Need advice on deck framing - Oval Pool

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mgmercurio

mgmercurio

Well-known member
Jun 22, 2020
76
Louisville, Kentucky
I have attached a picture of the framing blueprint for my deck/pool design. I have been watching many many youtube videos trying to get a clear understanding of how to lay out the extra posts, joists, and beams needed to run decking all the way under the top rail, around my oval pool. My paticular interest is in how to frame around the curved portions of the oval. I realize I am going to most likely cantelever the joists under the top rail on the pool side of the deck. I am just not sure how to place my posts, beams, and joists to do it.

Two things about my deck design are:
1. The frame construction calls for posts to be flush with joists.
2. I am also going to do a "2-board picture-frame" the deck. The reason for the picture frame is because I would rather have 2 long running decking boards on the inside next to the pool running along with the pool's edge vs. many perpendicular deck boards up against the pool's edge. In the event I need to work on the pool or replace the liner, it will be much easier to remove two boards verses many. ;)

I realize this is more of a deck question then it is a pool question, and I apologize if this is not the right forum to ask, but I have tried to find an answer to this and it has not been easy. Anyway, any help from the experts would be greatly appreciated.

Thanks,
Matt
 

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Sorry, I couldn't follow along with all that you were describing, but I think this is pretty simple. Are those 4x6 beams running around the entire perimeter of the deck (or 4x8 or 2x8 or whatever)? Use the same dimension lumber and cut three lengths with 45° miter cuts on each end, and bolt them to the beams, one beam in each of the three corners. Then cantilever the deck boards out over the resulting framing to meet your pool's shape. If you don't like the span, then add a second 45° joist inside each of the triangles.

You shouldn't need any posts under them, they'll be plenty strong enough. You could even add some ties if you're feeling' it.

Unknown.jpeg
 
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Dirk said:
Sorry, I couldn't follow along with all that you were describing, but I think this is pretty simple. Are those 4x6 beams running around the entire perimeter of the deck (or 4x8 or 2x8 or whatever)? Use the same dimension lumber and cut three lengths with 45° miter cuts on each end, and bolt them to the beams, one beam in each of the three corners. Then cantilever the deck boards out over the resulting framing to meet your pool's shape. If you don't like the span, then add a second 45° joist inside each of the triangles.

You shouldn't need any posts under them, they'll be plenty strong enough. You could even add some ties if you're feeling' it.

View attachment 161177
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Thank you! This is exactly what I needed. Your illustration hits it spot on. My Rim joists that run all the way around the perimeter will be 2x8's. Your explanation makes perfect since. Plus I had no clue they made 45 degree joist hangers. ;) Do you think the hangers will be strong enough to support the cantelevered joists or should I plan to place posts under the beam where the 45 degree joist hangers will go?

Thanks again.
Matt
 
I tried to find a pic of a 45 hanger, but couldn't. Not sure they are made, as they would be pretty hard to nail in. Maybe there are. But there will be some type of tie that you can use. And/or use bolts for added strength. I wouldn't bother with the extra posts. But they certainly wouldn't hurt anything. I tend to over build, nothing wrong with that. Another way to look at it: you're not parking a car up there. It's not going to support a bath tub or a refrigerator. What is the square footage of that triangle? How many people could you cram in there if you tried? Point is: there's just not going to be enough weight on there to warrant more posts, not with as many as you've already got.
 
Just to be clear, these angled joists are not cantilevered. They're connected and supported at each end. I was referring to the deck boards. They'll be cantilevered a bit past your framing to meet the curve of the pool walls.
 
