# Determine max weight capacity of deck



## Joe Carola (Apr 14, 2006)

Fantastic said:


> Anyone know how to determine the max weight your deck will support? I'm looking at getting a hot tub (800 liters) and want to place it on a raised portion of my deck. *Just don't know if I should be concerned?*


What does that mean you don't know if you should be concerned? Why wouldn't you be concerned, you're thinking about putting a hot tub on top of your deck. Common sense tells you that you should be concerned.


----------



## Daniel Holzman (Mar 10, 2009)

Normally available code for deck design does not include placement of a hot tub on the deck. For example, see item 5 on page 2 of the International Residential Code 2006 edition deck design, which specifically states that the code does not apply to placement of hot tubs on decks. So unless your deck was designed to a code that included placement of a hot tub (unlikely), or was specifically designed by an engineer to support a hot tub (unlikely), you need to do some computations to determine the strength of the deck before you put an 800 kg tub on it.

The process to determine the strength of the deck works as follows:

1. Determine the maximum load the deck is expected to be subjected to. This requires knowledge of the location of the hot tub, any additional loads to be placed, and assignment of live load on the remainder of the deck. Include loads due to sloshing of water, seismic if applicable, and wind.

2. Prepare a detailed drawing showing all structural elements that will be impacted by the hot tub, including posts, beams, joists, and deck material.

3. Analyze all impacted structural elements for all possible failure modes, which would include bending, shear, direct compression, buckling, and possibly torsion.

4. Evaluate the factor of safety afforded by the structure, make necessary structural improvements as required.

Since you are well outside code, you probably need an engineer for this one. Alternatively, put the hot tub on the ground.


----------



## illnastyimpreza (Aug 31, 2011)

LOTS of BIG wood...


----------



## Fantastic (Feb 21, 2011)

Joe Carola said:


> What does that mean you don't know if you should be concerned? Why wouldn't you be concerned, you're thinking about putting a hot tub on top of your deck. Common sense tells you that you should be concerned.


As in if decks can hold whatever you put on them based on how they are constructed....By the way thanks Dr. Obvious for pointing out the obvious about being concerned about placing a hot tub on top of my deck which obviously is common sense to be concerned about hence the reason I posted a question that you didn't answer... If you didn't know the answer you didn't need to post. 


And now an actual BIG thanks to Dan Holzmen for providing an answer... Which is what this forum is used for. 

THANKS DAN!!! I'll be working on figuring this out.


----------



## concretemasonry (Oct 10, 2006)

If you have an existing ledger attached deck system, don't forget to examine the connection of the attachment and any existing/rot/deterioration that could have affected the "house of cards" that a ledger attached deck is subjected to. - Not all loads go only vertical, since any vertical movement can cause a horizontal movement. The loads used in design are for perfect construction and are not for existing conditions.

There is always a Dr. Obvious that has seen many problems and is in high demand after the fact. Most profit from early opinions that result in bigger problems, but hate to see the results. The catch terms are "substandard maintenance", "deferred maintenance" and "unanticipated loads" when original designs are relied on.

A hot tub is an "attractive nuisance" and does attract more activity and concentrated loads beyond the tub and water weight and the average square footage loading and can be compounded by additional height.

Dick


----------



## tony.g (Apr 15, 2012)

Daniel Holzman said:


> 3. Analyze all impacted structural elements for all possible failure modes, which would include bending, shear, direct compression, buckling, and possibly torsion.


I thought that this would put the OP off, but obviously not!


----------



## cortell (Nov 27, 2010)

tony.g said:


> I thought that this would put the OP off, but obviously not!


Perhaps "figuring it out" involves getting an engineering degree. Who knows.


----------



## mcfarton (Apr 16, 2012)

of course you put more and more hot tubs on your deck till it falls then you rebuild the same way and you know how much it will hold


----------



## daveplot (Apr 29, 2011)

As someone that has a 500 gal. (1900 L) hot tub on a second story deck, you NEED an engineer to draw up some plans. what if your deck collapses and someone is injured? If an engineer sealed the plans you are better off. The engineer would take other loads into consideration too such as snow.


----------



## AtlanticWBConst. (May 12, 2006)

You cannot just place a hot tub on an elevated deck. 

The hot tub should have its own dedicated structural support system. This is sometimes accomplished by building what is essentially a "mini" deck of multiple footings and beams underneath the hot tub, and installing the actual deck around it (tub recessed with deck elevated around it). Or, by building a reinforcing system of multiple footings and beams under the deck location where the hot tub will be going.

If you want to do this correctly, you don't want to "guess". You should get it done professionally from a qualified, experienced, and educated source.


----------



## Fantastic (Feb 21, 2011)

I was not put off nor do I need a degree.... I am fortunate that I am friends with an engineer and he will be figuring it out for me...  

And that's the only reason I'm not put off because if I didn't have an engineer friend I would of said forget it LOL 

Thanks again for all the input. It is appreciated! If it turns into a project I'll post some pics.


----------



## cortell (Nov 27, 2010)

Fantastic said:


> I was not put off nor do I need a degree.... I am fortunate that I am friends with an engineer and he will be figuring it out for me...
> 
> And that's the only reason I'm not put off because if I didn't have an engineer friend I would of said forget it LOL
> 
> Thanks again for all the input. It is appreciated! If it turns into a project I'll post some pics.


Missions accomplished, then. Another person steered in the right direction. 

I admire the thick skin, BTW. You got some flak there, but you took it gracefully.

Best of luck!


----------

