Hot tub deck support


  #1  
Old 10-27-18, 02:13 PM
B
Member
Thread Starter
Join Date: Feb 2014
Location: Canada
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Hot tub deck support

Hi everyone.

I'm hoping someone could help me decide if what I have is adequate, and if not, what you think is needed. Of course...leaving it as-is would be fantastic if it will work.

We have a small hot tub that we want to put on our deck. The deck was just recently reinforced but not with the intention of putting a hot tub on it. I have included quite a few pictures. The deck itself is made up of the following:

-posts are true 6x6 fir
-posts are 8 1/2' and 9 1/2' between each post
-posts sit on concrete sonotubes buried 18" and sitting on 20"x20" concrete footing
-sonotube is attached to footing with rebar
-posts sit in 6X6" saddles (post anchor) with 4-6" rebar going into sonotube
-beams sitting on posts are 3 (triple) 2 x10" fir beams sitting in metal saddles (post anchor)
-deck joists are 2x10" and are 16"OC (some are 14" for some reason)
-There is only one row of bridging. They are not offset. They are 2x4" and are at the top of the joist not in the middle.
-The joists at the house side for the most part sit 4" into the inside of the house, they do not go deep into the house as in new construction.
- The window and sliding door are new.
-Sliding door has a steel i-beam (as shown) with 4 - 2X4" on each side. I don't currently have the i-beam stats but if I can get them I will post.
-the window has 3 - 2X4" supporting the window header.
-Filled weight of the hot tub is 2500lbs, plus add 1000lbs to the extreme for people, so 3500lbs total. If my calculations are correct that would be 71.5lbs per square foot.
- The tub is 8x8 feet
 
Attached Images        
  #2  
Old 10-27-18, 04:21 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,939
Received 3,951 Upvotes on 3,544 Posts
I'm sure our codes here are a little different then yours there and I am by no means a carpenter.

I had a friend who wanted to do what you want to do. He was knocked down due to insufficient fastening of the ledger board into the house. He ended up putting it under the deck.

With that amount of weight..... you don't want the ledger board to fail.

The others will stop by and offer their opinions.
 

Last edited by PJmax; 10-29-18 at 10:37 AM. Reason: typo
  #3  
Old 10-29-18, 03:18 AM
B
Member
Thread Starter
Join Date: Feb 2014
Location: Canada
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks...I wish I could put it underneath but it's a rental suite.
 
  #4  
Old 10-29-18, 04:42 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 27,657
Received 2,153 Upvotes on 1,928 Posts
A structural engineer is really the only one that can determine if your deck is strong enough to support the spa.

I don't see any attachment bolts for your deck's ledger to the house so right off the bat that makes me question the rest of the deck.

What most spa companies recommend is to build a support structure underneath the spa area for support. You install four footers and support posts/columns, beams and joists just like you would for a deck except it's only under the area where the spa will be located. They go this route mainly because it's known. With your old, existing deck there are so many unknowns. For example you don't know what footers are underneath it's posts.
 
  #5  
Old 10-29-18, 07:41 AM
B
Member
Thread Starter
Join Date: Feb 2014
Location: Canada
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks Pilot Dane. The joists rest on top of the outside wall so there is no ledger board to attach them too. What appears to look like a ledger board from the pictures is actually just boards cut to fit between the joists .

The footings were poured be me and a friend per the description in the original posting.

You are right about the engineer but still someone in here may have that background or experience. Just looking for that advice.
 
  #6  
Old 10-29-18, 04:30 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Posts: 27,061
Received 1,910 Upvotes on 1,716 Posts
Like Dane said, no one here is going to give you structural engineer type answers... and for free to boot. That is what they get paid for, and you get a paper with their recommendation and stamp... there is no substitute for that when you need to get a permit, an inspection, or when it comes back on you if it happens to collapse down the road.

Best I could tell you is that the joists should definitely be doubled under the hot tub... put in doubled joist hangers in front. Replace the blocking in back. Whether or not the front beams will now be overspanned and whether doubling joists is adequate to get you up to 70+lbs psf... only a structural engineer can answer that.
 
  #7  
Old 10-29-18, 09:59 PM
B
Member
Thread Starter
Join Date: Feb 2014
Location: Canada
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks Sleeper.

But I'm notoriously cheap.

Anyhow ...I appreciate the info. I had a friend say the same about the doubling of the joists. Not sure how I would replace the blocking though? What would I replace it with? I'm thinking to hang the extra joists I would need something to hang them from...but I can't think of what to do in tha area? I don't think I should be hanging them off the blocking.
 
  #8  
Old 10-30-18, 04:35 AM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Posts: 27,061
Received 1,910 Upvotes on 1,716 Posts
The new joists sit on top of the wall, your joists are obviously cantilevered. The blocking is just a board between joists, meant to close off the space and keep them plumb. After your new joists are in you put new blocking in that fits tightly.
 
  #9  
Old 10-30-18, 04:38 AM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Posts: 27,061
Received 1,910 Upvotes on 1,716 Posts
You are taking quite a risk by not going to an engineer. You've apparently not read enough deck collapse stories.

The new (and existing) joists sit on top of the wall, your joists are obviously cantilevered. The blocking is just a board between joists, meant to close off the space and keep them plumb. After your new joists are in you put new blocking in that fits tightly.

And the plywood sitting on top of your joists is running the wrong direction.
 
  #10  
Old 10-30-18, 08:09 AM
B
Member
Thread Starter
Join Date: Feb 2014
Location: Canada
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thank you. Of course... that makes sense. Remove the blocking, put the new joist in beside the other one, laminate them, replace the blocking...but first go to an engineer. Yup.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: