What is the best tool for cutting foamboard/rigid foam insulation?

Comparison test of various foamboard cutting tools.
Thank you to all of the commenters who gave suggestions!! ... Sorry if I missed yours. Forgot to mention hot knife--but it won't work on this type of board due to the fiberglass paper doesn't melt.
The foamboard is GAF EnergyGuard.
The best tool!! Olfa 18mm snape-off blade utility knife: www.lowes.com/pd/OLFA-1-Blade...
Olfa 25mm snap-off blade utility knife: www.lowes.com/pd/OLFA-1-Blade...
0:00 Intro
2:20 Utility knife
3:15 5-in-one tool
4:20 Taping knife
6:08 Kitchen knife
7:05 Snap-blade utility knife
8:20 Fuller insulation knife
10:05 Irwin dovetail flush-cut pull saw
11:03 Dewalt Japanese pull saw
12:17 Craftsman western style saw
13:16 Electric knife
14:10 Jigsaw with Bosch soft materials blade
15:24 Reciprocating saw with metal cutting blade
16:54 Circular saw (Skilsaw)
20:08 Conclusion
Disclaimer:
If you choose to imitate, duplicate or copy anything you may have observed in these videos, you do so at your own risk. The creator of this content does not take any responsibility for any action taken as a result of the information or advice on this KZbin channel (or other platforms) and shall not have any liability in respect of any injury or damage that may result.

[@DD-sn4iz]

I just spent 22 mins watching a guy cutting foam boards repeatedly at 5am in the morning, I can sleep happily now.

[@tekektron3575]

I wish I would have found a saw like this years ago! It does everything that we have asked of it so far. Works great kzbin.infoUgkxjpBI8OOeUXib_iT7UomCrQ-uauwZJ62c on cutting composite siding and plywood sheathing. I probably would not try to use it all day cutting 2X boards, but it's just the right size to throw in a job bag vs. your conventional heavy circular saw. Operating instructions very clear. Came package well. I would definitely recommend you buy this for a friend!

[@GeoFry3]

My favorites. Hot wire cutter is great for shapping and short cuts. Long cuts a long blade retractable utility knife.

[@katieh3236]

I just have to say, after recently dealing with someone who bullies my ideas, this video was a breathe of flesh air. In teaching, this is called a spirit of enquiry and exploration for the purpose of learning Thank you

[@ThePowerWithinOnline]

Your video was so helpful! I just bought a snap blade utility knife for $2. I loved the live demos and time stamps so I could see how the tools I already own performed. - Marisa

[@FamilyFriendlyDIY]

Thanks for the kind comment, Marisa!

[@richh8860]

Thank you for taking your time to explore the various methods involved and ultimately saving countless other people time,mess and money,truly informative,even from somebody on the tools like myself. Massive thumbs up to you Sir👍

[@FamilyFriendlyDIY]

Glad you liked it. Thanks for the awesome comment, Richard!

[@romygo4301]

Thank you for sharing it help a lot.

[@LochWatenan]

Thanks for the comparison. Appreciate the time and effort you put into that.

[@ranstar999]

Great job Dave!!! Very thorough! Thank you for all of your time and effort! Definitely like the knife/jigsaw combination for just about any type of cut.

[@FamilyFriendlyDIY]

Thanks 👍

[@katieh3236]

Dude I love how humble you are

[@rocketsurgery8337]

Glad you tried the Bosch blades. I've cut thousands of feet of polystyrene and I'm still using my first blade. Favorite part is almost zero dust it creates.

[@FamilyFriendlyDIY]

They're awesome. That's good to know about the longevity---I was wondering how long they'd last. ... BTW ... Like the handle. I use the term "rocket surgery" all the time when I'm explaining stuff at work. Seems to just go right by most people :-) Thanks again for the comment!

[@Tracer9GTRider8]

I'm going to do my shed with the non-papered styrofoam board. I had a feeling the utility knife would be the best way to go and watching your video confirmed that. Thank you!

