Just wrapped up a massive multi-level build for a friend—learned a ton about custom inlays

I did a similar custom inlay for my cousin's place in Ohio using Trex Transcend. We tried a compass rose design in the middle of a 20x20 platform. The framing was the hardest part becuase you have to add so much extra blocking to support those small cut pieces. I ended up using alot of scrap 2x8s just to make sure every edge of the composite had a solid place to land. One thing I learned the hard way is that even if you measure perfectly, the heat expansion on those dark boards can mess with your gaps. We had a 1/8 inch gap in the morning that basially disappeared by 3 PM in the sun. I actualy prefer a simpler picture frame border now because those complex curves are such a pain to maintain over the years if the joists settle even a tiny bit. My back still hurts thinking about the three days I spent on my hands and knees with a router and a jig.

I tried a similar geometric border layout on a project in North Carolina using TimberTech Azek. While the framing is a beast, my biggest headache was acutally the gap management. When you mix those dark charcoal boards with lighter grays for the borders, the heat absorption is totally different. During the summer, those tight miters in the geometric zones started pushing against each other becuase the dark boards expanded way more than the lighter ones. Now, whenever I help out with these experimental designs, I suggest using hidden fasteners like the CAMO system or Cortex plugs. It helps keep things secure but gives the boards a little room to breathe. If you didn't leave at least a 3/16-inch gap at the butt joints where those curves meet the straight runs, you might see some buckling once the sun realy hits that black metal railing and reflects onto the deck surface. It looks incredible on day one, but those tight tolerances can be a curse six months down the road.

Man, those curves sound absolutely insane to pull off! I’m just starting to plan my first small platform and seeing stuff like this is so inspiring but also totally terrifying. Since you did those massive circular zones, did you guys end up installing any built-in seating or benches that follow those same curves? I'm obsessed with the idea of a curved bench to match a layout like that, but I'm worried about how you'd even handle the structural support for it.

If you realy want to kill the expansion issues the other guys mentioned, you should've looked at the Decking Wing Arm from FastenMaster. It’s a game changer for those tight radius cuts. I did a similar multi-level job with MoistureShield Vision becuase that CoolDeck tech actually handles the heat cycles better when you’re mixing dark colors like Mochaccino and Cathedral Stone. For those circular inlays, did you guys use a heat blanket like the Heatcon kit to pre-bend the boards, or were you just kerf-cutting the underside? I’ve found that even with 12-inch on-center joists, those custom curves need some serious structural adhesive like PL Premium to keep from shifting over time.

Spot on with the extra blocking. It's the only way to keep those smaller decorative pieces from bouncing. One detail that usually gets missed on these custom inlays is the water management. When you pack that much extra lumber together to support the patterns, you're creating a massive shelf for moisture to sit. I always double up on the joist tape over the entire inlay area so those extra 2x8s don't rot out way before the composite boards do. It's a bit of a pain to apply on those tight curves, but it's the only way to protect all that framing work.

Quick update — that tip about the extra blocking for the small cuts was a lifesaver; it realy stabilized the whole inlay. I'm still struggling with the gap expansion between the diffrent colors though. Has anyone here actualy used that Wing Arm tool for the tighter radius cuts? I’m curious if it really holds up better against the heat shifting over time.