Whenever pouring concrete over a wood subfloor, a moisture barrier must be installed first to protect the wood from the water in the concrete and to allow the concrete to properly cure. Crack isolation membrane the tile council of north america. The subfloor will consist of 2 x 6 joists about 1 inch off the slab. Jul 17, 20 wood subfloor moisture posted on july 17, 20 by flooring professionals administrator in many of my weekly emails over the past few years, i have talked about concrete moisture, but rarely about moisture in wood subfloors and what can happen. Aug 27, 2010 moisture can come up through your subfloor, especially if you are installing over concrete or belowgrade. Vapor barriers have been associated with certain concrete slabongrade problems including curling and cracking. For what its worth, what i wound up doing is using the floor muffler underlayment, which is its own moisture barrier. Dec 19, 2018 before you install any flooring material over a concrete slab, it is important to inspect the slab for defects. This video describes the process of installing a moisture barrier over a concrete subfloor. If there is too much moisture in the concrete, and an impermeable layer is placed over it the moisture migration can delaminate the coating sealer or overlay. Concrete floor problems building science corporation. For concrete subfloors we recommend using a moisture barrier, not to be confused with a vapor barrier, the latter being less effective. I have read in some places that you need a vapour barrier to put over the concrete before installing the plywood and in other places to just glue the plywood to the concrete floor. For moisture to accumulate between the concrete slab and the flooring, it needs to find its way to that middle layer.
Jan 03, 2020 applying a sheet material that serves as a moisture barrier, such as a 6mil thick polyethylene pe plastic sheet overlapped with taped seams, can be one way to mitigate concrete moisture. Bone dry original penetrating concrete sealer is a permanent, low voc, cost effective solution to protecting finished flooring from concrete moisture related issues. A concrete vapor barrier is simply a sheet of polyethylene plastic visqueen placed directly on top of the subgrade before the concrete floor or slab is poured to help keep moisture from the soil from passing up through the concrete. Cmvc can be applied to concrete with moisture vapor transmission rates as high as 25 lbs. In order to achieve the proper vapor barrier, you must use a 14 x 14 vnotch trowel it has an ultra low voc content and is low odor, so you can relax knowing that you are. Moisture can come up through your subfloor, especially if you are installing over concrete or belowgrade. If the rh is over 80% then you have to use an epoxy coated system with a cementitious selfleveling underlayment to seal the concrete. In the mortar bed installation, the mortar bed is not bonded to the concrete rather it is isolated from cracks in the concrete by the cleavage membrane. Concrete may seem very dense, but it is actually full of small pores that will absorb water from the ground. Need some advice to install a plywood floor over concrete please. Whether it is an overwatered pour, a lack of a quality vapor barrier.
The only exception is when you want to install laminate over high moisture areas like basements and bathrooms where a moisture barrier is needed. Its dimpled, rugged gray plastic membrane provides a seamless mold and moisture barrier for any concrete, slabongrade floor in your home. As per the directions, i applied it over the subfloor and about 2 up the walls. A moisture barrier is need to protect the flooring against moisture or moisture vapor. Diffusion is a direct function of surface areaif i get 95 percent of the surface covered i am pretty much 95 percent effectiveand the parts that are left i have filled with concrete which is. Concrete vapor barrier what is a vapor barrier and do i. Many moisture problems associated with interior concrete floors and slabs on grade can be minimized or. When youre installing a wood floor over a concrete slab, the vapor retarder should be placed under the plywood subfloor. If your concrete passes the moisture test, then plastic sheeting at least 6 mils thick will prevent moisture from getting into your laminate flooring.
I think he is just handing me bs and hiding behind the moisture level issue. Also, with some types of membrane, the contractor can offset the sealantfilled soft joints in the tile, so they do not have to fall directly over the crack or control joint in a concrete slab in this case, create soft joints on both sides of the crack or joint figure 638, using a flexible sealant instead of grout. By restricting the planks ability to move, you can end up with damaged planks. Sealers that allow some vapor passage can be used, but most topical membrane sealers require a moisture vapor emission rate mver of 3 or 5 pounds square feet24 hours. Along with the moisture barrier, you may want to install an underlayment. Check with the manufacturer of the epoxy moisture barrier to make sure it will be suitable for your situation. Betty, i have never put a vapor barrier under carpet in a basement. This product is a 90 mil sound control, waterproof, and. Note any cracks in the substrate for future reference. Moisture is the numberone enemy of laminate flooring, and few manufacturers will honor the product warranty if you dont install a vapor barrier thermal insulation. Do i need to put any type of underlayment or vapor barrier underneath it.
