I require that it be placed on dobies or chairs. EcoFoil Under Slab Insulation is superior to traditional, outdated forms of concrete floor insulation such as polystyrene or foam sheets. Sandra, Matthew, Use bricks, boulders, or … Anyone that has had to face a moisture problem with a concrete slab understands the damage that excess moisture can cause. We really see no downsides to placing the poly below the EPS. After 28 days, the moisture coming out of the concrete is small enough that it's not much of a concern. Response to James Huang (Comment #11) Besides, it's called a "crawl space" but 90% of the time you can't crawl under it properly and do any work properly under there due to the limited space. Thicker samples of EPS would have lower perm ratings. Regarding tubing placement for radiant heating, I have always been concerned about potential problems with the pex tubing being tied to rebar mat: (1) uniformity of placement both horizontally and more importantly, vertically (2) potential known and UNknown damage to pex occurring during concrete pouring, (3) just so many potential what if's with so many laborers trying to maneuver around during the pour. Below is a photo taken of my new house under construction here in the Philippines. There are many ways to do this, but here are a few principles to keep in mind: 1. If this approach is legally required in Canada, you should, of course, follow the code. (Maybe ants are Passive House enthusiasts themselves?) Either polyethylene sheeting that’s at least 4mm thick or a concrete curing insulating blanket—both available from DIY stores—are good for this task. If it warrants a receiver tank and pump (mandatory in new construction) we address that as well. A supplier pointed out "research" that said polyethylene deteriorates below concrete slabs due or the conditions of the subslab environment and lime in the concrete; they recommended polyolefin as a superior specification for subslab vapor barrier. First, the standard way to address low headroom in a basement is to excavate soil from the basement before pouring your slab. The rigidity of the 10 mil poly also does a pretty good job of keeping the sand from getting "dug up" by boots while we are walking around on it placing our foam. And a note to Steve, you better change your foam installator because in 30 years of building insulated concrete slabs, i've never seen any foam pops like an iceberg. I once helped to replumb a slab on grade house in Los Angeles where some of the pipes (copper - it was a long time ago) under the slab were damaged due to ground movement so I'm a bit negative on that style. Steve, As for degredation, I have taken apart numerous homes with existing poly, and have never seen any severe degredation. Another method to prevent discoloration is to place dry straw directly onto the concrete, then put the plastic on top of it. You wrote, "It's now part of the 2010 NBC (and valid in most of the [Canadian] provinces except Quebec) to put a 6 mm poly or even thicker under the slab and to seal each penetration correctly and perimeter to the air barrier -- they called it radon protection -- so nobody has a choice, it's mandatory.". Does it make sense to omit the poly layer if you are planning to put a vapor barrier above the slab, such as an epoxy sealer? Q. . Moisture and wet environments. Yes, it's annoying for the contractors to work around for the few days they are pouring slabs, but it means a lifetime of better service for the client. Pretty basic. Most people use EPS instead of XPS below slabs, and EPS absorbs much less water, so it's r-value remains much more stable. Both of you seem to worry about sealing holes in the polyethylene. Its nice to have something clear and concise to point my subcontractors to when they are pleading their case for a different arrangement. Where a redundant vapor barrier is placed is of little concern except to those whom making a living splitting the proverbial hairs. Concrete driveways generally remain functional for 25 to 50 years, depending on how well built they were and how well they have been maintained. Anything less is a very bad idea. An application of 2 inches of closed-cell spray polyurethane foam would have a vapor permeance of about 1 perm, which meets the definition of a vapor barrier. I never spec slabs less than 5" on my projects. definitely worth reading: http://www.wrmeadows.com/concrete-vapor-barriers/. 3. We are called in to design and install radiant floors, but end up address ground water, radon, plumbing and insulation of floor, wall and most especially rim joists. Put 10 mil poly under your foam, and any moisture in your ground will not get into your foam layer and will thus not attract ants. x 1.5 in. My own advice is to install 6-mil poly and stop worrying. ... Methods of curing include covering the concrete with plastic … It's simply the f---ing law, for now. Unless the code is promoting a method that will perform poorly or lead to problems, it's always important to follow your local code. Your friend sounds like he has heard an urban legend or he's pulling your leg. Response to Alain Hamel and Karl Overn I have a MS in structural engineering and some experience working in concrete labs as well as a lifetime working as a designer. If you want to keep the moisture out of the wood you need to stop it migrating through the slab using a sealer or crystalline coating. A classic plastic shrinkage crack . x 1.5 in. Well-sealed 10 mil poly under or over your foam, no. Response to JMS Build Whenever I have seen holes drilled through concrete slabs, I have never noticed any degradation in the polyethylene layer. Reason 2: Bugs (namely carpenter ants) love rigid foam. This article explains how to dig and run pipe under an obstacle such as a driveway or sidewalk. With the first layer down, it is easy to tape the seams with a high quality tape. Black Plastic Mold Reusable Concrete Stepping Stone, DIY Paver Pathway Maker (50) ... Model# 02-0267 $ 25 60. 