I have been measuring and then cutting of course wall panels because I am converting a shed into a bedroom.

This is my first time at doing something like this and I have had little to no help. Which is fine, the internet can be a great teacher somewhat so I think I’m doing alright.

I am nearly done except for just a few more pieces, but they are the hardest pieces because they have to have several cuts in them to go around the outlets, and some electrical boxes up top and around a built in workbench/counter.

While working on this project, every panel I’ve put up, I have measured from floor to ceiling (or ceiling to floor). I make the measurement three times practically, one on one side of panel, one in the middle and then again on the other end. I did it this way because the top of shed or where the wood beam is is at an angle. I’m not sheet-rocking by the way, I’m sure that speaks for itself but still, as much info right? So to make sure I am cutting the right angle I figured that would be the best way.

So while in theory I would think this is the proper way to measure, each time I’m off and have to take off almost another inch. Not always quite that much and sometimes more than that.

I remeasure to see what I’ve done, and then measure my panel and sure enough, the measurements are the same, but when I go to put panel up, it’s always or almost always bigger and I have to go back and make extra cuts.

I’m grateful, that whatever I’m doing is leaving too much and not taking to much away, but I’m still curious what it is that I am doing wrong. I would think that it should be fitting like a glove each time but it doesn’t.

It’s frustrating and especially now that I am going to have a these weird cuts I am going to have to make for the angle of top of wall, and then around the beams, and then again around these junction boxes things, and then around the workbench/counter part, and the light switches and electrical panel sockets. I would like to be able to make the cut one time and not have to make adjustments afterwards.

I definitely thought I could use a measuring tape before this project and am just not understanding why my measurements just aren’t working like they should.

Clearly I’m missing something so any insights would be appreciated.

  • 1
    Hi, welcome to StackExchange but holy wall of text Batman! Paragraphs are your friend ;-)
    – Graphus
    Feb 2 at 8:27
  • I've edited to break this into what I hope are sensible paragraphs for you that don't interfere with the intended meaning and still includes all the relevant details. Feel free to further edit it if you see I messed up anywhere, cheers.
    – Graphus
    Feb 2 at 8:46
  • I'm still not sure exactly what the issue is (some pictures are always helpful, as is clear, concise writing, not folksy " I’m sure that speaks for itself but still, as much info right?" writing is very helpful. That said, if you're measuring long, my guess is that you're not holding the tape measure in a straight line from bottom to top (a 90° angle to the floor is a shorter measurement than an 80° angle), or that you're reading the tape measure at the wrong place where it curves into the corner. Again pics will help us help you with this.
    – FreeMan
    Feb 2 at 13:10

1 Answer 1


It’s hard to know what’s going wrong with your measurement, except to say that things in the real world are often neither level nor plumb. Assessing level and plumb with a decent 4’ spirit level is the first step.

Beyond that, here’s a few random tips/ideas that might help.

If reading a tape bent into a corner isn’t accurate enough for you, measure up and down to a point in the middle. If I have a wall to measure, I’ll measure from the floor up to 50 inches and make a mark. Then measure down to the mark and add. 50” is an arbitrary number, but it’s easy to add that to whatever the upper half number is.

Tape measure tips are notorious for being loose and inaccurate when pushing versus pulling. If you need to be really accurate, start at the 10 inch mark on the tape and measure from there. Hereinafter known as ‘burn 10’. 10cm is fine if you swing that way. Don’t burn 1 because math(s) is hard and 29 can turn into 30 or 28 very easily.

Measure from multiple points to figure out where to put a junction box hole. Start by measuring from one side and the floor to give your best estimate of where the hole should go. Then check your work from the other side and the ceiling. You can even check from a corner diagonally. Somewhere along the line it should be evident where the box really is.

If you’re still nervous about the cutout for the junction box, sneak up on it. If it’s a 2x3 box, cut a 1x2 hole, put the panel in place and see where to cut more.

If you cut too much, check the electrical aisle for oversized cover plates.

For strange awkward cutouts like rafter notches and angles, make a cardboard template. Cut the cardboard close to correct, then butt additional bits of cardboard or painter’s tape up to the exact cut point. Then figure out exactly where your cardboard template fits on your bigger panel by measuring from multiple reference points.

Don’t forget painter’s caulk as a fix-all for those unfortunate cracks and gaps.

It’s such good advice from @graphus that I had to edit it in: measure THRICE, cut once. (The parallel joke is, of course, “I cut it three times and it’s still too short!”)

One other rule I follow is, “no math in the morning”. I will literally pull out my construction calculator (apps exist) to divide 29-3/8” by two. This might just be me.

  • 1
    Excellent. If I could add just one bit of personal wisdom, measure THRICE, cut once is no harm at all!
    – Graphus
    Feb 3 at 10:03

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