[@FamilyFriendlyDIY]

All the best on your project! Thanks for the comment.

[@mrcryptozoic817]

Well, Dave, the method I use is a table saw/carbide blade. Set the fence to the right width, cut half way through the foam, turn it around and over and cut the second half. Perfect, precise cut every time. Don't try to cut all the way through at once. The foam will melt to the side of the blade.

[@ghostridergale]

I used my Table saw too, cut 4” thick styrofoam using a 60 tooth carbide blade. Cut thru the whole foam with one cut no problem. Insulated my whole garage with scrap sheets of foam I got for free. Also insulated my fold up garage doors with 1 1/2” thick styrofoam too. Made a huge difference with the amount of heat coming through the garage doors when the sun hit those doors too! Does add a little weight to your garage doors, but not too bad! Might be able to tighten the springs a little more if needed to that might help make it easier to lift the door up?

[@dianeperry3176]

This video is gold, thanks for going thru all these methods...gonna roll old school with the utility knife!

[@FamilyFriendlyDIY]

Thanks for the kind comment, Diane. All the best on your project!

[@WeazelJaguar]

I like to recycle left over aluminum clad insulated wall panels, into floating dock material. I keep an eye on job sites, large warehouses, office complexes that use them, then wait until the doors and windows are cut out. I found that when I ask nicely, most of it is free for the taking! So to cut them, some 20 feet long, i use a battery DeWalt circular saw. Flying metal, mixed with foam sucks! So, wear all the PPE, use a very long straight edge, do it indoors so the mess is easy to clean up and cut BOTH sides! From the job site, one edge is factory, and the other is a real butcher job. Then I cover the exposed edges with sticky back roofing flashing to help keep the water out. Two 4 inch thick panels sandwiched together makes for a great dock! Thanks for the video!

[@bkwhopper115]

Thank you very much for this video! I am brand new to cutting insulation and you just saved me so much time and money!

[@FamilyFriendlyDIY]

Glad I could help--- or I should say WE could help ... as all these methods were recommended by viewers! Thanks for the comment, Ben!

[@DianeHayes23]

I agree! I'm doing a shed to home conversion. I live in central Texas and want to use foam insulation for my floors. This video is perfect!!! Thank you!

[@blackbird6330]

Thank you for taking the time and energy to make this video. It's of great help.

[@FamilyFriendlyDIY]

Thanks for the kind comment, Blackbird 63!

[@ericbragancaNJ]

This was great - thanks - saved me making a huge mess. I used the box cutter to cut through my 2” boards making 3 cuts to get as square an edge as I could. Using the box cutter made it easy to make precise cuts to fit around pipes in my basement walls.

[@FamilyFriendlyDIY]

Thanks. Glad to hear it, Eric.

[@therealunclassified]

That jigsaw blade is magnificent. I'm picking up a jigsaw that cuts plexi. So this will be my new go to and way to cut exterior insulation.

[@landofstan246]

I like the Bosh blade with the jig saw. I am not in a hurry. Other saws make too much dust. That foam dust can be dangerous even after construction. Thanks for the video.

[@HandymanTim]

What do you mean by "dangerous even after construction"?

[@lambbrookfarm4528]

Dave, thank you for posting. My most recent project is a foam board cover for my wood fired hot tub. My choice for not powered cuts have been the Vaughan finish pull saw, although they are messy. For powered cuts I have used a 3.5" Bosch Aggressor jig saw blade. The jig saw works for well for plunge cuts and curves, although it is messy. The foam cutting jig saw blade looks like the cleanest cutting way to go. Thanks again, Brice

[@HSNart-of8qe]

I really appreciate your concern for the Earth! So imp and never mentioned by other you tube people

[@gettingstuffdone]

Loved the video! Had to watch to end to see all the options 😀

[@FamilyFriendlyDIY]

Thanks! Glad you enjoyed!

[@DontFuckWitDreDay]

Thanks for the video!!! Very useful 👍

[@bossman6174]

I use a vibrational cutting tool for small or short cuts. Works great but I saw those foam cutting blades for the jig saw and that works super for long straight cuts. Super . Learned something here. Thumbs up.

