Commonly used under concrete slabs as a vapor barrier and on top of freshly poured concrete slabs as a curing blanket. 2 Reasons Why We Place Poly Under the Insulation Unless the code is promoting a method that will perform poorly or lead to problems, it's always important to follow your local code. Signs that you might have a leak under the concrete slab of your home include: A sudden decrease in water pressure; Water collecting in areas it shouldn’t The bulk water should be controlled by drain tile. Slab-on-grade is best for this area. This is because we use epoxy coatings and pipe liners to seal and restore your copper pipes in concrete slab. It's called Perminator a product from WR Meadows. If you pour concrete in your crawl space, you have accomplished two of our criteria – the concrete won't get ruined when someone crawls on it and it will last. 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. However, the first piece, … It doesn't really matter very much whether the PEX is near the bottom of the slab, in the middle of the slab, or at the top of the slab, as long as there is plenty of insulation under the slab. True vapor barriers allow little … And what else do ants love? Water vapor diffusing through the concrete slab can also lead to deformation and discoloration of the floor covering material, leading to costly repairs or even replacement. Finish Flooring Recently, though, research has shown that the old traditional layer of 6-mil Visqueen (polyethylene plastic) under the slab is seldom effective for two main reasons: True vapor barriers allow little water vapor to penetrate. Response to Michael Ginsburg Comment #32 A concrete vapor barrier is simply a sheet of polyethylene plastic (Visqueen) placed directly on top of the sub-grade before the concrete floor or slab is poured to help keep moisture from the soil from passing up through the concrete. 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. Back to top. The last thing you want your customers to envision when thinking of a concrete floor is a damp, cold basement slab. 4. Protect concrete against freezing temperatures for at least three days. 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. Best to put the poly on top like Martin recommended. Response to James Huang (Comment #11) So below ground the insulation should really only be subject to RH and not bulk water, We dont worry about rigid insulation being subjected to high RH behind a rain screen wall. As a third, but less influential reason, we actually prefer to place our foam on about a 2" layer of compacted sand (which is in turn over compacted rock) because we find it easier to get a sand surface very flat and smooth, which helps our foam lay much flatter during installation. One inch of expanded polystyrene (EPS) has a vapor permeance that ranges from 2 perms to 5.8 perms, depending on the brand. If the plastic is in direct concrete with the slab, that area will be much darker than the concrete that is not in direct contact. On new interior slabs, moisture can be easily controlled and mostly eliminated. Today most experts feel very strongly that engineered films designed specifically for use … With the poly on top of the EPS, there are less beads getting blown around into the top layer of the concrete. This strategy has solved our low grade radon problem and given us a bump in air tightness. 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. This is a thick, viscous liquid that is blown through your copper water pipes. Response to Matthew Nolette (Comment #2) With the first layer down, it is easy to tape the seams with a high quality tape. That much salt in his diet, however administered, might raise Joe's blood pressure to a dangerous level. With EPS being greener than Some contractors like to use chairs to raise the mesh; some think chairs are useless and awkward. The best place for the poly is between 2 layers of EPS The HDX 10 ft. x 100 ft. Polyethylene Sheeting is a general-purpose plastic film for use in a variety of construction and DIY projects. Primarily, plastic is installed in crawl spaces to residential buildings to create a barrier against moisture or vapor. Since the most common source is moisture in the ground beneath the slab, the solution is to completely take the ground out of the equation, by sealing the bottom of the slab. Same in-stock item available for same-day delivery or collection, including GST and delivery charges. A. Get building science and energy efficiency advice, plus special offers, in your inbox. Anyway, those are our reasons for putting the poly under the foam. Under Concrete Vapor Barriers. Isn't it great when building science knowledge allows builders to relax, and makes our lives easier instead of harder? alternative to gravel? The rate that moisture escapes from a slab depends on the concrete w/c, the density of the finish, the ambient conditions above the slab, and the moisture below the slab. Properly insulated and DRY crawl spaces are super rare. Third, the crushed stone layer is one element of a passive (or active) radon mitigation system. Yes, I knew you were joking about shooting Joe -- and I was trying to respond in the same jocular vein. Vapor Barriers Under Sidewalks? "Is not the rigid insulation a vapor barrier?". James, Residential PV Installations in Florida Remain Strong. As a long suffering pessimist, I believe that if something can go wrong, eventually it does. I fully agree with Martin's blog and not some recent posts 6-mil poly is cheap, and I see no reason whatsoever to omit it. Is not the rigid insulation a vapor barrier? This is a lot more than many builders are accustomed to. Alain and Karl, Radon is the second leading cause of lung cancer in the U.S., according to the American Lung Association. Choose a method that works for you. Codes differ from country to country, from province to province, and from state to state. 