How can i install porcelain tile over a concrete slab with. It helps reduce mold and condensation in buildings and is resistant to decay so it will protect against. How to put down flooring on a cracked concrete slab home. The barrier comes in rolls about twentyfour inches wide. For a warm and comfortable basement, choose the dorken deltafl subfloor. The safest way to approach questionable concrete is not to cover it over with cbus but to fix the concrete. New concrete is heavy with moisture, and it must be a minimum of 30 days old before moisture testing begins. I am putting down the plastic barrier on top of the subfloor, and then the new pergo laminate on top of that. Im putting ceramic tile flooring in my kitchen and live on a 10yearold, groundlevel concrete slab. I have seen many blogs and read a lot, and know it can be done, but, need a bit of help. Curling and warping of concrete slabs 5 facts you should know. Mver floor preparation s452 seal strong a two part moisture mitigation system designed to create a moisture barrier between concrete and resilient flooring suitable for use up to 100% rh or 25 lbs cacl.
The house was built in the 70s so im not sure if there was any kind of moisture barrier under the slab. Determining moisture content of both the wood flooring and the subfloor is an important part of quality control in the flooring installation process. Subfloor coatings and toppings, concrete moisture barriers. Attached vapor barrier underlayment surface prep the. Pair with metallized seaming tape to ensure a full moisture barrier, even over concrete.
But for ceramic tile, the best subfloor is the cement slab itselfprovided the slab is stable and in good condition. Some contractors like to place a layer of sand over the vapor barrier, but most have adapted to placing the concrete directly on top of a heavyduty. The definitive test is done with a calcium chloride kit or a relative humidity meter. It insulates and cushions the flooring, making it more comfortable to walk on. Our original sealer can be applied to new and existing concrete surface and can be applied underneath or over the surface. A readytouse elastomeric waterproofing membrane for both commercial and residential tile and stone application. With any concrete subfloor, you will need a vapor barrier underlayment to protect the floor from any moisture that may come up from the subfloor. Concrete flooring installation 2020 home flooring pros. It should serve as an additional element of protection. Some underlayments such as cali complete when used with the metallic tape are also moisture barriers. Tile cannot be attached directly to painted concrete, as the thinset will not adhere well to the paint. This flooring adhesive with moisture and sound barrier provides a moisture barrier to protect your floor from any moisture transmitted from a sub floor, as well as filling in any cracks or ridges in the concrete. Jun 05, 2009 this video demonstrates how to install a moisture barrier over a concrete subfloor.
Snap the chalk line over the top of the concrete or moisture barrier between the marks on opposite walls making a cross in the center of the room. How to install laminate flooring over concrete 2020 home. Adding a subfloor over the concrete slab is one installation method. Dorken deltafl plastic subfloor system for basements. Without the proper moisture barrier, vinyl flooring acts as a moisture barrier, causing it to buckle, bubble and lift.
Best concrete floor vapor barrier the truth from a real. However, the fact that the cost of floor coverings over concrete floor slabs in the u. Drytek epoxy moisture vapor barrier ideal for concrete. We understand that flooring installers need to supress moisture as quickly as possible before applying primer, smoothing compound and floor coverings. Painted concrete can be made porous with sandblasting or other hard. Sounds like its going to crack, but im doubting this to happen. For more information about this video or fausfloor products visit. Tile is bonded with thinset to the surface of the membrane. Why underlayment matters to a tile installation project. The soil under a slabongrade, in the event of an improperly functioning vapor barrier. Laminate is a floating floor, and it needs to be unrestricted to properly expand and contract with temperature changes. Bone dry original is easy to apply using a pump sprayer. Installing a hardwood floor over a concrete slab american.
How to install the moisture barrier over concrete subfloor. Figure 1 typical detail of slab on grade with vapor retarder. This sheet material does not negate the importance of installing a vapor barrier underneath the slab. I have read in some places that you need a vapour barrier to put over the concrete before installing the plywood and in other places to just glue the plywood to the. Prepping a concrete subfloor for hardwood or laminate flooring. Redgard crack prevention and waterproofing membrane. When installing certain types of flooring such as sheet vinyl the moisture content of the concrete can be a problem. Wood subfloor moisture posted on july 17, 20 by flooring professionals administrator in many of my weekly emails over the past few years, i have talked about concrete moisture, but rarely about moisture in wood subfloors and what can happen.