[@selfsameday7448]

Very thorough search,thank you ! Good work !

[@FamilyFriendlyDIY]

Thanks for the kind comment!

[@EOTE_TX]

We just installed 2 layers of PolyISO over 7,000 square feet of a gambrel roof including hips and valleys and went through much of the same discoveries of which tools worked the best. Our choice was a bit of a surprise in that the best tool we found for the cuts was a Japanese saw with the teeth ground down on both sides to remove any "stick out" of the teeth. It would cut smoothly with very little dust and would penetrate the fiberglass on both sides easily. We also found that a super thin kerf blade with a high number of teeth on a traditional Craftsman Radial Arm saw allowed us to make straight end to end cuts very quickly and smoothly although the dust level required a mask and safety glasses. Find a Japanese saw with a handle like the DeWalt or Irwin for the best leverage in the cut.

[@marknathanks7592]

Yes that has been my experience, japanese pull cut fine kerf saw. Fast and short strokes

[@miguelp4812]

Your videos are awesome! Thank you.

[@FamilyFriendlyDIY]

Thanks, Miguel.

[@mambomachine6317]

Bandsaw works great for this also for angle cuts if you have one available nearby! The key to making clean straight cuts with a handsaw is to use a thick, straight piece of wood to ride the saw blade against while cutting. That stops the blade flexing.

[@FreeMissions]

What do you think about using a table saw with a finishing high groove/tooth wood blade?

[@hartleyroadmusic]

THANK YOU!! Great demonstration.

[@FamilyFriendlyDIY]

Thank you!

[@daytriker]

Watching you trying to pull those blades towards you looked like an injury waiting to happen. For my foam/PVC sheet cutting it looks like the Jig Saw is the cleanest (& safest) way to go so thank you for a good instructable video.

[@FamilyFriendlyDIY]

I hear ya. Thanks for watching, daytriker!

[@panagea2007]

I ground a knife edge on a fine jigsaw blade, the kind used for contours, and that works great. Fast, clean, and perpendicular.

[@tomhaire4758]

Thanks for this demo

[@davemall1]

For an outlet I would use a keyhole saw just like you would for drywall. For a perfect fit between studs, hold the foam in place next to the stud and use the same keyhole next to the second stud and saw at a slight angle to make the foam slightly larger than the gap between the studs. It will be a clean and tight fit that will need to be stuffed in. It does leave some mess behind and take a little longer, but the fit can be perfect with some practice.

[@oblongmana]

Funnily enough, the utility knife (especially OLFA blades) is well known in various crafting circles as the best tool for XPS board as well - where we use it often for making various large terrain models, model buildings, that sort of thing! Not just for big cuts, score and snap, up against a straight-edge - but also for whittling and shaping, so long as your blades are sharp.

[@solarsynapse]

Yes, the Olfa are the best I have used. It is amazing how much sharper they are and the black coating helps them glide through with less sticking.

[@LTVoyager]

If it weren’t for the paper on each side, it is hard to beat a hot wire cutting tool for foam. That is what they use to make foam airplane parts and the cut is clean, dust free and perpendicular.

[@psalm23sheepdog]

How fast is that method compared to what was shown here? I’ve seen them used, but never paid much attention to it.

[@jbird6609]

@@psalm23sheepdog I used wire cutter for making airplane wings. It wont cut through paper and it melts the foam making poisonous air to breath. You would have to have a jig set up to cut alot with it. I think its a bad idea. Works good for airplane wings though ,joking

[@daves3819]

If you are cutting anything that is made of beads (i.e regular Styrofoam insulation or graphite based insulation like GPS foam board) the only way to cut is via a jigsaw with a knife blade. I used the exact same Bosch blade but I cut 2 inches off as it is too dangerous to use the full length. I used the same blade for my house, garage, and 2 sheds all of which had gable ends ... so there was a lot of cutting!! Note, I used a Dewalt cordless jigsaw and since there was little demand on the motor when cutting the GPS foam board a battery lasts a very long time.

