I have a 1"x8"x3' solid composite board that I need to cut diagonally through the 1" dimension to compensate for an unlevel underlying surface. Is there any way to do this?

  • How much are you needing to remove from each end?
    – mmathis
    Dec 7, 2016 at 15:28
  • What type of "composite board" exactly? Is it particleboard/chipboard or MDF or something else? If it's particleboard this will be difficult but not impossible, MDF, much easier because it's not nearly as hard. It would also help to know what tools you have available, because I'd be suggesting you use a hand plane for this if one is available, but that's not much use to you if you don't own a plane. Next best option (very dusty) might be using a belt sander, but again only if you have one.
    – Graphus
    Dec 7, 2016 at 16:31
  • Actually it's AZEK solid PVC that cuts like wood but is uniform all the way through. I am putting this below a new exterior door unit as the facing below the threshold. For some reason the plywood behind it is out further on one end and when I put the Azek on top, it looks bad because one end is even with the threshold and the other end protrudes out 1/2". I was hoping to use a power tool with guides for more precision. I have a table saw, compound miter saw, hand plane, angle grinder, and belt sander. If I took it to someone with a planer, is it possible for a planer to do the job?
    – Jorabi
    Dec 7, 2016 at 18:58
  • 1
    Could you just shim underneath it instead of removing material from either the board or floor?
    – Steven
    Dec 7, 2016 at 21:41
  • Steven is right; why not just shim it? It will be a lot easier than trying to plane the board to mate perfectly with the underlying surface.
    – rob
    Dec 8, 2016 at 17:38

3 Answers 3


The best way to do this would be to put it on a slanted sled and run it through a planer repeatedly.

How you make the slanted sled is up to you. I would consider cutting a series of wedges from plywood and gluing them to a flat piece of plywood. You could also use shims (like for hanging a door) and nail them down to a piece of plywood.

Regardless of how you build the sled make sure that the piece you're planing is fastened securely to it (being careful not to allow your planer to hit any metal fasteners).

  • 1
    You might want to mention that the sled should be glued to the board, rather than any fastener being used, to prevent the risk of the planer knives contacting metal.
    – Graphus
    Dec 8, 2016 at 9:00

You may be overthinking this. For flooring, framing, and other larger-scale applications, it is much simpler to just shim components into alignment rather than planing the outermost component to an inconsistent thickness in order to mate with the underlying structure. Just shim it.

  • I think I will go with the majority and shim it from below. There are two reasons why I didn't think I should shim it: (1) attaching the shims would be a trial and error affair because I cannot see what I am doing and I would have to nail or staple the shims in place each time I want to try again. (2) there will be hollow spaces behind the azek piece. I suppose I could fill the area with something like mortar or silicone and push the board into it until it is even (either in addition to shimming or in place of it).
    – Jorabi
    Dec 8, 2016 at 18:22
  • You could use some double-stick tape until you get the right amount of shimming. If you use a pair of opposing wedges, you can quickly adjust how much they overlap. If this piece is just cosmetic, you can get it "close enough" and nobody will notice the difference.
    – rob
    Dec 8, 2016 at 19:04

I'm not familiar with the PVC board material you're using but if it is uniform throughout and cuts like wood this is doable using a hand plane. Ideally you'd want to use one with a cambered iron (a slight radius on the cutting edge) to be able to remove material fairly quickly, but without that I would start with power tools and then do the final bit using the plane.

So assuming you don't have a plane fitted with a cambered iron you could use the belt sander to hog off the bulk of the material (fitted with a fresh, very coarse belt in case that's not obvious), then dust off well and switch to the plane near the end to help not overshooting the mark.

Another option that I would give serious consideration to is working on the underfloor plywood rather than the AZEK. You could work the floor in place (again with the belt sander) checking periodically by putting the AZEK down and seeing how it lays. The plywood will get chewed up a bit no matter what angle you sand it and it will look ugly as hell, but it'll be flat enough for this purpose.

I can't visualise any way you could jig this or use guides, no matter which option you go with. So either way it would be vital to stop work periodically and check fit as you go.

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