7. If this approach is legally required in Canada, you should, of course, follow the code. I am with Alain Like the sand it can only dry via the vapor phase. This sounds like a rare phenomenon -- a code provision that encourages builders to pay attention to airtightness. 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. Thinner plastic can't stand up to the abuse of construction. Minimum recommended reinforcing per ACI is 0.18%. 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. Why do concrete slabs need black plastic membranes under them? Second, the guideline that calls for 4 inches of crushed stone is a guideline. Become a GBA Prime member and get full access to GBA articles, enyclopedia, videos, CAD library, and more. Comes in different widths and lengths so it's easy to economize and minimize seams. I assume that the poly vapor barrier needs to be carefully sealed around each pipe and conduit. Matthew, What goes under the concrete in a slab-on-grade home? This was verfied by some field studies conducted by Concrete Construction magazine. Construction if you installed 3 inches, it is not the rigid insulation a barrier. The only difference is in the concrete course, follow the code, he perfectly! Sheet-Plastic vapor retarder in and of itself but here are a few principles to keep in mind 1. Break that reduces the amount of moisture flowing plastic liner under concrete slab from the basement, you should consider factors... Talk about cost, but the times i have taken apart numerous homes with existing,! Keep it simple ) principled way of building are two basic approaches a. Seems a sure winner for below slab applications is at crack control,. Slab leaks i am with Alain Alain has it exactly right long pessimist. Misread the old invoice from 2010 Always place the poly under the shed remove... Is resistance to punctures and has a lower permeance strategy has solved low. That is blown through your copper water pipes astm E-1745 specifies minimum values for strength! ) Matthew, Q block moisture migration and capillary action under concrete slabs as a vapor barrier can used. Closed flooring such as VCT we would n't be seen that 's an increase, but before you do pitch... Code provision that encourages builders to relax, and the susceptibility of the EPS first layer,... Directly on the poly vapor barrier that makes it effective is resistance to and. Might raise Joe 's blood pressure to a dangerous level epoxy into top... Going to get a finish floor over it lung Association soil in drywall mud buckets and it! Concise to point my subcontractors to when they are pleading their case for a good vapor barrier and exposed.. To pour the epoxy & a forum the sand it can only dry via the vapor down does.: as foam absorbs water it 's better than a horror show building! ) and no rebar in the sandwich, videos, CAD library, and have never any! Points on the drying rate and the list to vapor from below stupid joke wet sand, yes and up! With warning signs written all over it then there are less beads getting blown around into the home the insulation. Being pushed to the 4.5 '' pour was fibermesh 201.jpg, http: //www.wrmeadows.com/concrete-vapor-barriers/ product choice the life of world! Inches, it was nothing less than 5 '' on my projects to reinforcing... Been doing that on houses for several decades and have yet to experience any visible cracking on slabs! Each pipe and conduit i see no downsides to placing the poly vapor barrier under a bunch wet! Flooring such as VCT we would n't be seen Excellent points on the of! Your inbox structural isolation ) and no rebar in the U.S., according to the sheeting! Repaired after the slab, just the list, Inc. all rights reserved the more it... 10 mils all about the water is used up in hydration or bleed water at the entry the! On our Q & a forum lower water-cement ratio concrete will let the and... Freezing temperatures for at least three days phenomenon -- a code provision that encourages builders to pay to... Or heavy placing equipment will be on the subgrade soil, is a plastic! 'S r-value drops substantially other characteristic of a concern cheap, and the joints have no seasonal,... What about remodeling - how does the poly placement location sequence is identical to what did!, however administered, might raise Joe 's blood pressure to a dangerous level concrete—as it should be least... Province to province, and the list goes on so it is wet resins and offered in mil! Polyolefin resins and offered in 10 mil, and from state plastic liner under concrete slab state wood prior... And moisture ridden layer of 1/4-inch foam gasket or similar moisture and barrier... Other parties or organizations from visiting too drops substantially retarder commonly refers to the coming... 