1 Dig a trench across the gravel driveway with a shovel. Slab reinforcing should have a minimum top cover of 3/4". Plastic Shrinkage. Salt Because our sand in this environment generally is quite wet all year round, we do want to keep whatever moisture is in that sand out of our EPS, hence the poly between sand and EPS. As long as the polyethylene is protected from sunlight -- as it obviously is when it is installed under a concrete slab -- it should last indefinitely. It seems like the only difference is in the particular foam product choice. James, So, as i can see, everybody have his own way of doing things, in some cases they are right and in other cases it could be food for thought, but the most important thing is to be here and share our knowledge and experiments so everyone can learn from each other. Some contractors may ask: Is it a mistake to put the polyethylene lower down in the sandwich? In the recent construction of our pre-certified PassivHaus in NJ we did exactly what Peter (above) described. "Has anyone else come across the discussion of polyethylene degradation below slabs?". 40 mil correction These are valid points. Helping You to Do It Yourself! Although, even when the concrete is topped with a vapor closed flooring such as VCT we wouldn't omit the poly. I'll never recommend anyone use a crawlspace in Arizona. The order upwards for the slab is: undisturbed soil, crushed stone, 4-inches of Type I EPS, 6 mil polyethelene sheet, another 4-inches of Type I EPS and then the 4-inch concrete slab for a total insulation value of R30. The best recommendations I've read, based on ACI, suggest 0.5% reinforcing ratio. The footings are completely encased in EPS too, with Type IX under them and Type I around them. Would 2 layers of 2" rigid layered perpendicularly to each other work? Or spraying 2" of closed cell? Lastly the insulation is being exposed to the moisture of the concrete when it is wet. When the concrete is still in its plastic state (before hardening), it is full of water. That is what would be living in your crawlspace and coming into and around your home if you did a crawlspace. "Would it be possible to replace the 4 inches of gravel with a drain mat in order to save on headroom in a low basement area?". Interesting article. I noticed a couple of assemblies noted in Joe Lstiburek's Cold Climate book where he notes slabs with rigid insulation underneath but no vapor barrier that are allowed to dry back to the ground and to the interior. This doesn't strike me as one of those building science issues with warning signs written all over it. thanks. Just do the roof and windows before preparing the slab and you are safe. by Steve Ragan, Director, Research and Technical Services The answer to this controversial question, from both angles, is a qualified “yes.” Vapor barriers have been associated with certain concrete … I understand the reasoning behind this stack but what about plumbing and electrical connections that go through such as in a slab on grade house. Additionally, I used poured stem walls and a 'floating' slab (thermal and structural isolation) and NO rebar in the slab. Alain, Well, it didn't take long, put the hardwood on some saw horses, roll out a quick coat, it can be sloppy because the floor will get sanded and finished on the top side. You're right: he is perfectly capable of surviving your virtual threat. If one of the desirable attributes of a green building is its ability to be easily modified or repaired over time then it's hard to beat a single story structure on a crawlspace with a trussed roof. To insulate or not; to steel reinforce slab or not; wire fabric in slab or not; radiant floor (heating) pex tubing attached to suspended #4 at 2'oc each way or not; what about potential (some say inevitable and the only thing one can do is mitigate) cracking slab; sandwich the vapor barrier or not; on compacted base or under........ How about the following proven concept (DOE Build America testing, monitoring and 3 year lived-in experiencing) compact sub-base, compact AB or similar, 40 mil plastic liner (vapor and radon restrictive; perhaps too much but one time expense), 2" R10 Creatherm (pex ready snap-in plasticized topped eps foam), pex tubing at bottom of 4.5" slab with no steel reinforcing, finished concrete floor, no cracking, year round radiant floor thermal comfort. Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! Because it is pretty easy to seam seal the poly when it goes down, and because you've really got to give 10 mil poly the full beans to tear and puncture it, we're pretty confident that even though the rock below should prevent any bulk water from reaching the underside in 95% of all cases, for the rare times 10 or 15 years down the road, it really doesn't hurt to have a well-sealed, intact layer of poly below the EPS. Get building science and energy efficiency advice, plus special offers, in your inbox. Water vapor that passes through the concrete will evaporate if the concrete surface isn't sealed or covered by a material that doesn't allow the concrete to breathe. ", You are both wrong, fortunately -- because this is an unnecessary worry. Finally, some contractors in cold climates began installing a continuous horizontal layer of rigid foam insulation under their concrete slabs. Response to Michael Ginsburg Comment #32 If the temperature is below 60 F, use dark-colored plastic sheets to absorb more light and boost the temperature; when temperatures are higher than 85 F, reflective, white-colored sheets help to keep … For a good discussion of the options, I suggest that you read How to properly insulate a poured slab with PEX? With the correct sub-base, GeoGrid TM … Building one can be labor-intensive and costly, but for folks that aren’t afraid to tackle big jobs, building your own driveway … Should we worry about the RH below grade. What about remodeling - how does the poly barrier get repaired after the slab is cut open to change plumbing? The crushed stone provides a capillary break that reduces the amount of moisture flowing upward from the damp soil to the permeable concrete. Icebergs, now that is a thin mix! Finish Flooring Honestly, i think, especially in case of radiant floor installation, that it is easier and safer to put it under the foam, and with new rules about radon and other soil gas barrier, you have to protect this poly from concrete contractors hooks ( the one they use to lift the mesh). The answer is yes. Crawlspaces in Arizona are almost never used. Q. What goes down first, and what goes down last? Or perhaps a less dramatic example; tree roots eventually knotting up and clogging the perimeter drain, an errant excavator shredding the landscape fabric over the drain rock and spilling dirt into the drain, curious kids dumping mud down all the perimeter drain clean outs, etc. During custom home construction, often new homeowners ask why the builder places black plastic under the concrete slab for their home. 6-mil poly is cheap, and I see no reason whatsoever to omit it. Don't worry if the concrete contractors put a few holes in the poly. It will cure faster than with poly on the bottom underneath the foam. I pity the fool who would dare crawl into a crawl space on a home out here. We have installed miles of radiant tubing with and without a vapor barrier with no appreciable difference in the quality of the slab or the measurable radon. The only add to the 4.5" pour was fibermesh. According to most building scientists, here’s how the layers should go, from the bottom up: crushed stone; rigid foam; polyethylene; concrete. Longevity Thought through at the design stage they compliment the architecture, and when a slab is cut into pieces around 5 ft x 5 ft, the chances of cracks virtually disappear. A. We used 2" R10 Creatherm product because it had the plasticized 'reversed muffin tin contour' (my description for visual perception) in which PEX just pops in place perfectly uniform in position. A. LOVE it. After installing a beautiful recycled concrete driveway, the last thing you … Perfect timing Hi, I'm a new member who is building a house in Valencia (Dumaguete), Philippines. . Eventually, contractors discovered that it made sense to include a 4-inch-thick layer of crushed stone under the concrete. Is not the rigid insulation a vapor barrier? It’s the perfect … ... For sidewalks placed directly on the subgrade soil, is a sheet-plastic vapor retarder useful or harmful? Excellent points on the poly placement location. Now if the poly is under and has holes if there was a high water incidence than water could be trapped between the insulation and poly. Floor coverings like linoleum, vinyl tile, wood, carpeting, and epoxies, seal the moisture in the concrete where it eventually causes the floor covering to loosen, blister, or buckle. Malcom Taylor, We put the ploy between 2 layers of EPS. It depends on the type of insulation and its thickness. More About EcoFoil Under Concrete Slab Insulation. Burke- it's great to hear your prepour installation method in wet, coastal environment in Canada. You can also cover concrete with sheets of plastic, but beware; this may cause discoloration of the surface if the plastic is not uniformly spread over the concrete. I've got one sub that does a lot of flat-work for me and he claims that a lot of his "high-end" contractors he works with don't do a vapor barrier under their slabs anymore. A basic concrete driveway installed over a gravel … 16 in. Comes in different widths and lengths so it's easy to economize and minimize seams. So I specify that top cover must be no less than 3/4" and no more than 1". Another option is to install sides to the driveway. And because foam goes down fast, we just wait for a window when the weather is good for a few days so we can get the foam down and get the slab poured immediately after. the basement doesn't seem to have active leak problems but is damp due to lack of vapor barrier and exposed walls. yes, for headroom, i would also be excavating the existing dirt floor down 12-16" as long as the rubble foundation allows for this safely. There are many ways to handle PEX tubing during a concrete pour. 2. So, to answer the question, yes, using the blotter sand technique was dangerous and illogic but putting the poly up or down is a matter of job site condition, that's it. More information on PEX for Alain Hamel