If you're decking is 2x wood lumber, the cantilever will be fine. If you're using composite lumber (like 1" Trex or similar), then you might get a little flex on some of the ends. If so, and if you're feeling industrious, you could add six more angled 2x8s to bring the framing even closer to the curved pool wall. But those will be tough to nail in. Bolts might work, depending on clearance. You can always add them later, if the longest cantelever doesn't feel stiff enough. I can draw that for you, if you need.
 
gb99 said:
mgmercurio: is this decking for an inground pool? If so, please post pictures of your progress as I'd like to do this for my inground pool in the future!
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It is for a 15x30x52 Aquasport above ground pool which I am burying 24' in the ground. I am going to leave roughly 28" above ground so I can build a pool-side bar on top of the stone wall that will abut to the exposed pool wall. I am not sure this helps you, but I can post pics of the progress ;)
 

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Dirk said:
If you're decking is 2x wood lumber, the cantilever will be fine. If you're using composite lumber (like 1" Trex or similar), then you might get a little flex on some of the ends. If so, and if you're feeling industrious, you could add six more angled 2x8s to bring the framing even closer to the curved pool wall. But those will be tough to nail in. Bolts might work, depending on clearance. You can always add them later, if the longest cantelever doesn't feel stiff enough.
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Completely understood...and yes I meant to say cantelevered decking....not joists ;) You are correct, I cant imagine craming a whole lot of people on that curved space. However, I am planning for a 60PSI live load. I am planning to build a covered bar with seating on top of the deck, plus there will be a place for eating as well as a few sunbathing lounge chairs. Yes..as you can imagine, I am planning to have large entertaining parties on this deck...so I expect there may be a large load at times. ;)
 
One thing I might do differently, I'd use 4x6 or 4x8 beams. I'd set those on top of the posts (with proper metal ties) instead of bolting 2x8s to the sides of the posts. And I'd set the joists on top of those. There is nothing wrong with the way you're doing it, especially for a deck. But you started to talk about loads, and what I'm describing is the stronger, longer-lasting way. Plus, you could use significantly less posts and hangers.

The rule of thumb I use: I picture the framing without nails to gauge how it will hold up! Wood that sits on top of other wood only needs nails and bolts and ties to keep it from sliding off. Wood that is connected next to other wood relies on the fasteners to support the weight, which is not as strong. You add some rust and termites to the mix, a little dry rot, and the "next to" framing will fail sooner.

Sometimes you don't have enough clearance for all that extra height, so you go with what you've designed. If there is enough metal (joist hangers), then that will be plenty strong. And I'm talking in terms of decades out. Though the pool water environment will not be kind to the hangers.
 
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I couldn't find a good pic of the ties you would use: at the post/beam intersections, post/pier intersections and even the joist/beam intersections if required. But this is the concept:

philbrickkrista-8.jpg
 
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I built an 18' x 12' deck like this, tied to house and cantilevered out across a single 4x12 beam (might have been 6x12) and only used two posts. Not sure I did the foundations exactly right (deep enough), but it hasn't budged in 20 years...
 
Dirk said:
One thing I might do differently, I'd use 4x6 or 4x8 beams. I'd set those on top of the posts (with proper metal ties) instead of bolting 2x8s to the sides of the posts. And I'd set the joists on top of those. There is nothing wrong with the way you're doing it, especially for a deck. But you started to talk about loads, and what I'm describing is the stronger, longer-lasting way. Plus, you could use significantly less posts and hangers.

The rule of thumb I use: I picture the framing without nails to gauge how it will hold up! Wood that sits on top of other wood only needs nails and bolts and ties to keep it from sliding off. Wood that is connected next to other wood relies on the fasteners to support the weight, which is not as strong. You add some rust and termites to the mix, a little dry rot, and the "next to" framing will fail sooner.

Sometimes you don't have enough clearance for all that extra height, so you go with what you've designed. If there is enough metal (joist hangers), then that will be plenty strong. And I'm talking in terms of decades out. Though the pool water environment will not be kind to the hangers.
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Thank you very much for all the good info. Yes...I completely agree with you regarding sitting the beams on top of the posts verses bolting to the side of the posts. In fact, that is how I truly want to do it...but as you correctly indentified...I might have a height issue. The top of the deck is only going to be 28" above grade....so by the time you factor in:

10" tall 6x6 posts sitting on concrete piers 2" above the ground (To keep ground water off the wood posts)
+
2"x8" inch beam
--------------
18"
+
2"x8" joist
---------------
26"
+
5/4x6 decking
---------
Total = 27 3/4"

I realize I could adjust my post height and get a few more inches of room and I may end up doing that...dunno yet.

