Simple Jig for Cutting Fiberglass Insulation




About: I've been attempting to build a house mostly by myself for the last five years... I finally more or less finished it before the bunker project and after recovering from cr...

I needed to insulate a house I've been building forever and wanted clean cuts so I didn't have any Voids in my insulation.

I made this from some scraps of wood and two hinges. It holds the insulation so it can be cut with a box cutter in a single pass.

Step 1: Assemble Materials

I had some long strips of 3/4 inch plywood ripped six inches wide, but anything handy will do. I made it about 30 inches long so it would do a 23 inch wide piece of insulation without having to worry about centering it.

I used two 3 inch door hinges and some screws and glue.

Step 2: Cut Pieces

From the six inch wide pieces of plywood I cut two lengths 28 inches long, one three inches long and one five inches long.

I ripped one of the long peices into two three inch strips and then cut out a notch so they formed a slot when rejoined.

Step 3: Assembly

I glued and screwed everything together as shown adding a spacer so when the guide was lowered it allowed about 3/4 of an inch for the insulation to compress and this seemed adequate for anything from R-11 to R-30.

Trial and error determined that it works best with the paper side down and with a good blade on a box cutter a single pass will slice through and give you crisp corners for a good fit.



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    5 Discussions


    9 years ago on Introduction

    If you have faced insulation, put the paper side down when cutting, it will cut easier.


    11 years ago on Introduction

    You're right AT. Simple is just using a straight edge but the house was so large and has ten foot ceilings that I had to make quite a few cuts so I drafted any visitors unlucky enough to cross the threshold and in a three minute lesson they could make perfect cuts for me as I did the stapling. I seem to get very few visitors by the way. I dunno why...


    11 years ago on Introduction

    Very nice. I'm not sure I agree with the "simple" part but very nice non-the-less. My idea of simple is a 2x4 and the floor or a piece of scrap plywood if the floor is already finished. :-)