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


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


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


so stay tuned


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


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


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


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


definitely a more jagged cut

see how it snaps


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


next up let's try the sharpened putty


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


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


all right now we're going to try some of

the manual things that cut all the way


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



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


it binds up in the cut because it cuts

you know it's obviously just splitting

the stuff

and since knives have somewhat wedge


the top wants to bind up so you've

really got to kind of muscle it through


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


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


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


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


it does not like this side once it gets


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


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


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


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


but i think we're gonna be in the same

boat but let's do it just to be fair


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


and it also did make

a mess

so let's see what else we got i think

now we're getting into the electric


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


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


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


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


it did not gum up the teeth either so it

looks like it would be pretty reliably


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


framing blade that's in here it's


yeah it's pretty sharp still

all right cuts cleaner


the reciprocating type cuts and the hand


actually pretty smooth cut in most

places it does definitely make

some fine particles

um definitely want to wear a mask but it


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


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


it cut it cut quick


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


not recommending the fine

142 there i'm not excited about doing

this but

let's go ahead and run it backward


is a pretty ragged cut

all right here are my thoughts

the easiest way and cleanest way to cut


seems to be with the utility knife and


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


this you can't cut out for electrical

boxes and stuff but

this you can you can


put it out deep enough where you can go

all the way through the foam

so if you had this you could score and


and then cut the back just like drywall

and then use it to

actually cut out boxes and stuff so this


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


and fast and you don't care if they're

neat i would recommend the skill saw

with the framing blade running the right


with the teeth actually cutting through

the foam

but for an all-around great foam cutting


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