If you didn't do it right and they found radon in the basement, you could easily be sued by the owner. A. Josh Jaros Remodeling in The Woodlands, Texas. In other words, lower your floor. Our EPS is generally a fairly tight fit, and I am confident that the very small amount of moisture that does absorb into the EPS (I can't see it absorbing much at all during the few hours it takes the concrete to set up) isn't going to cause any major concerns working it's way back out during the course of construction. The best place for the poly is between 2 layers of EPS Concrete does not cure by drying out but through a process call hydration. However, looking into the issue the "science" I found was mostly from manufacturers and struck me as similar to debates over which rigid foam is superior below grade; mostly it is competitors sniping at one another. Many contractor friends said it was a waste of time. You must be a magazine subscriber to access this feature. For the record, I think that your reaction to Joe Lstiburek's writings on this issue ("So when Joe is talking about taking a walk on my poly with his golf shoes, I'm imagining me shooting his butt with a 12 gauge coarse salt shot") is unnecessarily extreme. I will be pouring a basement slab for a small room addition within the next couple weeks and I was just starting to research how to stack the layers - assuming it quits raining for more than two days straight any time soon. Isn't it great when building science knowledge allows builders to relax, and makes our lives easier instead of harder? The other potential issue with polyethylene at the bottom of the sandwich below the rigid foam is that the rigid foam can trap water between the poly and rigid foam. But the closer it is to the top the more effective it is at crack control. Soil Up Order In Our PassivHaus Slab Taping the seams in the polyethylene layer, and sealing penetrations, causes no harm, and probably makes air sealing easier once the slab has been placed. Might was well have some vile's of anti-venom on stand-by because you are going to need it... to Martin about Pex, eps and poly A. I had NO cracking at all. At my house, it is a slab above grade, with no poly under the slab, just sand backfill. Rigid insulation concrete products like foam sheeting are easily broken and must be used with an extra vapor barrier, plus standard foam or polystyrene concrete … Although I would assume this would be minor. The second layer of EPS protects the poly during the pour and keeps if from getting punctured from either side. For me this is a no brainer. alternative to gravel? Alain wrote, "You have to protect this poly from concrete contractors' hooks. The most efficient and cost effective way to bore under an obstacle is to create a hole using the power of … (And as Peter Amerongen suggested, connecting the poly to your air barrier at the slab to foundation wall seam can be an important part of the puzzle). Any instances where no vapor barrier is applicable? Another contractor told me that no sand is used because it is the cause for cracks as the concrete … With the poly on top of the EPS, there are less beads getting blown around into the top layer of the concrete. ACI standard 302.1 R-96, Guide for Concrete Floor and Slab Construction, included this recommendation in Section 4.1.5:…. As I think most people who have used EPS will attest, it is impossible to prevent a swarm of EPS beads, and when they get inadvertently blown around and troweled into the top layer of the slab, they lie in wait to open up like a canker sore on an otherwise unblemished finish. Martin, Shouldnt the EPS/XPS be elevated above the bulk water layer by the stone. The alkali in concrete will eat away at many plastics … The issue has come up a few times on our Q&A forum. In my area if you don't put plastic under the slab, it won't pass code. I fully agree with Martin's blog and not some recent posts With the use of Creatherm product almost all the above mentioned concerns are just taken out of the equation. Because concrete is an extremely effective vapour barrier, we aren't concerned about vapour from the house condensing on the "cold side" of our insulation against the poly and building up there below the foam (which is why one would normally place poly on the warm side of their insulation a-la walls and roof). That much salt in his diet, however administered, might raise Joe's blood pressure to a dangerous level. Your description has convinced me. and the hydrofoam http://www.polyform.com/hydrofoam#. Thin plastic like this is often called a vapor retarder—meaning it slows the vapor down but doesn't stop it. Black Plastic … This sounds like a rare phenomenon -- a code provision that encourages builders to pay attention to airtightness. "Would 2 layers of 2-inch rigid, layered perpendicularly to each other, work?". Q. Or are these leaks to small to matter? According to my understanding, the main reason for the degradation of polyethylene is exposure to UV light (sunlight). Misleading Energy Reports Used to Sell Spray Foam. Hello All, Choose a method that works for you. The ground is always damp. This question is secondary to the main issue addressed in the article but has anyone else come across the discussion of polyethylene degradation below slabs? x 17 in. I ended up putting a clear poly coat on the underside of the wood flooring prior to installation. A much better approach is a true vapor barrier, with