don't really get paid more for spec'ing a bigger beam or a more expensive component. Sure, you could argue that if it takes a little longer to do that or increases the safety factor that it might be somewhat in their interest... but, nominally, these are licensed folks who went through fairly standardized and extensive training in school.

People's safety and lives depend on them doing consistent, accurate work. I think you will (SHOULD) find that they will be pretty analytic with the process. Definitely have them come out and do a walk-through with you first -- that should either be free or a fixed hourly cost that you'll know in advance. If you get a weird feeling, or it seems like they're trying to "sell" you rather than just analyze the situation and respond, maybe get a second opinion from another engineer. I kind of doubt that'll happen, though.

Do you want to tell us more about your specific project, by the way? What kind of tank are you considering? What's your floor made of? Some of us are wannabe, armchair structural engineers... maybe we can at least give you some general tactical considerations.

Ben

 

[sugartooth]

GSM: Good to see your post! I'm not upgrading the big tank, I'm upgrading a first floor tank. =)

Ben: Thank you again for your input. I'm especially paranoid about people picking up on the fact that I don't understand their work fully, and work it to their advantage. I would hope that engineers are more analytical than anything else, but I wanted to make sure I at least ask about that side of things.

As for my project, I would be more than happy to tell about it. I didn't want to tell that part in the first post because I was a little worried it would cloud things and not get to my question.

Here are my concerns:

System A: This is my primary concern. I am planning a 72" x 30" x 30" glass tank with teak, walnut, or african mahagony (not sure if weight of wood is that variable?)
I want this to be bookcase style, so I will have satellite 39 gallon cubes built into 'furniture grade' bookcase shelves flanking the larger tank.
I currently have a 5 foot tank there, and I am constantly nervous because it bounces when anyone walks by. It is on carpet.
This is a newer construction home and floors are engineered wood that give. The site super was nice enough to come by and have a look and he told me the floor should be able to hold it, but it definitely gives way to weight.

A contractor that came over for a different consult (basement) didn't think the floor is made for the load I currently have on there. He strongly suggested reinforcement.

 

[sugartooth]

System B: Marineland series 3 foot cube tank. In a corner on the first floor. Same thing as above. There is currently a 4 foot tank that weebles when you walk around.

The marineland will be 150 gallons, while the current tank is 130 gallons. The cube will be shorter and square, and the current tank is long and skinny.

I'm not so sure that it would be a problem, especially since it's in a corner.

 

[sugartooth]

System C: This one the architect had a gut reaction when he saw it. It's a 10 foot x 4 foot x 30" acrylic tank. The acrylic is 1" thick and on a wood stand currently. We had to shim it so it's sitting on engineered plastic shims.

This is on concrete in the basement. The sump is on a pallet purchased from Uline.

This one he said he was worried the concrete was going to not be able to take the weight over time. He would have to check with the engineer, but one solution would be to cut out the concrete where the tank is sitting and pour thicker concrete.

That would mean taking down the tank and moving it. My gut reaction to that was 'uh nuh we aren't''.

 

[sugartooth]

I also would like to mention, the first floor tanks are all currently parallel to the beams underneath. They sit about 6" away from the wall.

 

[bbrantley]

My guess is that on the first floor you're not out of bounds structurally but you may have issues with the deflection (and bounce) that you choose to ameliorate for your own comfort and sanity.

For those first-floor tanks, do you have any idea what the span is and where the tanks are in relation to the span (middle, near the edge, etc.)? Also, you said it was an engineered floor, but did you mean engineered joists (like TJIs)? If you have engineered I joists and you know their size, the span, and the mass distribution of the load, you can get simple guides that will show you deflection and indicate if you are within design constraints. (Obviously a structural engineer will be able to do the math and consult the tables as well!)

In many cases with suspended floors the limit becomes either your own personal comfort in the space (the bouncing and possibly visual concern with any bow) or the ability of your interior materials to handle the deflection elegantly. A lot of times you can end up with damaged walling, trim, tile, flooring, etc.... no structural risk to the home, but plenty undesirable nonetheless.

What kinds of options do you have in your basement? Is it a finished basement? Do you have access (or an interior wall that might conceal access) to the area where the joists above support the tank?

For the big tank on the concrete, that part I don't know too much about, but the good news is that static load on concrete is a pretty well-understood phenomenon. The engineer should just chew that problem right up and spit you out an answer. Unfortunately for you, if he does determine that the concrete could fail, you're definitely going to be moving the tank.


Like I said, I'm no s.e. I hope you'll find the conversation interesting anyway. At least it's worth about what you paid for it.

Ben

 

[klviper]

I am not a structual engineer but the basement I would think would be the least of your worries. Going by your dim that tank is 750 gal. x that by say 12 lbs per gal to account for rock/stand/ect. That puts you at 9000lbs. Now I don't know the stand config but say that is 1.5 steel going around the perimeter. that puts you at 495 sq/in. of stand contacting the cement. That equats to 18.18 psi.(granted more weight psi would be where the verticle columns come down in the stand due to deflection) Standard basement code in this area is a 4in thick cement with 3000 psi concrete i believe. I would think the basement one would be fine but I am no expert. Maybe they are worried about the ground fill under the concrete compressing.

 

[sugartooth]

klviper: Thank you about the info regarding the concrete. Yes, you are correct, the person was concerned that when they poured the concrete, that it would be uneven and thin in some spots and thicker in other spots.

 

[sugartooth]

<a href=showthread.php?s=&postid=15472823#post15472823 target=_blank>Originally posted</a> by bbrantley
My guess is that on the first floor you're not out of bounds structurally but you may have issues with the deflection (and bounce) that you choose to ameliorate for your own comfort and sanity.

Absolutely!


For those first-floor tanks, do you have any idea what the span is and where the tanks are in relation to the span (middle, near the edge, etc.)? Also, you said it was an engineered floor, but did you mean engineered joists (like TJIs)? If you have engineered I joists and you know their size, the span, and the mass distribution of the load, you can get simple guides that will show you deflection and indicate if you are within design constraints. (Obviously a structural engineer will be able to do the math and consult the tables as well!)

Thanks for this tip! The floor and joists are engineered wood. I haven't looked closely, but I suspect that the tank is not exactly on the joist. I would guess near it, but not in the middle. As for reading and following guides, that is a great idea and it didn't really cross my mind. I just figured the pros would do this lickety split


What kinds of options do you have in your basement? Is it a finished basement? Do you have access (or an interior wall that might conceal access) to the area where the joists above support the tank?

The basement is unfinished and I have access. The plumbing goes to the sumps that are in the basement as well.


Like I said, I'm no s.e. I hope you'll find the conversation interesting anyway. At least it's worth about what you paid for it.

Ben

I say, not bad at all for an armchair s.e.!! Again, you bring up some good points and I'm feeling a little bit more comfortable about how to proceed with quotes, etc. Thank you again.