Elevated Deck Support

[Tommytub]

I want to feel completely comfortable that my elevated deck will withstand the weight of a tub. When I had it built 2 years ago, I told the contractor that I would be placing a tub on it. Now that I'm ready to make a purchase and I called them back...they say they are not engineers and cannot give me the lbs per sq feet.

Any suggestions on who I could call to have someone take a look. The dealerships I'm shopping at do not know how to calculate this either.

I spent 10k on deck and potentially another 10k on a spa and just want to make sure that the 2 will fair fine together.

Thanks for any suggestions.

[Roger]

I want to feel completely comfortable that my elevated deck will withstand the weight of a tub. When I had it built 2 years ago, I told the contractor that I would be placing a tub on it. Now that I'm ready to make a purchase and I called them back...they say they are not engineers and cannot give me the lbs per sq feet.

Any suggestions on who I could call to have someone take a look. The dealerships I'm shopping at do not know how to calculate this either.

I spent 10k on deck and potentially another 10k on a spa and just want to make sure that the 2 will fair fine together.

Thanks for any suggestions.

Any of your local Architechs and engineering firms can legaly caculate and approve any deck, for a fee. Any one else will only be guessing based on standard load caculations. Which may or may not be fine for you. Ask your local lumber yard for load caculations for specific lumber sizes and spans, and do it yourself if that's what you are after. I believe the Ho Springs web site also has a caculator built into there deck building progranbut it will only give you how it should be built based on a specific load.

[Tommytub]

Any of your local Architechs and engineering firms can legaly caculate and approve any deck, for a fee. Any one else will only be guessing based on standard load caculations. Which may or may not be fine for you. Ask your local lumber yard for load caculations for specific lumber sizes and spans, and do it yourself if that's what you are after. I believe the Ho Springs web site also has a caculator built into there deck building progranbut it will only give you how it should be built based on a specific load.

Thanks for recommendation. I've decided for that it is worth it to me to have a structural engineer do his analysis to put my mind at ease. I have an appointment tomorrow. I'm keeping my fingers crossed.

[Amanda]

Thanks for recommendation. I've decided for that it is worth it to me to have a structural engineer do his analysis to put my mind at ease. I have an appointment tomorrow. I'm keeping my fingers crossed.

I would be interested to have an update on what he says. From what I have heard, usually 100 lbs/ sq. foot would do the trick for just about any spa 7-8', but I am definately not a structural engineer.

[NorthWoodsDipper]

I would be interested to have an update on what he says. From what I have heard, usually 100 lbs/ sq. foot would do the trick for just about any spa 7-8', but I am definately not a structural engineer.

Amanda, where did you get that spec. from? I am in the process of laying out my deck now and the Deck lady at Home Depot said 80 lbs/sq. foot was fine. I would really like to know before I build this deck...

BTW... I tried getting the "deck builder" software at the Hot Springs website to work, to no avail. Does it run for anyone else? I tried on both my home and work computers. I have the latest Java loaded and I disabled pop-up blockers.

Thanx!

Steven

[Tommytub]

Update for my elevated 5 1/2' deck....

I contracted a structural engineer to analysis my deck. I started by calling many architects and asked if there was a structural engineer on staff. Most cases there was not and I got names of individuals that they recommended. I found in my area this service will on average cost $200 to $500 for the analysis. (My deck was already built)

My hired structural engineer confirmed my fear that in theory my deck was not adequate to support the weight of a filled spa with the max tubbers. He gave me prints of the analysis and recommendations for increasing the strength.

For me, I'm adding another support beam for a fairly cheap fix (the span was too long), along with a few other easy fixes. For example, the existing (3) double deck beams that support my entire deck are not lag bolted together, which does not allow each pair of beams to act as a single beam with full strength.

I had to make the decision to return to my original builder or have someone else fix it. (I'm still on the fence with this one) When I hired out construction of my deck 2 years earlier, I indicated that I would be placing a spa on it in the near future. At that time, I did not give dimension/weight calculations, etc., so I got an aesthetically pleasing deck that might or might not hold the spa. (You learn by your mistakes)

As you can imagine, the original builder is a little defensive about the engineers results and although he is not an engineer, he sez it will hold the spa (but he will not put it in writing) and doesn't agree with the analysis.

I spent $8000 to construct this deck originally and if I could do it over, I'd hire the structurial engineer to work with builder up front so all issues could be worked through then.

I will be adding the extra support, even if the original deck is/was strong enough to hold the hot tub as my builder indicates. By adding the extra strengh, it cannot hurt, but most importantly ease my mind.

I know I didn't give exact dead load, live load, shear capacity calculations, etc. because it will vary by deck, span, footings, posts, height, etc.

Btw, I purchased the Sundance Marin. Should be available in 4 to 8 weeks, and the deck will be corrected within 2 weeks.