[@innerwoven_family]

thank you

[@gr8dvd]

@@innerwoven_family You’re welcome😀

[@wisecitizenry2844]

Great video! Thank you for doing it!

[@FamilyFriendlyDIY]

Thanks for watching!

[@robertarcher5213]

Brilliant video. I'm fitting new floors with King's pan foam insulation. I've been trying to thinking of a clean fast way of cutting boards.

[@FamilyFriendlyDIY]

Thanks Robert. Hope it was helpful!

[@teresagraef5684]

Love the vid, great content. The only other tool I can think of that might work is the foam cutting jig-saw like tool used by upholsterers. Cushion foam is tough to cut smoothly. Please keep up the vids!

[@FamilyFriendlyDIY]

Thanks! Did you mean something like this: kzbin.info/www/bejne/mWSsgZSJhbCUo9U Looks like another possibility.

[@13612]

I just finished up on a bus garage and cut 95% of the same type of boards for the roof and siding with a circular saw and a fence for accuracy between fiberglass z furring. Yes it makes a mess, but very fast if your proficient with a saw. I like the bosch blades as I would have rather have used those with a fence for the elimination of the dust this product makes hands down! The utility knife with the blade in the second notch out further is how I cut a stray board and it is very quick too if you are proficient with keeping parallel, but you have to be careful of paper cuts with your guiding hand as this is a very sharp product to run your fingers along at a fast pace. I always wrap my guide fingers with electrical tape for abrasive products to rip if that is a problem. Very good video on giving folks a rundown on what works best. Only way you would get faster is an improvised cutting block with a long blade like you made in the beginning out of a finishing knife. I had pondered making one before I had cut the many cubes of this foam on that giant garage I worked on just a couple of months ago.

[@dennisbarrett6148]

Best advice....utility knife with a shallow angle of cut. I took the blade out of the knife and held it by hand. This allowed a very shallow angle and cut like butter. After a while I put a band-aid on my finger tip. The notches on the back side of the blade got rough.

[@JayneCobb88]

If you want a square cut with a utility knife, score both sides before snapping. It also lets you snap much closer to an edge.

[@LTVoyager]

I was about to make the same comment when I read yours. Score the paper on both side and get a guide for the break on both sides.

[@JardinFoto]

Agreed, that works best for me

[@fartpooboxohyeah8611]

A multi tool for small cutouts, like electrical boxes. Also, a hand held sheet-rock knife works pretty good. Thanks for the video, awesome!

[@FamilyFriendlyDIY]

Good tips :-)

[@flyingcod14]

great video, thank you. I have had the same issues on thicker insulation (drywall).

[@FamilyFriendlyDIY]

Thanks for watching, Scott!

[@solidcarbonstorage3259]

I use a track saw but fit it with the vacuum (Karcher - it turns on automatically when the saw starts). Nice clean cut, 90 degrees and accurate (because it's a track saw). Only goes through 65mm depth of cut, so I use this as a guide and finish thicker boards with a kitchen knife - works fine for 75mm boards. Fast and clean. You can use Gap-o-tape foam edging if you want a really good fit and it's super quick to install being a friction fit with the foam.

[@solarsynapse]

Great testing saving people a lot of grief! I think some people wax the blades before cutting. I have a standard blade razor knife that has a flat foot to keep the blade straight. A serrated steak knife also works well and is good to plunge cut out a hole. A hot knife is recommended a lot with the advantage of sealing the edge. Some people use dental floss or a guitar string. I don't like any method that creates debris. Razor blades are small, inexpensive, quiet, do not require power and don't leave a mess.

[@alexd5188]

Would a box cutter do the job?

[@solarsynapse]

@@alexd5188 Would need to be VERY sharp and they don't cut deep.

[@solarsynapse]

Just tried a heated serrated steak knife, works great! Also, the Olfa black blades are the sharpest slickest razor snap blades I have used. Far better than other brands.