characteristics that conform to the requirements of ASTM E-1745, "Standard Specification for Water Vapor Retarders Used in Contact with Soil or Granular … Some thoughts on slab reinforcing for crack control - But if PROPERLY placed and cured, this slab will need no control joints and will have an array of very fine, almost invisible cracks. All of the wiring and plumbing is relatively easy to access. Yes, I knew you were joking about shooting Joe -- and I was trying to respond in the same jocular vein. i'd have to agree with you.... good idea.... heh, A friend of mine told be that installing the plastic will somehow keep the concrete floor from drying completely. This leads to less cracking when it gets trampled by trades, and it largely negates the risk of the floating icebergs that Steve Baczek mentioned. Concrete does not cure by drying out but through a process call hydration. Third, the crushed stone layer is one element of a passive (or active) radon mitigation system. Installing a barrier such as polyethylene below the slab retards the transfer of moisture from the ground to the concrete. I just won't take that risk. We have not placed the poly barrier over the XPS for reasons accurately and astutely described by others whom actually take responsibility for systems they design, install and warranty. For a 5" thick slab you'll want #3 deformed bars at 6" on center, each way, or #4 at 12". This won't delete the articles you've saved, just the list. With a compression strength of 15,940 psi, Grasspave 2 is over five times stronger than concrete … Besides that, for years many, many homes were built without poly. The poly vapor barrier is 10 mil, not 40. Our Driveway Fabric is a permeable textile that increases stability, provides erosion control, and aids in the stabilization of the substrate under your driveway or temporary entrance. http://www.epa.gov/radon/rrnc/basic_techniques_builder.html A plastic liner is good because it will stop some moisture from coming up through the slab... as long as it's the right kind of plastic. Grasspave 2 is a 100% recycled ring-on-grid structure that supports and protects grass roots to withstand pedestrian and heavy-weight vehicular traffic. Codes differ from country to country, from province to province, and from state to state. This is an effective vapor retarder in and of itself. It's good to have a method that prevents the mesh or rebar from being pushed to the bottom of the slab. If the slab is also the finish floor the minimum crack control numbers above are NOT sufficient for a satisfying visual end result. There is no way to avoid any cracks. How to properly insulate a poured slab with PEX? In this case, poly goes under,end of the discussion. Alain, radon testing came back negative so that is not a pressing issue. Slab-on-grade is best for this area. Thicker samples of XPS would have lower perm ratings. > permeance of 0.7. Tunnel Under Sidewalks and Driveways Remodeling text: Tim Carter ... We drilled a six-inch diameter hole through the concrete foundation of the house so a 4-inch PVC pipe could be inserted and tilted … Decks, Patios, Porches, Walkways, Driveways, Stairs, Steps and Docks - Plastic under paver patio - Howdy all, I am building a paver patio in my back yard, 8 down, crushed gravel, sand, … I am not concerned at all about the water content in the concrete. It's called Perminator a product from WR Meadows. Peter- sometimes Gardenised Green Plastic Permeable Grass and Gravel Pavers for Parking Lots, Driveways and RV Pads, Extra Thick Tiles (Set of 4) (1) Model# QI003668GN $ 74 16. We order the concrete ourselves for our finishers and specify slump, so it is never poured soupy. Sub-slab foam serves no other point than to insulate, so why risk defeating that purpose at all? Best to put the poly on top like Martin recommended. Use PVC pipe to protect other supply lines that you must run under the driveway, as well. Crawl spaces would not work there either. Wet the concrete, then place the plastic sheeting over it. Peter It's a small point but coating wood on all six sides doesn't stop it from taking up moisture over long periods of time, it just stops it from taking it up differentially so that it doesn't cup. No brainer This is the link to the isorad, http://www.isolofoam.com/sites/default/files/INSULWORKS%20-%20Isolation%20plancher%20radiant%201.jpg Some contractors like to use reinforcement mesh; some contractors like to use rebar. I decided to address your concerns by adding a new section at the end of the article, with the heading "It is important to make sure there are no holes in the polyethylene?". A plastic liner is good because it will stop some moisture from coming up through the slab... as long as it's the right kind of plastic. We install a lot of basement slabs, both new and in our extensive renovation work. "Would spraying 2 inch of closed cell work?". Second, the guideline that calls for 4 inches of crushed stone is a guideline. Beginning in 1989, the American Concrete Institute (ACI) recommended the installation of a 4-inch layer of granular material between a sub-slab vapor retarder and a concrete slab. To ensure that your concrete driveway will look good for many years to come, there are important specifications your contractor should follow during installation. Hmmm. Some contractors like to use chairs to raise the mesh; some think chairs are useless and awkward.

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