[NorthWoodsDipper]

TommyTub,

Would you please tell us what the engineer recommended for your layout? I am wondering specifically how far apart your piers are, and how far apart your joists are.

When I figured out the lbs/sq ft of the spa I would like to order, I added the weight of 5 THIN BEAUTIFUL women and myself and came to just under 100 lbs/sq ft. Any information you could give me on your construction would be very much appreciated!

Steven

[Tommytub]

I've attached a couple of pics of my deck (hope it posts ok)

I'm not sure that I can answer your question. For me, because I spent alot of money on the deck and hot tub, I felt it was in my best interest to have the engineer make the decision for me. Remember, only an engineer you hire or yourself can make the right decision for you. A couple hundred bucks for this advise is worth it in comparision to what you will be spending on your setup with spa.

With that said, here are a few facts about my deck...

My deck is free standing cedar deck on 2x6 joist 16" o.c. with double 2x8 beams on 6x6 footings 42" depth at 68" off grade. An auger was used to dig the holes at a 12 diameter and dry cement was placed into the holes that should have formed an approx 30" footing.

The surface is layed diagonally with 2x4 nailed down.

Because my deck was already standing, we will place another beam between the 2 beams closest to the house. This is needed because of the original builder decided to make a change from the original plan. I have an air conditioner unit that the builder decided to go around instead of moving it or asking my opinion, which created a longer span (just over 7 feet). This is the primary reason I need to add an additional beam.

If I had contacted this engineer before the construction, he would have evenly space the posts no more than 5 feet, used 2x8 joists 12" oc with double 2x10 beams. He also recommended that the flooring be screwed down with 3" decking screws. The beams not be lag bolted to the sides of the posts as the weight would be placing stress on the bolts instead of the posts. My beams sit onto of the notched out posts and then are lag bolted to the part of the post not notched out. This places the weight onto the post. My double beams need to be lag bolted thoughout so that it acts as one support beam.

Once the 2 additional posts are install, there will be 5 posts under the spa, and the 6th post (displaced by my AC) will be a foot within the footprint of the hottub.

I hope I didn't completely confuse you, that is why I added a couple of pics.

If anyone has additional comments, please add them. Again, a few hundred bucks to hire an engineer might be worth it. It was for me.

[pattyb]

FWIW I was never able to get the Hot Springs deck builder tool working either.

We are adding a free standing 10x12 extension to our existing deck for the new hot tub (at this point looking like Sundance Optima, but have not sealed the deal yet).

After downloading a more current version of JAVA I was able to get the deck design tool working on LOWES.COM We created several designs using 6x6 footers - with 2x8 and 2x10 joists. When you are done the tool provides a 12 page report with several diagrams, material list, and specifications. The live and dead loads are provided on page 7 of the report. For our new deck using 2x8 the PSF was 99, using 2x10 the PSF was 151. To be on the safe side we're going with the 2x10 joists. Not sure this tool is 100% accurate, but it helped us in our decision. Good luck.

[Roger]

Update for my elevated 5 1/2' deck....

For me, I'm adding another support beam for a fairly cheap fix (the span was too long), along with a few other easy fixes. For example, the existing (3) double deck beams that support my entire deck are not lag bolted together, which does not allow each pair of beams to act as a single beam with full strength.

Here you are only allowed to lag bolt your ledger to the house. The header/s should be bolted together with a stagered up and down pattern every 16 inches using 1/2 carrigge bolts, nuts and washers. This spreads the load through all joists.

I won't put it in writing either but if that is 2x decking and about a 6' span between posts and those are 2x10" or 12" joists on 16" or less spacing, it looks to me like it will hold it also. I am however concerned a bit about the distance between the 2 posts on one header. And if it is over 8' then one more post on each header beam should do it. I love messing with engineers because we deal with them all the time in my job and sometimes they can be.......well lets just leave it at that. I would follow his recomondation to be 100% sure, except exceed it by using bolts all the way through the headers. Just as easy.

[DIYTech]

Tommytub,

Have you ever figured out whether your deck can support the spa (w/water and people)? You can try designing the deck you have in either HotSprings deck designer or in Lowe's deck designer. Usually a hot tub requires a little more support right underneath it. Also, it would be good to check to see if your area has any codes about hot tubs on top of decks. This may be the deciding factor.

I want to feel completely comfortable that my elevated deck will withstand the weight of a tub. When I had it built 2 years ago, I told the contractor that I would be placing a tub on it. Now that I'm ready to make a purchase and I called them back...they say they are not engineers and cannot give me the lbs per sq feet.

Any suggestions on who I could call to have someone take a look. The dealerships I'm shopping at do not know how to calculate this either.

I spent 10k on deck and potentially another 10k on a spa and just want to make sure that the 2 will fair fine together.

Thanks for any suggestions.