How to cut last composite deck board against house/solid objects after tracksaw cut

Question

I've seen several (youtube) professional deck builders uses a track saw to make a nice cut line for breaker boards and edge picture frame boards. I got a cheap track saw hoping to do the same for about 4 cuts rather than making about 100 cuts trying to get boards to line up. I think I know the procedure (1/8" shim underneath for protection, set blade depth to bord depth, zip across), BUT I don't see how you cut the boards against solid objects that the saw cant get to because it runs into them (e.g. against the house). I don't THINK these builders remove the boards to cut, and it my case, the accent board is in there with wall flashing and butyl calk and cortex screws which will completely barrel out once removed, so I'd rather not remove the boards to make this cut.

Is there any other way to finish this cut? Only think I can think of (and looking at one of the cuts in the picture below seems to suggest) is a multitool. No one seems to make a specific composite blade for multitools but I did get a quality carbide blade). I guess if I'm really careful with the multitool I might be able to make a cleanish cut? Any other suggestions?

Answer 1

They make circular saws in a variety of sizes. You can get 14" ones for cutting concrete and I've seen 4-1/2" saws. No matter how small the circular blade, though, there's still a base around it so you can't cut to the edge.

You have to either temporarily tack down the board at the edge to get the alignment, then pick it back up and cut is on a miter saw or with your circular saw, or you have to cut it in place with a non-circular saw. I suppose you could finish it off with a cut-off disk in a small rotary tools like a Dremel™, that should get you all the way to the end, at least at the top. Once the top is cut nicely, the rest won't matter too much since it will be hidden by the trim board.

Your oscillating multi-tool, with a wide blade is probably about as good an option as you're going to get. Draw your cut line then clamp^* a nice straight 2x board down and go to town^**.

The line will be your guide for the 2x, and the thickness of the 2x will be your guide to ensure your cut is vertical. It appears in that screen shot that there's something below where the cuts are, so you probably don't want to cut deeply into that if you've got a similar set up, so make a mark on your blade to use as a depth guide.

^*If your deck is similar to the setup here, your "clamp" might be two screws to hold the straight edge down, or it could be a spouse/roommate/children/friendly neighbor holding a beverage of choice standing on the board to keep it from moving. Of course, if someone is standing over you while you're cutting, you're likely getting a bit "friendly", so make sure it's someone you're friends with. ;)

^**"Go to town" as in "get cutting" not "whale away at random with an axe". You're probably going to want to make this a nice cut, at least the top 1/8 - 1/4" since nothing else will show.