[@EdieBabeMonster]

Nice demo. I appreciate your time and energy. I have done a lot of insulating myself. I agree that the best tool overall (especially if you only have 1 option) is a good utility knife. Personally, I prefer the wider locking blades for insulation. Having them “lock” is the most important safety aspect.

[@FamilyFriendlyDIY]

Thanks for the tips, Edie!

[@InToTheBlackHole]

I use an insulation knife for scoring. The blade is very narrow, very sharp, and will score down to almost 3/4 of an inch without much pressure. That way it snaps a lot cleaner. For cutting boxes I use a multipurpose tool. Very accurate, easily maneuverable, especially in tight places, and makes a very clean cut.

[@vance7274]

Dave... Another great video and it will be helpful to many DIY folks. Keep 'em coming, DIY Dave. I would make the recommendation that clamping the foam board to the OSB would stabilize the stock and make for a much cleaner cut / result. Safety is also a concern. If possible, always clamp your stock whether it be foam, ply, laminate, OSB, PVC, etc. Kick-back with skilsaws is nasty and can result in serious injury.

[@innerwoven_family]

Seriously good comment, Thank you!

[@troylindsey1444]

Good info. Thanks

[@fx1c333]

For modeling 5mm thick rigid foam I use a 6" scraper blade at 45 degrees " \ " mounted into a jig and then just push foam to the blade works a treat for me haven't tried anything over 20mm.

[@Chris_at_Home]

The electric knife is great for fiberglass. I have one just for that. I’ve done quite a bit of foam board work and I just use a utility knife. I always cut it a little smaller and seal the edges with the door and window spray foam because it is flexible. I use the smaller pieces to seal the rim joist in the basement and between floors.

[@FamilyFriendlyDIY]

Great info, Chris.

[@we-will-see-what-happens]

Thanks for risking your life to make this video!!

[@FamilyFriendlyDIY]

I hope it was worth it, Josh. :-) Thanks for the comment.

[@keithwilliams5547]

I cut foil sided foam board on a regular basis. The best tool I found is a 3" putty knife sharpened on the long edge. Clamp my straight edge down and cut along about halfway through. Then come back and cut the rest of the way through on the second pass. Keep a fine file on hand and give the edges a stroke or two every 5 to 6 cuts. Scoring and breaking the boards I use, which have tiny fiberglass fibers in the polyurethane, releases those fibers in the air. Never use a hot wire or hot knife on any polyurethane board as it releases deadly gases.

[@ChiefNate]

I do commercial and industrial roofing, and we use this very often. They make a knife designed for this with a straight edge that works like a charm, and a Sawzall is easily the best, especially considering speed and the accuracy of the cuts when you get good with it

[@ChiefNate]

The trick with the foam knives is to score your cut first, then go all the way through

[@LovelyKauai]

This past weekend I was cutting 2 in rigid foam. It cut fine with a snap-off blade tool on 48 in cuts or less for a dormer bath. Cutting full-length panels, I used a thin kerfed Skill-Saw set for 1¾ depth cuts and dust mask. It was fast and made fine tears in the foam. I vacuumed after each 14 ½ wide panels was cut and then snapped the cut while working from the floor. I suspect the laminated panel would show tearout but I am not using them in the bath. Instead, I will use a reflective product before sealing the walls with green drywall. Overall, the circular saw worked very well. Thanks for your informative video!

[@FamilyFriendlyDIY]

Thanks for all the info, Scott 👍🏻

[@reggiem1668]

Thank you for the video! I found the Bosch jigsaw blades to be very impressive! I used on 1.5” insulation board and they do get hot so if cutting long strips it may be best to stop part way through for 20-30 seconds. If you do, pull blade out because it will melt back a bit from the blade. Otherwise, this blade made very accurate and near 90° cuts! I won’t cut foam board with a break off utility blade cutter again. It requires multiple passes and will likely be a very “wavy” and messy cut comparatively!

[@FamilyFriendlyDIY]

Thanks for the input. Good info!

