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

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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.

  • If you'd share a picture or two, that may inspire other ideas.
    – FreeMan
    Apr 30, 2021 at 11:41
  • This wide shim from this youtube video seems ideal: youtube.com/watch?v=A5cLNTH5pMo but these seem custom made wondering if I could just buy them somewhere Apr 30, 2021 at 11:42
  • Well, I meant a picture of the gap, not the shim. My bad... TBH, whatever method works with whatever tools you have or can get your hands on is the way to go. In my mind, it'll take you quite a while to sand down some "slivers" of wood to make tapered shims out of them, but it will probably take far longer waiting for them to rot that way, so sanding is a better option.
    – FreeMan
    Apr 30, 2021 at 14:44

4 Answers 4


Given that a "standard wood shim" is a wood shingle that's too narrow to be a shingle - buy a pack of wooden shingles.

If you want more (with the grain the other way) buy a clapboard or two.

Or simply use a bunch of normal shims next to each other.


Larger shims I usually just cut to fit from plywood. The layers in the plywood allow you to change the depth pretty easy by chiseling and just lifting the layer up until you want it to end.


This strikes me as an XY question. Why not just slap a 6-foot scrap of lumber on the side of the joist, tight against the floor? No whittling necessary.


I've seen videos for jigs for cutting shims on a table saw. I'm sure you could find one that you like and use it to cut shims out of a wider board. Most 10" table saws have a depth of cut of about 3.25 - 3.5", so that should be 2 to 3 times as wide as store bought shims.

You might also be able to adapt the jig for use on a band saw. That would allow you to make shims up to the max cutting depth of the band saw, maybe 10-12". Some have an even deeper cut capability.

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