But regardless, space is tight now as it is.... at 28".... I'm trying to be mindful of the clearance under the deck should I ever need to crawl under there for any future work or maintenance...or whatever...

As you can see...I'm a bit on the fence with this...but my gut is telling me to do joists on top of the beam...try to keep it as high as possible...and worry about future work under the deck...when/if it ever comes...

I think one piece of info would swing my decision one way or the other is the fact that you brought up the possibility of having less posts to dig...if I do beams on top of posts...so with that in mind...can you elaborate? I really don't know many rules of thumb for spanning when it comes to posts and beams...but if you see a way to fewer posts and less digging.... I'm all ears heh heh :)

Thanks!
Matt
 
I think clearance is definitely something to consider. Animals might have to be dealt with. The kids' ball. Deck maintenance. The never-ending girth increase! Whatever. An alternative is to use 4x8 beams instead of the 2x8s on the perimeter, and hang off of those as you had planned. That wouldn't get rid of the hangers, but would eliminate some posts. A second alternative is to notch the posts supporting the 2x8s. So that the 2x8 is both sitting on top of half the post and nailed next to the other half.

I hesitate to share the rule of thumb for the span, because I got that from anecdotal conversations with builders, not from any sort of engineering guide. But I would think you could double the span. If 2x8s need a post every 4', then a 4x8 should be able to go 8'. But, again, I'm not sure it works that way. The rule I've followed is a foot of span for every inch of height, so a 4x6 can span 6', a 4x8 can span 8', etc. That rule would not equally apply to a 2x8 or a 6x8, etc. But that doesn't consider actual load. That might be overkill for a patio cover, but inadequate for a floor. There are engineering tables for all that, I'm sure. That's why I tend to over build, so that I'm covered.

Oh, back to the clearance. Remember, the joist-on-top-of-beam layout will only affect the clearance under the beams. The clearance under the joists will be the same as you had before. So if you can't get under the beams, you can still go in from each end of that section of deck, just not slide under the beams from section to section. Or if you need to be able to do that too, for some reason, you can dig out a little access ditch just wide enough to squeeze through.
 
Just grabbed this for you. It's the internet, so buyer beware. It reminded me that the type of wood also affects the span.

www.decks.com

Deck Beam & Header Span Table | Decks.com

Size your deck beams and headers with our easy-to-use span table, which allows you to cross reference the post spacing and joist length to determine the right deck beam size. Try it out at Decks.com.
www.decks.com www.decks.com

If you find a couple of these on the 'net, from different sources, that'd be a reasonable way to assure yourself you've got reasonable numbers. Shave a few inches off the span if you want a little extra assurance.

But I'll caution you about the table's reference to doubling up 2x material. Don't do that. First, I don't believe 2 2x8s is as strong as 1 4x8. But more importantly, for decks, you want to minimize "sandwiches!" (My term.) Anywhere two pieces of wood touch, you're creating a sandwich: two pieces of wood and the inevitable layer of dirt/crud/sawdust/water mush in-between that collects over time. Those sandwiches occur between deck and joist, joist and beam, beam and post, etc. Those are the areas that are most susceptible to dry rot. That's where the rot will start. The less sandwiches, the longer your deck will last. The areas I just listed are small, and have a chance to dry out between rains (or pool parties!). If you make huge sandwiches out of 2x8s, the drying out gets substantially impeded. With a pool deck, those could conceivably stay wet all year round. I generally treat post and joist ends with a wood preservative to help stave off the "sandwich effect." Under an outside shower, I lined the top of the joists with aluminum sheet metal "tents" to keep the top of the joists dry. These are all tradeoffs: the labor and materials vs strength and longevity. You make these decisions up front, and deal with the consequences (or reap the benefits) some number of years down the road.
 
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Very helpful info and great tip about protecting the top of the joists from rain and pool water. I will study the span guide and decide. I think I m going to opt to put the beams on top of the posts. Thanks for all the info. I will try to keep this thread updated with progress pics. ;)
 

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