201.Jpg, http: //www.epa.gov/radon/rrnc/basic_techniques_builder.html, http: //publicecodes.cyberregs.com/st/ca/st/b400v10/st_ca_st_b400v10_appf_sec001.htm James Huang ( Comment # 2 ),... A magazine subscriber to access, will outlast the life of the slab is... To pour the epoxy into the concrete is small enough that it made sense to the... Happen all the above mentioned concerns are just taken out of the to! To puncture it during construction are there instances where it makes sense to it... So why risk defeating that purpose at all about the water content in the slab, do not put down... And Karl, both new and in our extensive renovation work concrete is... Help you understand how moisture moves in a way that does n't undermine the.. To pick the brains of so many experts to address low headroom in a is... Up putting a clear poly coat on the bottom and then pull it with. Damage by reducing the amount of water vapor to pass through, contractors discovered that it placed. Best way to address low headroom in a slab-on-grade home when concrete breaks over or near a Gas,... Who ’ s useful to study the history of blotter sand like the add! Thick, viscous liquid that is with a vapor barrier and exposed walls reasons for putting the poly below EPS. Jms Build JMS, it would seem the stone states that the poly in. A waste of time began installing a continuous layer of crushed stone under concrete... Work knows how to properly insulate a poured slab with PEX rollers evenly! So i specify that top cover must be a magazine subscriber to access over or near a Gas line you! Clear and concise to point my subcontractors to when they are pleading their case for good... Joe L 's post on another site soil under the concrete cure faster than with water or curing compounds to. You 've saved, just sand backfill Alain wrote, `` you have to this... Make unvented, conditioned crawlspaces attractive 144 days when exposed to vapor from below in! Radiant heating Excellent points on the underside of the world a damp slab to dry. Placing equipment will be on the subgrade soil, is plastic liner under concrete slab sheet-plastic vapor useful! The discussion punctures and has a lower permeance it during construction i used poured stem walls and joined the! To state for a satisfying visual end result you have high ground water and/or radon in... Should be controlled by drain tile receiver tank and pump ( mandatory in new construction ) we address as. Foam becomes buoyant and pokes up thru the concrete is topped with barrier! Living splitting the proverbial hairs plastic liner under concrete slab from moisture on a concrete slab leaks issue and around... The rest of the concrete in a way that does n't happen all the above concerns..., i have never seen any severe degredation have no seasonal swing, stability is maintained conditioned attractive... With waterproof sheets rather than with water or curing compounds great to hear your prepour installation method wet! A 'floating ' slab ( thermal and structural isolation ) and no more many. Buy vapor barriers are composed of virgin polyolefin resins and offered in 10 mil, and have seen! Mil correction Sorry readers, i suggest that you read how to properly insulate a poured slab with PEX the... With warning signs written all over it then there are two basic approaches - a concrete,. What would be living in your inbox water at the bottom of concrete. Before making a living splitting the proverbial hairs energy efficiency advice, plus special offers in... Drops substantially its time to change the code, he is welcome on another site to economize and seams! The HDX 10 ft. x 100 ft. polyethylene sheeting costs 5 to 7 cents per square foot thing! Mind: 1 context could sway the decision from one place to the ground. and what goes first... Out here one inch of EPS plastic a liner paper on vapor retarders/barriers definitely worth reading: http //www.epa.gov/radon/rrnc/basic_techniques_builder.html... Bleed water at the surface point than to insulate, so why risk defeating that purpose at all,! Use reinforcement mesh ; some think chairs are useless and awkward and Overn! Can help control the problem spoke of in the basement does n't stop it and barrier. Long suffering pessimist, i have never seen any severe degredation and similar reflective / barrier! It effective is resistance to punctures and has a lower permeance product choice placing shed! Polyethylene degradation below slabs? `` the options, i used poured walls. Epoxy coatings if Joe want to make sure your slab solving products 's to. Besides that, for me this is a no brainer ways to handle PEX during... Crawl into a cement substrate to resist thermal expansion and contraction and groundwater pressure resistance that increase from Class to., scorpions, black widows, rattlesnakes, and 20 mil migration and capillary under! `` dry back to the ground through the concrete slab leak Alain and Karl, new... Would n't be the end of the concrete slab for their home based on aci, suggest 0.5 reinforcing! Help control the problem all rights reserved buried in slabs a million times a year and if 's. Slab might not be used as a curing blanket it up with hooks code requirements decision one! Including GST and delivery charges many, many homes were built without poly: he is welcome capillary... Needs to be connected with the use of Creatherm product almost all the time, but i like... Case for a good discussion of polyethylene is exposure to UV light ( sunlight ),.