Deck reinforcement?!?

[Orthofunk]

My builder doesn't want to be liable for the reinforcement of our deck to support the hottub, so I am in charge of telling them what to do.

We ordered a Maxxus, which weighs 6000lbs when filled.  What kind of reinforcement will be necessary to support it?  The tub will be on the lower level of a 2 level cedar deck... only 3 steps down to the patio.

Thanks in advance.

[fletch49]

I racked my brain with that question. I put a spa on a deck 8' up. After searching the internet through, with no luck, I had my friend who is a civil/structural engineer take a look at my deck. He informed me that the tub must support itself. He said the deck must have 2x12 beams and 6x6 posts supporting the corners of the spa. In addition, the joists should be 2x10 12"o/c.

Other than that, his only concern for my situation was the loading of the ledger board on the wall and the 5x5' windows directly below the ledger board. His concern was how much load the metal brace above the windows would take. For that he pulled out his calculator and told me to keep the spa 2' away from the wall/ledger board and make sure the load on that end of the spa is being carried by the 2x12 beam 6x6 post and not the ledger board lagged to the wall.

Hope that helps...
 

[Orthofunk]

Thanks Spazz,
That is very helpful!

Are the four 6X6 posts set in concrete?
There should be two 2X12 beams...  one for each side of the hot tub??

What is the difference between the joists and the beams?

Thanks again

[Gary]

If your builder cannot figure it out I would get a new builder. You also need to check your local codes.

Generally 100lbs per square foot will do. Also check with spa manufacturer.

Gary

[Mike134]

I don't blame the builder for not wanting to be responsible......They don't have the expertise for designing decks for unusual loads, they just build according to industry standards.

My deck is 11 feet up with 2x12 joists on 12" centers with 6 2x12's forming the 11'  long  beams. The posts are crossed braced on all 4 sides.  It only took the structural engineer 6 hours to design and draw the needed plans.

Because this is up in Northern Michigan with heavy snow loads the deck is designed for 165 lbs per sq. ft.

You can't beat the peice of mind having an engineer do the design loads.

[Guttboy]

Mike....

You are right DONT blame your builder.  A good deal of builders subcontract "sub" out your deck or they may not offer that as an option.  They also may only be comfortable building one that they have "pre-canned" that they know will support X ammt of people on it.

Ask your builder if they can recommend a decent deck company.  That is what our builder does...the deck company is doing all the computations/analysis on the deck for the tub.

Home that helps....

Mike

[Vinny]

Remember ask your township - they may REQUIRE a Structural Engineer to approve the plans.

My township told my friend who wanted to add a tub to his deck that he needed a engineer to sign off on it. Now I am building from scratch and am waiting to see if mine passes without an engineer. When I asked the inspectors they told me that I didn't need anything special when I submitted the plans.

[Drifter]

To fashion the "beams" bolt two of the  2 x 12's to the 6 x 6 "posts" (one on either side)  Make sure you bolt all the way through both 2 x 12's and the 6 x 6. I'd also run a 2 x 4 from the bottom of the 2 x 12 down alongside of the side of the 6 x 6 and nail it to the 6 x 6.  The posts need to rest on concrete footers which should probably be 16 inches round and at least 36 inches deep. Wile the concrete is not yet set sink an 18 inch piece of rebar down 12 inches so that 6 inches sticks up. Drill the bottom of the posts and set them on the pins. Next you need to build the frame on top of the "beams" so that you can attach the decking. This frame is called the "Joists.  Under the hot tub I'd use 2 x 10's and  use 12 inch centers.  The part you need an engineer for is to tell you where the "beams" need to be. How far apart ect.  Good Luck!

[Brewman]

In our city, you submit your deck plans to the building department, and they tell you the minimum diameter of the footings, based on your plans.  Footings have to be 48" deep, since we live in a winter freeze area.  

I'd start out by contacting the place that issues building permits in your area, and expand out from there if you need to.

Brewman