Hot Tub vs. Concrete over Corrugated

[Streetcar]

Will your house be damaged if the beam deflects from the heavy load?
What is under the porch, can supports be easily added for the hot tub?
No easy way to determine strength of slab
Porch can be reinforced with carbon fiber if the beam is adequate.

 

[dodge man]

My degree is in civil engineering and I had both structural analysis and structural design classes. That said I was a land surveyor and never did any structural design but what that background did do was give me the knowledge to know that no one on this board can answer your question.

If I understand the situation you have a 12 foot span of a 6” slab. It sounds like one side sits on a steel beam. What does the other side sit on? Sounds like it was poured over corrugated steel which wouldn’t add much strength. If I’m reading this correctly a 6“ slab spanning that much doesn’t sound very strong. Probably fine for foot traffic. The question is how strong is the concrete and what if any reinforcing is in that slab? Takes a structural engineer to figure it out.

 

[Streetcar]

You are looking at $2000 minimum for engineer to review and rate your slab.
Corrugation is form work not structural.
If properly installed and reinforced the slab is strong enough for your hot tub.
I just installed similar slab rated for truck loading

 

[riptides]

You are looking at $2000 minimum for engineer to review and rate your slab.
Corrugation is form work not structural.
If properly installed and reinforced the slab is strong enough for your hot tub.
I just installed similar slab rated for truck loading

Seems awful high.

But insurance, repairs or bodily injury.....

 

[Streetcar]

The price for structural review is based that somebody will require to spend several hours measuring and testing concrete for strength and rebar.measuring beam and span. Then engineer can take that information and run calculations. I am guessing slab will not be adequate for that hot tub. Failure mode would probably be excessive deflection. The free engineer analysis is worth what you paid for it

 

[dodge man]

On a flat slab, you can take pavement cores. I’ve done this hundreds of times on asphalt and concrete pavement. The problem is in this case you take a core you are damaging the slab and any reinforcement.

They make devices, such as a Swiss Hammer that can give an estimate of the concrete strength. It’s a non destructive test. The problem is what is the reinforcement? I’m not sure there is a way to figure that out. Maybe some kind of x ray machine?

Add in the fact I’m not sure what a hourly charge is for a structural engineer is. Probably at least $150 an hour, maybe more. It’s easy to get $2000 wrapped up in this.

The best thing to do is put the hot tub somewhere else.

 

[Egon]

There are corrugated steel forms that are part of a concrete floor design.

 

[mkendrix]

If the hot tub must be on the porch, then a few hundred dollars for a concrete pad under each corner and a stack of blocks with HARDWOOD shims to hold floor up is cheaper than a structural engineer. Last engineer I used was $180/hour to rate a load bearing beam. 2 hour drive round trip from office to job site is more than material.

 

[JohnnyMX]

Found the engineer plans for the house and specifically the porch. The concrete was to be 3,000psi with #4 rebar laid 12" center running both ways. The corrugated steel is 3" deep 18gauge under the 6" slab. The beam is under a 9' wall on the exterior + the truss. The rest of the foundation is on 12" eReward ICF walls.

 

[dodge man]

Nice looking porch, looks like a great place for a hot tub. If I recall a number 4 bar is 1/2” diameter, sounds well built but I still can’t tell you if it will hold a hot tub.