Where plastic sheets must be joined, overlap the sheets by several inches, and use strong vinyl tape to. Most other flooring materialsincluding hardwood, laminate, or carpetwill perform best in a basement environment if they are installed over a subfloor of dricore, or plywood or osb elevated slightly on sleeper boards. Applying a sheet material that serves as a moisture barrier, such as a 6mil thick polyethylene pe plastic sheet overlapped with taped seams, can be one way to mitigate concrete moisture. Drytek moisture vapor barrier is a singlecoat, 100% solids, liquid applied 2part epoxy coating specifically designed for controlling the moisture vapor emission rate from new or existing concrete slabs prior to installing drytek underlayment, decorative toppings and most resinous coatings. With the right moisture protection, you can turn a damp, moldy basement into a safe and livable family room or workshop. Its hard to see, but i have indeed left an appropriate half inch expansion gap between the wood and the drywall. Suited for interior and exterior substrates, redgard creates a continuous waterproof membrane barrier with outstanding adhesion and reduces crack transmission in tile and stone floors. Permeation of water vapor through concrete slabs can. Need some advice to install a plywood floor over concrete. Moisture problems between the flooring and the slab. The concrete slab is the air barrier, and the ripped and torn and punctured polyethylene sheet is the vapor barrier. Dips, bulges and cracks occur frequently as concrete cures and ages. Adhesive glue with moisture barrier and sound barrier. Looselay the first layer over the slab or over the moisture barrier above the slab, with 14inch expansion gaps between the sheets.
The misconception around slab curl and vapor barriers has been much. How to put a wood floor on concrete home guides sf gate. We have a partial concrete slab that we are planning to subfloor over to make a level floor throughout the house. Dec 29, 2019 installing a vapor barrier over a plywood subfloor will cause moisture to be trapped within the material which causes mold and mildew growth and can lead to warping of the laminate. Cracks and gaps can be filled with portland cementbased fillers. The condo has had laminate flooring in it for years. Installing a vapor barrier over a plywood subfloor will cause moisture to be trapped within the material which causes mold and mildew growth and can lead to warping of the laminate. In the thinset installation, a crack isolation membrane is bonded to the concrete. In this section, we breakdown the main ways water can get into your concrete, which causes a buildup of excess moisture, and list effective methods to prevent moisture problems from occurring. Theres a wide range of moisture barrier products on the market and various installation techniques. Should i use a 6 mil poly moisture barrier for engineered.
Can i install underlayment under laminate with attached. The concrete mix itself, in the event the slab is insufficiently cured or. For optimal moisture control you will want to overlap the poly barrier by at least six inches. This installation contains the moisture in the slab, increases the subfloors stability, and helps to keep the finished floor from swelling, buckling, or cracking.
Signs a concrete floor has moisture issues buildings. Before you install any flooring material over a concrete slab, it is important to inspect the slab for defects. A liquid coating is then applied to the bare concrete subfloor, such as customs cmvc 100% solids moisture vapor and alkalinity barrier. The concrete subfloor has no direct access with the ground. Does a floor above a first floor, basement or crawlspace have to be reinforced for concrete. Im up in the oakland hills, so the temperature extremes arent.
Confusion and debate over the use of vapor retarders will likely continue into the future. Americover has a high performance 15 mil vapor barrier for installation under concrete floors and slabs that will retard moisture migration and radon from escaping through the surface of the concrete floor. Drytek moisture vapor barrier is a single coat, 100% solids, liquid applied 2 part epoxy coating specifically designed for controlling the moisture vapor emission rate to new or existing concrete slabs prior to installing underlayment, decorative toppings and most resinous coatings. Can i install underlayment under laminate with attached padding. Testing with either method will tell you how precisely how much moisture is present, making it possible to choose a surface flooring that is appropriate. Where plastic sheets must be joined, overlap the sheets by several inches, and use strong vinyl tape to secure them. Oct 14, 2019 snap the chalk line over the top of the concrete or moisture barrier between the marks on opposite walls making a cross in the center of the room. By itself, laminate flooring is a poor insulator, and if you dont add an underlayment, the floor can feel uncomfortably cold sound insulation. When rolling out the moisture barrier you want to go from wall to wall and cover the entire floor. This product is a 90 mil sound control, waterproof, and crack isolation membrane. Why underlayment matters to a tile installation project the.
Installing underlayment for laminate flooring hunker. I have been researching a lot and would like to install a plywood floor over concrete in two bedrooms in our basement. This video demonstrates how to install a moisture barrier over a concrete subfloor. Vapour barriers are a good idea to prevent radon gas from coming up through any cracks in the floor.
Home subfloor coatings and toppings concrete moisture barriers applying. It is vitally important to test your concrete slabs moisture before installing flooring over it. Premium foam underlayment for laminate and floating wood floors. Construct a subfloor with sheets of 34inch pressuretreated plywood over the moisture barrier. Bostik vapor barrier membranes provide essential moisture mitigation and suppression for subfloors. This is a moisture barricade that protects finished floors from moisture over concrete slabs and subfloors.
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