So I have a long gap between a joist and floorboards on one half of 6 foot joist that I'd like to close.
I'm toying with the idea of just adding shims to the top of the joist rather than lifting up one end of the joist from the sill and adding shims to one end. (There were already 1/2" shims on both ends since we had to bring a nominal 8" joist up to an actual 8"). We already tried to jam and lever up the one end of the joist and it doesn't seem to budge.
My question is how can I get an extra wide shim? I've seen shims online but they all seem to be "long" rather than "wide". I'd like to get a shim across 3 feet of the joist with a bigger gap on the end vs the middle. Something like this "floor board" sliver that these Irish carpenters talk about seems ideal. https://www.youtube.com/watch?v=prvQRhagLjI
If I cut it myself, can I just chisel a piece of wood out and then sand one edge to a taper? I don't own any power tools or a table saw :( Just a chisel, sandpaper and a Japanese saw.