[@dannyo3317]

I did not have great luck with the snap off razor knife against my cutting guide. It wanted to flex like when you used the detail dovetail saw and did not cut as straight of an edge as a heavier but somewhat difficult to use knife.

[@RonaldDCass]

1988 I had a one acre roofing project to cover a metal roof with insulation board & a PVC membrane. We first had to put 1.5 X 8 inch wide strips between the ribs. Over a thousand 4X8 sheets were needed. I designed a machine that had two mandrells each turned by a heavy duty drill. Each mandrel had round pizza cutter wheels spaced 8 inches apart to cut the top & bottom of the sheet 1/2 way through. (Kinda like a gang saw) after a sheet was run through, the pieces could be snaped off. We could run 50 or 60 sheets through in less than an hour!

[@phillipdavidhaskett7513]

I use a curved linoleum knife that will cut the facing on both sides with a slight sawing motion. It's long enough to make beveled cuts, too.

[@KJD1955]

I was working with Styropor rather than foam board - you know, the stuff that looks like it's made of cottage cheese. I found that the best cut was with a Bosch nano-saw ... a kind of miniature chain saw. It cut much more neatly than an insulation knife, and the plate allows you to cut at an accurate 90°. The only downside is that everywhere ends up looking like winter wonderland.

[@mikeredhead2894]

Thanks brother.

[@rbpe3thatsme841]

Thank you, You've help me out.

[@centexan]

Ah, well. When I used my sharpened putty knife, I cut on the silver radiant barrier side and my foam board did not have any covering on the flip side. And one reason I chose it over any saw was the no miss no fuss aspect.

[@shootsteel]

Festool make a specific insulation saw ... add a rail and dust extractor to rock your world ... expensive, but perfect cuts every time and if you have a lot of cuts or regular use the payback is fairly quick.

[@SuperUncleRyan]

I have been doing this for 28 years and my favorite way to cut this foam board is with a table saw. Beautiful and accurate cuts every time. Messing as can be but I just use a shop vac as I go.

[@leoboutilier4219]

What blade do you use?

[@SuperUncleRyan]

@@leoboutilier4219 Just the regular wood blade. Combination type. Not even a fine blade.

[@MrSteeDoo]

Thumbs up on that one. Use a junk blade.

[@jimurrata6785]

Fuller has just rebranded a bread knife. I've been using one since the '80's for the old fireblocking type battery insulation.

[@chesterwatson4087]

One suggestion - place your hand holding the insulation on top with the bottom piece on the table. Provides a more stable hold.

[@Rico-Suave_]

Thank you very much

[@richardlusk2160]

I have a lot of experience with this issue and slightly different. My iso boards are 3.5 inch and also 4 inch 4x8. I cut with my portable ryobi 5 inch circular saw for a 2.5 inch square cut and then finish with a 4 inch dry wall tool. The rounded portion of the blade has been sharpened with a knife sharpener and a stone. Cuts like butter with two passes of the tapers tool. The rounded portion is doing the cutting.

[@MinnesotaBeekeeper]

Thank you!!!

[@katieh3236]

Love this eco friendly guy

[@leighsheppard8614]

Scary! I thought you were going to lose a hand a few times. You should definitely try a Proxxon 37080 Hot Wire cutter. Best off-the-shelf Hotwire table available and at a reasonable price. It will give you smooth, precise, repeatable, and effortless cuts every time! (With NO SAWDUST!!)

[@CozyCalmAmbiance]

but can't cut through the paper?

[@innerwoven_family]

20:10 ! lol thanks for doing this. That was what I was going to use

[@FamilyFriendlyDIY]

Thanks for watching!

[@InssiAjaton]

I have seen a rotary blade with a pattern similar to the Bosch blade wavy edge. Or it might even have been a rounded corner octagon. Anyway, it was used to cut woven fabric in MULTIPLE LAYERS at a single stroke for the same template. To prevent scratching the table top, there were two forks lifting the pack a little up while cutting. I had not expected to see such "rotary scissors", but was immediately impressed.

