Hey, what's with the spam posts about buying t-shirts and shoes? The other characteristic of a good vapor barrier that makes it effective is resistance to punctures and tears. This water destroys the bond and the barrier fails. When you read in a sealer data sheet that the MVER needs to be 3 pounds or 5 pounds, what that means is the number of pounds of water vapor per 1000 square feet per 24 hours. Is a vapor barrier necessary under a concrete slab with foam insulation and if so, where does go? Once the best vapor barrier has been chosen, a good quality concrete and good placement techniques are important. Checking out the 2016 National Hardware Show, SawStop's Portable Tablesaw is Bigger and Better Than Before, Podcast 307: Shed Foundations, Wasted Foam, and Deep-Energy Retrofits, Podcast 305: Asbestos Flooring, Panned Return Ducts, and Adding On to a Log Home, Plus, get an extra 20% off with code GIFT20, Simple Way to Make Old Walls Straight and Plumb, Expert insights on techniques and principles. The 10-in. Installation … It is also possible that too much water or cement paste would be absorbed from the concrete by the sand, but probably not under most circumstances. Although it may seem water-tight, this grade of material allows a lot of water vapor to pass through. During custom home construction, often new homeowners ask why the builder places black plastic under the concrete slab for their home. Radon is the second leading cause of lung cancer in the U.S., according to the American Lung Association. It was soon determined, however, that unless the seal was absolute, moisture that did get into sealed walls could create serious structural problems and health issues, such as allergic reactions to mold festering within walls. The last thing you want your customers to envision when thinking of a concrete floor is a damp, cold basement slab. Install a plastic vapor barrier: If your concrete passes the moisture test, then plastic sheeting at least 6 mils thick will prevent moisture from getting into your laminate flooring. Special plastic sheets are laid on the ground before concrete is poured, completely isolating the slab from the ground. These vapor retarders are typically polyethylene or polyolefin sheeting materials. A 10-mil vapor barrier may be sufficient for residential construction in terms of puncture resistance, although the 10-mil barriers can't completely isolate the slab from ground moisture. The usual solution would be 6-mil polyethylene with taped seams, but a number of posters think there are much better products on the market. "I have learned so much thanks to the searchable articles on the FHB website. It’s that Fick’s Law thing. I am installing a floating laminate floor on top of a concrete slab in my basement. Reflectix 48 in. Thinner plastic can't stand up to the abuse of construction. Before one can make the best decision regarding whether or not to place a vapor barrier under a concrete floor slab-on-grade, it is important to understand the sources of moisture, how it moves through the slab, and how it adversely affects certain floor coverings, adhesives, and coatings. Polyethylene (poly) plastic sheeting with a thickness of 10 mil or 15 mil is the most commonly used vapor barrier under slabs. Anything less (or nothing at all) is a recipe for myriad problems down the road. PERMINATOR provides the vapor barrier industry with a highly effective, economical choice for helping to reduce the penetration of moisture and water vapor through the slab into the structure, thereby helping to reduce fungus, mildew, and mold growth. I can confidently say that I expect to be a life-long subscriber." Thin plastic like this is often called a vapor retarder—meaning it slows the vapor down but doesn't stop it. But when adding insulation to an existing slab, the vapor barrier is laid over the top of the slab before the foam insulating panels are installed. do NOT contact me with unsolicited services or offers; post id: … Copyright 1999-2020 ConcreteNetwork.com - None of this site may be reproduced without written permission, Minimize water vapor moving through a slab by choosing the right vapor barrier and installing it properly, By Bill Palmer, Concrete Network Columnist, Toughest product on the market with superior puncture resistance, Single-coat, 100% solids, liquid applied 2-part epoxy coating. Alt… All vapor barriers should conform to ASTM E-1745; but consider going with a barrier that has water vapor permeance less than 0.3 perms. ASTM E-1745 specifies minimum values for tensile strength and puncture resistance that increase from Class C to Class A. Vapor retarders are typically specified according to ASTM E 1745 and have a permeance of less than 0.3 US perms (0.2 metric perms), when tested by ASTM E 96. Many concrete sealers may prevent the intrusion of water but not water vapor. 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 Fill under Concrete Slabs." Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine. Read the entire article at Fine Homebuilding’s Green Building Advisor. Moisture in concrete can occur from a variety of sources: ground moisture that contacts the slab through either capillary action or as water vapor, high air humidity or drastic changes in relative humidity in its environment, leaking plumbing that passes through the slab, and more. Anyone that has had to face a moisture problem with a concrete slab understands the damage that excess moisture can cause. Since we were running hydronics, we laid down 4" of closed cell 3lb foam before pouring the slab. Water vapor leaves the surface of a concrete slab at a rate that is called the Moisture Vapor Emission Rate (MVER). I say this because your concrete slab is like a sponge and it will soak up moisture when it is present. Bostik Slab-Cote™ Extreme Moisture Vapor Barrier Coating is a single coat, two-component, 100% solids, epoxy formulated to dramatically reduce moisture vapor transmission and surface alkalinity from substrates. I know this works from an insulation/ water vapor barrier standpoint....but will it also work to keep out the nastiness discussed in this article? - M.K. The newer very low permeability barriers, such as those from W. R. MEADOWS, Fortifiber, Interwrap, Raven, Reef, Polyguard, Stego, Grace Construction Products, Strata Systems, and Layfield are 15 mils (15 thousandths of an inch) or greater. She’s planning to pour a new layer of concrete over the old and wonders what type of vapor barrier she should use. Huge rolls of vapor Cement barrier insulation. 6 mil poly, which is 0.006 inches thick and has a rating of 0.06 perms, is also sufficient for most applications but may not be as commonly stocked as 10 mil or 15 mil. Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features. Here is information to help you understand how moisture moves in a slab and how using a vapor barrier can help control the problem. 1 mil is equal to 0.001 inch of thickness. The flooring is Pergo Outlast+ with built-in padding and barrier but since it is going on top of concrete it is recommended to put a > 6 mil vapor barrier underneath. Bottom line: If you want to make sure your slab on ground gets dry and stays dry, use a vapor barrier. Vapor barriers also block gases, such as methane or radon. Find out where to buy vapor barriers and other problem solving products. Moisture Barrier Under Concrete New buildings that are built on concrete slabs may already have a moisture barrier built in to the concrete slab. W. R. MEADOWS. Make sure you have help, smallest role weighs 150 pounds+. Their 15 mil vapor barrier also controls radon gas, is resistant to hot/cold temperatures, resistant to soil chemicals & pollutants, and like I said allows virtually Zero water vapor transmission up through the slab. By the DIY experts of The Family Handyman Magazine. This specification has three classes of vapor retarders (or barriers--the terms are still often used interchangeably), Class A, B, and C. For all three classes of vapor retarder, the permeance (a measure of how much vapor can pass through) must be less than 0.3 perms. The concrete slab is the air barrier, and the ripped and torn and punctured polyethylene sheet is the vapor barrier. Since concrete is porous, water vapors transmits from the ground through the concrete slab into your basement. 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. The 15 mil thickness of this vapor barrier won't easily tear, split, or puncture allowing us to go about our work without having to repair holes while we are pouring the concrete. She’s planning to pour a new layer of concrete over the old and wonders what type of vapor barrier she should use. Front-line technology produces an extensive line of water repellent products. Install dimpled polyethylene to create an air space between the concrete and the finished floor, sealing off dampness and giving moisture a chance to dissipate. And dampness is only part of the problem, water vapor moving through a concrete floor can: But it doesn't have to be that way. Concrete under slab insulation vapor barrier - $100 (Berlin Center) < image 1 of 3 > QR Code Link to This Post. Slabs that lack under-slab vapor barriers will nearly always have some water vapor emission from water below the slab, and newer slabs, even with vapor barriers, will need time to dry out. This type of barrier is especially prevalent in areas with wet, swampy ground. Sealers that stop all water tend to fail after a period of time because the water collects at the barrier/concrete surface. This thicker material is much less susceptible to tears or punctures and has a lower permeance. ACI 302.1R-11 "Guide for Concrete Floor and Slab Construction," doesn't advocate universal use of vapor barriers but does make recommendations for their proper use. One of the reasons those old basement floors were like that was because they had no vapor barrier beneath them, leaving an easy path for water vapor from the soil to migrate into the slab, assuring that the cold clammy damp feeling never went away. We will never sell or distribute your email to any other parties or organizations. Best practice here in BC has us placing poly as per discussed to perimeter with penetrations caulked, in addition to a perimeter of Big-O or slotted rigid 4"pipe looped in pea gravel trench 12" deep under slab, to a tee up through the slab and tied to 4" ABS pipe up and through roof with possible inline low cfm draw fan, this creates a slight vacuum under slab and radon takes the easy way out. A 15-mil vapor barrier can be about 25 cents per square foot. ACI 302.2R-06, Guide for Concrete Floors that Receive Moisture-Sensitive Flooring Materials, estimates that concrete with a w/c of 0.5 will dry to an MVER of 3 pounds/1000 sq. ft/24 hours in 82 days with a vapor barrier, compared to 144 days when exposed to vapor from below. That’s the subject of this week’s Q&A Spotlight. All of the problems associated with moisture vapor movement in a concrete slab will go away in time as the slab dries, as long as there is no source of additional water into the slab. Most experts today don't think that's low enough, and a few materials have recently become available that have permeance values less than 0.03 perms—some as low as 0.01. © 2020 The Taunton Press, Inc. All rights reserved. This was verfied by some field studies conducted by Concrete Construction magazine. A. 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