Flush beam spacing on a ground level deck
Hi everyone, first post so be gentle. I am building a small ground level deck on a slope by a pool. The deck will only be 10′ deep by 27′, with a return of 18’x8′ forming an L shape. It will be around one corner of an in ground pool.
On the edge closest to the pool, I will be running a double rim joist and the joists that attach to that will span 8′ and set on a 2×10 beam with a 2′ overhang (2×8). My question is since I don’t want to dig out the 15″ approx it would take to get a 2×10 beam under the pool side edge, I want to use flush beams, so how far apart should they be? Do I run them to overhang at the post location for the away side beam? Also, do I triple a 2×8 to make the flush beam?
My background is a commercial contractor who has specialized in building repair and some light interior build outs. I have also been a site supervisor for new construction. The last deck I built was a ground level deck, but about 15 years ago, so I forgot everything about that one!
Thanks
Replies
If I’m following you correctly you are trying to build the deck to the pool edge or over the edge a little? Also, assuming you are limited to footing location b/c you can’t get too close to the pool edge and risk damage to the pool? If my assumptions are correct I would keep it simple. Run your joists parallel to the pool edge and have flush girders perpendicular to the pool edge. You can cantilever the flush girders and hanger joist off of those. This way you do not need to incorporate girders/joists to support your main flush girder. Can refer to IRC for approved joist and girder spans. There are a lot of deck span tables available on the net, but make sure you are using IRC tables and/or your local code authority reference for your approved spans.
I'm actually going to be about a foot away from the pool edge, I don't want to risk any back fill coming out (the ground slopes away from the pool). Since I am going to be running my Azek decking parallel to the pool sidewalk, my joists will be running perpendicular to the pool/rim joist.
My problem is getting a cantilever beam (2-2x10) under the joists closest to the pool. I don't want to excavate the additional 12-15" that close to the pool edge needed to get that beam under there. According to the IRC tables, a 2x8 joist can span 11'10" in my scenario with 2' overhang, and I am acually only spanning about 8 to 9'. So if I absolutely have to I could come 2' from the parallel rim joist and dig out for a beam, but the ground is like concrete.
So could I run a flush beam parallel to my joists, perpenicular to the rim joist, and have it going over a pier footing 2' from my rim joist (pool edge side)? the away side will be setting on a cantilever beam (2-2x10).
It does make it a bit more complicated running joists in the direction that you are, but if you refer to https://www.awc.org/pdf/codes-standards/publications/dca/AWC-DCA62012-DeckGuide-1405.pdf it deals with everything you will encounter with a deck. The IRC and your municipality base their codes off of this. If you cannot find a solution using this as a guideline, an engineer will need to be consulted. If you refer to the section in the AWC addressing header and trimmer joists it will help guide you through. Or you can give your local inspector a call and simply tell them what you plan to do and they will tell you if it’s okay. This will probably be your simplest approach. Without seeing all the details clearly it’s a bit tough to tell you exactly what needs to be done. Truthfully, a ground deck is a lot less worrisome than a raised deck and often do not require permit or inspection. No risk of collapse. The deck just acts as pavement. Good luck.
That's what I am getting my info from.
My decking will be perpendicular to joists and pool. Here is a rough layout of the deck dimensions.
I would construct with flush beams running perpendicular to the pool. You can cantilever the flush beam off of footing on pool side. Would install a beam on the angle at inside corner as well. Running decking perpendicular to the pool edge, so you will use 10’ and 8’ lengths of decking. I’m not a fan of butt seams with decking. You will not have any butt seams running decking perpendicular to the pool. It would look good to have a angled cut where the two sections of deck meet or can weave the boards on the inside corner which looks really good, but more time consuming. This method is the most common procedure for decks of your dimension and shape. I see it as kind of like a wrap around porch, but for a pool not a home.
Kind of what I was thinking. I went ahead and dig out a trench for a parallel beam poolside. I was going to do the beam in the middle for the angle and had planned on doing a diagonal trim board down the middle of that angle to separate the joint deck boards.
Thanks for the input I truly appreciate your time.