[@FamilyFriendlyDIY]

Sounds pretty cool. Thanks for the comment, Pellervo!

[@DSherrattRoofing]

Thanks for a good and varied show of the various methods and options. Here in the uk we have to install boards of up to 6 inches thick between our studwork and roof joists etc and a tight fit is a imperative. If we don’t get an accurate cut and therefore a tight fit then we have to use ridiculous amounts of expanding foam to fill the gaps. We’ve tried numerous ways but always resort back to using the good ole 20 inch handsaw. We find it achieves both a straight cut and a square cut. It’s not as easy as it looks to get consistent tidy cuts that fit the first time. It not only takes the right tools but also an half decent tradesman who has patience as well as skill. The purpose made insulation saws look like a great piece of kit but not so sure they’d be worth the investment.

[@FamilyFriendlyDIY]

Thanks for sharing, Daniel.

[@coffeeisgood102]

Really appreciate this video. I have seventeen 4 X 8’s to cut for my project.

[@FamilyFriendlyDIY]

Glad it was helpful, Harold!

[@coffeeisgood102]

@@FamilyFriendlyDIY in case your interested how this turned out. I decided on the jig saw method. Could not find the blade you were using so used my fine tooth metallic blade and that worked great. For cutting small pieces, like to make a notch, I used my pocket folding knife which to my surprise did a real decent job, tho I don’t think it would be good for larger areas.

[@1622steve]

I've had success with a jigsaw and a high TPI hacksaw blade. I use a straight edge for precision cuts.

[@djcald430]

I need to cut a fairly precise angle along a 2" foam board so the Bosch Blade would definitely be the best.

[@jamesmchugo9422]

I’ve cut many sheets of ridge foam board. A shape utility knife, score and snap is the best, easiest and cleanest way to cut the stuff. When installing it have a can of spray foam with you so you run a bead along the edges and set the foam board into it, any imperfections with you cuts will be sealed. Saws are the worst way to cut foam board. The dust from the cut is almost impossible to clean up, it sticks to everything, can melt to your saw or melt the board pieces back together and you shouldn’t breath the stuff into your lungs. If the edge isn’t square enough for you to fit the pieces together and spray foam can’t fill the gap, then trim the edge up with a long utility knife so you can fit the pieces reasonably well together. Anything less than 3/8 of an inch is good enough, and remember to put a bead of spray foam between the edges to seal them, although flush is better, close is good enough, remember the spray foam will close all the gaps and give you a continuous moisture barrier. Once the finished wall goes up and covers the insulation no one is going to see the foam. Don’t sweat it if your cuts are not absolutely perfect, as long as they’re air sealed you’re good.

[@ajmedeiros77]

Just get the longer blade utility knives. I’ve got the 18 and 25mm olfa and can’t work without them. Love them. Thanks

[@allencolvin4320]

I know it is not recommended, but a tablesaw or skillsaw has always been my go to. Spray foam fill in gaps just fine. It is still cheaper than an ER visit!

[@andywright2606]

I've just finished lining my shed with this 2" foilboard and I can tell you the best way to do this is with a 1mm metal cutting disc on a 5" cordless angle grinder. Trust me it's quick and precise, perfect cut every time. Try it, it really works well, obviously wear a mask though. Clearly won't work on 100mm thick board but for this 2"/50mm stuff your working on is fantastic. Cheers Andy

[@FamilyFriendlyDIY]

Great tip. Thanks for sharing, Andy!

[@MrBrianDuga]

I paid a lot of money for a centerfire blade that goes on the circ saw or table saw. It works OK. I like the idea of a tablesaw because pcs can be cut like plywood. I've attached that blade to a track saw and had good results.

[@jlane9055]

Hi Dave I put foam board on top of my insulated walls in our mobile home and found out of all the ways you showed a jigsaw is a good way but.. I went with the electric knife. As you showed it binds up, but not if you use 1 blade in the electric knife. I did it standing with no backing of a table, quick&easy.

[@FamilyFriendlyDIY]

Great idea! Wish I’d thought of that!

