Replies

1. 
   Guest_ | Jul 08, 2000 09:26pm | #1

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   you have to determine the bearing capacity of the supporting posts....

   the carrying capacity of the beams....

   and the load capacity of the joist system...

   usually you work it the other way...what is the load you are trying to design for???... and then you support it...

   most codes require decks be built for 40 lb. / sf

   here in Ri they have to be designed for 60 lb/sf..

   but those are uniformly distributed loads...

   you are going to be doing a point load... ((8x8 or 10x10 or whatever.. concentrated in the locus of the hot tub))

   the short answer is you should have an engineer or a competent person design your construction....

   b but hey, whadda i no ?

1. 
   Guest_ | Jul 08, 2000 11:03pm | #2

   *Mike is right on. There are a lot of things to consider - Way too many to cover in a simple explanation on a discussion board.

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   Guest_ | Jul 09, 2000 03:34am | #3

   *The most important parts of the equation that Mike left out was FOOTINGS and diagonal bracing. Loads that large require a concrete footing to distribute the load. I am not talking about the kind of footing one constructs by dumping dry bag mix around the post when they drop it in the hole, I mean a concrete pad either with rebar or plenty of concrete.I just did one for my uncle who didn't get the job because he was $1500 high on a HUGE deck with a 4 ton hot tub in it. The guy who did get the job didn't even get the 12 foot long 4x4 posts he used below the frost line, much less onto a footing. The end result will be a deck that slowly settles into the earth! And you can bet it won't go level either. It went in last fall, so we should see some movement by know.That is the first thibg I want to check out next time he calls me down there!The real sickening part is that the guy is a doctor and collects rare cars (no income problem) rather than listen to us or read the quote he just flipped to the last pages, compared the numbers, and dialed the winner!-Rob

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   Guest_ | Jul 09, 2000 04:06am | #4

   *rob.... here's the part i <>>(((you have to determine the bearing capacity of the supporting posts.... )))naturally .. as u no...the bearing capacity of the posts is determined by the bearing capacity of the soil and the footings designed for the posts to bear on... so .. i didn't leave it out ... i just folded it in to the engineering that must be done..your example is the perfect reason tom should get a design for his installation befroe he goes further...

1. 
   Guest_ | Jul 11, 2000 05:03am | #5

   *OK mike, I'll let it go this time.BTW, I did the math on the above mentioned deck.The tub is supported on 6 4x4 posts. the 2 center posts have roughly a ton apiece on them.That means the end of the post applies 18,000 psf to the soil!!Maybe they threw a big rock in the hole to support the post for "safety."-Rob

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   Guest_ | Jul 11, 2000 04:10pm | #6

   *Second grade math was how they built the space shuttle, low bid wins. so of course it works for a docter too! Always bid last, Make your bid slightly lower then the cheapest guy and put a big star next to it with the words plus extras. At least you can have a conversation with the client and explain your view point. Big business does it like that, how many times have we seen "Lowest prices, guaranteed" Basically they don't want to sell at a discount but will if forced to. It is ethical to do that if you tell the person what you are doing. Offer to do it at a lower price then what you would like but tell him/her that at that price I will do it as "fill in". See if price really is the issue or just a method to select a "winner" from out of confusion. When people get mutiple bids they are just telling you, I don't know what I'm doing. I don't know enough to make a judgement as to value. Take the accounting out of the equation, offer your services at the lowest price and the value that you provide as an extra. Most people want the extra but only understand that it's worth more when you ask for more and explain why.Bid last, and tell them you need a copy of their quote to offer the best deal.

3. 
   Guest_ | Jul 13, 2000 06:14pm | #7

   *Do not, install a hot tub on your deck. It weighs 3500 pounds full of water, the pumps will transmit sound and vibration to your house. Elevation has everything to do with how to size footings and posts and beams for an elevated spa pad.We build the deck around the spa. Check out Pro-Dek. com. Good luck

4. 
   Guest_ | Jul 14, 2000 03:31am | #8

   *Pro-Dek,That's a pretty nice web site, and some really great work you do, but outside of one picture of a deck with a spa, I didn't see anything on the site to help Tom with his question.Rich Beckman

5. 
   Guest_ | Jul 14, 2000 06:55am | #10

   *Thanks for visiting my new site Rich. I probably was'nt much help to Tom but the point I was trying to make was that an elevated spa pad should be used, usually 6x6 post and beam constuction , separate from the deck. Decks should not be structually designed to support spa's.

2. 
   Tom_Lafferty | Jul 14, 2000 06:55am | #9

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   We are considering installing a hot tub on our deck. What is the best way to determine the load that our deck can support?