Cutting and installing EPS tips
tdbaugha
| Posted in Green Building Techniques on
I have about 350 sheets of EPS, 1”, 2”, and 3” that I’ll be installing below grade in a few weeks. It’s all 15psi for what it’s worth. Is the best way of cutting it like drywall, score and snap or is it worth buying a hot knife of some kind? Secondly, where the sheets are installed vertically, I was going to use an EPS compatible construction adhesive to stick them to the wall. I want to avoid fasteners as to not penetrate the waterproofing membrane. It just needs to hold it in place until backfilling takes place. Any suggested glue or tips? Thanks!
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Replies
tdbaugha,
My first suggestion would be to establish a cutting station on a tarp and do all the work there. Any way you end up cutting the EPS you are going to end up with a lot of foam beads, and it's easier to deal with them if they are somewhat contained in one spot.
I've never had much luck with scoring and snapping. The edges end up uneven and you get a lot of small pieces falling off. I use multiple passes with a utility knife (box cutter) to cut right through into a backing sheet. For that I use a sacrificial strip of strip of XPS.
I needed to cut a lot of foam and did not want to generate foam dust in the shop so I replaced the blade with a red-hot wire. It worked well for me a little slow but that seemed safer than having the wire get to hot.
Zero dust.
Note I did remove 100% of the wood dust from the saw before I stated.
I used 18 inches of 24 gage nichrome wire and a dumb 12V battery charger for a power supply pulling 4 amps
.
I used a pulley and spring connected to the arbor to tension the wire.
Walta,
Nice clean cuts!
Thanks Walta and Malcolm. I read through the other longer thread from ~8 years ago and it seems like the hot wire rig is the way to go for clean cuts.
A saw blade will cut the foam and leave a clean smooth surface but it will fill your shop with static charged foam dust that clings to everything.
The other option is to make the cuts outdoors and pollute your yard with the foam dust.
I did see a specially designed saw blade that claimed 80% less dust.
Walta
I've used a sharpened wide paint scraper to good effect with minimal dust. BTW, you sharpen the side of the scraper, not the blade and pull it toward you.
I don't know if I'd want to cut 350 boards like that, but for the occasional dozen or so boards it surprisingly works better than a long bladed utility knife and is way cleaner than any power tool.
Most boards are going to be solid sheets, but there will be cuts at the edges, corners, and whatnot.
Not really interested in foam beads going all over my property. I’ll try the sharpened paint scraper first and hot knife second.
I just finished cladding my house in foil-faced EPS and found that the higher rear edge of a track saw rail and a 25mm Olfa Knife worked best on 3/4 and 1 in thick sheets. The rail is non-slip so it won't skate around and the 25mm blade is heavy enough that it won't twist or wander through the cut. The key to really clean edges is to cut at a low angle with the blade extended all the way out. Defenitely set up a dedicated cutting table, a 4x8 sheet of plywood and some sawhorses works well.
I had to cut a whole lot of 3" thick EPS over the years. By far the cleanest, straight and accurate cuts were done with a Metal or Concrete blade in a circular saw or table saw.
Make a cutting guide "shooter board" for your circular saw from plywood.....like a track saw....but spray glue (super 77 adhesive) some non slide material pad to the bottom of the guide. Pad material sold at any hardware store or Rockler as a bench top non slide pad for bench tops, or shelf liner, or even non skid pad for area rug. I also now use 1/4" staples in to help hold the pad in place for years to come. The cutting guide will not slide on you 98% of the time.....no clamps needed.....
I now started using a battery saw with this procedure. sometimes need to cut the foam on both sides due to thickness.
By far the easiest way I have found.
cutting EPS any other way makes an absolute mess.
for xps or especially polyiso....a well worn joint compound knife works very well
dirkgently,
My job site homemade track saw. Very useful for most sheet goods.
Started cutting and installing EPS foam of various densities and thicknesses and thought I would share my tips for the next person that finds this thread.
The sharpened drywall knife works fine, basically a better utility knift however it is not fast and you're not really able to cut perfectly straight lines and its a bit messy. The marshalltown "Bullet" blade for a circular saw or table saw works amazing, no mess, fast, easy. 5/5 stars. I attempted to glue the boards to the foundation at first with Soudabond Easy which is a polyurethane foam glue for EPS, XPS, etc. 0/5 stars. Its a mess, has almost zero holding power so you need to hold the boards on for 20-30 minutes while it sets up. I also tried power grab ultimate adhesive, 2/5 stars. Works but not great. Gorilla Glue Heavy Duty Ultimate was the best adhesive, it would mostly hold the sheets instantly, and a couple needed to be reset after 10 minutes or so. 3/5 stars The problem with these adhesives, other than them taking forever to work is the cost, you burn about $10 of adhesive every 50sqft which adds significant cost. I have since switched to PMF anchors: https://www.trufastwalls.com/plasti-grip-pmf. 4.5/5 stars. Fast, reliable, inexpensive. The only thing better would be to buy a $600 nail gun designed for fastening insulation to concrete. AwesomeFramers on IG has a post on this where they are installing 4" rockwool to a stem wall. If I were to do this for a living, this is the tool for the job.
Hope this helps
For the Marshalltown Blade, are you referring to their "CenterFire Circular Rigid Foam Blade"? The "Bullet" blade seems to be a vinyl cutting tool, not meant for circular saws.
Yes, this one. https://www.acmetools.com/bullet-by-marshalltown-725-in-centerfire-dust-free-foam-blade-for-cutting-eps-xps-and-poly-iso-insulation-cc52-1507/894335000640.html?gad_source=1&gclid=EAIaIQobChMI_Kqj1pbDhgMVlimtBh21XQTxEAQYASABEgJTWPD_BwE