I’ve finished off many flights of stairs with a bead of silicone. It blends everything together. I believe some of the commercial rubber stair treads these days actually recommend you leave a gap and caulk it. CFR would be the one in the know on that spec. Now if you’re installing up to a beautiful stain grade wood stringer then it’s prolly best to cut it perfect and leave the caulking out of the equation. Sheetrock? Paint grade? A little caulking is just fine. Let’s get you to where it’s a finishing touch and not a band aid.
One thing you can do is measure the width of all your stairs. Some will inevitably be wider than others. I’ve seen walls bow so you could have up to 1/2” or even 3/4” difference from top to bottom, or somewhere in between, a flight of stairs. Start with the widest stair and make that your first one. If you blow it and have too big of a gap for your liking, you can always set that tread aside to be used on a narrower stair. I do this all the time with stair nose when a flush fit against a nice wood stringer is critical cus you only got one shot at it before you gotta order another one at $60.
Let’s get started. Cap-a-treads are 48”? wide. Your stairs are prolly 36”? You got some tread width to spare. Cut a couple test pieces a couple inches wide and take them in and set them on the stair to check your stair with them. How much overhang is there. You got 2 pieces, one for each side. Dummy proof them and mark them R and L. Check them both cus they may not be the same. This lets you know how much you will be ripping off of the back of the tread. Cut the test pieces to size and check em again. You like the fit? If so then take these measurements and transfer them to your tread. While you’re at it you can check the rest of the stairs. You might get lucky and they’re all close enough to just rip a set amount off of each tread. Or maybe only 2 or 3 are different but not all. Write the amount to be ripped off on each stair so when you’re working each stair one by one that measurement is right there for you. I made this the first step in templating stairs because the jig I linked for you bumps the back of the stair. More expensive jigs work from the nose of the stair. No need to dump $250 on a jig if this is a one time deal.
Now you’re getting ready to start templating. You’ve never done this before so we’re gonna take it slow and check and recheck things until you get comfortable. Get your stair jig set up and template your widest tread. Crank the knobs tight. Take the jig and transfer it to the tread. Use a sharp pencil and transfer some clean lines. Just for giggles take the jig and set it back on the stair you just templated. Does it still fit perfectly? Did it move? You haven’t cut your tread yet so if you notice a problem now is the time to figure out what it is and correct it before you start cutting.
Alright, now you’re satisfied that your template lines are accurate. Make your first cut but purposely make it big. How big you make it is up to you. 1/4”? 1/8”? Got balls of steel? How risky are you? Visually compare the cut to the line you’re supposed to cut it at. Does it look right? Do you need to adjust your angle? Is the cut clean? Need a new saw blade cus you smoked the tread? If all is good then you will nibble it down to the line. now you’re ready to cut the other side. Same steps, cut it big and compare the cut to your line. If you like it then cut it down to 1/16” big. 1/8” if you’re unsure. Take the tread in for a test fit. You like the look? Yes it’s big but you can angle it in enough to check each side. Take it out and nibble it down then test fit it again. Seems like a pain but since you’ve never done this before, we’re trying to avoid unsightly gaps or you having to buy a new tread due to cutting one short. Do one or two this way and you’ll get the hang of it enough to eliminate some of the extra testing and checking.
One thing you’ll notice is that since the bullnose on the Cap-a-treads is pretty big, angling them in can be a little tricky. For solid stair treads some guys will put a slight bevel on one side of the tread to ease dropping them in. Be careful if you do this because a degree or two of bevel over a 3/4” thick tread isn’t that bad but that same amount of bevel over 2” is really noticeable. Take your time, maybe even cuss a little. I do. The extra time you take now will be visually appreciated every time you walk up and down your stairs.
By the time you finish this flight you’ll be as good as half the installers HD or Lowes has. I’m joking… or am I?
You got this. Just break it down into individual steps
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