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djonesax 03-06-2010 08:46 AM

Extend deck with out new posts
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Here are some pictures of my deck that I want to extend. I would like to add as much possible on each side of it with out adding new posts unless. I have been told that I should not go farther than 4 feet. The edge bands are 2x10 and the joists are 2x8. Also I want to put my hot tub on the deck which holds 220 gallons. Will it be strong enough to hold the weight?

So the question is how can I accomplish this?



Daniel Holzman 03-06-2010 09:02 AM

So you want to cantilever your deck and put on a hot tub that weight approximately 2000 lbs? Good place to start would be your local code enforcement official. If you want to bypass the code official, or there are no codes in your area, you should hire a structural engineer to evaluate your specific condition. The code official may tell you to do that anyway.

Whether the hot tub can be held is a function of the specific geometry of your deck, and cannot be answered without detailed information regarding the specific sizing and connections of structural elements on your deck, the proposed location of the tub, local code loading requirements, and knowledge of the foundation.

Scuba_Dave 03-06-2010 10:20 AM

I would not put the hot tub on the deck
I'd cut out & build it into the deck, sticking up about 1'
I'd build something underneath to support the hot tub

What you are trying to do would probably mean a total rebuild to support the hot tub & cantilever
What you can do will be determined by local codes & your Building Dept

jlhaslip 03-06-2010 01:06 PM

Maximum cantilever of 24 " is a good idea.

AtlanticWBConst. 03-06-2010 01:56 PM

Do not install a hot tub on that deck, the way it is. Do not attempt to attach a cantilever area either for a hot tub.

Bare in mind that you are adding over 1000 pounds of weight. Dependent on the size of the tub, the amount of water it holds, and the number (and size) of people (in it/ around it), also outdoor furniture, pots, plants, etc = on that deck adds up.

Hot Tub Unit + Large Volume of Water + People = A LOT of WEIGHT.

Here's an example of proper dedicated "structural" support for a hot tub (there are three sets of these beams, each with three 6x6 support posts, on 12" dia. sono tubes):

Gary in WA 03-07-2010 03:44 PM

And after the picture they added solid joist blocking to prevent roll-over, post caps and bases for positive connections, and had the local Building Inspector OK-it for their liability Homeowner's Insurance.

Be safe, Gary

djonesax 03-08-2010 08:54 AM

OK. So I guess I'll leave the hot tub on the concrete patio under the deck. What about just extending it with out worrying about the hot tub. Can I cantilever a 4 foot extension?


drtbk4ever 03-08-2010 12:08 PM

Hi djonesax, Please clarify what you want to cantilever?

Do you want to cantilever the joists out over the beam (to add width to the deck as measured from the house) or do you want the beam cantilevered over the corner posts (to add length)?

Were you planning a complete rebuild? Regardless of which form of cantilever you wanted, I think it would be easier to start from scratch.

djonesax 03-08-2010 02:07 PM

I want to make it larger the cheapest way possible. I was thinking to add 4 feet to each side. It was suggested to me to use cantilevers on each side to support the 4 foot extensions. I was told not to go further than 4 feet using a cantilever.

I have never done this before but am confident that I can do what ever needs to be done if I have a plan. I need to know a reasonable approach and what needs to be done. Maybe there is an article somewhere about extending deck that someone can point me to.


Scuba_Dave 03-08-2010 02:17 PM

How far out does the deck come from the house ?
Cantilever needs to be designed to carry the load
For a 4' cantilever you may need to go 8' in along an existing joist for support
You then need to re-inforce the exisiting deck due to up-lift from the cantilever
In some cases you need to go with a larger joist size based on the cantilever
Yours look like only 2x6's (2x8 ?) will need bigger joist for the cantilever
You then need a larger ledger board against the house

Local codes will dictate what you are allowed to cantilever
So the 1st step is talking to you local Building Dept on what they will allow & what they will require
You may even need to pour bigger (and more) concrete supports (sono-tubes)

drtbk4ever 03-08-2010 02:42 PM

1 Attachment(s)

Originally Posted by Scuba_Dave (Post 411588)
Local codes will dictate what you are allowed to cantilever
So the 1st step is talking to you local Building Dept on what they will allow & what they will require

Yes, this is the first step. 4 Feet seems a bit much in my opinion, but the building codes will dictate that for you. For example in my jurisdiction, the maximum joist cantilever is 24 inches and that is only with joists at least 10 feet long.

From what you are saying is you don't care which way to cantilever as long as it doesn't involve adding more posts. It doesn't matter which direction you go, it will involve a complete rebuild. But if it is permitted you may be able to add 2 feet in each direction. But again check with your local building department.

Thurman 03-08-2010 04:07 PM

Maybe I read the OP wrong, but--It seems like he's wanting to add four (4) feet to the existing 2x10 edge bands, with NO post. IF this is the case, I would not recommend this at all. David

djonesax 03-08-2010 04:22 PM

The joists are 2x8 and the banding or whatever its called is 2x10. I didn't want to put more posts in because I have a garden and retaining wall under the deck. if I put more post in they would have to be placed after the garden wall, into the yard and would look really out of place. If I have to add more posts then the best I can do is go to the side about 8 or 9 feet. If I did that, I suppose I could get the hot tub up there as I could add all the posts needed.


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