Wallpaper and Wallcoverings - Double cut failures

I've been doing some wallpaper repairs on heavy vinyl commercial wallpaper with a rough textured surface. In the areas that I'm patching, I'm dry hanging the patches with clay based adhesive, and double cutting the seams after about 20 minutes, using the standard straight edge and utility knife (fresh blades always when needed).

Almost invariably, my seam edges still overlap very slightly after cutting. I've never worked with a paper this heavy before, I have no problems with double cut seams on different (lighter) paper at this same location. Can anyone offer me some advice or just flat out tell me what I'm doing wrong?

Thanks in advance.

If the doublecut is being done properly, the only thing I can think of is make sure the blade is being held perfectly perpendicular to the wall so you don't make a cut with a 'beveled edge'.

Are you using an oval or barrel seam roller to push the seams in place?

I'm using a wooden barrel on the seams. Have also tried using a hard rubber roller which I normally use on countertop laminate, because this paper is so thick and deeply textured (textured vinyl layer/fabric mesh layer/vinyl backing). I'm not doing anything different than I normally do, the only real difference is the paper itself. I thought maybe I'd missed something in "Paper Hanging 101".

I've tried cutting the seams immediately, letting the paper set for over an hour and then cutting the seams, freehanding it, etc., and the only thing I can think of is that I'm somehow stretching the paper when I cut. Thanks for the reply, I'll happily try anything you might suggest, I'm out of ideas.

Type II vinyl is pretty hard to stretch, and it generally doesn't expand after pasting. It still sounds like the way its cut is the culprit. I use a stiff 6" putty knife as a straight edge/trim guide when cutting, using an 18mm break-off knife, changing blades every cut. Look for Tajima blades, they are the sharpest money can buy.

Sound advice, I'll try the breakoff blade on it tomorrow, and I'll give my drywall knife a try insead of the 12" guide I normally use.

Thanks again.