[@soleyjackinourcampervan5362]

What brand of electric knife and what do you mean by 1blade? Trying to decide if I should use an electric knife or jigsaw.

[@jlane9055]

@@soleyjackinourcampervan5362 I had a cheep walmart brand and paid less than $10 dollars, they use 2 blades just use one of them.or buy a blade for your jigsaw

[@motoman869]

I recently did thousands of bourd feet using 3.5" polyiso. Fastest was to mark set the fence and throw it through the saw.

[@jasonratliff9198]

For regular xps or eps i made a hot wire table saw. Stopped at a vape shop and got some resistance wire to make it with

[@kennedycarey898]

Hey! Love these videos! Super helpful! Do you know if the use of interior Polyiso board under the roof deck would pass code for an inspection?

[@FamilyFriendlyDIY]

I believe the inspector usually goes with whatever the manufacturer or the manufacturer's documentation says is okay. Most polyiso board seems to be used on the exterior anyway, so I'd think you'd be okay, but you can always call/email the permits office and ask. They'd probably love to answer your questions. My inspectors have been glad to offer advice. ... and I've heard a good repour with the inspector goes a long way. Thanks for the kind comment!

[@georgem.323]

I cut mine on a table saw with a vacuum attached to collect the dust while wearing a dust mask. worked great and fast.

[@FreeMissions]

Were the cut pieces clean afterwards? Did they still have some remnant dust falling off?

[@georgem.323]

@@FreeMissions I don’t recall having much dust on the pieces so long as you had really good dust extraction. Without dust extraction yes lots of dust. It has been quite some time so don’t recall 100%.

[@guyhowell8176]

I really like the Milwaukee battery operated 9” demo saw

[@tsschoolman]

I use a 4" drywall taping knife sharpened on both sides, buy yourself a 6' straight edge. If you work on the floor you can hold the straight edge with one hand and one knee while you slice with the side drywall knife. You can get so accurate there will be very few cracks to spray foam, most panels just push in tight. If your knife is sharp you should be able to shave off a 1/16 of an inch if need be no problem. It is time consuming to insulate this way but the results are awesome.

[@doanehoag870]

Dave: what about cutting the higher density XPS extruded foam board; the Dow Corning pink or blue XPS foam? Also, it has a higher R value and isn’t susceptible to water damage.

[@CAMPFIRESKY]

I'm trying to build a box to cover my attic stairs. I'm using R-10 2 inch foam board but could not get the length to snap. Just ordered the Bosch T313AW3 Soft material blades for my jigsaw. Hoping it gives me nice 90 degree cuts. THANKS for this video !!!

[@FamilyFriendlyDIY]

Thanks for watching!

[@deniseg4741]

Thanks for the video. I've just ordered my bosch blade. I have 5" thick foam. I need clean cuts for my giant letters.

[@FamilyFriendlyDIY]

I'd love to hear how it works. Thanks for watching Denise!

[@frrapp2366]

basically this is what i have found tho i haven't tried the jig saw i only used the single sided foil foam, a sheet rock knife and the long utility knife seem to work the best , i use a 4 ft ruled strait edge to keep my cuts strait but had to be carful to cut strait down and not angle my cut also picked up a Hot knife at HF works good for odd shapes

[@coolramone]

👍Razor blade type cutting knife (box cutter)

[@deliveryguy7402]

I use a tool called a foam board cutter. It's a long skinny rod on an industrial heater that melts the board as it cuts. No mess, no shards. Costs $29.00.

[@jakeseverson]

You the man

[@rich4501]

Watched this video then started cutting 2” foam board. My opinion - utility knives and blades are great for the first cut. BUT the foam board dulls the blade So Much, you have to switch blades for the second cut. My recommendation - take the foam outside (not in your garage), and use the circular saw with a dust mask AND disposable coveralls. The dust gets everywhere, but if you need straight/clean cuts, it’s the only way.

[@ladwiss]

great video

[@FamilyFriendlyDIY]

Thank you!