How to cut
2 Inch Foam Board
The best tool for cutting foamboard/rigid foam insulation
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hey y'all dave voskos here a while back
i did a video on getting r30 with 2x6
rafters
and i got a lot of comments on how to
cut the foam board we used in that video
so today i've actually done a comparison
test
on cutting all this foam with the
different recommendations
and the outcome is surprising
a lot of good suggestions a lot of
interesting stuff today
and there is actually one tool
that can do it all and it's not that
expensive
so stay tuned
[Music]
all right so i don't want to waste a lot
of this because all the little bits and
pieces we cut off will be around for a
really long time
probably so i am using these
scrap cutoffs to start with these are
all too short for me to do anything with
unless i cut them this way 22 and a half
inches to fit in between joists but then
you got to spray a bunch of foam around
them
so what we're gonna do is use these four
foot strips
and we're gonna make all our cuts this
way so we're doing all four
foot cuts with all the different
types of cutting devices and see how
that works out
we run out we got more foam up there and
full 4x8 sheets
but i really hope we don't have to get
to that because i don't want to waste
all that foam
i just hate the thought of all these
foam scraps sitting in a
landfill somewhere for a long time so
trying to make this as eco-friendly as
possible
some of you recommended scoring and
snapping the boards like drywall
so here's the utility knife this is uh
one of my own thoughts i've sharpened
the edge of this five and one tool and
we're just gonna see if that works
almost as well i don't think it'll work
as well as this and we're gonna start
off with these because when you score
and snap things it
it works better if you have a little bit
of leverage so you can work with a
little bit of wider board so we're going
to do that just to be
fair typically when you snap drywall you
use a drywall square
so that's what we're going to try to use
with this to make it easier
so
wow look at that i have to say i am
totally surprised
with how well that worked
it's not a perfect 90. it actually
slopes this way on this side
and then if you go down to the other
side it slopes the other way
but man
that is a pretty clean break
but we gotta test some other stuff next
is the sharpened five in one tool we're
gonna try to score and snap it the same
way
definitely a more jagged cut
see how it snaps
so
clearly the five in one tool
is not nearly as nice of cut maybe if i
got it sharper
but if you have a cheap utility knife
why not use it right
so far looks like the utility knife is
winning
next up let's try the sharpened putty
knife
or taping knife
hey i'm actually really hopeful about
this one
that made a pretty neat line and it
actually went very deep
all right that made a good cut the
second cut wasn't as good i'm wondering
though if we can just
snap this backward without making a back
cut
i've seen that done sometimes with
drywall but
let's see if we can do that we'll make
one more cut and i'm sure if this works
with one of these it would work with any
of them
once you cut the front and you can just
snap the back as well
i don't know let's see if it works might
cut out a step
no i guess you can't snap it backward
once again though it made a beautiful
cut
all right now we're going to try some of
the manual things that cut all the way
through
you obviously can't score and snap with
a utility knife right in the middle of
one of these boards
but you could jab all the way through
and cut out a nice little square hole
with some of these things we'll start
with a kitchen knife for these we're
going to start by
marking a line and then trying to follow
it with the cut
so
[Music]
the knife makes a fairly neat cut but
the thickness of it and this is a fairly
thin knife
this is what i actually use to skin fish
but
it binds up in the cut because it cuts
you know it's obviously just splitting
the stuff
and since knives have somewhat wedge
shape
the top wants to bind up so you've
really got to kind of muscle it through
there
let's try this snap
off blade utility knife
so the recommendation was to extend it
as far as you could and then just cut it
just like a knife
[Music]
that actually worked pretty good
and it's probably my fault that i just
didn't get the angle of it right
i was a little too shallow on my angle
and didn't get through the back of the
paper at the same time
but it didn't seem to bind up like the
knife
and cut pretty easy i didn't have to
muscle it through there
and um i think had i got the angle right
it would have cut through on the first
pass
so that is an excellent choice
next up this is actually
an official insulation knife
made by fuller that is a main looking
knife there
let's try it out i've just gotta say
i don't know if you can hear this
this thing is very sharp
very sharp i hate to walk up on somebody
in a dark alley with one of these things
so it's got two sides so i'm going to
try the
closer serrations first and then we'll
try these broad serrations
second
it does not like this side once it gets
this
i don't know if you can see the angle on
that once it cuts it
it's just got too fat of a blade to get
through it this doesn't work well at all
let's let's try the other side though
we're just going to continue this cut
[Music]
i tell you what it's not even worth
trying to go on with this
it is so hard to cut it's actually i
feel like it's dangerous i feel like i'm
about to like
jerk it and stab myself or something so
uh i'm not recommending this we're gonna
go ahead and throw this one out but you
know in a survival situation this might
actually be something good to own
next we're gonna try this little erwin
dovetail saw
detail dovetail saw
all right it's a little too flexible
to push back through the board the board
has so much friction
that it binds up as you might have
noticed and flexes back on you
it also seems to gum up the teeth
with paper and foam
so unless you're just cutting out a
small like
electrical box or something let's see if
we can plunge it
no wouldn't recommend it let's move on
let's try
the bigger pool saw and actually what
