Building Homes or Extensions/Insulation question...


Mr. Johnson,
I've got a 4x8 sheet of Dow styrofoam "Scoreboard" insulation (one and one-half inches thick), and I need to cut it into smaller pieces.  What's the best way to cut it and get a fairly clean edge?  I have a circular saw with a plywood blade on it, and I also have a Rockwell "versacut" mini circular saw.  Is there a special kind of blade professionals use, or do you just have to use a utility knife with a new blade?
Any advice...suggestions...tremendously appreciated.
Warm regards,

Hi David, the more teeth he better when cutting soft material like that.. A plywood blade is a good start and either saw will work as long as you can get a deep enough cut.  Sawzall  works good too but if you want a clean crisp straight cut a circular saw is probably best.  Set your blade so it just cuts the 1 1/2". Too much blade penetrating through can create friction and may cause some of the foam to melt.  Another method I like is using a large extendable blade utility knife, you know the kind that has the segmented blade you break off as needed.  I extend the blade out a couple inches and run it along a straight edge while keeping the knife at a ninety degree angle to the foam board.  It gives a nice clean cut with no dust! Sincerely Bruce Johnson

Building Homes or Extensions

All Answers

Answers by Expert:

Ask Experts


Bruce E. Johnson


I can answer any construction related question in regards to carpentry, concrete, drywall, masonry, structural elements of any type of building, residential or commercial. Interior or exterior.


Custom Commercial and residential buildings. Churches, theaters, schools and auditoriums. Most recently I am working with the Catholic Church on several design build committees. I have a website related to scheduling and project supervision. Although my expertise is more related to multimillion dollar commercial, educational and theatrical projects my generous credentials in residential and remodelling construction make me a viable source of information regarding all forms of building questions.

©2016 All rights reserved.