i'm going to do is i'm going to try to
finish this cut so we don't waste it
i think you'll be able to tell if it
works good or not just finishing up this
cut
if you can't tell or if i can't tell
we'll start over with a fresh sheet
okay that starts coming up the blade
i think that would affect the cuts the
future cuts
there's paper hung in there really good
you actually have to
pull it out so
cuts here and there not not too bad but
look at how messy this cut is
i mean it's got it's like see all that
it just makes a mess
i think almost anything with these saw
blades
they cut like that they're gonna end up
making a mess let's see
what's next we can try the the big hand
saw
but i think we're gonna be in the same
boat but let's do it just to be fair
[Music]
all right that worked better than the
japanese saws
better than the pull saws but it still
does look like after a few more cuts
it's going to end up gumming up the
blade
and it also did make
a mess
so let's see what else we got i think
now we're getting into the electric
stuff
the power tools let's try the electric
kitchen knife this is a hamilton beach
uh i think we found this in someone's
storage building we were cleaning out
so the way it works is these it has two
knife blades side by side
and they move in opposite directions
to saw through something
it just doesn't have the power or the
speed it's so thick it gets wedged and
it's cut
just like the knife what else have we
got
let's try the jigsaw with these
supposedly foam cutting blades
insulation cutting blades i don't know
this is what
was recommended when i looked up on the
internet blades to cut
foam they're like a serrated not even a
serrated that's like a wavy knife edge
so let's put that in the jigsaw and try
that out
so
wow that actually did work really good
that made a smooth cut
it was fast
of course it's noisy and it's a power
tool but
so far as far as the power tools go that
is in the lead
i don't think it's faster than scoring
and snapping it yet but
that is not bad
what's next i know reciprocating saw
with a metal blade that was recommended
as well
so we'll pick that long
metal blade brand new right out of the
box power blast
this is also going to feel a little bit
dangerous wielding this big
reciprocating saw while trying to hold
the board at the same time
but on a job site you know it's not very
likely you're going to be clamping this
to a table or something to cut it
you're probably going to be doing it
like this at least i would you know i
don't recommend it but
i would probably cut it like this so i'm
going to cut it the way i would probably
cut it
[Applause]
that was very fast
okay paco what is the matter
very fast but pretty messy
you can see got the crumbles once again
i think most of that right there is from
this saw
but
it did not gum up the teeth either so it
looks like it would be pretty reliably
consistent
to make those cuts so if you don't mind
the mess
and you already have a reciprocating saw
not a bad idea all right next
i guess is the skill saw i'm gonna wear
a dust mask for this because this is
gonna blow some stuff i think
the first skill saw cut we'll make his
regular
framing blade that's in here it's
actually
yeah it's pretty sharp still
all right cuts cleaner
than
the reciprocating type cuts and the hand
saws
actually pretty smooth cut in most
places it does definitely make
some fine particles
um definitely want to wear a mask but it
actually
you know it's not as bad as i thought i
remembered it being when
you know i thought it was pretty messy
and it is it is a little messy
let's try it with the blade in backwards
running it backward is not as clean a
cut
does okay in the foam but it really
tears up the paper
all right let's try the fine tooth okay
this is the
fine tooth 140 tooth
osb plywood steel blade running in the
right direction
that's all particulates in the air
and i'm going to go ahead and tell you
right off the bat i'm still wearing my
mask because
that is such a fine dust it put in the
air
it cut it cut quick
but
i just don't like
i don't like that fine dust
you can breathe that in really easily
it's at least the stuff that
you know chops it into little chunks
you know i don't think that's going to
do as much damage as this fine
almost powder like dust
so
not recommending the fine
142 there i'm not excited about doing
this but
let's go ahead and run it backward
[Music]
is a pretty ragged cut
all right here are my thoughts
the easiest way and cleanest way to cut
it
seems to be with the utility knife and
obviously
either one of these would work the same
just scoring and snapping
if you only had one tool and you were
doing it all by hand
this would probably be the tool you want
because
this you can't cut out for electrical
boxes and stuff but
this you can you can
[Music]
put it out deep enough where you can go
all the way through the foam
so if you had this you could score and
snap
and then cut the back just like drywall
and then use it to
actually cut out boxes and stuff so this
is
the best all-around hand tool now
having said that if you need to make
perfectly square cuts
because obviously when you score and
snap the cut
is not going to end up perfectly square
so if this cuts need to be square
i would recommend for cleanness
the bosch
blades whatever these are called i guess
it's a bosch
t313 3.
now that would cut square it would do
the plunge cuts it could do the boxes
and everything and it can do it pretty
quickly so i would recommend that if you
need all your if you like all your cuts
to be neat and square
and fast but if you're looking for
square
and fast and you don't care if they're
neat i would recommend the skill saw
with the framing blade running the right
way
with the teeth actually cutting through
the foam
but for an all-around great foam cutting
tool
up to two inches at least snap off
utility knife
all right well thanks for watching that
concludes the test y'all let us know in
the comments what you would use and why
and maybe there's something we haven't
even thought of
wow you just can't beat that just can't
beat it
that is a great tool
and that is a great tool yeah when i go
back to cutting this stuff again
these are the things i'm going to be
using
